Root Cause of Failures in PWB Lamination


Reading time ( words)

Introduction

Understanding the interactions of the materials, oxide treatment, and the lamination process will help you get to the root cause failures in multilayer fabrication.

When troubleshooting multilayer defects, it is necessary to again understand the effect certain process parameters have on quality and reliability. Truly, the quality of a multilayer printed circuit board (prior to desmear/metallization) will depend on several factors that will now be presented.  

Interlaminar Bond Strength

There are several quality aspects of a multilayer PCB that should be measured on a regular basis. One key determinant of the reliability of the multilayer package is the interlaminar bond strength. The interlaminar bond strength is the strength of the heat-resistant bond between the pre-preg and the copper foil. Ideally, one strives for optimum resin flow encapsulation of the pre-preg with the treated copper innerlayer. The stronger the bond between the pre-preg and treated copper, the lower the chance of delamination. Figure 1 shows an example of delamination. In general, heat excursions increased the stress within the bond and that will lead to failures. So the bond between the copper and the resin needs to be as robust as possible.

The simple definition of delamination is, “a separation between plies within a base material, between a base material and a conductive foil, or any other planar separation within a printed board.” Again, we are referring to a separation. (More on blister and laminate voids in another column.)  It is a huge concern that separation of the pre-preg from the copper foil is often misinterpreted for a blister. Indeed it is more serious than that. As an example, higher temperature resin systems may require more adjustments to the printed circuit processes such as: lamination cycle, baking, hole cleaning, drilling and routing. Polyimide resin and cyanate ester are the most commonly used high-temperature resin systems. These resins have Tgs in the 250°C range.

Read the full column here.


Editor's Note: This column originally appeared in the September 2014 issue of The PCB Magazine.

Share




Suggested Items

Preventing De-wetting Defects In Immersion Tin Soldering

01/04/2023 | Britta Schafsteller, Atotech
Immersion tin is well accepted as a high-reliability final finish in the industry. Due to its excellent corrosion resistance, it exhibits major market shares, particularly in the automotive industry. During the soldering process, an intermetallic compound (IMC) is formed between copper and tin. One remaining concern in the industry is the potential impact of the IMC on the solderability of the final finish. In this article, typical failure modes in soldering immersion tin are described and correlated to potential root causes for the defects.

Candor: UHDI Under Development

12/21/2022 | Nolan Johnson, I-Connect007
Candor Industries is a PCB fabricator investing in UHDI fabrication capabilities in Canada. To support advanced packaging, as well as the current pace of IC process shrinks, PCB fabrication capabilities must shrink to keep up. Sunny Patel, Candor’s technical sales manager, brings us up to speed on what Candor has learned in their journey to add UHDI. What we gain from this interview is that, while certainly not insignificant, the stretch to add UHDI may be not as far as one might think.

MKS Discusses the Cutting Edge of Technology

12/20/2022 | Nolan Johnson, I-Connect007
During a recent tour of the MKS facility in Beaverton, Oregon, I met with Todd Templeton, Chris Ryder, Kyle Baker, and Martin Orrick. As a reminder, MKS acquired ESI in 2019 and has retained the ESI brand. In this interview, they explain their approach to HDI and ultra HDI, the current state of base materials, and what the future looks like on the cutting edge of technology.



Copyright © 2023 I-Connect007 | IPC Publishing Group Inc. All rights reserved.