How many greenfield fabrication plants do you think have been built in the US in the past 10 years?

I can think of three, and two of them were designed and built by the same person and corporate parent. There’s Whelen Engineering, the OEM that opened a captive shop in 2015. The brains behind that, Alex Stępiński, then designed and built GreenSource Fabrication, which launched in 2018. And perhaps we can count TTM’s new plant in Chippewa Falls, built in a converted 20-year-old, 40,000-sq. ft. warehouse and officially opened last winter.
Now we can add one more to the list. More surprising, an EMS company built it.

Last month Benchmark Electronics opened the doors to its 122,000 sq. ft. state-of-the-art factory in Phoenix. The company, the fifth largest EMS in the US and 18th in the world according to the CIRCUITS ASSEMBLY Top 50, is known for putting components on boards, not making the substrates themselves. The new venture is a leap of faith, buoyed by the desire to control the product development from end to end.

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Down the radiation rabbit hole!

Increased use of x-ray inspection throughout the component and PCBA supply chain to check the quality of optically hidden joints and features can elevate a component’s level of radiation dose during assembly. A simple and sensible question, therefore, is can this cause any issues? For example, could this increase the risk of component failure, either a complete, temporary or intermittent failure, that happens during manufacture or potentially at some later time in the field? A sensible and simple question perhaps, but, unfortunately in my experience, one that generates many further questions and uncertain answers.

In general, the industry consensus, together with the reality that x-ray inspection has been widely used for years, is that for most components there is probably not an issue with the radiation doses likely during x-ray inspection. But here we enter our rabbit hole of additional questions: What constitutes the “not most” components?

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Are your components in balance?

Warping of flat or planar printed circuit boards is a significant yet common problem when manufacturing and assembling PCBs.

Warpage can prevent pick-and-place machines from accurately placing components. Warpage can cause the lead-free wave solder machine to pick up solder and flood the board with solder. Even worse, a warped printed circuit may not fit in the case or cause problems with automated handling equipment (buffers, etc.).

A few items cause warpage, all known and preventable. The primary reason why a PCB will warp is uneven or imbalanced copper percentages in different layers. When a design is presented to a PCB manufacturer, the fabricator will run a check of the percentage of copper on each layer. This is to ensure the design is balanced; i.e., the copper plane percentages are even about the center. Consider, for instance, a typical 8-layer PCB. A copper power plane would be on layers 4 and 5 and signal layers on the remaining layers. The innerlayer 4-5 has an almost full copper percentage on both sides. The remaining layers are low-copper-percentage signal layers. The stresses locked in by lamination will even out or equilibrate.

Is poor stencil design the culprit?

This month we illustrate solder balling and incomplete reflow when reflowing through-hole components with pin-in-paste.

Solder balling pin-in-hole reflow (PIHR) close to the body of the connector suggests poor design of the stencil for this application (FIGURE 1). There is no standoff on the corner of this part, which may have permitted the paste to be displaced when the component was attached. There should always be free space around the paste deposit to permit placement and reflow, without contacting the paste.