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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The controversial technology could help cut the carbon footprint of daily living.

We know the pandemic has forced many to work from home (WFH) and as a result driven up demand for products like PCs and home IT equipment. There has also been a large reduction in commuting to and from workplaces, which many have enjoyed and vowed to continue even after lockdowns are lifted.

These changes ought to benefit the planet by reducing greenhouse gas emissions and other pollution. We should consider the impact of the extra demands placed on data infrastructures to handle this upsurge in remote working, however. It takes energy to move all that data back and forth, although arguably this would happen whether workers are at the office or at home.

Data center businesses have blossomed during the pandemic, with an uptick in demand for their services. These include work-related services as well as home entertainment. Netflix has reported record consumption, although the rise has flattened recently, perhaps as content has become exhausted.

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