how many thermal cycle in total over the duration of 3500 hr? if it is
less than 2,000, it is not stringe at all for end of life test.. (hi-rel
product), consider the temp range is not that high (-30 to +80 = 120 C
overall... Assuming non condensing...).
jk
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Howard P. Stevens
Sent: Wednesday, January 22, 2003 7:36 PM
To: [log in to unmask]
Subject: [TN] Thermal Cycling tests for assembled and completed circuit
boards
A customer of Metallic Resources (manufacturers of bar solder) assembles
circuit boards. One of the many tests the boards go through is a
thermal cycling test to see if thermal shock can cause failure in the
circuit board.
The customer's test specification is Spec Number TSC7514g, section 5.4,
reference specification TSC 7010g. (We do not know what this means.)
The customer cycles the circuit board from -30 degrees celcius to +80
degrees celcius. The board temperature is dropped to -30 and held for
thirty minutes. The board temperature is then raised to +80 and held
for thirty minutes, until the temperature is lowered again and so forth
for a total of 3,500 hours. The customer is now noticing solder joint
failures on this double sided board on the top, which is both
through-hole and SMT (failures of solder paste joints on the top), and
on the bottom, which is just through-hole (failures of bar solder
joints). Solder joints, both top and bottom, show much cracking and
some flux residue.
The first question is: is this customer using their own test or is there
an IPC test for thermal cycling of a completely assembled circuit board?
The second question is: is the customer's temperature range too extreme,
which is causing severe thermal shock, which is then causing joint
failures due to different co-efficients of expansion and contraction
(board, solder, lead)?
The third question is: is the use of 3,500 hours of thermal cycling
realistic and/or too long?
Any comments would be appreciated.
Sincerely,
METALLIC RESOURCES
Howard P. Stevens
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text
in the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for
additional information, or contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
|
