Pascal
I believe I was a bit hard by saying that there might not be much of accelerated tests. It is possible to do so but I am convinced that highly accelerated thermal cycling does not give meaningful answers. The tests have to consider the deformation properties of the materials to be tested which means that the test cycles become longer. I contributed some words to an ASM book about testing of lead free assemblies to be published this year.
Power cycling is a possible way, but the possibilities of accelerating are limited as well
- Also in power cycling you have to care for the relaxation of the solder materials
- The temperature swing you can apply is limited if you dont want to carbonize your components in the test. Plus the generated heat is determined by the transformation of electrical energy into thermal energy and that's different from component to component.
Mechanical tests are very critical
- You dont have the influence of the temperature on the changes of the structure of the solder. Werner mentioned this point earlier in discussions.
- Also in bending tests you have to care for stress relaxation due to creep (slow cycles)
- In bending, the strain the solder joints see is not the same at each point of the PCB.
EMPA
Swiss Federal Laboratories for Materials Testing and Research
Centre for Reliability
Guenter Grossmann, Senior Engineer
8600 Duebendorf
Switzerland
Phone: xx41 1 823 4279
Fax : xx41 1 823 4054
mail: [log in to unmask]
>>> [log in to unmask] 12.01.2005 11:32:08 >>>
Werner, and maybe Jean-Paul, or Günther,
What would you recommend as "accelerated life test" if not a thermal cycling
? Power cycling ? Mechanical test ? Any combination ?
Merci beaucoup,
Pascal Guihéneuf
Nortel Wireless
UMTS NPI/LCM
GSM/UMTS Environmentally-Friendly Core Team Leader
ESN 574-5382 or 33.1.69.55.53.82 (phone)
ESN 754-2704 or 33.6.64.04.27.04 (mobile)
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]]
Sent: lundi 10 janvier 2005 23:39
To: [log in to unmask]
Subject: Re: [LF] Lead-Free Acceleration Factor
Hi Ofer,
I would not recommend thermal shock for anything other than perhaps product
screening.
Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting 7 Jasmine
Run Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
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