Hi Inge,
If you could, I'd appreciate that. I've seen (and used to "grow") very large Ag-Sn platelets and "yes", phase boundary sliding does occur along the platelets/Sn-matrix interface. BUT I've never seen it causing anything I'd call embrittlement.
Regards,
Vladimir
SENTEC
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca
-----Original Message-----
From: Inge <[log in to unmask]>
Date: Wed, 15 Apr 2009 19:52:13
To: <[log in to unmask]>
Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?
Vlad, it seems to me as all solder joints with large 'crystals' or
'dendrites' or 'platelets' or whatever they are named can cause local weak
bonds. It has to do with concentration of internal forces along the flat and
elongated crystal surfaces. I have no scientific explanation at hand, but
can dig in my stack of papers if you are interested.
Inge
----- Original Message -----
From: "Vladimir Igoshev" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, April 15, 2009 7:37 PM
Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?
> Werner,
>
> We've been through it and not just once. I wish I could have those samples
> to look at, as I've never seen anything like "Ag-embrittlement". Please
> correct me if I'm wrong but a couple of months ago Dave H. "spelled out" a
> final verdict of an IPC committee on the issue.
>
> Regards,
>
> Vladimir
> SENTEC
> 11 Canadian Road, Unit 7.
> Scarborough, ON M1R 5G1
> Tel: (416) 899-1882
> Fax: (905) 882-8812
> www.sentec.ca
>
>
> -----Original Message-----
> From: Werner Engelmaier /* <[log in to unmask]>
>
> Date: Wed, 15 Apr 2009 13:19:34
> To: <[log in to unmask]>
> Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?
>
>
> Vladimir,
> Oh yes, there is 'Ag-embrittlement'—it just never reached the same level
> of notoriety as 'Au-embrittlement.' The whole 5-year effort of the IEEE
> Compliant Lead Task Force (CLTF) was started by 'Ag-embrittlement' when
> TI started production in Singapore and their J-leads were Ag-plated. It
> all hit the fan when the first customer, IBM in Austin, had PLCCs dropping
> off the PWBs on bed-of-nail testing.
>
> Werner
>
>
>
>
>
>
>
> -----Original Message-----
> From: [log in to unmask]
> To: TechNet E-Mail Forum <[log in to unmask]>; [log in to unmask]
> Sent: Wed, 15 Apr 2009 12:41 pm
> Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?
>
>
>
>
>
>
>
>
>
>
> Werner,
>
> I would say that Ag-Sn platelets do the same thing to solder joints as
> Au-Sn.
> There is no "Ag embrittlement". :-)
>
> Vladimir
> SENTEC
> 11 Canadian Road, Unit 7.
> Scarborough, ON M1R 5G1
> Tel: (416) 899-1882
> Fax: (905) 882-8812
> www.sentec.ca
>
>
> -----Original Message-----
> From: Werner Engelmaier /* <[log in to unmask]>
>
> Date: Wed, 15 Apr 2009 11:45:28
> To: <[log in to unmask]>
> Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?
>
>
> Vladimir is correct.
> "Gold-embrittlement" is the weakening of the SJ structure by too many weak
> interfaces with the crystalline AuSn-IMC platelets and the solder. The
> more such
> IMC [AgSn-IMCs do exactly the same] platelets results in higher density of
> such
> interfaces and an increased SJ weakness.
> The dull, grainy, lumpy appearance stems from these IMC-platelets pocking
> through the SJ surface.
>
> Werner0A
>
>
>
>
>
>
> -----Original Message-----
> From: Vladimir Igoshev <[log in to unmask]>
> To: [log in to unmask]
> Sent: Wed, 15 Apr 2009 11:29 am
> Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?
>
>
>
>
>
>
>
>
>
>
> Because you had different materials at the interface. With thick Au your
> joints
> had a relatively wide band of "weak connection" at the Au/Sn-Sn interface.
>
> Regards,
>
> Vladimir
> SENTEC
> 11 Canadian Road, Unit 7.
> Scarborough, ON M1R 5G1
> Tel: (416) 899-1882
> Fax: (905) 882-8812
> www.sentec.ca
>
>
> -----Original Message-----
> From: Guy Ramsey <[log in to unmask]>
>
> Date: Wed, 15 Apr 2009 11:19:59
> To: <[log in to unmask]>
> Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?
>
>
> The point is the connections made on thick gold were substantially weaker
> than those made to nickel though thin gold.
>
> I don't know if there was nickel in the weak connections. But, they were
> dull, grainy, lumpy and weak, compared to the connections made through
> thin
> gold.
>
> Guy
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev
> Sent: Wednesday, April 15, 2009 8:45 AM
> To: [log in to unmask]
> Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?
>
> It just tells you had good solder joints. In many cases laminate (board)
> breaks when a load is applied to properly formed solder joints.
>
> Regards,
>
> Vladimir
> SENTEC
> 11 Canadian Road, Unit 7.
> Scarborough, ON M1R 5G1
> Tel: (416) 899-1882
> Fax: (905) 882-8812
> www.sentec.ca
>
>
> -----Original Message-----
> From: Guy Ramsey <gramse
> [log in to unmask]>
>
> Date: Wed, 15 Apr 2009 08:37:31
> To: <[log in to unmask]>
> 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 are20correct. 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 I
> ntermetallics, 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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