Richard, I took from your email:
.....
With the flash gold over nickel or the ENIG plating the gold will be
absorbed into the solder and you will form a solder joint to the nickel.
....
The reason I asked about dissolution rate, temperature and time, is
that I assumed one could have the solder join formed with copper if
the Nickel is let completely to dissolve in the molten solder.
Do you think this is not feasible?
I value your opinion.
THX, Ivan
Il giorno 16/gen/06, alle ore 14:59, Stadem, Richard D. ha scritto:
> Others have responded that the cost of immersion silver is usually
> much
> less than ENIG.
> But what you need to consider also is whether to use the nickel with
> flash gold, standard electroless nickel/immersion gold (ENIG), or
> immersion silver.
> When soldering to the immersion silver finish the silver will be
> absorbed into the solder and the solder joint will be formed on
> copper.
> With the flash gold over nickel or the ENIG plating the gold will be
> absorbed into the solder and you will form a solder joint to the
> nickel.
> Either of the flash gold over nickel or ENIG requires plating of
> nickel,
> and as such the process is susceptible to nickel skips, which you have
> already experienced. Not much fun.
>
> The solder joints formed on copper will be stronger than those
> formed on
> nickel because of nickel's much slower rate of dissolution into the
> solder joint. Because of the slower dissolution rate, the assembly
> requires more heat, and for a longer time, especially under the BGAs.
> BGAs do an excellent job of insulating the solder spheres.
> If you have BGAs or chip scale components, you will be much better off
> with immersion silver finish on the PWB. If you have high impedance/
> high
> frequency circuitry you will also be much better off with immersion
> silver.
> Buy a sample of boards and qualify the assembly with the different
> plating no matter which one you choose.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Sumxplore
> Sent: Friday, January 13, 2006 11:55 PM
> To: [log in to unmask]
> Subject: Re: [TN] enig bad board
>
> Looks like this is the beginning of my nightmare with more to come
> after
> reading those valuable feedback by technetters.
>
> No,I haven't try immersion silver but certainly I will explore
> it.Anyone
> can let me what is the cost differences between Immersion silver and
> ENIG?
>
> Thank you.
>
> ----- Original Message -----
> From: "Lee Parker" <[log in to unmask]>
> To: "'TechNet E-Mail Forum'" <[log in to unmask]>; "'sumxp'"
> <[log in to unmask]>
> Sent: Saturday, January 14, 2006 1:34 AM
> Subject: RE: [TN] enig bad board
>
>
>> Sumxp
>>
>> It is likely the thickness of the gold is inadequate and the
>> underlying nickel has oxidized. I would measure the gold thickness
>> (XRF) and compare it to the minimum specified. The silver color after
>> erasing is most likely the nickel that is under the gold and with the
> oxides removed.
>>
>> There are many other alternatives these days to ENIG such as
>> immersion
>
>> silver. Have you evaluated into any of these?
>>
>> Best regards
>>
>> Lee
>>
>> J. L. Parker Ph.D.
>> JLP Consultants LLC
>> (804) 779 3389
>>
>>
>> Best regards
>>
>> Lee
>>
>> J. L. Parker Ph.D.
>> JLP Consultants LLC
>> (804) 779 3389
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of sumxp
>> Sent: Friday, January 13, 2006 10:48 AM
>> To: [log in to unmask]
>> Subject: [TN] enig bad board
>>
>> Hi,
>>
>> We noticed few ENIG bga pads black in color instead of gold.It turn
>> silver when use eraser to remove away the black color pad.What is the
>> defect mode?
>> Any reliability issue?Is it advisable to continue using these pcbs?
>>
>> Thanks......
>>
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