Flexible Printed Circuits (FPC) provides a remarkable possibility for the packing designer as well as electronic designer. These versatile electronic electrical wiring systems can be shaped, curved, twisted and also folded up right into endless dimensional arrangements … restricted only by a designer’s origami creative thinking. Here they supply considerable design advantages over a 2 dimensional and also rigid PCB. This added dimension could make flex PCB developer’s dream, but with the addition of versatility come some “policies” that should be followed to make particular a durable design is attained.
Various flex PCB manufacturing techniques and also material sets are used for flex PCBs and an immediate distinction is the dimensional properties. Inflexible printed circuits boards are generally a lot more dimensionally secure vs. the basic polyimide movie made use of as the foundation in 98% of the flex PCB produced. This boosted dimensional variability suggests a flexible circuits requires various design policies compared to its inflexible printed motherboard loved one. Regrettably, a lot of the design software application available usages rigid PCB design guidelines and also this can produce PCB manufacturing as well as functional issues for the flex PCB. Getting a flex PCB design all set for manufacturing is referred to some in the sector as “flexizing” the design.
The here information leading 5 of the a lot more usual methods “flexizing” makes a design a lot more durable, many more producible, as well as prepared for flex PCB manufacturing.
1. Firm joints as well close to bend point:
A solder joint is formed by an intermetalic bond of the solder alloy to the copper trace. While the copper trace is normally flexible, regions that have been soldered come to be extremely inflexible and stringent. When the substrate is curved near the side of the solder joint, the solder pad is either visiting break or flake. Either circumstance will certainly cause significant practical problems.
The bottom line is that creating a flex PCB with standard PCB software application can lead to some major manufacturability as well as dependability concerns. It is well to collaborate with your flex PCB manufacturers or a flex PCB design specialist to either “flexize” the design before beginning fabrication or produce the layout directly from a net list. This will certainly assure that the design can be produced to satisfy your demands.
2. Anxiety factors in conductors:
Because flex PCB is utilized in both fold to mount as well as dynamic bending applications, trace configurations that serve in a stiff PCB could create troubles in a flexible circuits. Conductor traces with sharp corners as well as severe times at the base of solder pads become natural “tension points” when the area near them is flexed. This can lead to trace fracture or delamination. A great flex PCB layout will certainly have a smooth distance for conductor turn points (as opposed to sharp edges) as well as a gentile radius from the trace to the pad fillet rather than a sharp angle. Selective accessory of supports will certainly avoid bending in soldered areas and is a typical design practice.
3. Spacing in between solder pads as well as adjacent traces:
Here is the tradeoff, i.e. design compromise, which will be made based on product # 1. When the coverfilm or soldermask openings are made larger, the edges of the surrounding conductor traces could be revealed if they were directed too near a solder pad. This can cause shorts if solder bridges in between connector pins or pads. Physical dimension of the flexible circuits is an additional aspect that can impact enrollment capacity. As a whole even more space is needed between a solder pad and also a nearby conductive trace to accommodate the coverfilm or soldermask placement resistance.
4. Stacked traces:
Traces on opposite sides of the dielectric should not straight “stack” on each other. Traces in stress (outside of the bend radius) could split when the flexible circuits is bent if they directly line up in parallel with a trace on the contrary side. The traces in tension are forced farther from the neutral axis of the folded up area and also can crack, specifically with duplicated flexing. A good design practice is to keep the copper in the neutral axis of a bend by designing this region as a single conductive layer. When this is not feasible, an appropriate design will “surprise” the traces between top as well as bottom copper layers to prevent top as well as lower positioning.
5. Solder mask or coverfilm openings:
During the flex PCB manufacturing the flexible circuits could show dimensional adjustment after exposure to processes like pumice scrubbing up, copper plating, and/or etching. While some adjustment can be made up, flex PCB design rules normally need larger resistances to suit succeeding enrollments for coverfilm, stiffeners, or pass away cutting. Added consideration is needed for the glue eject that occurs throughout lamination of the coverfilm dielectric. Complicating the prediction of compensating design attributes is the myriad of procedures as well as series called for to create a custom flex PCB. The bottom line is the openings in the coverfilm generally have to enable even more space in a flex PCB design.