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In this issue, we discuss some of the challenges, pitfalls and mitigations to consider when designing non-standard board geometries. We share strategies for designing odd-shaped PCBs, including manufacturing trade-offs and considerations required for different segments and perspectives.
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Sensible Design: When Coatings Go WrongAugust 23, 2016 | Phil Kinner, Electrolube
Estimated reading time: 2 minutes
This month, I consider some of the more common, and often very frustrating, problems that may be encountered when coating electronic circuit boards and components. I also discuss some practical solutions.
As we all know, nothing in life is straightforward. In any engineering discipline, if there is the slightest chance that something might go wrong, you can bet your bottom dollar that it will. The secret is to be prepared for it. For the purposes of this column, I’m going to concentrate on the use of conformal coatings for the protection of electronic assemblies, highlighting some of the potential pitfalls associated with the choice of coating and the method of application. In each case, I will suggest an approach that should mitigate the majority of problems you are likely to encounter.
Problem: The quality and performance of a conformal coating material could be compromised according to the method of application.
This issue is commonly encountered when a product is transferred from one circuit manufacturer to another; for example, a product may be dip-coated in one country but selectively coated in another, with the specification requiring that the same material be used at both sites. The problem that arises here, however, is that using a material formulated for dip-coating in selective coating equipment can result in poor yield due to excessively fast drying and bubble entrapment.
One of my customers spent six months trying to solve a bubble issue internally, without realising that the root cause of this problem lay in the material formulation. After working with the customer, we found that by changing the solvent blend, the bubble entrapment issue could easily be resolved. Moreover, this solution simplified the process and reduced the cycle time. And since the non-volatile formulation remained the same, there was no need to re-qualify.
Problem: Achieving incorrect coating thickness, especially with acrylics.
The IPC specification allows a dry film thickness of between 30 and 130 microns, with the greater thickness being achieved by the application of multiple coating layers. Trying to achieve a 130-micron dry film thickness from a single selective-coating process with a solvent-based acrylic material is a recipe for a disaster, likely to result in excessive bubble formation, film shrinkage, coating delamination and additional stress on components. The result is poorer protection, rather than an improved overall level of circuit protection. Aiming for a uniform 30-50 microns and focusing on achieving perfect coverage at each application is a much better approach to improving the protection of electronic circuits.
Achieving the correct coating thickness is important; bear in mind that if the coating is too thick it can lead to entrapment of solvents in areas where the coating does not fully cure. Similarly, it can cause the coating to crack as it cures or as the result of changes in temperature, or due to mechanical shock and vibration.
To read this entire article, which appeared in the July 2016 issue of The PCB Design Magazine, click here.
On the cusp of another IPC APEX EXPO, we focus on how bare board fabricators can maximize their time and investment at the show. We visited with Matt Kelly, IPC chief technologist, and Julia Gumminger, IPC professional development and events manager, as well as Udo Welzel and Stanton Rak, the chairs of the technical program committee, to discuss the technical depth and breadth that the 2024 show will bring to fabricators and professionals all along the supply chain.
Each quarter, IPC releases a list of standards that are new or have been updated. To view a complete list of newly published standards and standards revisions, translations, proposed standards for ballot, final drafts for industry review, working drafts, and project approvals, visit ipc.org/status.
IPC’s efforts in government relations and advocacy have been pivotal in getting legislation like the CHIPS Act passed. In February, IPC President and CEO Dr. John W. Mitchell was back in Washington, D.C., representing our industry in a meeting convened by the U.S. Department of Commerce, where he discussed workforce issues in our industry and how to ensure that our businesses have the workforce they need. In this audio interview, he reviews his concerns and solutions on workforce development.
Like any great tech industry event, IPC APEX EXPO pushes us out of our busy 24/7 manufacturing bubbles. It forces us to pay attention to things that are important but not always present in our day-to-day lives. But there is so much to see and do. This issue of PCB007 Magazine previews many of the important events taking place at the show this year and highlights some changes and opportunities. Let us help you map out your show plan. This issue is focused on the PCB fabricator’s show experience and how you can get the most from your valuable time and investment in attending the show. So, buckle up. We are counting down to IPC APEX EXPO 2024.
It’s been another busy week in the industry. We lost another old friend last week. The EIPC show happened, and Pete Starkey provided us with complete and compelling show coverage, from start to finish. Recently, we posed the question, “When is it time to introduce embedded components into your PCB design?” which was asked and answered by design aficionado Kris Moyers in the latest issue of Design007 Magazine. We are proud to be a part of the exciting Global Insights weekly newsletter, which Nolan Johnson and Brian Knier explored in their interview, and we rounded out the week with some big merger news. Here are my picks for the past week’s must-read news items.