Trouble in Your Tank: The Desmear Defect Guide


Reading time ( words)

Introduction

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.

Possible causes:

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.

Share




Suggested Items

PCB Technologies’ InPack to Focus on Miniaturization, Packaging

05/16/2022 | Andy Shaughnessy, Design007 Magazine
I recently spoke with PCB Technologies’ Jeff De Serrano, Yaniv Maydar, and Alon Menache about their new venture, InPack. They explain their plans to focus on advanced packaging, miniaturization, and other high-end technology, with much faster time to market, and they offer a view of the global market as well.

EIPC Technical Snapshot: Supporting Autonomous Driving

05/12/2022 | Pete Starkey, I-Connect007
EIPC’s 17th Technical Snapshot webinar on May 4 focused on developments in automotive electronics, particularly on advances in the technologies required to support the evolution of autonomous driving. The team brought together two expert speakers to present their detailed views on topics encompassed within “CASE,” the acronym that appears to be taking over the automotive industry.

Catching up with EISO Enterprises’ President Gary Chien

04/19/2022 | Dan Beaulieu, D.B. Management Group
While there are many Chinese companies now selling in the United States, I wanted to find one in Taiwan that is penetrating the U.S. market. I was delighted to come across EISO Enterprise Co. Ltd., a printed circuit board fabricator located in Taiwan. I know that the American companies are usually looking for PCB global partners in countries other than China, which made my conversation with Gary (Jung Kun) Chien all the more interesting, especially when he shared his thoughts on the U.S-China trade wars.



Copyright © 2022 I-Connect007. All rights reserved.