Solvents in holes can heat and "pop."

This month we look at voids or missing conformal coating. Depending on the lack of coating and position, this condition may result in acceptance or rejection. Normally with conformal coatings, small voids not specifically associated with electrical termination or bridging connections are acceptable, depending on the level of inspection criteria.

FIGURE 1 shows voids or bubbles in conformal coating under UV dark light. I would suggest both these cases require rework, as the electrical termination points are exposed, and there is no protection. Most likely, solvent coating has run into the holes. As the coating starts its first transition from a liquid, the voids expand from the holes. Then they pop, leaving the surface or pads with no protection.

It is suggested too much coating was applied on one pass, and initial evaporation could not occur, resulting in a volcano-like reaction from the holes. Each of the holes associated with coating voids had limited solder fill or cavities. In the past, we have seen the same problem with selective coating around press-fit connectors.

Which holds up better: mesh-mounted or mechanically tensioned, mesh-free frames?

Ah, stencil tension. A subject near and dear to my heart and one I’ve written about before in this space. In fact, we covered the subject a few years back, when we discussed how the loss of tension on a conventional mesh-mounted stencil can adversely impact printing results and why other solutions may prove superior. In recent years, studies undertaken to evaluate the impact of stencil tension on print performance have, indeed, confirmed these assumptions.

Before we get into the outcomes of our company’s work, let’s review the basics of conventional mesh-mounted frame stencils and mechanically tensioned, mesh-free frame systems. To be fair, mesh-mounted stencils are the industry standard. They are the predominant stencil type employed for electronics assembly. The alternative approach is mechanically tensioned, single-frame solutions that allow manufacturers to use one frame alongside multiple foils for various assemblies.

Do you know the quiet leaders? Often they are the ones who get things done.

In 1981, when I started in the electronics manufacturing services (EMS) industry, two things really surprised me. First was that EMS factories saw tomorrow’s tech before the rest of the world. Second was the amazing amount of knowledge resident on the factory floor. That second point always drives me to challenge folks who believe it is impossible to succeed without a college degree. As long as I’ve worked in EMS, I have been exposed to factory workers who learned on-the-job the same things I did in college.

A couple months ago, I had a great conversation with Lois Kenon, a rework/repair specialist at TeligentEMS in Havana, FL. She went to work in the service sector after high school, planning to try a few jobs before going to college, but ended up staying in manufacturing. We spent time talking about her leadership philosophy, and I felt it made sense to share some of that philosophy in my column.

Supply chain fatigue taking hold? It’s all in a day’s work.

I can’t think of a more exciting time than now, especially for the PCB industry. Risk has always been a friend and catalyst to our industry. There has rarely been more types of risk, and never as varied, for all industries and companies, large and small, to navigate. As varied as it may be, all those challenges seem to boil down to three basic categories: technology transfer; geopolitical posturing; and logistics fatigue. The single common denominator to all? People.

My bet is that dealing with new technology, and the transfer of that technology to displace or enhance tried-and-true methodologies, is the easiest for our industry to wrap itself around. The risk and reward of new technology is well understood. It has been the hallmark of how and why we are in business and prosper. However, for those in the auto industry, which has over 100 years of understanding of mechanical and internal combustion equipment, the dawning of hybrid and electronic technologies to propel a vehicle, let alone control and monitor performance – with or without a driver – brings nothing but risk. For our industry, supplying this transfer from mechanical to electronics creates a different type of risk. Now “consumer” products must be as rugged as the toughest military or aerospace application, or even more so, because the sheer number of lives at risk are greater and the operating environment less controlled.