Maybe Mike will weigh in on this one. I'll offer this as additional
information for one of the previous posters: organics can either be occluded
in the tin deposit or actually codeposited. If you saw a thorough analysis
of the electroactive organic species in a tin bath (or any plating bath for
that matter) you'd be amazed. Mike calls it organic soup. It is.
The occluded or codeposited organics migrate upward through the grain
boundaries of the metal deposit and accumulate at or near the deposit
surface. This migration takes place over time but is accelerated by heat.
Blowholes are pretty much the worst manifestation of it. Perhaps Rudy will
weigh in on whether or not these offending organics can be monitored and
effectively controlled at the source?
Regards,
Roger Mouton
----- Original Message -----
From: "R Sedlak" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, June 21, 2006 8:33 AM
Subject: Re: [TN] Blowholes pandemic
> Organics are common to most electroplating baths, as they are used as
> brighteners/levelers, or in other words, additives to improve and make the
> plating more uniform....
>
> Problem is they decompose, and every so often need to be removed, by a
> process called "carbon treating". This process is long, involved, and
> interferes with production, thus is easily put off, if the plating looks
> good...
>
> No way I know to test the plating for excess organics, other than by doing
> effectively what you are doing, melting it, and checking for blowholes.
>
> Maybe Mike has a better idea.... I think of him as "Mr. Plating".
>
> Rudy Sedlak
>
> "Tempea, Ioan" <[log in to unmask]> wrote: Thanks Mike and Rudy!
>
> I will change my question to: what on Earth are the organics doing in the
> plating? Is this normal?
>
> Any suggestions on how to control the AVL or the Incoming inspection of
> these parts to avoid the issue?
>
> Thanks,
>
> Ioan
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of R Sedlak
> Sent: Wednesday, June 21, 2006 11:12 AM
> To: [log in to unmask]
> Subject: Re: [TN] Blowholes pandemic
>
>
> I will go farther, and suggest that Mike is almost certainly correct, this
> being the source of most "blowholes".
>
> Rudy Sedlak
>
> "Barmuta, Mike" wrote: Ioan: The blowholes you are seeing could be the
> result of organics in
> the tin plating outgassing during reflow. When heated they release CO
> and CO2 gases creating voids.
>
>
> Regards
>
> Michael Barmuta
>
> Staff Engineer
>
> Fluke Corp.
>
> Everett WA
>
> 425-446-6076
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Tempea, Ioan
> Sent: Wednesday, June 21, 2006 5:57 AM
> To: [log in to unmask]
> Subject: [TN] Blowholes pandemic
>
> Hi Technos,
>
> for a couple of days I see occurences of blowholes in the joints of,
> guess what, SMT 0603 resistors.
>
> The reflow recipe did not change and we're talking about 2 different
> established products, we have run many of each before. One is WS, the
> other one no-clean. Each one uses different brand of solder paste, SnPb.
>
> I have changed the paste with fresh one, no positive results. I have
> changed the reels with different date codes, Bingo! But even the "bad"
> parts were quite fresh, less than one year old. One of them is pure Sn
> plated, don't know about the other ones.
>
> The question is: where on Earth can humidity stay in a ceramic resistor?
> What else can be the cause of the blowholes? Did not bake the boards,
> since changing the components worked, so I guess the PCBs are out of the
> hook...
>
> Thanks,
>
> Ioan
>
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