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April 2009

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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:
Wed, 15 Apr 2009 08:58:27 -0400
Content-Type:
text/plain
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text/plain (334 lines)
Regards,
George
George M. Wenger
Andrew
0.000152"



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 David D. Hillman

Sent: Wednesday, April 15, 2009 8:49 AM

To: [log in to unmask]

Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?



Hi Guy! I am metrically impaired - what is 3.8 micron in inches? Is your



3.8 micron referring to micrometers or nonSI units? (Given our recent SI



units discussion, my question is way too ironic!).



Dave Hillman

Rockwell Collins

[log in to unmask]









Guy Ramsey <[log in to unmask]> 

Sent by: TechNet <[log in to unmask]>

04/15/2009 07:37 AM

Please respond to

TechNet E-Mail Forum <[log in to unmask]>; Please respond to

Guy Ramsey <[log in to unmask]>





To

[log in to unmask]

cc



Subject

Re: [TN] Gold/Tin Intermetallics, why are we afraid?













We build a lot of boards with electroplated gold finish, primarily for

the

semiconductor test sector of our industry.

 

On one occasion we were populating little printed circuit wave guides

with

SMT SMA shrouds. We noticed very poor solder appearance and very weak 

solder

connections. Some connections broke while attaching the cables. 



We determined that the gold plate was 3.8 micron. And judged the

thickness

of the gold to be the cause of poor mechanical performance of the solder

connection. 



We replaced the boards with versions having about 0.3 micron gold plate.



The

connections were much stronger. We were able to install all the cables,

no

connection failures. To satisfy my own curiosity, I attempted to break

one

of the connectors off the board. The solder connection did not fail. The

copper peeled off the board.



Thoughts? 



Guy



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

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

Sent: Wednesday, April 15, 2009 2:42 AM

To: [log in to unmask]

Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?



Thank you, George,

sometimes one needs kind of technical pragmatism.

Inge 



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

From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.

Sent: tisdag 14 april 2009 23:41

To: [log in to unmask]

Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?



I think both you and Vladimir are correct.  If the bond Ingemar,



I think both you and Vladimir are correct.  If the bond sits are room

temperature without any power cycling or mechanical stress it probably 

won't

degrade.  I assume Vladimir has seen the same kinds of failures I've

seen

and there has always been a thermal and/or mechanical stress associated 

with

the failures.



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 Inge

Sent: Tuesday, April 14, 2009 5:15 PM

To: [log in to unmask]

Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?



You mean that such a bond degrades even if just being in constant room

temperature and no power switching?

Inge





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

From: <[log in to unmask]>

To: "TechNet E-Mail Forum" <[log in to unmask]>; "Inge" 

<[log in to unmask]>

Sent: Tuesday, April 14, 2009 11:07 PM

Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?





> Hi Inge,

>

> Yes, the intermetallics itself is strong, BUT it doesn't count, as all



> failures I've seen goes at the tin/intermetallics interface. The

larger 

> were the platelets, the worse it looked.

>

> Regards,

>

> Vladimir

> ------Original Message------

> From: Inge

> Sender: TechNet

> To: [log in to unmask]

> ReplyTo: TechNet E-Mail Forum

> ReplyTo: Inge

> Sent: Apr 14, 2009 16:55

> Subject: [TN] Gold/Tin Intermetallics, why are we afraid?

>

> These infamous IMCs are like parias or ghosts in most people's mind in

our

> business. I shocked our production guys recently by giving the advice

to 

> let

> the boards go on. Large crystals and bad looking. But I always  try to



> avoid

> exaggerations. If no serious temp changes are predicted, nor any

severe

> power switching, why rework and risk introducing failures?  The actual

> components were very hard to rework, the cost had been unacceptable. I

can

> see many of you get  the coffee wrong. I don't mean to spread quality

> distractions, I talk about very few boards and a unique situation. My

> statement was based on the fact that a gold tin intermetallic bond is

> extremly strong and can last long, if not exposed to what I pointed at

> earlier. I expect to be hammered down in the shop floor until only the



> nose

> is visible....

>

> Inge

>

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>

>

> SENTEC

> 11 Canadian Road, Unit 7.

> Scarborough, ON M1R 5G1

> Tel: (416) 899-1882

> Fax: (905) 882-8812

> www.sentec.ca

> 



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