Seems sometimes as we knew better 1935 than today. Remember old Philips TV 'backplane' K12 (think it was)from the 70's, with line transformer mounted the new way in thru holes? Earlier, the hot transformer was fastened with screwdown on chassis, and leads were soldered from board to transfomer pins. 'Modernised' K12 mechanical support was omitted, the transformer pins were directly soldered on the board, and most of the weight was on the solder joints. Yes, you guess right what happened after one year, or two, or three years. The hot transformer pins, the mechanical load and the switch on/off several times a day year round caused such fatigue and creep that there was no solder left in the hole, and the screen went black. Many they were at that time, who went nuts in the middle of a game, rushed off the chair and hammered the poor box with heavy fists. With some luck, there could be a temporary connection and an image for some more hours before it blackened again. Myself, an!
d hundreds more techies, removed the cover, heated the solder joints, sucked the old 60SnPb solder with copper braid, resoldered with high Lead solder, and went back to the sofa with a satisfied grin..... Back to 1935. Opened my granpa's old Philips with its enormous glass valves. This was a hot environment for solder joints! The valve sockets became aged and looked tired after many years. My granpa's radio ran every day for 40 years (he loved the old box). When I opened it many years after his death, I found, under much of dust and debris, quite untouched solder joints, looked like new ones! They knew about soldering, the old Philips guys, because each lead was wrapped one or two turns around the valve socket pins before it was soldered. Result: no mechanical load.
This may look like a bottle message in this HiTech world, but old experience is not necessarily out...
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Werner Engelmaier
Sent: den 28 oktober 2004 14:59
To: [log in to unmask]
Subject: Re: [TN] Solder Strength over temperature
Hi Rich,
The tensile strengths of 63/37, 90/10 and 95/5 solder alloys are highly
temperature and strain-rate dependent. I have a graph of tensile strengths of
near-eutectic Sn/Pb, but not the others. Bet generally, 90/10 and 95/5 solders will
be stronger than near-eutectic alloys.
Wht do you need this info--the strength of properly attached solder joints is
more than adequate for any strss-producing loading condition--other things
will fail first. This may change with LF-solders.
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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