yes -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Sent: Wednesday, June 25, 2008 2:28 PM To: [log in to unmask] Subject: Re: [TN] Power amplifier growth Do you want to see this phenomenon in an earlier state? I made some investigations on MESFETs with this issue. /Inge ----- Original Message ----- From: "Wenger, George M." <[log in to unmask]> To: <[log in to unmask]> Sent: Wednesday, June 25, 2008 5:10 AM Subject: Re: [TN] Power amplifier growth The transistor in your photograph is a Freescale 9 Shawn, The transistor in your photograph is a Freescale 900MHz 60W RF Power MOSFET. The epoxy seal around the ceramic lid of the transistor appears to be intact. Even if it wasn't there is nothing that is going to leak out of the transistor package to cause the kind of growth seen in your photograph. The growth appears to be limited to the drain (i.e., output) lead of the transistor. The bias of the drain lead is most likely 26 to 30VDC and there would also, as Ingemar pointed out lots of RF current in this area. Do you know what solder paste was used to solder the power transistor? With the DC bias, high RF current and high temperature one has the conditions to accelerate corrosion especially if there are flux residues or other contaminates present. I'm assuming that you removed the lid from the power amplifier when it stopped working to take the photograph and it wasn't just sitting on your desk exposed. If it was something corrosive might have dropped on the power transistor. Regards, George George M. Wenger Andrew Wireless Solutions Senior Principal FMA / Reliability Engineer 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 (office) (732) 309-8964 (cell) [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Elder Sent: Tuesday, June 24, 2008 3:55 PM To: [log in to unmask] Subject: Re: [TN] Power amplifier growth Thanks for the thoughts, Shawn. We are still investigating the source of the "growth". No, the transistor no longer works. Cheers, Dave Upton, Shawn wrote, On 25/06/2008 1:14 a.m.: > I wonder though if temp spiked suddenly, enough to cook the part but > not enough to heat up the PCB? Well, above what the PCB had already > been cooked--it does have some discoloration. I'm wondering about > sudden spike, then the transistor goes open circuit. Fast enough to > blow the guts out, but not long enough to discolor the pcb above and > beyond what it has already seen. > > Thermal compound and/or flux residue interacting with whatever leaked > out of the power transistor when it went? Almost looks like is left > over in the oven when a pie (high in sugar) has a spillover. > > Lastly, just to verify: the transistor is bad, right? Or is it still > working? > > Shawn Upton, KB1CKT > Test Engineer > Allegro MicroSystems, Inc > [log in to unmask] > 603.626.2429/fax: 603.641.5336 > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey > Sent: Tuesday, June 24, 2008 5:04 AM > To: [log in to unmask] > Subject: Re: [TN] Power amplifier growth > > Looks like less of a growth and more of transmogrification. > Looks like Q100 got pretty hot. > > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Elder > Sent: Tuesday, June 24, 2008 1:01 AM > To: [log in to unmask] > Subject: [TN] Power amplifier growth > > Has anyone seen anything like this? > The growth is on a 100W power amplifier that has been sitting, powered > up, under load, on a desk, for six months. > > Dave > > http://sites.google.com/site/taitpcb/ > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 15.0 To > unsubscribe, send a message to [log in to unmask] with following text in > the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt > or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET > Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the > posts: send e-mail to [log in to unmask]: SET Technet Digest Search the > archives of previous posts at: http://listserv.ipc.org/archives Please > visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 > for additional information, or contact Keach Sasamori at > [log in to unmask] or 847-615-7100 ext.2815 > ----------------------------------------------------- > > ======================================================================= This email, including any attachments, is only for the intended addressee. 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