I have to sound of the caution: even with round robin, you will not get
that much of info.  (1) size of the parts (CTE mismatch) vs environmental
op temp and extreme temp - that including parts thermal dissipation got a
lot to do with IMC grow and reliability.  (2) I have seen power BGA IMC
grow significantly compare to the signal BGA.  you also have current
enhanced diffusion.  (3) rate of temp change place a role for CTE mismatch
.  (4) rigidity of the board and placement in relation to the design
neutral point are also place a role (5) impact/shock that in relation to
the parts joint stress ... etc. etc.  round robin should be done for the
best in the class MFG practice for minimize IMC, but not risk free as
Victor want a number he can go back to his customer to say IPC said the
thickness below x um is OK.  ;-).
my 1 cents.
                jk
> David,
>
>    Thanks for the vote of confidence.   I like to see and review all
> possible ROUND ROBINS DATA when it comes to IMC formation thicknesses.
>
> Victor,
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of David Hillman
> Sent: Wednesday, September 16, 2015 9:44 PM
> To: [log in to unmask]
> Subject: Re: [TN] BGA Reworked Intermetallic
>
> Hi Vlad - what data do you have that 10 micron thick layer of IMC results
> in the failure of the BGA? There is TONS of subjective comments in the
> published literature but no hard data of failures. As a basic materials
> engineering principle, IMCs are brittle but that specific material
> characteristic seems to be the only reason folks make statements that a
> "thick" IMC is bad. Should we work to keep IMC layers minimized?
> Absolutely but I don't believe, as technologists, we should keep
> propagating the myth about thick IMC layers without having published,
> reviewable data.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> On Wed, Sep 16, 2015 at 9:38 AM, Vladimir Igoshev <
> [log in to unmask]> wrote:
>
>> 10 microns thick layer is a perfect way for a disaster down the road
>> :-).
>>
>> There are no parameters for E-Ni, but the appearance of the interface
>> and a P-enriched layer ‎is important.
>>
>> Vladimir
>>
>> Sent from my BlackBerry 10 smartphone on the Rogers network.
>> Original Message
>> From: Victor Hernandez
>> Sent: Wednesday, September 16, 2015 10:11
>> To: [log in to unmask]
>> Reply To: TechNet E-Mail Forum
>> Subject: Re: [TN] BGA Reworked Intermetallic
>>
>> On ENIG surface I don't see much of an increase in the IMC formation
>> thickness. However, on Cu it is a different story. I have measured IMC
>> formation greater than 10 microns. Not sure of the below statement
>> about E-NI parameter. Please explain!!!
>>
>> Victor,
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev
>> Sent: Wednesday, September 16, 2015 8:12 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] BGA Reworked Intermetallic
>>
>> The "magic" Number should stay the same 1-3 micron but you'd also have
>> to keep an eye on what happened to the layer of E-Ni underneath.
>>
>> Regards,
>>
>> Vladimir
>>
>> SENTEC
>>
>> Sent from my BlackBerry 10 smartphone on the Rogers network.
>> Original Message
>> From: Datacom - Juliano Ribeiro
>> Sent: Wednesday, September 16, 2015 09:09
>> To: [log in to unmask]
>> Reply To: TechNet E-Mail Forum
>> Subject: [TN] BGA Reworked Intermetallic
>>
>> Hi to all,
>>
>>
>>
>> When we reworked the BGA, removed the component of the board and
>> replacement another BGA, what's the intermetallic thickness ideal
>> after the rework?
>>
>>
>>
>> p.s: Our pcb is ENIG finished and the solder is Tin Lead.
>>
>>
>>
>> _____________________________
>>
>> Juliano Bettim Ribeiro
>>
>> DATACOM
>>
>> ENGENHARIA DE PROCESSOS
>> Rua América Nº 1000 - Eldorado do Sul - RS CEP: 92990-000
>> +55 (51) 8446-2135
>>
>> +55 (51) 3933-3000
>>
>> Ramal: 3484
>> [log in to unmask] www.datacom.ind.br
>>
>>
>>
>>
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