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Lightning Speed Laminates: The Benefits of Understanding Engineering Disciplines for PCB Design

I started my PCB industry career in 1987 in the Flexible Interconnect Division of Rogers Corporation. That division of Rogers was sold many years ago, but I learned a tremendous amount working there. My first responsibility was learning flexible circuit design and I was in the ideal surroundings to learn.

I had responsibility for a new product from beginning to end of life. I designed flexible circuits, many times from scratch using schematics and mechanical drawings. In the beginning phase of the product life cycle, I designed the circuit and panel layout, designed the tooling, and established the build sequence for the prototype. In my learning stage and after all the tooling arrived, I went to the prototype department and helped them build the circuits from beginning to end. I cannot express how valuable that experience was, seeing the tooling I designed, working with the various process steps in the build sequence, and finally shipping the parts.

After multiple revisions of prototype circuits, the customer would usually go into high-volume production, and it was a very different circuit design discipline for designing the circuits and tooling for mass production than it was for prototype circuits. High-volume production requires the designer to consider all customer circuit properties and specifications, and perform CpK analysis to ensure the circuit will have good manufacturing yield at high volumes. 

Over the years, I’ve taught several engineers circuit design. I am convinced that if the designer has a very good understanding of the different process steps it takes to make a circuit, they will be a much better designer. As an example, if a designer encounters a need for exception when designing for annular ring, the designer who knows the circuit fabrication process well will make a much better design decision than a designer who only knows the annular ring design theory.  

My circuit design experience also included rigid board design, which was different than flex circuit design, but the basics were the same. After my circuit design experience, I was a technical support engineer for the flex circuit materials division of Rogers and later a technical support engineer for the high frequency circuit materials division of Rogers. In the technical support role, I worked directly with our circuit fabricator customers and that caused me to work with many processes for making flex circuits and rigid high-frequency PCBs. Also, because I worked at a materials company, I had to understand the material engineering aspects of the circuit material, how it interacted in different PCB processes, and its end-use. Additionally, I was a part-time student in electrical engineering at ASU during most of my engineering experience in the industry. My diverse engineering experience was influenced by the engineering theory while I was working in the industry. The overall diversity of my engineering background has proven to be extremely beneficial for me at Rogers Corporation.

My point is that having a very diverse engineering background is extremely beneficial for understanding PCB designs. I think most engineers today probably do not have the opportunities I had. I would strongly recommend design engineers get very involved in circuit processing, manufacturing, and circuit materials engineering. When a PCB designer understands these different aspects of PCB technology, they will certainly be able to deliver circuit designs that will be more robust and have better manufacturing yields. The high-volume manufacturing yields of a PCB are directly related to profit and that is the connection between good circuit design and a successful circuit-product.

An aspect related to PCB design is software. There are many different software programs that the circuit designer needs to work with, and some of these programs allow the designer to run simulations. This is another tool for designers to build on their design expertise. The simulation software can be used to model a circuit design, change different features of the circuit, run the simulation again, and learn what the design change will do for circuit performance. The benefit of running many different simulations can be very educational for a circuit designer.  

Another aspect of engineering that can be beneficial for the PCB designer is having a good understanding of practical statistics. Since PCB design is focused on the customer’s specifications, it is beneficial for the designer to have a good understanding of standard deviations, CpK analysis, histograms, box plots, etc. These statistical tools help with the circuit design process, but they can also help with optimizing yields, troubleshooting, failure analysis, and design modifications.

In summary and in my opinion, the following topics need to be well understood for a PCB design engineer to gain expertise: circuit materials, major processes in PCB fabrication, defining stackups, understanding the PCB build sequence, statistics, and simulation software. Additionally, there are many resources for PCB design at IPC.org, IEEE.org, and the websites for companies that make PCB software for routing and stackups.

This column originally appeared in the August 2021 issue of Design007 Magazine.