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A-sap of Semi Additive Process in PCB Manufacturing Technology

2020-09-08

I spent most of my career in the PCB industry. Like many people, I entered the industry by accident. When I graduated from college with a degree in economics, I was looking for positions in the financial sector, accounting and human resources positions in a small flexible circuit PCB board manufacturer. To be honest, I didn't even know what a flex circuit was at that time, so they were taking a real risk by hiring me. What I initially received there was not financial training, but manufacturing process training - taking time to study products and learn processes so that I could understand better.


By that time, 125 micron (5MIL) line width and spacing had reached the technical limit. Today, PCB manufacturers are producing 25 micron (1mil) line width and spacing design. In fact, most of us use smartphones with a PCB width and spacing of 30 microns. These mass commercial designs are produced using MSAP or an improved semi additive process. This process starts with a very thin copper foil and uses addition rather than subtraction to form circuit patterns. The MSAP process requires a lot of capital investment, and the corresponding manufacturers usually have to meet the high volume requirements.


The market for electronic products is changing rapidly. Today, it is not only high-yield applications that require 25 micron line width and line spacing, but also military, aerospace, medical, automotive and industrial designs are moving towards smaller and smaller feature sizes. For the currently available subtraction etching processes, design solutions usually require multiple stacked vias and multiple laminating cycles. This solution greatly increases the cost and has the problems of low reliability and yield.

Today, three U.S. PCB assembly supplier adopt the alternative solution, a-sap Gamma Process, namely averatek's half addition process. In general, this process first etches all copper from the laminate and then applies liquid metal ink (LMI) Gamma )A very thin electroless copper coating is obtained. The circuit pattern is determined by lithography, and the circuit pattern is formed by electrolytic copper. At present, this process can achieve 15 micron line width and line spacing, and higher-order processing technology can even achieve more fine feature size.


The addition process has brought exciting new choices for PCB designers and manufacturers. Using thinner line width and line spacing allows designers to use fewer layers for wiring, which reduces the overall size and weight of PCB, and reduces the demand for multi-layer micro through holes; from another perspective, designers can increase the area of existing PCB. As with any new technology, explore and implement a-sap Gamma The greatest potential of technology will drive designers and manufacturers to look at things in a creative new way.

 

From the manufacturing point of view, even if the addition process is opposite to the subtraction process, a-sap Gamma The process can also adapt to the traditional subtraction etching process and equipment. This process requires the addition of a series of relatively simple tanks and heaters, as well as the manufacturer's original electroless copper plating equipment and lithography equipment. Once the circuit diagram is generated, it can be produced like any reduction method.

 

This addition method can not only match the existing PCB manufacturing process and equipment, but also can choose the addition method and combine with the subtraction method in PCB design. Let's take an example and redesign a highly complex 12 ply board with the original stacked vias and multiple laminating cycles. Available a-sap Gamma The four layers are generated by the process and combined with the other four layers produced by the subtractive etching process, which greatly simplifies the design. The number of PCB layers is reduced by 4 layers, the material cost is reduced, and only one laminating cycle is needed.


Let's look at the second example. The original design is 10 layers, the line width and line spacing are 75 microns, and three laminating cycles are used. The goal in this example is to significantly reduce the overall size of the PCB. Using a-sap  Gamma Technology, the line width and line spacing of all layers are adjusted to 25 μ M. In general, the number of PCB layers is reduced from 10 to 8 layers, and three laminating cycles are still used, but it has a significant impact on the number of PCBs on each manufacturing panel. The original design allows only 70 PCBs per panel. After the line width and line spacing are adjusted to 25 μ m, the number of PCBs arranged on each panel increases to 400. In order to achieve the packaging goal, the size is significantly reduced, and the total design cost is also significantly reduced.


In PCB manufacturing, addition method and subtraction method cooperate with each other, which is really attractive. The rapidly changing electronic market drives the packaging design size to be smaller and smaller, and the technology used is becoming more and more complex, which leads to manufacturers' need to innovate additive technology to meet the needs of PCB designers. It will be interesting to observe and learn when early adopters of this technology work with their customers to develop design and find the best way to make it.

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