Introdution to the case for Rigid Flex PCB technology

Posted by iFast PCB on October 4, 2016 in Rigid Flex PCB

When to make use of flex PCB design

It’s obtaining harder to fit everything in the box; it’s additionally obtaining more pricey. One option guaranteeing to help developers fulfill the dimension constraint directly is rigid flex PCB technology, however the majority of design teams attempt to avoid using rigid flex PCBs when item price is an issue. However is it really as expensive as we think?

To start with, consider the cost of the conventional rigid-cable-rigid PCB assembly to one based upon rigid flex PCB innovation. The former construction functions well for short-run layouts; nevertheless, it calls for ports on each board and the interconect, all of which increase BoM price. In addition, the rigid-cable-rigid design is prone to ‘cold joints’, and decreased life span. In contrast, rigid-flex PCB circuits remove these joints, making them far more dependable and able to supply on the whole greater product top quality and longevity. So while rigid flex PCB technology is absolutely not new, various considerations now make it far more practical– not the least of which is price.

Simulate the cost

In some designs, rigid flex PCB design will not be a feasible option, and you need to do your due diligence in identifying the break-even factor where the prices are about equal. This sort of rate simulation can be done by considering the overall estimated costs for PCB fabrication and assembly. The PCBs can be estimated before design, as long as the criteria of design are well comprehended (for instance, the layer stack-up, approximated by means of count, track and space ratios, etc.).

We carried out a PCB manufacturing cost simulation with a real rigid flex PCB design and a relative rigid-cable-rigid equivalent. The element BoMs for comparison changed only in the wire and ports needed for the non-flex version. For our simulation, the typical design is consisted of four-layer PCB boards that utilize flexible wire and connectors between them, while the rigid flex PCB design is a four-layer PCB with 2 inner flex layers. Manufacturing expense for both layouts is based upon actual PCB maker quotes, and includes the expense of assembly.

Discover your break-even factor

As the job quantity portrayed in Number 1 strikes 100 units, the rigid flex PCB design ends up being a more affordable alternative compared to the conventional design technique.

A crucial factor for this price savings is that rigid flex circuits do not utilize connectors/cables or need any type of port assembly. Likewise, they feature raised integrity and procedure returns. Yet that’s simply the tip of the iceberg.
Because rigid flex PCBs require no cable assembly, their overall assembly effort is minimized, as is their examination complexity– both which drive down price.

In addition, less elements need to be purchased, reducing the supply chain danger. Rigid flex PCB can be developed to make product maintenance more convenient and as a result, even more economical over the course of the item lifecycle.

What regarding design time?

While the price of PCBmanufacturing, assembly, screening, and logistics are essential consider considering the feasibility of rigid flex PCB innovation for any offered project, design and development prices can not be neglected. Rigid flex PCB design typically requires the mechanical team to help with the flex section of the design, and PCB integration with the end product. The process is really time consuming and pricey, in addition to vulnerable to mistakes.

Making issues worse, PCB design tools typically neglect the folding and suitable elements of rigid flex PCB design. Rigid flex PCB technology design needs designers to believe and work in 3D. The flex parts can be folded up, turned and rolled to adhere to the design of the system. But traditional PCB design tools do not support 3D board design or the meaning and simulation of bends and folds up in the flex part of the design. They don’t also support the definition of different layer stacks in various parts of the design, consisting of the locations comprising the design’s flex component.

Due to this, rigid flex PCB developers have actually been compelled to by hand translate both the rigid and flex areas of their 3D design into a flat, 2D depiction ideal for PCB fabrication. After that they have to manually record all locations of the design that are flex, and double check that no components or vias have been placed near the transitions between the design’s rigid and flex sections. This process is governed by several added guidelines, a lot of which are, not as well remarkably, not sustained by the majority of PCB design software application.

Generally, the added initiative it has actually required to design rigid flex PCBs as compared to standard rigid PCBs making use of traditional PCB design software program has actually made them much less cost competitive. Fortunately, contemporary design devices with sophisticated 3D abilities, and assistance for the interpretation and simulation of bends and folds in the flex portion of the design, as well as the meaning of other layer stacks in other parts of the design, are now available. These devices usually eliminate the need to deal with the flex part of the design with mechanical CAD tools, conserving designers and design groups both time and money.

Design in 3D to ensure success

Early control between the designers and the PCB manufacturer, supported by the use of a contemporary PCB design tool, is an additional factor making rigid flex PCB modern technology a much more economical choice. Rigid flex PCB designs call for closer cooperation between the developer and PCB manufacturer than standard rigid board designs. The tradeoffs required to create a successful rigid flex PCB design translate to a collection of design guidelines the designer could establish with the fabricator’s input. These considerations consist of the number of layers in the design, products choices, advised sizes for traces and vias, adhesion techniques, and dimensional control. With the appropriate design tool, these factors to consider can be plainly specified and given the appropriate weight they are worthy of at an early stage so that the rigid flex PCB can be effectively optimized, even more maximizing its general expense as well.

There’s no denying that existing sector trends and consumer demands are pushing designers and design teams to their limits, forcing them to look for brand-new options to the digital design challenges they currently deal with. These challenges, and specifically the needs being positioned on today’s smart phones, are pushing rigid flex PCB technology into the mainstream, and making it a lot more commercially practical for a variety of applications. The availability of modern-day PCB design tools that support 3D product development, early collaboration, and all necessary rigid flex PCB meanings and simulation considerably reduce the pain of rigid flex PCB design and make it a much more compelling remedy– one that under the right situations is less costly compared to rigid flex PCB design. For today’s design groups, that option might just imply the distinction in between item success or failure.

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Mentor extends rigid flex PCB & high-speed PCB layout in Xpedition

Posted by iFast PCB on October 4, 2016 in Rigid Flex PCB

Mentor Graphics has actually revealed the initial phase of its Xpedition printed circuit design flow to resolve the boosting intricacy of today’s sophisticated systems designs. The Xpedition flow supplies sophisticated innovations to enable design and verification of 3D rigid flex PCB frameworks, as well as to automate layout of high-speed geographies with innovative constraints.

Flex PCB and rigid flex PCB, mentor comments, are now located in all kinds of electronics items, from little consumer devices to defence, aerospace and also vehicle electronics. The Xpedition rigid flex PCB technology enables a streamlined design process from initial stack-up creation through manufacturing.

Engineers can design intricate rigid and rigid flex PCB in a completely sustained 3D environment (3D design and verification– not simply a 3D sight), causing a correct-by-construction approach for optimum integrity and item top quality. 3D verification ensures that bends remain in the appropriate setting, and elements on the PCB board do not interfere with folding; this can be examined early in the design stage to avoid expensive redesigns. Users can then export a 3D strong design to MCAD for efficient bi-directional PCB-enclosure co-design.

Assimilation with Mentor’s HyperLynx high-speed evaluation modern technology allows optimization of signal and power stability across complicated rigid flex PCB stack-up frameworks. For fabrication prep work, the Xpedition flow supplies all flex and rigid information utilizing the ODB++ common data layout. This approach removes information obscurities by clearly interacting the finished board intent to the maker.

” Advisor’s Xpedition circulation gives numerous board outlines, stack-ups, and also bend locations which permit us to specify a rigid flex within the design environment, and also export a folded 3D action version for efficient mechanical design assimilation,” stated Charles Ietswaard, PCB design engineer at NIKHEF, the national institute for sub-atomic physics in The Netherlands. “The automated rigid-flex capacities in Xpedition assist us handle the expanding intricacies of today’s sophisticated PCB systems.”

For effective rigid flex advancement, vital functions and capacities consist of:
– Definition of the rigid flex stack-up with special outlines for each region, making it possible for less complex design adjustments compared to stack-up by zone. Requirement flex materials (e.g. laminates, ’em bedded’ or ‘bikini’ cover layers, stiffeners, adhesives, etc.) can be included in the stack-up.
– Complete support of flex bends to handle where and how the PCB flexes, consisting of parts placement on flex layers, flex directing, plane form fills, tear drops

and trace drops. As soon as bends are specified, the design can be viewed and confirmed in 3D to ensure there are no accidents.
– Powerful interface with intuitive and easy selection controls to correctly handle the design.
– Electric rule checking (ERC) using an adjustable local guidelines mosaic and a thorough set of post-design checks for first-pass success.
– Flex-aware signal and power stability analysis, enabling accurate modelling of adjoin as it goes through different stack-up areas.
– Design for manufacturing (DFM) recognition and brand-new product intro (NPI) tools to make sure seamless PCB design to PCB fabrication administration and effectiveness.

Automated layout for high-speed layouts; this Xpedition launch likewise features advanced layout automation to resolve raising complexity in high-speed designs and emerging guidelines for high-end computing chip-sets, inlcuding;
– Tabbed transmitting, an adjoin geometry utilized to decrease crosstalk and impedance suspensions, can be produced and modified on high-speed traces.
– Designers can develop and change a transmitting technique with sketch plans that specify a path for trunks of nets, consisting of trace protecting.
– Improved tuning allows much better comments and control throughout interactive editing and enhancing to achieve high-speed restraints.
– Nets which call for back drilling can be specified in layout and outcome for PCB manufacturing.
– Designers could import Polar stack-ups and also layer mapping directly into the constraint supervisor to simplify design startup.
– A brand-new user interface makes it possible for review of all design guideline checks in the design for quick identification and resolution of electric and manufacturing design violations.

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IPC the First Automotive Stand on Performance Requirements for Rigid PCB

Posted by iFast PCB on October 4, 2016 in PCB News

BANNOCKBURN, Ill., USA– In September of 2015, IPC supplied revision D of IPC-6012, Qualification and also Performance Specification for Rigid Printed Boards. Structure on this base requirement, IPC has developed the initial automotive addendum, IPC-6012DA, Automotive Applications Addendum to IPC-6012D Qualification and Performance Specification for Rigid Printed Boards.

This addendum resolves the dependability of rigid published boards which must survive the vibration and also thermal biking atmospheres of digital interconnects within the automotive sector. Some of the highlights included with IPC-6012DA are the identification of automotive performance classes, recommendations for sustainability and reliability screening identification, as well as solder makes density coverage over conductors, aircrafts, and also nearby surface install devices. The addendum likewise offers requirements for opening size, opening pattern accuracy, as well as pattern function accuracy requirements.

” This is a vital action to a standardized degree in a challenging field of providers and also needs,” stated Jan Pedersen, chairman of the IPC-6012DA Automotive Addendum to IPC-6012D committee and also elderly technical consultant at Elmatica. “IPC-6012DA, addresses the particular requirements and specifications for structure as well as providing printed motherboard for the automobile industry, which are not covered in the base basic IPC-6012D.”

The busy committee will not be relaxing on their laurels. Later on this year, an activity group will certainly be established to prepare the requirement for the medical sector, a sector not yet integrated in terms of PCBs. Customers as well as vendors in the medical field will certainly be welcomed to take part.

” The idea behind the automotive addendum was to discover a consensus in the forest of company specifications, an usual file explaining fundamental PCB demands for the vehicle market,” included Pedersen. “Now that IPC-6012DA is finalized, we are really proud understanding this standard will bring the auto requirements for both customers as well as vendors up to a standardized rank.”

IPC-6012DA is readily available currently for all those entailed with PCBs for the auto market. Find out much more about IPC-6012DA.

About IPC
IPC (www.IPC.org) is an international sector organization based in Bannockburn, Ill., dedicated to the competitive excellence and also economic success of its 3,700 member firms which represent all facets of the electronics industry, including design, published board production, electronic devices assembly and test. As a member-driven company and leading source for sector criteria, training, market study and public plan advocacy, IPC sustains programs to fulfill the needs of an approximated $2 trillion global electronics sector. IPC keeps extra workplaces in Taos, N.M.; Washington, D.C.; Atlanta, Ga.; Brussels, Belgium; Stockholm, Sweden; Moscow, Russia; Bangalore and New Delhi, India; Bangkok, Thailand; as well as Qingdao, Shanghai, Shenzhen, Chengdu, Suzhou and also Beijing, China.

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Laser Processing Technology in PCB Substrate Manufacturing

Posted by iFast PCB on October 4, 2016 in PCB Manufacturing

If there’s one immutable regulation regulating the creating as well as manufacture of electronic tools it’s this: each succeeding generation needs to be thinner, smaller sized as well as cooler than the last.

Obviously, it goes without claiming that the gadget– whether it’s a wearable designed to keep track of and track one’s health stats, a mobile phone made to connect into the electronic ecological community, or a specialized gadget created to connect to the common Internet of Things (IoT)– must also be a lot more dependable, more effective and also more feature-rich than its precursor. In addition to new requirements for extensive battery life as well as longevity.

While these form variable as well as effectiveness developments drive the design of digital devices, making those devices a truth as well as obtaining them to market is only possible when the entire electronics worth chain keeps up. As a vital gear in the worth chain, PCB manufacturers need to do their part as the market moves forward. Modern technology developments driven by design continuously tax PCB manufacturers to not just offer handling companies that deal with the current dimension as well as power restraints, yet to do it more successfully … as well as without adding price!

Mainstreaming of HDI laser processing techniques
For PCB producers, it’s increasingly apparent that in order to stay on top of the increasing rate of development, supplying a collection of solutions that includes high-density adjoin (HDI) processing is not simply a great to have, however it is a necessity. Handling techniques that were previously reserved for an elite couple of are ending up being typical practice throughout the PCB production segment.

With the fostering of HDI processing, PCB manufacturers can make the interconnects and also PCBs that help with the usage of smaller parts that could do even more and also consider less, as well as work as the integral parts of the contemporary devices demanded by the market. As an example, this mainstreaming of HDI processing methods by multilayer PCB producers frees developers to incorporate a higher variety of smaller sized components on both sides of a raw PCB, and also at a pitch size that allows for more signal website traffic in smaller sized geometries.

The instance for CO2 lasers
An essential step in the manufacture of HDI PCBs involves high-precision drilling of tiny openings called microvias that allow thick electric connection in between the various layers in motherboard. This need to drill holes in PCBs is the application that brought lasers right into PCB manufacturing in the very first area.

In the 1980s and also with the 1990s PCB manufacturers looked to carbon dioxide (CO2) laser tools to produce blind vias– openings of a pre-defined deepness in the PCB material.

While CO2 lasers have a variety of advantages over mechanical boring devices, their usage is still limited to regarding 20% of PCB suppliers. Also though their longer wavelength makes CO2 lasers excellent for permeating the glass fibers in FR4, the predominant material used for PCB substratums, it usually calls for an extra oxide treatment on copper in order to ablate the steel, which tends to reflect instead than absorb light power.

UV systems, which use non-visible spectrum, can easily pass through copper but are not as effective at puncturing glass fibers with constant top quality.

Mechanical using drilling
Although mechanical drills lug a lower up-front expense and also can pierce via numerous boards concurrently, the greater costs connected with maintenance, constant little bit substitute and also restrictions on accuracy is tipping the cost-of-ownership formula for lasers.

With more mainstream adoption of HDI, via dimensions are shrinking considerably. This produces a problem for mechanical drills because opening sizes have lessened and more are being packed into the very same PCB real estate. A mechanical drill can just drill a number of hundred HDI-sized holes before calling for a little bit substitute. Considering that a relatively normal PCB design can need 75,000 to 100,000 vias from 50 to300 µm in size, this constraint is a showstopper. Consequently, producers that were formerly material with mechanical exploration remedies for through creation are increasingly aiming to embrace laser-based remedies for high-volume production.

Price of possession considerations
The complete cost-of-ownership equation starts to turn in support of CO2 laser exploration systems when through sizes, both blind as well as through-hole ranges, loss in the array of 50 to 200 µm. With the capability to form thousands of top notch vias per secondly, CO2 laser boring technology is playing an essential duty in allowing mainstream multilayer PCB suppliers to perfectly relocate right into the HDI market.

Materials and also markets
Certainly there are a multitude of variables that go right into laser selection. Also though the auto field is transforming to HDI and laser by means of processing for the miniaturization benefits there is a simultaneous emphasis on design for reliability. In this market, where high-frequency applications are ending up being more typical (believe radars as well as sensors), typical FR4 products might not be the finest choice of substratum product. As a result, UV-based systems and also other handling innovations may be more relevant in this market, where the options for substrates are not as limited.

By comparison, mobile phone suppliers are driving their vendors toward ever minimizing sizes and also very slim products. Typical mobile phone PCB thickness is roughly 0.5– 0.7 mm, but thinner boards with boosted layer matter are on the horizon. Industrial as well as modern technology roadmaps prove to that within the following couple of years PCBs thinner compared to 0.4 mm will certainly begin to be made use of in handheld gadgets while the complete variety of layers will remain to increase, relying on item complexity. In this market situation, laser pierced vias will be the only strategy available for refining these PCBs successfully in high quantity.

Dominant laser for inflexible PCB manufacturing
For the foreseeable future, CO2 laser boring is going to be the dominant laser innovation in rigid PCB production with other modern technologies such as UV obtaining a tiny yet stable foothold that can expand gradually as products come to be much more specialized.

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Versatile PCB: What’s in a Name?

Posted by iFast PCB on October 3, 2016 in PCB News

Versatile PCB is an usual term that is synonymous with versatile circuits. While the term “PCB” is generally made use of to describe stiff published wiring, “adaptable PCB” is a little contradictory due to the fact that “boards” aren’t really adaptable. Some firms, like All Flex, design and also manufactures flexible PCBs, however not rigid PCBs.

There are many resemblances between both, yet also significant distinctions.

Design
The shortest distance between two factors is a straight line, so a circuit trace on a flex circuit should look like a circuit trace on a stiff circuit board? In fact there can be considerable differences in between making a stiff PCB as well as an adaptable PCB. Since of the flexibility function, there are distinct problems affecting robustness. Since flex can flex, one requires to be certain that bending does not crack or break solders joints near a bend area. For this factor, design features like radiused corners as well as filleted pads are usual on versatile circuits. Another problem is that the substratum made use of for flex is not as dimensionally secure vs. its rigid cousin. Allowances for dimensional adjustments could be needed for versatile PCB design. Many PCB design software program is customized to rigid printed circuit materials as well as attributes. Tradeoffs happen when this exact same software application is used to design versatile PCBs [1]

Manufacture
Rigid PCBs and versatile PCBs have very comparable manufacture actions and also commonly utilize the very same tools as well as tools suppliers. For example, photo imaging the base circuitry layer could utilize basically similar modern technology. The differences develop because of the distinction in between taking care of a rigid board versus a versatile substratum. Some ultra-thin circuits are extremely lightweight as well as need special product dealing with systems. While a PCB is reasonably very easy to take care of, a thin flexible circuit could looking for special clamping, fixturing or vacuum systems to hold it in place while processing. Some very high-volume versatile PCB makes process circuits in a continual reel (reel-to-reel). Reel to reel handling uses substantially various product handling systems vs. systems processing distinct panel sizes.

Tooling
Both PCBs and flexible PCBs make use of similar tooling such as CAD documents, picture tools and electric examination fixtures. Probably the biggest difference is around the cutline interpretation. Versatile circuits supply unlimited arrangement chances that typically causes very weird shapes and also dimensions. Circuit boards often are rectangular or may have some notches or curved outlines routered. As a result of this subtlety, steel regulation dies as well as tough tool dies are possibly utilized much more often for versatile PCBs than for boards, at the very least for ultra-high-volume applications. Laser interpretation of the circuit synopsis is additionally a common flex circuit procedure. Other differences in tooling entail fixturing that might be needed to handle adaptable substratums.

Coverlay/Covercoat
Adaptable PCBs call for various dielectric products such as adaptable photoimagable soldermask or laminated coverlay (also called coverfilm) vs. the non-flexible PCBs. This produces materials with special properties and also obstacles. Materials have to flex and also bend, with some applications needing numerous cycles, without breaking or flaking. A number of design attributes have to be thought about with dynamic flex applications, consisting of: copper grain direction, circuit pattern layout, coverfilm thickness, and also trace geometries. One of the most usual adaptable dielectric is laminated movie dielectric bound to the substratum with heat and also pressure, a remedy hardly ever utilized for stiff PCBs.

Applications
Versatile PCBs constitute concerning 10– 15% of all PCBs produce internationally, so there are much more applications that use hardboards than flex. The largest benefit for flex is that it could reduce the dimension, weight and amount of hardware used for several digital plans. It is ideal explained as an “digital interconnect packaging option.” The idea of an “origami flex circuit” likewise enters your mind. If you have an application that calls for several planes of interconnections, or there are energetic flexing or stretching requirements for parts of the plan, after that a flexible PCB could be your finest choice.

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Step 6: Power and also GND airplane design; single-point grounding

Posted by iFast PCB on October 3, 2016 in PCB Design

For a high-density layout, designers have to be especially mindful to utilize as couple of vias as feasible for signal routing, especially within high present conduction courses. This stays clear of a “Swiss cheese effect,” where all layers in the PCB stackup are perforated by a great deal of vias, boosting DC resistance as well as jeopardizing thermal and also EMI efficiency. As stated in [6], numerous COMPUTER board issues are mapped back to alternate signal return paths, which cause common-mode currents and emitted discharges. If the return course is not interrupted by a void or slot in the GND aircraft, high-frequency signals carry out along the trace to the tons and after that return quickly under that trace because of shared combining.

Given that all capacitors decouple efficiently just around their regularity of self-resonance, it is tough to realize a large spectral distribution of decoupling from VIN as well as VOUT to PGND. The multilayer PCB is leveraged as a low equal collection inductance (ESL) capacitor by piling VINand VOUT planes above or listed below PGND planes. In the buck-boost converter instance design, VINand VOUT copper polygons lie on the leading as well as bottom layers to supply low-resistance conduction courses to the power terminals (component 2). The internal layers of the PCB are filled with as much copper at GND possibility as possible, as revealed in Figures 2, 3. AGND and also PGND are typically represented by two different ground symbols in the schematic. Just one link factor in between AGND and PGND is required, normally at the IC’s exposed thermal pad (DAP).

Step 1: Choose the PCB structure and stackup specification1.1 A multilayer PCB structure is vastly premium to a single- or double-sided PCB to reduce transmission loss, lower thermal resistance, alleviate EMI, as well as decrease noise as well as interaction between traces and also parts.1.2 Understand the stackup construction in regards to board density, copper weight, and also plan of core as well as prepreg (pre-impregnated fibreglass/resin compound) layers [7].1.3 Using a four-layer or six-layer PCB stackup allows a tightly paired, solid GND airplane on layer 2. An instance of a four-layer stackup is POWER-GND-SIGNAL-POWER/ SIGNAL.1.4 Improve the coupling to and also performance of a GND aircraft under side of a two-layer design by defining a low-height PCB. Otherwise, double-sided designs are essentially delegated to two single-sided settings up.1.5 Use GND aircraft( s) to protect delicate small-signal traces from power phase switching sound.1.6 Recognize that finest practices for PCB design closely straighten with high thickness and also tiny remedy size.Step 2: Identify high di/dt existing loopholes and high dv/dt voltage nodes2.1 Minimize the location of high current, high di/dt power loopholes as well as gate-drive loops, as these develop H-fields that can magnetically pair to nearby low-impedance circuits.2.2 Minimize the area of high-voltage AC nodes with big dv/dt changes– for instance, switch, boot and high-side gate drive– as these stand for E-fields that could capacitively combine to close-by high-impedance circuits.2.3 Avoid slots, spaces and sectors in the GND plane that increase the return existing path length, resulting in common-mode noise currents and emitted emissions.Step 3: Power stage layout3.1 Component selection and also floorplanning of the MOSFETs, decoupling capacitors and shunt resistor ought to target the absolute smallest location and area of “warm” loops.3.2 Reduce power loop parasitical inductance, consisting of partial inductances from the MOSFET package deals, decoupling capacitor, shunt resistor and PCB affiliations, as it brings about voltage overshoot, ground bounce, buzzing, EMI and also power loss [3].3.3 With a power loophole configured for straight present flow, add a GND aircraft on the layer instantly beneath to function as a guard layer for H-field self-cancellation and also decreased parasitical inductance.3.4 Connect multiple decoupling capacitors in alongside minimize equivalent collection resistance (ESR) as well as ESL.3.5 Undesirable SyncFET spurious turn-on is highly pertaining to high switch-node dv/dt in addition to gate loop and also common-source parasitical inductances (Figure 1). Take steps to alleviate this by reducing gateway pull-down resistance as well as utilizing snugly paired gate and source (return) traces.3.6 Place a resistor in collection with the boot capacitor for a crooked gate-drive design [6] This attenuates voltage and current multitude prices of the turn-on transition without influencing turn-off changing loss.3.7 Locate switch-node snubber networks as well as antiparallel Schottky diodes for dead-time conduction exceptionally close to the SyncFET.3.8 For optimum thermal area shapes in convective atmospheres, prevent air flow watching of low-profile power MOSFETs by taller elements, such as the filter inductor and also electrolytic capacitors.3.9Switch-node copper acreage is a compromise between handling dv/dt-related sound and also supplying appropriate heat-sinking for the low-side MOSFET( s). Huge aircrafts with high Air Conditioner voltage end up being transfer and also receive antenna structures for radiated EMI.3.10 Remove GND aircraft copper directly beneath the inductor to lessen capacitive coupling to GND, especially if a great deal of turns are had to acquire the inductance.3.11 Separate the inductor terminals’ copper pours to prevent increasing the inductor’s equal parallel capacitance (EPC), reducing its self-resonant frequency (SRF). Tip 4: Control IC placement and also steering area layout4.1 Consult tool data sheets for particular design recommendations and format examples.4.2 Keep the IC near to the MOSFETs for minimized entrance drive trace lengths. One option with a two-sided design is to locate the IC on the contrary side of the PCB about the MOSFETs.4.3 Connect the IC’s exposed thermal pad to the GND aircraft( s) below making use of a number of thermal vias for heat-sinking.4.4 Locate the VIN, VCC and also boot capacitors close to the IC.4.5 Connect the VCC capacitor’s negative incurable to PGND, as it behaves as the return for the low-side gate drive.4.6 Keep the FB trace short by situating the responses resistors surrounding to the IC.4.7 With low-IQ converters that demand high-resistance responses elements, be mindful that the FB node is particularly at risk to sound pick-up.4.8 Use brief traces for other crucial analog nodes such as error amplifier outcome (COMP), frequency collection (RT) and also slope settlement (SLOPE) inputs.4.9 Use a committed GND aircraft moat for small-signal element return currents. Connect this aircraft to the IC’s analog GND pin (AGND).4.10 Connect PGND as well as AGND at the IC for single-point grounding.Step 5: Routing of crucial traces– gate drive, existing sense, voltage sense5.1 Make the gate motorist trace ranges from the controller to the MOSFETs as short and also straight as possible to lessen entrance loophole parasitical inductance. Use at the very least 20-mil trace widths.5.2 Reduce typical resource inductance (the mutual impact between the gateway loophole and also switching loop) by tying the entrance drive return directly to the resource terminal of the MOSFET.5.3 Route eviction drive traces orthogonal to the power stage to prevent mutual combining.5.4 Place eviction and resource traces alongside each various other on one layer or up and down aligned on surrounding layers to lower inductance and also high dv/dt sound.5.5 Place the low-side entrance drive trace close to a PGND aircraft such that the return current is equally coupled in a course underneath the trace.5.6 For extremely high duty cycle procedure, reduce the parasitic inductance in the boot capacitor revitalize existing path through the low-side MOSFET.5.7 Route the current-sense traces as a firmly combined differential pair. Locate current-sense filter components close to the IC.5.8 Use keep-outs to make sure that vias for ground-referenced feeling return are separated from GND planes.5.9 Sense VOUT at the point where exact regulation is required (normally at the factor of load). Keep VIN as well as VOUT sense nets far from high di/dt loops.Step 6: Power and also GND airplane design6.1 Keep the copper airplanes solid and also continual by minimizing the variety of vias used for signal directing.6.2 Use many vias in parallel close to the decoupling capacitors’ terminals to attach to power as well as GND airplanes. Location positive and adverse through sets near each other for change cancellation.6.3 Fill in both leading and also lower layers of the PCB with as much copper at GND potential (ground fill) as possible.6.4 Beware of covert antenna frameworks where the transmission course dimension approaches one-quarter wavelength (or a several) at the regularity of interest.6.5 Finally, review the PCB format and also eliminate any type of design-rule offenses [8]

Table 1: Summary of PCB layout guidelines for DC/DC converters.

Summary

It’s reasonable to claim that PCB design specifies the efficiency that a switching power converter ultimately achieves. In completeness, this series of write-ups supplied a step-by-step method to PCB design. The prime benefactor might well be the developer or their credible service technician, who avoids plenty of hrs of debugging time for EMI, sound, signal stability and also various other issues associated to a bad layout.

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DC/DC converter PCB design, Part 3

Posted by iFast PCB on October 3, 2016 in PCB Design

One crucial innovation in the field of DC/DC power converters is the awareness of higher and greater thickness layouts. In the promote smaller-footprint solutions, designers are currently concentrating on usable power density to extract one of the most power each unit area or quantity from the converter circuit. Because the power converter is a vital as well as ubiquitous piece of the total remedy, a thoughtful printed circuit board (PCB) layout represents a chance to boost density while supplying added system-level advantages, also. One instance is electro-magnetic disturbance (EMI), which is a significantly troublesome concern during item design as well as qualification. A compact, maximized power phase design enhances EMI in terms of both exhausts as well as immunity.

In this three-part series [1], I reviewed PCB format factors to consider for fast-switching DC/DC converters utilizing a step-by-step technique. Actions 1 and also 2 from part 1 examined the PCB layer stackup as well as determined the high-di/dt existing loops and high-dv/dt voltage nodes of the converter. Actions 3 and 4 partly 2 supplied an evaluation of power phase as well as control IC element positioning for ideal switching in addition to thermal and also EMI efficiency. In this last installment, I cover steps 5 and 6: the transmitting of essential traces for eviction drives, current sense and comments network; and also an evaluation of power and also ground (GND) aircraft design of the multilayer PCB substratum as well as ground splitting up methods. For a total recap of DC/DC converter PCB format standards, see Table 1.

Step 5: Route the MOSFET gateway drives, current sense, comments and various other critical traces

Comprehending gate-loop and also common-source parasitic inductances

MOSFET switching actions and also the effects for waveform buzzing, changing loss, device tension and also EMI are very closely related to the parasitic inductances of the changing loop and also gate circuit emerging from tool package and also PCB format connections [2,3] From Figure 1, we need to recognize the duty of two parasitical inductances emerging from the entrance drive circuit design.

Figure 1: SyncFET parasitic turn-on causes undesirable shoot-through in phase-leg configurations. This is related to variation present from switch-node voltage dv/dt (a), and also negatively induced source voltage from body diode reverse-recovery-current di/dt (b).

LG is the self-inductance of the gate loop, including lumped contributions from the MOSFET package deal and also PCB trace routing, and LS is the common-source or mutual inductance shared by the drain and also gateway present paths [4,5] As received Figure 1, common-source inductance LS1 of the control MOSFET (CtrlFET) increases switching loss since the di/dt of the main loophole creates an adverse comments voltage that restrains the surge as well as fall times of the gate-source voltage. Throughout body diode reverse recovery, common-source inductance LS2 adds to spurious turn-on of the simultaneous MOSFET (SyncFET).

Lessening gate-circuit parasitic inductances

Formerly I went over the top- and bottom-layer layouts for the 4-switch buck-boost converter [5] in components 1 and also 2. Numbers 2, 3 reveal the inner-layer art work for this PCB.

Eviction driver traces running from the control IC to the 4 MOSFETs, which lie on layers 3 and 4, are kept as brief and also direct as possible to minimize gateway inductance. A Kelvin connection links eviction drive return traces directly to their particular MOSFET resource terminals, lessening common-source inductance. The return currents for the low-side MOSFET gateway drives flow on the GND aircraft back to the PGND pin of the IC. To decrease gateway loop location, gateway and resource traces are routed side-by-side as differential pairs utilizing 20-mil trace sizes.

Gate loophole parasitic inductance also enhances the moment needed to refresh the boot capacitor. This is particularly crucial for high responsibility cycle operating problems when the SyncFET has a short transmission time. Number 1 highlights the boot capacitor refresh present course in green.

Routing present and voltage sense traces

Figure 3a shows the traces for present feeling routed as a snugly combined differential set from the shunt resistor to the IC current sense inputs. Kelvin sensing at the shunt is essential for precision. Keepout limits make sure that vias related to the sense return trace are isolated from GND aircrafts, and also existing sense filter parts are located as close as feasible to the IC.

Figure 3b reveals the VOUT sense area at the point where the most precise policy is accomplished, generally on the cheapest layer in the stackup before current flows to the tons. VIN and also VOUT feeling traces are low resistance to GND, yet are still vulnerable to the high di/dt loops of the converter.

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Tip 4: Steering IC place and also bottom side PCB design

Posted by iFast PCB on October 2, 2016 in PCB Design

If the steering IC has integrated entrance drivers, it ends up being important to locate the IC as close as possible to the power MOSFETs. The gate driver traces that run from the IC to the MOSFETs are kept as brief and also straight as feasible to reduce parasitical gate inductance.

On a single-sided PCB design, the only option is to position the steering IC on the top (part) side of the PCB close to the power tools. However, accomplishing brief gateway drive links is typically made complex by the power stage format (specifically if even more than 2 MOSFETs are required, as in the 4-switch buck-boost, multi-phase buck or increase, and full-bridge converters). The necessary signal-level elements, attaching traces as well as vias that usually border the IC also make its positioning harder. It is often advantageous in a two-sided layout to put the IC under (solder) side of the PCB. This helps gateway drive circuit efficiency as well as shields delicate analog circuits from changing noise as well as high operating temperature levels characteristic of power devices. Number 2 shows this technique for the bottom side layout.

Number 2: Bottom layer of PCB (layer 6) watched from listed below. Small-signal parts surrounding the steering IC are located on a different ground (GND) island.

Higher-profile electrolytic capacitors are positioned on the bottom side for three reasons. They are of similar elevation to the banana links for the power terminals in this design and, thus, impose no height charge. Second, they conduct low- to mid-frequency existing harmonics [9], making extremely close placement to the MOSFETs superfluous. Third, air movement shadowing from the electrolytic capacitors is greatly inconsequential, as the lower-profile, heat-dissipating MOSFETs are sited on the leading side of the PCB.

The noise-sensitive small-signal elements for the compensation network, feedback resistors, frequency established resistor, soft-start capacitor and also current sense filter lie near their corresponding pins (COMP, FB, RT, SS, CS, CSG) and have a committed analog ground (AGND) plane that ties to the IC’s AGND pin. Power ground (PGND) connects to the subjected pad of the IC with thermal vias to inner ground airplanes. PGND attaches to AGND in your area there as well for single-point grounding.

Summary

Reducing converter losses is an essential requirement to enable compact awareness and an adaptable implementation of the converter within the intended system. Thoughtful placement and also layout of the power stage components in a PCB design allow better changing performance, higher performance, lower operating temperature levels and lowered broadband EMI for less complicated regulative conformity [8]

Keep tuned for component 3 of this collection, when I’ll dig right into the detail of routing essential traces for gate drives, result voltage comments as well as existing sense, as well as lastly ground monitoring, in tandem with a polygon plane design of the outer as well as inner layers of the multilayer PCB.

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DC/DC converter PCB design, Part 2

Posted by iFast PCB on October 2, 2016 in PCB Design

High efficiency, high density and also reduced production expenses drive the constant development of DC/DC converters for an increasingly large variety of power supply applications for automobile, commercial, personal electronic devices and communications markets. To attain these design targets, a small yet innovative published motherboard (PCB) format design of the switching converter goes a long means in the push for a smaller impact option. The PCB design itself is generally a multi-objective discipline, as it straight affects electrical, mechanical, thermal and also electromagnetic actions.

Component 1 of this three-part collection [1] focused on power converter PCB design and relevant considerations. The four-switch buck-boost converter topology provides a convenient system to study PCB design, as you can quickly theorize the analysis to various other geographies. Actions 1 and 2 (covered in component 1) talked about multilayer PCB stackup and also the important current loopholes as well as voltage nodes of the switching converter. Right here in part 2, I will certainly check out action 3, the power element positioning for optimum switching regulatory authority efficiency, looking also at power phase thermal design and also electro-magnetic interference (EMI) considerations. Step 4 explores steering IC as well as small-signal part floor preparation and location.

Action 3: Power-stage element positioning

Based on the high di/dt existing loop recognition outlined in action 2 (part 1), thoughtful and also tactical positioning of the power stage parts is vital. With raising switching rates and lower package parasitics, the bottleneck in power MOSFET changing efficiency is shifting from silicon to the commutating loop parasitic resistance [2] Utilizing the synchronous buck-boost geography example layout in recommendation 3, the display capture in Figure 1 highlights positioning of power MOSFETs, large element ratio footprint existing shunt, and also input as well as result ceramic capacitors on the PCB’s top layer.

Figure 1: To the left is the PCB leading layer with power-stage component design showing tight Air Conditioner current-loop conduction paths. To the right is a schematic of the 4-switch buck-boost power train, consisting of power MOSFETs, shunt, inductor, and input as well as output capacitors.

The lower-profile MOSFETs (3 mm x 3 mm) and ceramic capacitors (1210 footprint) are intentionally found on the top side of the PCB. The taller parts (inductor and mass capacitors) are on the lower side. Input capacitors are located near buck-leg MOSFETs. Outcome capacitors are situated adjacent to boost-leg tools, resulting in a limited, symmetrical format for both changing legs. Note that the shunt resistor increases the size of the location of both switching loopholes. A shunt resistor with a wide aspect proportion (1225 footprint) and also a shorter conduction course gives reduced inductance as well as decreased lengths of power loopholes 1 as well as 2, signified by the while borders in Figure 1.

H-field self-cancellation

Power-loop parasitic inductance increases MOSFET changing loss and also peak drain-to-source voltage spikes. It likewise aggravates switch-node voltage buzzing, affecting broadband EMI in the 50- to 300-MHz array. While lessening the physical dimension of the loop by focusing on component positioning is important to reduce loop inductance, noise combining additionally depends on field distribution/orientation, making the design of a PCB’s internal layers notable.

As reviewed in recommendations 4– 8, an easy shield layer is developed by putting a ground plane as close as feasible to the changing loophole using a minimal dielectric thickness. The straight existing flow on the top layer sets up a vertical flux pattern. The resulting electromagnetic field induces a current, contrary in direction to the power loophole, in the shield layer. By Lenz’s regulation, the present in the guard layer creates a magnetic area to counteract the initial power loop’s magnetic field. The outcome is an H-field self-cancellation that amounts to lower parasitical inductance, lowered switch-node voltage overshoot, and also boosted suppression of EMI [7] Having an uninterrupted, continual shield plane on layer 2 underneath and at closest distance to the power loop provides the most effective efficiency. Slim intralayer spacing is specified in the PCB stackup, making use of a 6-mil core dielectric for instance.

Power stage thermal design

While a high-density format is usually positive for conversion performance as transmission voltage drops are lowered, it might create a thermal efficiency bottleneck. A push-pull dynamic remains in play here: The same power dissipation in a smaller sized impact ends up being unacceptable. To take full advantage of thermal efficiency in convective airflow, place the MOSFETs on the top of the PCB. In this arrangement air movement is not watched by taller parts such as the inductor as well as electrolytic capacitors. Depending upon the application, it is possible to find the inductor on the bottom side of the PCB, because it may hinder warm transfer if positioned on the top. Owing to its size, the inductor fundamentally serves as its own warmth sink.

With respect to the 4-switch buck-boost converter being talked about here, the low-side MOSFET of the non-switching leg is held back in pure dollar or boost methods. This offsets the surrounding high-side gadget that carries out the inductor existing constantly with concomitant power loss. On the other hand, with deep buck or boost operation (that is, low dollar or high increase responsibility cycle), the switching-leg MOSFET option tilts towards managing low-side power loss and also temperature increase. As revealed inFigure 1, the high-side MOSFETs’ drains pipes are connected with short links to the VIN or VOUTpower terminals via heat-spreading copper aircrafts. Their drain tabs are additionally joined by countless thermal vias to equivalent copper airplanes under layer. Thus, the high-side MOSFETs are effectively heat-sinked.

The thermal challenge of this design is the low-side MOSFETs whose drain tabs are attached to switch-node copper polygons with via connections to the inductor listed below. Currently, the essential variable below is switch-node copper location. Provisioning for low EMI positions a focus on a marginal switch-node copper area to reduce capacitive coupling related to high dv/dt switch-node voltage changes [8] and reduce e-field radiated exhausts. Nevertheless, a bigger switch-node copper location helps in thermal dispersing relevant to dissipation from the inductor and low-side MOSFETs. A PCB format for bigger 5-mm x 6-mm footprint MOSFETs with lower thermal insusceptibility is achieved with a relatively minor edit to the layout in Figure 1.

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Sharing The PCB stackup layout for the PCB fabrication

Posted by iFast PCB on October 2, 2016 in PCB Manufacturing

This representation consists of electric layers and also linked copper weight, substrate (dielectric) layers classified as core and also prepreg, solder mask, by means of drill kinds, and relevant layer thicknesses that aggregate to the total PCB height. A core of provided elevation is provided with copper foil adhered on both sides. Similarly, various plies of material pre-impregnated fiberglass, or prepreg, are combined to accomplish the preferred prepreg thickness. The stackup choice proven to here is called layer pairs and refers to the order of the core as well as prepreg layers throughout the layer stack [6] Number 2 programs top, middle as well as bottom cores sandwiched by two layers of prepreg. Other stackup class frequently sustained by PCB suppliers are displayed in Figure 3. The stackup is specifically vital if blind or buried vias are prepared, as the drill sets are defined to fit the layer stackup style.

Figure 3: Alternative layer stacks for six-layer PCB: inner layer sets (a), as well as accumulation (b).

One industry-standard of laminated thickness specification is 62 mils (1.6 mm). 1 ounce (oz) copper describes a weight of 1oz/ft2 and also matches to an aluminum foil height of 1.4 mils (0.035 mm). Therefore, trace resistance is derived based on the trace length and also width, and the resistivity of copper at the relevant operating temperature level.

Step 2: Identifying high variety rate current loopholes

With an eye towards recognizing the layout-induced parasitical inductances that trigger too much noise, overshoot, sounding as well as ground bounce, it is crucial to determine the high multitude rate present loops, or warm loops, from the converter schematic. As illustrated in Figure 4, loops 1 as well as 2 (shaded in red) are categorized as high-frequency switching power loops for the dollar as well as boost legs, specifically. During a MOSFET switching occasion where the variety price of the commutating current could quickly go beyond 5 A/ns, just 2 nH of parasitic inductance causes a voltage spike of 10V. Inasmuch as the rectangle-shaped present waveforms in the identified power loops are rich in harmonic material, a serious danger of electromagnetic field combining as well as radiated EMI exists. Clearly, it is vital to minimize the efficient loop size and also encased location in loopholes 1 as well as 2. This decreases parasitical inductance, enables magnetic area self-cancellation [4], and minimizes the radiated power rising from exactly what are successfully loophole antenna frameworks.

Figure 4: Buck-boost converter schematic with vital loopholes categorized for high slew price currents. Power loops 1 and 2 are for the buck and also increase legs, specifically. Loopholes 3, 4, 5 as well as 6 signify MOSFET gate vehicle driver loopholes during turn-on and turn-off changing shifts.

In contrast, the existing moving in the filter inductor is largely DC with a superimposed triangular surge. The price of change of current is inherently restricted by the inductance, as well as any type of parasitical inductive part added by the collection links is basically benign.

Loopholes 3– 6 in Figure 4 are classified as gateway loops for the buck and also boost legs. Particularly, loopholes 3 and 4 (outlined in green) stand for the high-side MOSFETs’ gateway vehicle driver circuits provided by their respective bootstrap capacitors. Loopholes 5 and 6 (blue) assign the low-side MOSFETs’ gate drivers supplied by VCC. The turn-on and turn-off existing courses, signified by solid as well as dashed lines, specifically, are delineated in each case. To demand as well as release the MOSFETs’ reliable gate capacitance throughout turn-on and turn-off changes, high multitude price present approximately 5A top– relying on gate driver stamina, series gate resistance and inductance, and MOSFET capacitance– streams briefly in each gateway loophole.

The low-side gateway vehicle driver loops’ confined locations are lessened by placing the VCC decoupling capacitor really near the VCC and PGND pins. In a similar way, the high-side gate driver loopholes’ enclosed locations are decreased by placing the bootstrap capacitors close to their respective SW as well as BOOT pins [ 7] Eviction vehicle driver traces from the controller to the MOSFETs are maintained as brief as well as direct as feasible.

Summary

A four-switch buck-boost topology facilitates the conversation of power converter PCB design, beginning with an understanding of the called for PCB stackup and also identifying the vital converter switching loops from the schematic. Vigilantly minimizing these loophole locations throughout design of the PCB is necessary to abate parasitic inductance, electromagnetic field coupling, and also radiated EMI.

Stay tuned for Parts 2 as well as 3 of this write-up where I explore the information of power stage component floor-planning, thermal design considerations, strategic placement of the PWM controller, routing of vital traces for gateway drives, present feeling and comments, small-signal element positioning and transmitting, as well as finally polygon airplane design of the multi-layer PCB.

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