I don't understand the question as posed either, call me if you like Graham,
but possibly this is due to oxide on the surfaces and not enough flux
activity. An example: sometimes solder paste appears not to have melted
during reflow, even though the peak profile is well over the alloy MP. What
is actually happening is that the solder particles do melt but they don't
coalesce because they are oxidised. To explain a different way: effectively
what you have is a lot of ceramic coated solder balls, [ceramics are metal
oxides]. Why they are oxidised depends on a number of factors usually
associated with the flux in the paste being cooked off in the ramp to reflow
stage, or otherwise being (made) inadequate for the situation.
Regards
Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guenter Grossmann
Sent: Wednesday, August 15, 2007 3:18 PM
To: [log in to unmask]
Subject: [TN] Antw: Re: [TN] Lead-Free Problems? and Tin Lead too!
Graham
I don't know if I understood your question righ, but they must melt
together, otherwise you would have to heat the solder joint to 327°C to melt
the lead. Are there tin- lead phases and lead tin phases with gaps in
between or is the surface of the joint uneven?
Best regards
Guenter
_____________________________________________________
EMPA
Swiss Federal Laboratories for Materials Testing and Research
Centre for Reliability
Guenter Grossmann, Senior Engineer
8600 Duebendorf
Switzerland
Phone: xx41 44 823 4279
Fax : xx41 1 823 4054
mail: [log in to unmask]
_____________________________________________________
>>> Graham Naisbitt <[log in to unmask]> 08/15/07 12:24 pm >>>
Techies
Apropos the earlier exchange, take a look at this link: http://
news.bbc.co.uk/1/hi/technology/6946042.stm
Maybe all will be well with the XBox in 2011?
How about this curious problem: I have a client suffering from an
apparent refusal of the tin and lead to meld together in his process
but on on 1 to 10 individual joints per assembly. It looks like a
cold joint (stay off this Dewey!) yet the joint is hard but separated
metals - anyone got any clues? Pretty much every conceivable test has
been run without a solution.
What could prevent tin and lead melding - Mr Hillman or Mr Pauls?
Kindest regards
Graham Naisbitt
[log in to unmask]
www.gen3systems.com
Phone: +44 (0)12 5252 1500
Mobile: +44 (0) 79 6858 2121
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