Failure Mode: Hole Wall Pullaway


Reading time ( words)

Hole wall pullaway (HWPA) is an insidious defect that is not usually a cause of electrical failure. What happens with HWPA is that the copper plating in a plated through-hole (PTH) is pulled away from the dielectric of the drilled hole wall. The hole must not be filled with any sort of a hole fill in order to see HWPA.

There are two distinct types of HWPA: stress-relieving and stress-inducing. In stress-relieving HWPA, the condition appears to distress the PTH, allowing it to survive hundreds or thousands of thermal cycles without failure. In stress-inducing HWPA, the stress appears to greatly increase, causing the PTH to fail in just a few thermal cycles. What we consider a failure is an increase greater than 10% in the overall resistance in the circuit. A crack that partially bridges the copper at the internal interface is enough to cause a failure.

This column is based on my experience in test reliability of interconnect stress test (IST) coupons. I am addressing HWPA that features moderate to severe outgassing. There may be HWPA due to thermal stressing of the board without any significant outgassing, but this type of HWPA is subtle, and it presents as a dark line between the plating and the dielectric of the hole wall. This type of HWPA is rarely detected.

Stress-Relieving HWPA

Stress-relieving is the most common type of HWPA. It appears that the adhesion of copper plating to the dielectric is reduced most likely due to problems with the application of electroless copper plating adhering to the dielectric of the hole wall. At the same time, the adhesion is strong at the copper’s internal interconnection. In fact, experience suggests that the adhesion of the electroless copper is stronger than the copper plating. This process frequently produces strong interconnections to copper inner layers. This condition may result in a hole wall that looks like a stack of forward or backward “Ds” running the length of the hole where the top and the bottom of the “Ds” is at an internal interconnect.

To read this entire article, which appeared in the August 2015 issue of The PCB Design Magazine, click here

Share


Suggested Items

Zuken Teams With Nano Dimension for 3D Printing Design Flow

11/22/2017 | Andy Shaughnessy, PCB Design007
At PCB West, Zuken shared a booth with Nano Dimension. Zuken has been working with Nano Dimension for some time, and adding support for 3D printing and nanotechnology to its design tool platforms. I sat down with Zuken’s Humair Mandavia and Nano Dimension’s Simon Fried to learn more about this alliance, and to find out more about this odd-looking box being demonstrated in Zuken’s booth.

AltiumLive Summit—Munich, Germany, Part 2

11/13/2017 | Pete Starkey, I-Connect007
Pete Starkey continues with his review of the AltiumLive PCB Design Summit held recently in Munich, Germany. The second day commenced with a new product launch. “Working together is hard” it read on the screen. Statistics indicated that 33% of new products were late getting to market, of which 28% were late due to insufficient collaboration, and up to 50% of potential revenue could be lost through being late to market. Then the screen read “NEXUS makes it easy!”

AltiumLive Summit—Munich, Germany, Part 1

11/07/2017 | Pete Starkey, I-Connect007
Altium held a very successful AltiumLive PCB Design Summit in San Diego, California at the beginning of October for the benefit of their North American design community, and followed it three weeks later with a counterpart European event in Munich. And what an eye-opener it proved to be—literally hundreds of delegates, a superbly organised and managed programme, billed as a completely immersive two-day interactive design experience on a theme of learning, connecting and getting inspired.



Copyright © 2017 I-Connect007. All rights reserved.