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The printed wiring board fabrication process is an intricate maze of interrelated steps, both chemical and mechanical. A thorough understanding of each of the process steps is critical in minimizing or eliminating non-conforming defects—the ones that cost the fabricator money and can lead to lost customers. It is also critical to note that these profit-killing defects may have their origins elsewhere in the process. That is the difficult thing about troubleshooting—the defect is often blamed on the process (such as electrodeposition of copper) because that is where the problem is first discovered. However, this is often false, as the origin of the defect may have had its humble beginnings in a previous process step. To be successful at troubleshooting a problem, common sense usually applies. Basically one must first:
- Identify the problem or problems (be as specific as possible)
- Determine possible causes (looks for links to those other less obvious processes)
- Identify methods and procedures to test to see which causes apply
- Test the assumptions
- Implement corrective action
While this sounds like an oversimplification, this approach is required to properly identify and attack the problem at hand. A structured routine is really what is required. In upcoming columns we will attempt to provide some insight as to the cause or causes of non-conforming defects and the potential solutions. We will discuss process parameters and the importance of control of the processes. Let’s discuss the step-by-step methodology for troubleshooting.
Identify the Problem or Problems
first and foremost, you must have a clear sense of what you are looking at. In troubleshooting, I firmly believe in the team approach to solving the problem. However, the team must agree on what the defect is: is it hole wall pull-away (HWPA) or resin recession; is this an interconnect defect (ICD) or simply a line of demarcation? These are just a few examples.
Editor's Note: This article originally appeared in the April 2016 issue of The PCB Magazine.