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The Dow Chemical Company has developed a new epoxy‐based system to serve the growing need for high‐performance dielectric substrates, requiring high thermal reliability (high T_g, high thermal resistance) and high signal speed and integrity (low dielectric constant and low loss factor). The system is based on advanced, proprietary resin technologies. The process latitude of this system is very similar to traditional high T_g FR‐4 products. The optimized rheology of the system leads to consistent, controlled flow. The copper foil JTCHTEAB from Gould Electronics, where AB stands for advanced bond, is interesting in this context as it was developed for use on high‐performance laminates with a typically lower ability for copper bonding, such as high T_g and low D_k/D_f substrates. When the “LDk‐HTd” resin is used in combination with the JTCHTEAB copper foil, the copper peel strength fully meets the industry standard for high T_g FR‐4 laminates.

To give an overview of the problems that can occur with base laminate materials when converting to lead‐free soldering and to give guidance on possible solutions.

The paper contains a number of correlations between different physical measurements and their impact on real‐life processing conditions. The problem areas are highlighted and the corrective actions that need to be taken with base materials are described.

Results suggest that conventional FR4 resins might still be suitable for standard lead‐free applications that require only a few reflow cycles. However, with the growing complexity of board designs and the increasing number of solder cycles, better thermally resistant products are necessary. Other key resin parameters such as adhesion or toughness are also essential to enhance reliability.

The value of the paper lies in its provision of guidance on critical base material properties. It describes the change in physical properties that laminates will experience when moving to the higher temperatures needed for facilitate lead‐free assembly. Selection criteria for base materials are given that will help to minimise the impact of these higher temperatures.

This paper seeks to give an overview of problems arising with the change to lead‐free soldering and to give guidance on possible counter actions in the context of the chemical structure of the base material.

The paper contains a number of correlations between different physical measurements and their impacts on real life processing conditions. The problem areas are highlighted and the corrective actions that need to be taken on the base materials are described. The impact of the choice of flame retardant on material properties is demonstrated.

Results suggest that conventional resin systems seem to be still suitable for standard FR‐4 applications with only a few reflow cycles. Higher thermally resistant products are necessary for more complex structures that require multiple reflow cycles. There are basically two ways to increase the thermal resistance. Replace dicyandiamide by a phenolic hardener or change to a bromine‐free flame retardant. Both approaches are successful in raising the decomposition temperature, with the latter having the additional advantage of achieving better electrical performance and lower density.

The value of the paper lies in its ability to provide guidance on the critical base material properties. It describes the change in physical properties that laminates will see when moving up in temperature to facilitate lead‐free soldering. Selection criteria for base materials are given in order to neutralize the impact of the higher temperature.