Gold plated contacts soldered to printed circuit boards
Gold plated contacts soldered to printed circuit boards
(OP)
Good Morning:
I am inquiring about any metallurgical or otherwise reactions that may take place as a result of using tin-lead solder to fix gold plated contact leads to printed circuit boards?
I am inquiring about any metallurgical or otherwise reactions that may take place as a result of using tin-lead solder to fix gold plated contact leads to printed circuit boards?





RE: Gold plated contacts soldered to printed circuit boards
One problem is intermetallic compound (IMC) formation between tin of the solder and nickel. When electroless nickel (Ni + 1-12% P alloy) (EN is used commonly as a barrier layer beneath the gold), is soldered nickel diffuses into the solder, forming an NiSn IMC, and leaving a P-enriched, weakened interface. A good reference (has photos) for this reaction (although gold was not used in this example) is http://www.alphametals.com/products/solder_solutions/pd...
Another problem is whisker growth. A photo of eutectic composition Pb-Sn whiskers grown from a semiconductor-heat sink soldered connection.
http://nepp.nasa.gov/whisker/photos/pom/2003dec.htm
The solder manufacturers Alpha Metals and Kester have technical info on their websites:
http://www.alphametals.com/products/solder_solutions/te...
http://kester.com/en-us/technical/knowledgebase.aspx
AMP (Tyco Electronics) also has technical information on electronics connections:
http://www.amp.com/products/technology/tech_articles.st...
There are many other metallurgical issues, such as thermal fatigue, void formation from the Kirkendall effect, and whisker growth, although most work is on lead-free solders. E.g., see the June 2003 issue of JOM, etc. http://doc.tms.org/servlet/ProductCatalog?container=JOM...
http://nepp.nasa.gov/whisker
http://www.calce.umd.edu/lead-free/tin-whiskers/TINWHIS...
RE: Gold plated contacts soldered to printed circuit boards
Regards,
Jim