Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

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Homologous Point

Keith Luke

#6453

Homologous Point | 6 June, 2000

In the Chapter 3 on "Thermal & Mechanical Stress," Harry Charles mentions a "homologous point" in 3.5. We are unfamiliar with this term. What is this point? What are the implications of solders in operating environments below their homologous point?

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Charles Harper

#6454

Re: Homologous Point | 6 June, 2000

The homologous point is the temperature midway betweeen the melting temperature (of the solder) and absolute zero. Below this point the solders are harder, stronger, and more resistant to fatigue. As solders are exposed to higher temperatures above the homologous point they become softer and more subject to fatigue and solder joint failure.

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