Years ago, ahead of a US election, I used this space to pen an open letter to the new president. I wrote that the race for office was heated and intense, but the winner should put aside any ill feelings and work toward the betterment of all Americans.

The column was timed to hit readers’ desks in November, just after the election results were announced. Magazine deadlines being what they were, of course, I wrote it in early October – more than four weeks prior to election day. In short, I submitted it to the printer having no clue who was actually going to win.

More than a few readers didn’t catch that little nuance, and they filled my inbox with screeds both positive and negative about the outcome, projecting their own biases on my musings and utterly missing the point I was trying to make about leadership.

Since then, I’ve stayed away – far away – from anything that even hints of politics, sensing it’s too charged a subject to use even as a metaphor for a larger point.

So, when an industry friend whom I respect more than he will ever know suggested I write an editorial about electronics companies requiring vaccination, and, in his words, “come out swinging in favor of it,” my first reaction was indifference.

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Is the board preheat process optimized?

This month we look at incomplete fill of plated through-holes. During any soldering operation a balance of flux and solder/paste chemistry and soldering temperatures creates good and reliable joints. In FIGURE 1 the solder has not filled the hole completely but still exceeds the requirements of IPC-A-610, class 2 of 50%; measured, it may be 75% filled.

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Reconfigurable with dedicated-like support.

As board complexity has increased with decreasing pitches, thicknesses and component sizes, ensuring support for thin, high-density substrates – essential to cost-effective, pinpoint accuracy stencil printing – continues to pose challenges. Using vacuum to secure miniaturized assemblies is, for the most part, a successful technique but requires the use of dedicated tooling plates, which can be costly. Considering the quantities of dedicated tooling blocks needed in a high-volume manufacturing environment, finding a suitable, lower-cost alternative has been a longstanding ambition. And, while commercialized automatic pin-based tooling systems are a good option for some applications, they are not as effective for high-density, thin boards.

How, then, do we bridge the gap and provide similar quality substrate support without requiring a dedicated tooling plate for each product and each SMT line? One solution lies in a high-flow vacuum system that supports the PCB – no matter how densely populated – through an almost counterintuitive use of airflow, low-pressure vacuum and reconfigurable metal plates (FIGURE 1). The plates – which are tooling height, approximately 2.0mm thick and constructed of different lengths – can be configured and overlapped to form a box, the top of which is constructed slightly smaller than the PCB perimeter so the edges of the substrate sit on the frame. The rising table contains a vent, and support pins are placed for stability. Once positioned, the tooling cube creates a semi-sealed environment where the vacuum pulls air through the table vent to create substrate stability during the print cycle. Unlike a conventional vacuum connected to a tooling plate, which uses a sealed technique to generate incredible pull (trust me, don’t get your finger anywhere near the vacuum pipe!), this new approach floods the area with tremendous amounts of air, allows for leakage (unlike dedicated plates) and securely holds the PCB with low vacuum. While there is upfront time to set the plates in the desired location, this system provides the support needed for thin, high-density, heavily routed PCBs without the expense of dedicated plates, and it can be reconfigured for an infinite number of board sizes.

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A little information goes a long way – but can carry added cost.

“My company has traditionally specified the finished thickness for each flex printed circuit (FPC) layer, and total thickness. This is because it’s understood some material layer thicknesses (i.e., adhesives) change during the manufacturing process due to compression and curing. As a purchaser of FPCs, we are less concerned with the initial raw material thickness than the finished thickness.

“We have received feedback, however, that the FPC market in general specifies the raw material thickness used in FPC fabrication, and not finished thickness. The assertion was nearly all customers purchasing FPCs follow this rule to minimize miscommunication. Is this common practice?”

Answer: The level of detail we see on customer drawings is all over the map, but the majority of customers that do specify individual materials will indicate the raw material thicknesses and then the overall finished circuit thickness.

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