Dear Luc, dear all,

The 96 degrees C SnPbBi melting phase can be present in small quantities (i.e. lead-free solder plus SnPb finishes) and already cause rapid joint degradation in temperature cycling tests as soon as the top temperature of the test exceeds 96. Answer: 
temperature cycling up to 100 or 105 degrees C seems an adequate test.
By the way, this alloy has a solid state phase transition at 80 degrees C, probably comparable to tin pest. This might degrade the material even more rapidly.

Regards, 
Erik
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Erik E. de Kluizenaar
Philips CFT - Electronic Packaging & Joining (EP&J)
Building SAQ-p,  p/o box 218,  5600 MD Eindhoven - The Netherlands
Tel/Fax: (+31 40 27) 36679/36815
E:mail  [log in to unmask]
PHILIPS worldwide homepage:  http://www.philips.com
Internal PHILIPS only:   http://pww.cft.philips.com/cfteurope/processtech/elpajo/index.htm
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[log in to unmask]@[log in to unmask] on 99/12/11 02:14:23 AM
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Subject:        [LF] Assembly Ind - lead free electronics
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   Hello,

   I like to understand which test can demonstrate the risk of having
   a failure on board due to lead-bismuth-tin low melting phase.

   As the low melting phase is 98deg C , i wonder if failure can occur just
below : e.g. at 80 deg C or above.
   The joint solder average composition will be far from the ternary low melting
eutectic anyway.

  Today i think about a creep test with a component coated with Sn-5%Bi
soldered on board with SnPb paste and place on bottom side of a board
+ mechanical loading (hanging) , the whole being place in an oven at various
temperature.

 Please let me know if a better test exist.

  i like to thanks people contributing to this New Frontier project
(lead-free) challenging the electronic industry.

    Luc Petit ( [log in to unmask])

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