Hi folks - Doug and I have been freezing marshmallows in liquid nitrogen
and showing middle school students how to be human fog machines this
afternoon thus I am late in replying to this topic. JSTD-001 allows for a
user to provide objective evidence demonstrating that a component with a
specific thickness of gold plating is not going to result in the
degradation of solder joint integrity due to gold embrittlement. Gold
embrittlement occurs when you exceed 3 weight% gold in the solder joint
and form the AuSn4 intermetallic phase (note that there is some "debate"
on exact gold weight % you have to exceed - opinions vary from 2-5%). The
AuSn4 is very brittle and causes solder joints to crack/fail. "Flash"
gold or immersion gold is typically less than 10 uinches thick and will
not cause the gold embrittlement phenomenon as you don't exceed the gold
limits. So, if you have connectors or other components that utilize a
"flash" gold plating and you have objective evidence (that means testing,
cross-sections, confirmed XRF plating measurements, etc. - not just a
vendor certification) then you can meet the JSTD-001 requirement. However,
the problem is that gold plated solder cups typically have too thick of
gold plating so if you don't pretin the solder cup to flush the gold
content to a lower level, you will have an embrittlement problem. The IPC
JSTD-001 Handbook has a good section on gold embrittlement. You will also
find good information on the topic in Klein Wassink's book (ISBN
0-901150-14-2) and the AWS Soldering Handbook (ISBN 0-87171-618-6).
Dave
Bob Landman <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
02/05/2010 06:58 AM
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Re: [TN] Tinning gold-plated solder cup of connectors
Dean,
I understand that thick gold coatings can result in internetallic
embrittlement with solder but isnt it true that very thin coatings
disolve into the solder and do not result in embrittlement and that is
why ENIG is specifically exempt?
If Dave's solder cups are gold flashed then why is there a problem? Is
it that their plating is thick?
the DS amendment standard says:
"Surfaces exhibiting gold finish thicknesses of 0.254 micro-meters (10
micro-inch) or less (a.k.a. ''gold-flash'') are
exempt from this requirement."
Also, what is the difference between -001 and 001-DS?
Bob
Sent from my iPhone
On Feb 4, 2010, at 7:26 PM, "Dean Stadem"<[log in to unmask]>
wrote:
> J-STD-001DS specifically does not allow ANY gold on areas to be
> soldered, except for ENIG on circuit boards, and ENIG only as defined
> per IPC 4552.
> Objective evidence is also not considered to be immediate pull or peel
> test readings, because gold embrittlement is a time-variable
> phenomena.
> Gold cups have been proven to be especially susceptible to brittle
> fractures from gold nucleation over time. I had to deal with that when
> several wires broke from vibration inside of torpedoes, so I know they
> are especially vulnerable. The gold content in the solder was proven
> to
> be less than 2%.
> I am sure Werner will weigh in on this as well.
>
> R. Dean Stadem
> Consulting Engineer
> Analog Technologies Corp./Lumagine, Inc.
> 11441 Rupp Drive
> Burnsville, MN 55431
> (952)894-9228
> [log in to unmask]
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave He
> Sent: Thursday, February 04, 2010 5:54 PM
> To: [log in to unmask]
> Subject: Re: [TN] Tinning gold-plated solder cup of connectors
>
> Great, Bob. This is what I am looking for. Two Qs
>
> 1. The amendment is for J-STD-001 DS, will it cover J-STD-001?
> 2. Does " Surfaces exhibiting gold finish thicknesses of 0.254
> micro-meters
> (10 micro-inch) or less (a.k.a. ''gold-flash'') are exempt from this
> requirement." cover SMT component? I guess so but it not clearly
> stated.
>
> Thanks.
>
> Regards,
>
> Dave He
> Ext: 333
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
> Sent: Thursday, February 04, 2010 2:34 PM
> To: [log in to unmask]
> Subject: Re: [TN] Tinning gold-plated solder cup of connectors
>
> Gold flash is also exempt according to the amendment #1 of J-
> STD-001DS -
> isn't the SAMTEC part gold flash?
>
> http://www.ipc.org/4.0_Knowledge/4.1_Standards/J-STD-001DS-Amend1.pdf
>
> 3.9.3 Gold Removal Gold shall be removed from at least 95% of the
> surface
> to-be-soldered of all component leads,
> component terminations, and solder terminals. A double tinning process
> or
> dynamic solder wave may be used for
> gold removal.
>
> Exceptions:
>
> Electroless nickel immersion gold (ENIG) finishes on PCBs are exempt
> from
> this requirement.
> Surfaces exhibiting gold finish thicknesses of 0.254 micro-meters (10
> micro-inch) or less (a.k.a. ''gold-flash'') are
> exempt from this requirement.
>
> These requirements may be eliminated if there is objective evidence
> approved
> by the user prior to use that there are
> no gold related solder embrittlement problems associated with the
> soldering
> process being used.
>
> Bob Landman
> H&L Instruments, LLC
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Gregg Owens
> Sent: Thursday, February 04, 2010 5:16 PM
> To: [log in to unmask]
> Subject: Re: [TN] Tinning gold-plated solder cup of connectors
>
> Dear Dave:
>
> J-STD-001's only exception to gold tinning is ENIG plated PCBs. Also
> it
> provides that the entire requirement be ignored if you have data to
> support
> that no gold embrittlement issues exist without pre-tinning.
>
> Gregg Owens
> Technical Writer - Avionics
> Space Exploration Technologies Corporation
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave He
> Sent: Thursday, February 04, 2010 12:19 PM
> To: [log in to unmask]
> Subject: [TN] Tinning gold-plated solder cup of connectors
>
> Does gold plated solder cup of connector need tinning per J-STD-001?
> Or
> is
> this a exemption? Thanks.
>
>
>
> Best regards,
>
>
>
> Dave He
>
>
>
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