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How to increase PCB wire-width and wire-pitch capabilities to 1mil to better support customers in the military, aerospace and medical markets.

April 25, 2022

Cesgate's goal is to stay at the forefront of technology. Two years ago, we started building a five-year technology roadmap.
To this end, we set up a market representative committee composed of R&D personnel and innovation directors from high-end clients. There are representatives from the military, medical, communications, and other markets and from different applications in those markets.

 

Throughout the roadmap, we see some momentum toward product miniaturization. When making a product smaller, we usually start by reducing the trace width and pitch resolution. The diameter or geometry of the through-hole is then treated to reduce the thickness of the medium, the thickness of the copper layer, etc. This is part of the product miniaturization process.


In general, more and more customers need to downsize their products, and the size of electronic products is one of the driving factors. A number of technologies and industries have sprung up in the last 10-15 years to bridge the development gap between wafers, chips, semiconductors, and PCBs. Given that the semiconductor industry follows Moore's Law, the volume of semiconductors is shrinking at an exponential rate, leaving PCBs far behind. One solution to this gap is to create an IC board field that uses some of the processes of semiconductors and processes and materials used in PCB production.

 

We found that by achieving a 1mil line width/line pitch, we could save our customers a lot of hassle, simplifying the design of the system and facilitating its miniaturization. Smaller sensors, for example, could help the medical field, especially companies that make systems for surgical devices and other invasive devices. Most of them use FPC, which we both design and supply.


The aerospace industry also wants to make products smaller to reduce signal loss in dB/mil units. As long as the line width/line pitch is small enough and the shape is fine enough, the signal loss can be very low. We know that this 1mil linewidth/linewidth capability not only enables us to support customers who want to minify their products, whether in the aerospace, medical, or military sectors, but also helps them improve system performance.

 

It's easy to buy off-the-shelf equipment specifically designed to make a particular product directly, but it's much more complicated when it comes to matching equipment and processes to a full line of products, R&D activities, and future products.


We invested two or three years ago in a very special etching and developing system to achieve dense and fine wiring. The next technology that needed to be addressed was lithography, which was easily solved by purchasing an LDI with a laser wavelength of 18μm/linewidth. This will also be possible in the future when customers require 20μm line width/line pitch. In fact, we are already using the equipment to make such products.

 

The most challenging and expensive process is the wet process. This is a 22 meter long automatic device used for etching, developing and stripping of resist. In addition to equipment and processes, conventional resistors must be upgraded to one capable of supporting 1mil linewidth/pitch or 20μm linewidth/pitch and sufficiently sensitive to the wavelengths generated by LDI. So it also changes the basic requirements that we have for suppliers.

 

When we brought this 1mil linewidth/linewidth process to market and introduced it to medical customers, they designed a 20 to 25μm linewidth/linewidth FPC based on this process. So far we have produced and received feedback from the original equipment manufacturer.

 

In terms of production and technology, we are serving the multi-variety, small volume, high performance market. We are manufacturing rigid bonded PCB, rigid PCB, ceramic PCB, high power and 120 GHz high frequency PCB. This means that we are working with a variety of resin systems and material suppliers from around the world, including Korea, Japan, the United States and Germany; IC substrate industry, PCB industry, flexible industry and hybrid PTFE base suppliers. It is difficult to have a process that supports the lamination of rigid flexible plates made from polyimides pressed together with the outer layer of PTFE, because PTFE and other types of Teflon ® are very soft materials, while polyimides are very hard materials. It needs to be drilled, milling and electroplated, as well as understanding material changes before and after lamination (CTE can affect dimensional stability, etc.). The entire process requires continuous learning until the components are assembled on the PCB, and sometimes the field environment has some impact, all of which should meet the customer's reliability requirements.