With China’s policies and regulations in the third plenary session,with the horn of the reform and opening up sounding, PCB is as a basal or important parts of electronic industy.In the early 1980 s ,foreign merchant(here do not include Hong Kong and Taiwan),Hong Kong merchant, Taiwanese merchant or joint ventures,they had the scale of investment in China mainland to built PCB factory.At that time, Shengyi electronic, Shennan circuits,Weimei, Pulin,and other smaller PCB factories with single and double layer production, were born.Nearly 30 years, from scratch, from weak to strong, in technology and management and product cost level, on the scale, there are encouraging progress.Double-digit growth every year, in 2007 and 2008,the aunual output value is nearly 16 billion USD,which is up to one-third of the world and become the world’s first.
World has more than 2000 PCB factories,and there are more than 900 PCB factories in China.Japanese,the USA and Taiwan mainly have the high,new,sharp technology.Second,Hongkong and other foreign enterprise and large state-owned enterprises in the PCB.In the second half of 2008 and 2009, starting to affect the PCB manufacturers in the financial storm, local companies standed huge test.One night, purchase order plummeted ,and employee was fired, or even the factorise were closed.Local PCB manufacturers have a very large space in technology, management, scale, and market direction . Learning from advanced enterprises, is an effective means.To change the direction of products, to improve product class, to fight for the market shares, one of the key means is to improve manufacturing technologies and to implement technical transformation.
The follow information we learn from many peers and superiors has simple introduction to some technical problems.
(1) Base material
The base material used in HDI board is required to be thin;the thickness is 3 mil or below;the copper thickness is 1/3 OZ or 1/4 OZ,to implement the small-hole,fine-line,and high-level thin boards.Auto electronic products need to use base material with high heat resistance and high reliability , to ensure stability.Semiconductor packaging (PKG) need packaging base material with fine circuit,high flatness,small hole spacing and high reliability.Copper thickness of More than 3 oz is needed by power board.
(2) micro-via technology
According to some technical articles, the fore-forming ways used by PCB manufacturing industry are:machinery drilling,punching,laser drilling,light drilling,chemical etching, plasma etching,jet perforation and so on,while in real application, more comprehensive and muture pore-forming ways are machinery drilling and laser drilling(CO2 laser and UV laser)
Generally, holes with diameter 0.25mm (10 mil )or below is call micropore in industy.For micro hole drilling, the common methods are as below:
1, mechanical drilling, mainly used in the through hole. At present, the commonly used microporous bit diameter generally have 0.1mm (4 mil), 0.15mm (6 mil), 0.2mm (8 mil) and 0.25 mm(10 mil);
2, the CO2 laser drilling, mainly for the HDI blind holes for base material;
3, UV laser drilling, it is mainly used for burning copper for HDI blind holes.
Because the hole diameter is more and more small,which brings challenges to electroplating, for stability and accuracy of product ,also a challenge!
(3) the light painting technology
The emergence of CAD technology, make the PCB product a higher level in precision and manufacturing efficiency. Now DPI20000, a kind of light painting machine, can realize fine line width and line space.Within a minute, making the film of 24 “x 30″size is unimaginable in the ninety’s.At that time, it took one hour to make such a film.
There are dozens of CAD software at present.Most of the PCB factory will ask the customer to provide GERBER light painting standard format.General PC (CAM350) can realize the basic editing functions, to achieve customer requirement combined with the actual production.Of course, more powerful workstation can realize more editing functions such as GENESIS2000, but expensive.The raw data provided are mainly composed of GERBER, other ,such as documents, documents of drilling and milling, network, exterior files, etc., usually is with below format .
（1） Gerber (RS274D&RS274X)；
（2）HPGL1/2 (HP Graphic Layer)；
（3）Dxf&Dwg (Autocad for Windows)；
(4）Protel format (DDB＼pcb＼sch＼prj)；
（5）Oi5000 (Orbotech output format)；
（6）Excellon1/2 (drill\rot)；
（7）IPC-D350 (netlist)；
（8） Pads2000 (job)
(9）Aperture table (Dcode)。
(4) plating technology
The rapid development of microelectronics technology and the rapid development of PCB manufacturing towards to multiple stratification,horizon, functionalization and integration,make the PCB designer largely use the design of tiny holes,narrow space, and fine wire to design PCB,which makes the PCB manufacturers more difficulty.Plating faces the above questions.Especially the multilayer board whose aspect ratio is more than 5:1 and whose blind holes are deep, make the regular vertical plating process not meet the technical requirements of high quality and high reliability.
Especially the increasing number of micro-blind hole in laminated board not noly need horizontal plating,but also use ultrasonic vibration to promote liquid in micro-blind holes replacement and circulation.And use the pulse electric current and actual test data to adjust controllable parameters, to achieve product technical requirements.Horizontal plating technology can solve needs of the high aspect ratio through-hole and uniformity of products electroplating .
(5) lamination and positioning technology
Multilayer board has the main problems in physics: uniformity of lamination and adhesion, and positioning system.
On heating mode, in addition to the commonly used electric heating and hot oil heating, there is laminating technology which uses the copper foil resistance directly heating, to ensure the quality of the laminate.No pin positioning technology instead of pin positioning technology, and using X – Ray positioning hole, to improve the accuracy of positioning of multilayer PCB board.
(6)surface treatment technology
1. The hot air leveling (HAL or HASL)
Hot air leveling is most commonly used.Its advantages are very common and low price and long saving.The disadvantage is that flatness is restricted.Composition proportion of HAL is 63% tin and 37% lead. Melting point of tin lead alloy is lower than any other alloy melting point.It is 183 ℃. Due to environmental problems, at present, hot air leveling lead free is required.While using HASL lead free ,whose melting point is 217℃,for SMT, it is also a challenge.Equipment is from the traditional vertical to horizontal HAL.
2 Organic coating (OSP)
Organic coating process is simple, low cost, good flatness, superior to HAL, but short retention time. The retention time is required a month in the industry .Once the package is opened, the board is required to use.
3. Immersion nickel/gold (based Ni/Au)
Immersion nickel/gold process is complex, with a wet process, good flatness, but expensive.It have a thin gold system and thick gold system.
4.Immersion silver
The main advantages of immersion silver is able to provide good performance, small contact resistance, good flatness.Silver is cheap, safe and coplanar, the most suitable for high speed signal transmission and RF (radio frequency) board, simple process, less pollution.It has a long life.It can be shed and applied again, and don’t affect the aperture size.It would not incur the thermal deviation relative to PCB.It is a simple process for assembly, and can allow makers and assembler to rework many times.
5. Immersion Tin
Because now all the solder is based on tin , so the tin can match with any type of solder.Adding organic additive into tin liquild can make a granular structure on tin layer,which solves the tin whisker caused after immersion tin process.In the process of welding ,the movement of tin whisker and tin may cause reliaability problems.Adding organic additive into tin liquild also has good thermal stability and weldability.
(7) detection technology
Impedance tester solves impedance testing requirements of board of communication and high frequency PCB. AOI (automatic optical testing), solve the line problems that may appear after the internal and external layer line etch.The detected problems will be quickly repaired, which improve the final qualified products, and reduce the production cost; Quadratic element and cubic element improve the precision of product testing; Many varieties, small batch products is also the current demand.Before PCB was tested by test fixture .Every kind of PCB needing one matched fixture.But now, flying probe test solve the outstanding problems , to guarantee electrical OPEN/SHORT test, and so on.
Only matching with market, improving the technical levels, may companies have greater space for development.Optimization of enterprise technical level unceasingly, improving enterprise competitiveness, China PCB manufacturer will go further and more steady.