Indium Corporation - Through-Hole Assembly Options for Mixed Technology Boards

Our thanks to Indium Corporation for allowing us to reprint the following article.
By Ross B. Berntson, Ronald Lasky, Ph.D., PE, Karl P. Pfluke, Indium Corporation of America

ABSTRACT


Surface mount assembly has dominated its through-hole predecessor since the early 1990s. The higher density and lower ultimate cost of SMT makes it a preferred assembly technology. However, the mechanical strength of through-hole connections continues to make throughhole the technology of choice in assembling connectors.


This presentation will describe the primary methods currently used for through-hole connector assembly: 1) selective wave solder, 2) pin-in-paste (PIP)i reflow, 3) hand soldering and 4) solder preforms. We will show how solder preforms are an excellent alternative when PIP provides insufficient solder.


The wave solder method requires specialized equipment and processes to solder connectors. Pin-inpaste reflow evolved as a way to accomplish through-hole assembly without additional equipment or process steps. In the PIP method, the additional solder required to fill the though-hole barrel is deposited by overprinting the pad in the area of each connector pin, using standard SMT equipment. During reflow, the solder wicks to each pin forming the solder fillet...


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