The "very hard, but brittle" does not apply literally in general PbSn alloys
Clayton ; as you can imagine it's rather difficult to "temper" lead to
brittle stages .
However the strength from closer crystalline formations does benefit the
joint ; as it is still very much plastic strength , not static.
Actual annealed solder is so soft you could chew it (leadfree if possible) ,
often inadequate strength requiring hardening agents (Ag) .
In steel (as "metal" example) yo're quite correct, as our pricey Lingstrom
pliers chronically crack due to very hard but brittle temper .

With Au or Ag content it's becoming different picture again ; but that's
another story .
I'd say likes Guenter may elaborate , this is the basic gist of it .

Also on the appearance as with recent Eric's notes ; lower temps and quicker
cooling upon wave exit will steer you clear of "dull" joints .

paul


-----Original Message-----
From: Clayton Gardner [mailto:[log in to unmask]]
Sent: Wednesday, 2 February 2000 10:25
To: [log in to unmask]
Subject: [TN] Strength of Solder Joints



Technet,

I have recently read in an article that the most favourable type of solder
joint is formed from rapid cooling of the solder.

I am a bit confused with this as I have always been under the impression
that rapid cooling of metals results in tight compact grain structures (very
hard, but brittle). This is in contrast to slow cooling that forms long
grain structures resulting in a stronger and tougher material (which I would
have thought is what would be ideal for a solder joint - good shock
resistance).

Regards....


Clayton Gardner
Engineering Manager

A.E.M.S
11-13 Fiveways Boulevard
Keysborough VIC 3173
AUSTRALIA
Ph. 61 +3 9701 5499
Fx. 61 +3 9701 5422
Mb. 0416044552
Email:  [log in to unmask] <mailto:[log in to unmask]>
WEB:  www.aemspl.com.au <http://www.aemspl.com.au>

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################