Patty’s Perspective: Staying Current on Wet Processes

Estimated reading time: 4 minutes

I live in Pennsylvania, in a town of 4,000 people, and I can walk to the library, grocery, post office, and a couple of restaurants and always meet someone I know. Running into people I know at the farmer’s market and drugstore was something of a shock to me when I first moved here but I enjoy it quite a bit. 

I’m writing this a few days after our Memorial Day parade, which consisted of two bands, the local veterans organizations (French & Indian and Civil Wars are especially studied around here), several parade floats, a number of county and town officials in cars (including Miss Pennsylvania), and best of all, numerous fire trucks and emergency vehicles. I can count 11 or 12 volunteer fire companies within a 5–7-mile radius of this little town—and that’s nowhere near the whole county. I’m a big fan of volunteering, so I find this kind of thing heartening, as I do with the fact that our recent Day of Giving raised almost $340,000 for local charitable organizations. If you don’t have this where you live…move! And let me move on now to our topic for this month.

My undergraduate degree is in chemistry (a zillion years ago) so the PCB wet processing area was a natural for me. Ah, the smell of ammonia and formaldehyde and acids! The beauty of an automatic plating line and the preciseness of a well-synchronized conveyorized DES line! The sense of triumph when we actually processed thousands of innerlayers with 5 mil line and space—in the early ‘80s—successfully and with high yields (yeah, manual inspection). Of course, I haven’t worked in a PCB facility for quite a while now, having branched off into marketing, sales and R&D as well as other parts of the process. And now, “I are an editor!” (How did that happen?)

But, back to wet processing. More than one of our writers has said the PCB manufacturing has not changed much—and in a sense that’s true. There are still the myriad steps: image, etch, strip, laminate, drill, PTH, image, electroplate, strip and etch—or some variation of these. What has changed significantly is the required precision of those steps to achieve ever finer features at ever higher quality and reliability on ever more persnickety materials for ever more demanding customers in ever shorter time spans at ever lower costs and prices. How the heck do PCB companies accomplish this?

Not alone, of course. The suppliers of both chemistry and equipment have been hard at work to help their PCB customers keep ahead of the curve. Much improved chemistry with better process windows, more reliable control, and lower toxicity have been at the forefront. And much research and improvement have gone into equipment in the form of both automation and—shall we say—efforts at process consistency (think spray and pump technology). So, let’s look at what these people have to say and hopefully you will pick up some pointers and tidbits and learn about some new processes at the same time.

To put everything in perspective, we turned to specialty chemical company MacDermid Enthone (yours truly worked for two of the original companies). Don Cullen, Jordan Kologe and Ted Antonellis filled us in on not just what’s new in chemistry but also in analysis and automation.

Lately, one of the areas of concern for both PCB manufacturers and their customers is the final finish on the PCB—and the greatest of these seems to be in the ENIG, ENEPIG, etc., types. Atotech’s Rick Nichols next presents an article on autocatalytic gold—as opposed to immersion gold—as a final finish being championed by the automotive industry for its high reliability.

Coming at it from the equipment side of things is Viking’s Marc Ladle with an interesting article on how changes in equipment design can have a profound effect on the chemistry. I think suppliers on both sides will tell you how important it is that they work together. Our next article comes from Uyemura, in Japan. Tetsuya Sasamura and colleagues address a different final finish, this one without nickel—a gold/palladium/gold process. According to the article, it is very good for extremely fine features. Another recent area of concern is via filling and we have an article by Saminda (Sam) Dharmarathna, et al., of MacDermid Enthone, on an electroplated via fill process which looks most interesting. This process can electroplate copper in a via while keeping the surface copper thin—quite a trick!

This month, Mike Carano’s “Trouble in Your Tank” column on troubleshooting PTH failure mechanisms fit well with our wet processing topic. We hope you benefit from his practical knowledge and are storing his columns for future reference! Our final column this month comes from Elmatica’s Didrick Beck. The subject is Lean manufacturing and the differences between standard and non-standard product lines. Good information to know. OK, so some of these articles have a lot of charts and graphs, and data that may seem daunting, but the information is worth reading so don’t skip over them.

Finally, getting back to volunteering, I’m looking forward in the months ahead to doing more local volunteering at our library, the historical museum, the animal shelter, and of course gardening. We are already moving one of our editors into the role of shepherding our columnists (interested in writing for us?) and I’m backing off on more editorial duties to free up some time. Not gone, just moving aside a bit to get into some other interests, so keep on reading and I will see you next month when we fill you in on the latest in solder mask technology. You are subscribed right? (Gotta ask!)  

Patricia Goldman is managing editor of PCB007 Magazine. To contact Goldman, click here.

This article originally appeared in the June 2018 issue of PCB007 Magazine, click here.