Reading time ( words)
Several defects that are related to the desmear process are presented in this month’s Trouble in Your Tank.
Inadequate or excessive desmear will lead to several PTH defects and failures. Resin smear, ineffective texturing of the resin, and even overly aggressive desmear will contribute to poor plating, adhesion failures and a myriad of other non-conforming defects. However, proper troubleshooting protocol dictates that the engineer also looks at drilling as the contributor to these and other defects. As an example, drilling can cause torn out glass bundles, extremely rough hole walls as well as excessive smear. Poor drill practice may also lead to wedging at the B-stage-to-copper foil interface. These are just a few of the defects that are presented in this column.
Root cause of these defects and the subsequent effect on PTH quality and reliability are also presented.
1. Excessive Etchback
Description: Excessive glass and excessive positive etchback.
Characteristics: Can lead to plating folds, barrel cracking, glass voids, and uneven copper plating in the holes.
a) Temperatures of the solvent and permanganate steps are too high.
b) Dwell times in the solvent and permanganate steps are too long.
c) Concentrations of the solvent and/or permanganate steps are too high.
d) Excessive in feed rates (too high of a chip load in drilling).
e) Drill is punching its way through the stack.
To read the full version of this column which appeared in the May 2017 issue of The PCB Magazine, click here.
Dan Beaulieu, D.B. Management Group
It’s always good to catch up with old friends, especially when you can start working together. This is the case with my friend John Johnson, who has joined American Standard Circuits. I caught up with John to see what he has planned for ASC, where he will, in part, be using the Averatek A-SAP process that he was previously involved with. John shares some of his background, and talks about the best ways to use this semi-additive process PCB fabrication process that opens the capability window for forming trace and space. This process enables ultra-fine lines.
I-Connect007 Editorial Team
Michael Carano is a noted subject matter expert with respect to process control, electroplating and metallization technology, surface finishing, and reliability. So, it was only natural that we sat down to talk about mechanizing an existing facility given today’s fickle environment. Will any of the CHIPS funding trickle down to bare board fabrication? What process can be adjusted on the factory floor? The focus needs to be more than just on manufacturing and getting work out the door, he says, but also process control.
Pete Starkey, I-Connect007
“Summer is over, now it's back to work!” This was the opening line of the invitation to the 18th EIPC Technical Snapshot webinar, Sept. 14, following the theme of advances in automotive electronics technology, introduced and moderated by EIPC President Alun Morgan. The first presentation, entitled "The fully printed smart component—combining additive manufacturing and sensor printing," came from Jonas Mertin, a thin-film processing specialist at the Fraunhofer Institute for Laser Technology.