PCB007 Magazine

PCB007-July2018

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8 PCB007 MAGAZINE I JULY 2018 Do you spend time, as I do, musing on the language of PCBs? We have developed our own lexicon to convey as much by picture, as by word, what exactly we mean. I'm talk- ing about words like micro-etch (hyphenated or not) and stripper (a whole new meaning), metalization and metalize (one "l" or two?); terms like mouse bites, measles, voids, vias, pits, etc. And that's not mentioning the myriad acro- nyms, from PCB right through to ENIPIG (we don't stop at just three letters, oh no). Which brings me to solder mask (one word or two?). We have chosen to make it two words in this issue, and plan to keep it that way, re- gardless what some of our contributors say. But, why do we say "mask" at all? What exactly does that mean? I know some say sol- der resist, which is more ap- propos, as this material does indeed more or less repel or re- sist the solder. The mask part per- tains to the underlying circuitry that is masked or protected from the sol- der. But, as one of our experts this month has pointed out, sometimes there will be no solder, in which case the solder mask is protecting against nickel-gold or immersion tin or one of the other final finishes. We can go on and on… But with all the things that can now af- fect the solder mask—finer fea- tures, higher-temper- ature solders, final finish- es, direct im- aging, ink- jet—we felt it was high time to give it a lit- tle more atten- tion. As one of the last processes a PCB sees, you want it to do its job well and precisely; now is not the time to be scrapping your expensive multilay- er—or any board for that matter. With that, let's get to our lineup this month and start learning. We first wanted to learn what was new in the solder mask area, so we met with Elec- tra Polymers' Shaun Tibbals and Antony Earl. We discussed the dif- ficulties of clearing small holes of solder mask and the problems with plugging holes—opposite require- ments that are often specified. The conversation ranged further into direct imaging of fine features and the project- ed use of inkjet for solder mask—there are advantages and disadvantages. One area of concern with solder mask that is covered (ooh, a pun) by Atotech's Rick Nichols Patty's Perspective by Patty Goldman, I-CONNECT007 More Than a Word: Solder Mask

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