Werner, in NEMI, we conducted a large test matrix according to JEDEC JESD22-A104B (July 2000) "Temperature Cycling", with additional requirements
-40 (+0,-5) to 125 (+5,-0) °C (Condition G of Table 1)
0 (+0,-5) to 100 (+5,-0)°C (Condition J of Table 1)
using the guidelines from IPC-SM-785 and concluded Sn3.9Ag0.6Cu joints are better than or equal to PbSn.
Perhaps you could provide references to the tests you cite where inferior fatigue life was found, because our data would not support that at all.
Ronald W. Gedney
Vice President Operations
Phone: 703-834-2084, fax 703-834-2735
-----Original Message-----
From: Werner Engelmaier [mailto:[log in to unmask]]
Sent: Thursday, November 21, 2002 9:28 PM
To: [log in to unmask]
Subject: Re: [LF] Cross-contamination
Hi Keith,
Without getting the test details, concluding that "Lead-free joints are
usually stronger and survive thermal fatigue better than tin-lead joints" is
dangerous. Unless the testing follows the guidelines of IPC-SM-785 or
IPC-9701, serious fallacious conclusions can result.
Most of the fatigue results reported are from tests designed to totally
ignore the creep-characteristics of solder [no dwell times at T-extremes] and
also use an extreme cycle condition [-55/-40<=>+125C] that assures
confounding damage mechanisms. Thus, no valid conclusions regarding product
reliability are possible. To date, virtually all properly run accelerated
T-cycling tests have shown inferior creep-fatigue reliability for almost all
LF-solders.
Werner Engelmaier
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