“Bargain” materials can result in subpar outputs.

We’ve covered understencil cleaning topics in this column many times. Admittedly, if the stencil printing process were perfect, understencil cleaning wouldn’t be required. But it is not an ideal world; we have board stretch, interspace challenges, and the compromise of printing speeds versus pressures to achieve balanced aperture filling.

Here is the basis for some of these challenges: If all the apertures were identical, the filling process (print speed/print pressure) could be optimized around one architecture. But, with the reality of different aperture shapes and sizes, the filling process must have a middle ground. The larger apertures fill more efficiently; thus, the filling process can deliver slightly too much fill on certain apertures, causing excessive material which may lead to solder paste bridging.

Conversely, the smaller apertures have a lower filling efficiency and, under the same speed and pressure setting, can be starved of solder paste, causing an insufficient fill. Insufficient deposited material can also result from an aperture with a low/tight associated area ratio. A low area ratio aperture has a lower transfer efficiency, which means that some of the material may remain in the aperture after filling. Eventually, this unreleased material can block the aperture, requiring understencil cleaning.

And will capital equipment makers stay put, relocate or – shudder! – exit the business?

In many ways, the past three years have seemed very much like a dream, with life shifting from normal to masked panic and social distancing, to light at the end of the tunnel, to where we mostly appear to be now: back to normal! But while most faces are uncovered, businesses have taken down Plexiglas separating cashier from customer, and retail floors have only a few faded "stand here" decals visible on the floors, not all is truly back to normal.

Geopolitical strains have developed in Asia and an unprovoked war is taking place in Europe. Both series of events – combined with the pandemic – put unprecedented strains on a global supply chain that for decades relied upon political stability and free access to countries around the globe. While the pandemic focused most of us on the here and now, it also caused companies – and countries – to pivot on where and how they source product.

Can your preferred choice be dropped in?

Let’s set the scene. You have been using the same vapor degreasing fluid to successfully clean complex circuitry and printed circuit boards (PCBs) for years, only to learn that your trusted line of cleaning fluids will soon be discontinued. What do you do? How do you choose a replacement that meets the PCB cleaning challenges that you and many other fabricators face?

Bluster, manipulation and gaslighting – all in a week’s work.

“... 90 percent of the startups founded by dweeby young men in San Francisco are simply trying to answer the question: ‘What things isn’t my mom doing for me any more?’ Creating a frictionless future seems to mean launching speedy meal delivery, dog walking, and laundry apps. ‘There is a tendency in Silicon Valley to want to be revolutionary without, you know, revolutionizing everything ...’ Too many moonshots are still sputtering on the launch pad. It is not yet clear that innovations such as social media, cryptocurrencies, or the metaverse yet represent any net positive for humanity. As skeptical economists never tire of pointing out, the digital revolution has so far had little quantifiable effect in lifting productivity.”

– John Thornhill, Financial Times

“Money talks, but it doesn’t tell the truth.”

“Time heals all wounds, right up to the moment that it kills you.”

– Herbie Cohen

And still they come.