Hello Steve and Ingemar, I have some important news about the problem! This corrosion happens too when the lead frames are only Ag without Pt, so we can discard the Pt. But most significantly is the fact that this phenomenon comes to view before the duration tests. After the hybrids are produced (the bonding is still not made), they are stored in trays. These trays are put one on the another forming little columns. When the storage time is long (sorry, I can not cuantifize how many days), the spots appears but only in the hybrids placed in the borders of the trays. We have soldered the bonding wire on these hybrids and they works perfectly, so the problem is only of external appereance. I think that the cause is the typical slow reaction of silver with sulphur that leads to Ag2S. This reason is the same that makes "dirty" the silver crockery, but the spots are red not black. I include a photo of the device to make my explanations easier to understand. Thank you all for your help! Best regards Jose -----Mensaje original----- De: TechNet [mailto:[log in to unmask]]En nombre de Creswick, Steven Enviado el: jueves, 26 de agosto de 2004 12:00 Para: [log in to unmask] Asunto: Re: [TN] Corrosion in lead frames Jose, To the best of my knowledge, Pt will not oxidize with a red color. I don't recall ever seeing such a condition develop. Approximately how large are the red spots? Do they run up and down the edges of the conductor, or are they all across the surface of the conductor? Are they on the ceramic as well? Are they just in areas where flux has been? How hot, and how long does it take for the spots to develop? More questions than answers ... Steve -----Original Message----- From: Jose Antonio Garcia Ontalba [mailto:[log in to unmask]] Sent: Wednesday, August 25, 2004 1:21 PM To: [log in to unmask] Subject: Re: [TN] Corrosion in lead frames Steve, You are right, I am speaking of an alumina substrate with a Ag/Pt metallization, but I have just realized that I was wrong in my first message: the lead frame is really Ag/Pt and the coating is pure Ag. There is not more metalls involved. I think the red spots are oxides of Ag or Pt or maybe both. But the oxides of silver are not red coloured, aren't they? So, the red spots have to be oxides of Pt... Maybe the tempeature helps the reaction of oxidation of Pt. Anyway I am not sure. What do you think? Thank you very much! Regards Jose -----Mensaje original----- De: TechNet [mailto:[log in to unmask]]En nombre de Creswick, Steven Enviado el: miércoles, 25 de agosto de 2004 18:02 Para: [log in to unmask] Asunto: Re: [TN] Corrosion in lead frames 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. 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