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

Print


Suggested Items

iNEMI’s PCB Roadmap Explained

05/01/2020 | Pete Starkey, I-Connect007
In an informative and enlightening webinar, iNEMI Project Manager Steve Payne was joined by Isola Group CTO Ed Kelley to explain, review, and discuss the details of the recently published “iNEMI 2019 Roadmap for Organic PCBs.” Pete Starkey provides an overview.

Improving Copper Distribution in Pattern Plating Using Simulation Software

04/28/2020 | Pete Starkey, I-Connect007
Technical Editor Pete Starkey had the opportunity to sit in on a webinar presented by Robrecht Belis, manager of the surface finishing business unit at Elsyca—a Belgian company specialising in the simulation of electrochemical processes.

IPC Europe Shares Technical Education and Standards Awareness

04/22/2020 | Pete Starkey, I-Connect007
Against a background of COVID-19 uncertainty and unprecedented challenges, but recognizing the vital importance of continuing to educate engineers and share the knowledge and skills required to manufacture boards and assemblies of the highest yields and reliability, the IPC Europe team hosted a technical webinar for the European electronics industry, featuring the expertise of two of I-Connect007’s regular columnists: Mike Carano and Jan Pedersen. Pete Starkey provides an overview.



Copyright © 2020 I-Connect007. All rights reserved.