Hi Joyce! Very few materials are "perfect" - all have their advantages and
disadvantages. I can't do Victor's homework for him - he'll need to partner
with his plating vendor to insure that he gets a quality plating. We are
both on the same page, we've both been burned by material characteristics
which turn bad due to improper plating processes. I just hate so see a
material choice taken out of the designer's tool box because of a bad
incident that many times was a misapplication or happened due to
unique/unusual circumstances. Now I'm off to the Diet Coke machine to use
your 1.34 cents!
Dave
"joyce"
<[log in to unmask] To: "'TechNet E-Mail Forum.'" <[log in to unmask]>, <[log in to unmask]>
om> cc:
Subject: RE: [TN] Zinc Plating Finish
09/11/2003 12:33
PM
Please respond to
joyce.koo
Dave,
I assume you are going to teach Victor how to do plating? Or Victor is
going to teach his vendor how to do plating? Are you going to put in
the dwg notes that zinc coating should comply with Mil-std xyz with no
whisker growth visual inspection at abcX? Very good.
"fur coat" is still exist more than you think... It is usually blowed
away and shorted somewhere else (far away from the source due to more
more strong cooling fan required for the morden high power
microprocessor).... The FA normally is either "no fault found" when you
un-plug the board or hardware upon removing, (80-90% of time), or
shorted and burned you can't find it any more, or cause leakage current
and got probed, cutted upon destructive fault isolation.... It is just a
problem we think is "no longer a problem" (may be not for the guy burned
before, but for newbees, it is just a "no problem")...
My 1.34 cents...
jk
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Hillman
>Sent: Thursday, September 11, 2003 1:12 PM
>To: [log in to unmask]
>Subject: Re: [TN] Zinc Plating Finish
>
>hor
>Hi Joyce! Yep, zinc plating can produce whiskers but the
>behavior and physical structure of those whiskers is quite a
>bit different than a tin whisker. Zinc whiskers have been
>shown to have a preferred growth along the {1120} crystal
>plane. Zinc plating can also be rendered "immune" to whisker
>growth by an annealing treatment which can be applied to zinc
>plating used for nuts/screws/bolts hardware applications. Its
>a good thing that we can deal with zinc (unlike tin) plating
>and its whisker issues, otherwise there would be lots of "fur
>coat" problems with all the zinc plated hardware running
>around the planet.
>
>Dave
>
>
>
> "joyce"
> <[log in to unmask] To:
>"'TechNet E-Mail Forum.'" <[log in to unmask]>,
><[log in to unmask]>
> om> cc:
> Subject: RE:
>[TN] Zinc Plating Finish
> 09/11/2003 11:56
> AM
> Please respond to
> joyce.koo
>
>
>
>
>
>
>Even galvanic corrosion may (not say is) not be a problem,
>fretting corrosion should be a concern.
>http://www.amp.com/products/technology/articles/dd68_1.stm
>If the force is very high (stress) and on/off is not that
>often, you may (not say are) worry about cat whiskers
>(zinc).... If you are un-lucky, you may have "fur coat"
>instead...Dave is going to tell me he filled up nitrogen,
>argon in the package... I guess...;-(
>
>jk
>
>>-----Original Message-----
>>From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Hillman
>>Sent: Thursday, September 11, 2003 12:36 PM
>>To: [log in to unmask]
>>Subject: Re: [TN] Zinc Plating Finish
>>
>>
>>Hi TechNet! Steve - you have fallen into the galvanic series trap!
>>There is the potential for a galvanic reaction between Zn and Sn but
>>there are several other factors which need to be considered - the
>>Galvanic Series chart is only a first order approximation of
>a possible
>>reaction. Your cathode-to-anode ration, the type/use of coatings
>>(postcoat, chem film), the "chemistry" of the use
>environment, and how
>>"sealed" the electronic assembly is designed all play a role in the
>>amount and type of corrosive attack on the Zn plating. There will be
>>a paper at the IPC Fall meeting on the subject of galvanic
>>compatibility of the new immersion finishes and aluminum which
>>may be helpful.
>>
>>Dave Hillman
>>Rockwell Collins
>>[log in to unmask]
>>
>>
>>
>>
>> Steve Gregory
>> <[log in to unmask] To:
>>[log in to unmask]
>> m> cc:
>> Sent by: TechNet Subject: Re:
>>[TN] Zinc Plating Finish
>> <[log in to unmask]>
>>
>>
>> 09/11/2003 11:16
>> AM
>> Please respond to
>> "TechNet E-Mail
>> Forum."; Please
>> respond to
>> SteveZeva
>>
>>
>>
>>
>>
>>
>>Hi Victor!
>>
>>What will probably happen is that the Zinc will start to corrode
>>because of the galvanic action between itself and the tin, or tin /
>>lead. Go to:
>>
>>http://www.ccfast.com/ccfcorrosion.html
>>
>>There you will see a Galvanic Series chart, and a simple explaination
>>about Galvanic action. Zinc, and Tin or Tin / Lead isn't all that far
>>apart in the chart, but far enough that the Zinc will corrode.
>>
>>-Steve Gregory-
>>
>>
>> Fellow TechNetters:
>>
>> What are the exposures of having or selecting a ZINC
>plating finish
>>for an ELECTRICAL CONTACT such as a solder less
>> crimp connector and straight pin connector. What can occur if these
>> finishes are mixed mated with a SnPb or Sn finish surface.
>>
>> Victor,
>>
>>
>>
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