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June 2008

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Subject:
From:
"Wenger, George M." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wenger, George M.
Date:
Thu, 26 Jun 2008 10:43:02 -0400
Content-Type:
text/plain
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text/plain (357 lines)
I didn't recognize you in the photo.  You might want to p
Steve,



I didn't recognize you in the photo.  You might want to post the

attached photo on your site.





-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory

Sent: Thursday, June 26, 2008 9:51 AM

To: [log in to unmask]

Subject: Re: [TN] Power amplifier growth



Thanks Inge! I try hard.



Maybe it's because I stay connected most of the time:



 http://stevezeva.homestead.com/files/Staying_Connected.jpg



Steve



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar

Sent: Thursday, June 26, 2008 7:39 AM

To: [log in to unmask]

Subject: Re: [TN] Power amplifier growth



Thanks, Steve,

you are the most available person I've ever met! In most cases, the

person I call or mail to, is out of office, on vacancies, on meeting,

not reading daily, answering sporadically etc.

You are unique.



Inge 



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory

Sent: den 26 juni 2008 14:03

To: [log in to unmask]

Subject: Re: [TN] Power amplifier growth



The pidgeon has landed, and left a big poop. You can see the MES he made

here:



 http://stevezeva.homestead.com/files/Strange_Growth.jpg



Steve



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar

Sent: Thursday, June 26, 2008 2:24 AM

To: [log in to unmask]

Subject: Re: [TN] Power amplifier growth



I'll send a pidgeon to Mr Gregory 



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey

Sent: den 26 juni 2008 03:06

To: [log in to unmask]

Subject: Re: [TN] Power amplifier growth



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/

>

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