New-Tech Europe Magazine | Q1 2023

Credit: Samtec

stencil. A customer might have to do this because they have other devices that require a .004” thick stencil, or because they don’t have the time or budget to handle the expense of using a stepped stencil. In this study, we designed the stencil apertures to be bigger than the pads on the PCB (i.e., overprinting). The solder that’s printed beyond the pad in all four directions will coalesce and flow back onto the pad and lead during the reflow process. We didn’t experience solderballing or other problems. Part Two This is the second in a series of three blog interviews with David Decker, the Manager of Samtec’s Interconnect Processing Group

of .006” (0.15 mm) is common for bigger connectors (for example, on .100″ pitch, with 15 or more pins). It makes sense to think that the stencil has to be as thick as the coplanarity spec. At the same time, other devices on the same board may require a thinner stencil, for example, .004” (0.10 mm). It’s possible that using a thicker stencil could lead to other problems, like solder joints bridging. At Samtec, IPG works with the connector designers in the new product development process. When we begin testing the soldering process, we use a .004”, .005” and .006” thick stencil, and we use varying aperture designs, to optimize the stencil design. So our stencil recommendation has been fully vetted, and we know what works and what doesn’t work, for the most part. Unless it fails in our testing, a .004” stencil can be used. And likewise, rarely does a .006” stencil not work. We have stencil thickness recommendations on the product pages of our website (here’s an example). All of the details of these recommendations have been tested and can be trusted. We recently completed a solder joint study with Phoenix Contact about using solder stencils on connectors that are thinner than the connector’s coplanarity spec. This study shows you can successfully solder connectors with a .006” (.15 mm) coplanarity spec using a .004” (.10 mm) thick

(IPG). In these blogs, David answers some of the most frequently asked questions about achieving quality connector solder joints, as well as other connector-processing related issues. BTW, here’s the link to the first blog. Our goal is to provide short answers that address the main issue of the question. If you want more information about a particular subject please contact IPG. BTW part deux, here’s a link to the first blog. What are common problems with two reflow oven passes and inverted components? This is a common question because this is a common processing method. Our connectors are typically some of the smaller components on a PCB and

image: Connector with an offset center of gravity Credit: Samtec

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