Jose,
Could the red-orange color be from exposed, oxidized copper?
You did not say whether the lead frame was copper, phosphor bronze, or maybe a Kovar (Fe, Ni, Co) composition.
.... although, I am confused by a lead frame having Ag/Pt plating. Hmmm. Possibly, are you speaking of an alumina substrate having Ag/Pt metallization (traces) on it?
Steve Creswick - Gentex
-----Original Message-----
From: Jose Antonio Garcia Ontalba [mailto:[log in to unmask]]
Sent: Wednesday, August 25, 2004 10:59 AM
To: [log in to unmask]
Subject: [TN] Corrosion in lead frames
Hello together!
I have an hybrid circuit with lead frames for bonding encapsulated with gel.
These lead frames are used for bonding the wires of aluminium only with heat
(without using solders, flux, etc.). We have made some durations test, after
them appears some red-orange spots on the lead frames preferably in the
borders, and, in some cases, comes into view blue parts too. We have seen
with Infra-Red photographs that this part (wire+lead frame) is by far the
warmest of the PCB when it is working, because through it comes high
electric flow.
The lead frames have a coating of Ag/Pt and the gel's major components are:
silicone, Pt (polymerization's activator) and alumina (for the thermal
conductivity). The lead frames have not solder nor flux residues.
So, anybody could tell me what is happening in the lead frame? I suppose
that a chemical reaction involves the Ag and/or the Pt but I have no idea
which could be!
Thank you all for your help!
Best regards
--
José Antonio García Ontalba
Quality department
NAGARES, S.A.
Ctra. Madrid-Valencia, Km. 196
16200 Motilla del Palancar (Spain)
Tel: 00 34 969 18 00 21
Fax: 00 34 969 33 11 31
E-mail: [log in to unmask]
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