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July 23, 2006

Epoxy replacement for solder??

I cannot believe by this time someone hasn't come up with an epoxy based (or something similar) solder that you just glue the parts to the board. Think of the benefits. No reflow ovens or wave solder systems. What is the hold up in this area?



Scott Myers

Experts Comments

Regarding the use of adhesives to replace solder, this concept has been discussed and tested for years. The most recent work I have seen on it is from the 2006 Pan Pacific Microelectronics Symposium in Hawaii, where Fritz Byle and Jin Liu, of Kester, made a nifty presentation on the use of epoxies for soldering. The problem historically has been that the less metal in the epoxy the weaker the electrical flow; fixing that problem with more metal then reduced the structural strength of the glue. They were able to surmount these problems by embedding carbon fibers into the epoxy. For more info see:  Electrically Conductive Adhesive.

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Mike Jones
Vice President
Micro Care
Mr. Jones is an electronics cleaning and stencil printing specialist. Averaging over one hundred days a year on the road, Mike visits SMT production sites and circuit board repair facilities in every corner of the globe, helping engineers and technicians work through the complex trade-offs today's demanding electronics require.

Conductive epoxies where going to revolutionize the electronic assembly industries in the late 70's when they were first introduced to the industry. Unfortunately nothing conducts like metal. Epoxies have issues with X, Y,Z conductivity. They may conduct one way better than another. Additionally epoxies are not totally hermetic. Moisture can penetrate them causing corrosion on the base contact, leading to resistance failure and eventual failure. This can be corrected by using board and component finish design. In spite of these issues epoxies have found a section of the market to be used in but for standard electronics they have not been able to compete with the reliability and conductivity of solder.

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Karl Seelig

Deck Street Consultants
In his 32 years of industry experience, Mr. Seelig has authored over 30 published articles on topics including lead-free assembly, no-clean technology, and process optimization. Karl holds numerous patents, including four for lead-free solder alloys, and was a key developer of no-clean technology.

Epoxies are being used as a solder replacement and for some time now. Some products just cannot take the heat of soldering example LED's.

Epoxy conductive chemistry however has some issues with long term reliability and for now an intermetallic bond is the most reliable.

Epoxy use raises many issues with component and board cleanliness, the surfaces must be very clean but also free of out-gassed chemicals so solder and flux seem to do better here.

Also these conductive epoxies cost much more than solder. Also they are next to impossible to rework.

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Peter Biocca
Senior Market Development Engineer
Kester
Mr. Biocca was a chemist with many years experience in soldering technologies. He presented around the world in matters relating to process optimization and assembly. He was the author of many technical papers delivered globally. Mr. Biocca was a respected mentor in the electronics industry. He passed away in November, 2014.
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