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October 2005

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Subject:
From:
"Fineline Circuits, Inc" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Fineline Circuits, Inc
Date:
Mon, 17 Oct 2005 14:11:26 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (381 lines)
Mike:
Our bath is a non peptone stanneous fluborate and lead fluborate bath. But
regardless you are right in that we have to get away from lead in the shop.
The scenario Rudy laid out is what we have thought of doing but we are not
sure how long it will take to leach out the lead in the solution..
It may be best to just make a new electrolytic tin tank.
Everyone thanks for the input.
Sona

----- Original Message -----
From: "Barmuta, Mike" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, October 17, 2005 11:12 AM
Subject: Re: [TN] (2) [TN] Electrolytic Tin Plating


Hi Ed: In Sona's original question about going away from tin/lead it does
not state which type of bath electrolyte is being used, fluoborate,
sulfate/sulfonic or sulfamic acid.

Regardless you still have to strip the plating and deal with the lead in the
spent stripper solution, subsequent rinses and post strip surface clean/prep
operations.

Bottom line, you have to deal with the regulatory issue of lead in your
processes and effluent. And it's only going to get worse. To me it makes
more sense to remove it from operations totally if it's not required.


Regards

Michael Barmuta

Staff Engineer

Fluke Corp.

Everett WA

425-446-6076

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Edward Szpruch
Sent: Sunday, October 16, 2005 5:56 AM
To: [log in to unmask]
Subject: Re: [TN] (2) [TN] Electrolytic Tin Plating


Mike,
Most of PCB wet processes are involved with using of sulfates.Solubility of
Lead Sulfate is neglible,so are the chances to find lead in wastestream (
provided wastewater treatment has settling or filtration stage)
Edward

Edward Szpruch
Eltek Ltd
P.O.Box 159 ; 49101 Petah Tikva Israel
Tel  ++972 3 9395050 , Fax  ++972 3 9309581
e-mail   [log in to unmask]
web site : www.eltekglobal.com

> -----Original Message-----
> From: Barmuta, Mike [SMTP:[log in to unmask]]
> Sent: ו אוקטובר 14 2005 22:00
> To:   [log in to unmask]
> Subject:      Re: [TN] (2) [TN] Electrolytic Tin Plating
>
> Sona: The short answer is to remove lead from your processes and
> wastestream.
>
> Obviously if you are only going to use the tin for an etch resist then
> strip
> you don't have all the issues I outlined below, required for a final
> solderable finish.
>
>
> Regards
>
> Michael Barmuta
>
> -----Original Message-----
> From: Fineline Circuits, Inc [mailto:[log in to unmask]]
> Sent: Friday, October 14, 2005 12:42 PM
> To: TechNet E-Mail Forum; Barmuta, Mike
> Subject: Re: [TN] Electrolytic Tin Plating
>
>
> Mike:
> I don't think I would want to get into this process where the operation
> window is so tight.
> My next question is than why even bother going from tinlead to tin since
> for
>
> lead free you are stripping tinlead anyway and providing other finishes
> other than HASL.
> Sona
>
>
> ----- Original Message -----
> From: "Barmuta, Mike" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Friday, October 14, 2005 2:15 PM
> Subject: Re: [TN] Electrolytic Tin Plating
>
>
> > Sona: Back in the "old" days we did a lot of tin plating as the final
> > finish
> > on Teflon MLB's, typically for high frequency signal generators. You
> > definitely didn't want to mess these up or it could get real expensive
> > rear
> > quick.
> >
> > It's a very tricky process but if all factors are controlled properly it
> > works. Unfortunately most people doing tin plating these days are only
> > using
> > it for etch resist and are not aware of the multiple issues needed to
> > produce an acceptable electroplated tin final finish.
> > So let me give you some pointers on how we did it.
> >
> > 1. Bath Type: Lea Ronal(Rohm and Haas) Bright Acid Tin Sulfate
> > Electrolytic
> > Plate. This is a fine grain structure finish not requiring any type of
> > reflow processing. Due to low porosity and tight grain structure of the
> > deposit it is not as susceptible to staining as a matte/semi-mate tin.
> >
> > 2. Underplate: To help prevent slivering you need an electrolytic nickel
> > underplate between the copper and tin
> >
> > 3. Rinsing: To minimize staining after tin plate you need multiple
> rinses
> > cold followed by hot. Any acid drag over in final rinsing will result in
> > staining.
> >
> > 4. Resist Strip: The resist stripper chemistry has to be designed for
> > compatibility with bright tin, if not you will get staining.
> >
> > 5. Etch: You need to control your etcher(ammoniated), pH, chemistry,
> temp,
> > speed, etc, to minimize undercut which will produce slivers. Again
> rinsing
> > is critical here too.
> >
> > 6. Soldermask Prep: Do not scrub the panels.
> >
> > 7. Soldermask Bake: Bake at 140C for 60-80 mins AT temperature. If you
> > have
> > discoloration you probably have done a poor job of rinsing somewhere
> above
> > or have poor water quality. Poor air circulation in the oven can also be
> a
> > cause.
> >
> > 8. Tin Plate Bath Control: Control of the multiple component organic
> > brightners, levelers and grain refiners is critical. Also the stannic,
> > stannous, sulfuric acid constituents, cathode agitation, amount/velocity
> > of
> > filtration, trace metal impurities, organic build-up, etc, need to be
> > monitored and properly controlled.
> >
> >
> > If done right the end result will be an acceptable product but screw up
> > just
> > one factor and you will have garbage. You need to ask yourself how much
> > you
> > are willing to commit to offer this type of final finish and is it worth
> > it.
> >
> >                                                        Regards
> >
> > Michael Barmuta
> >
> > Staff Engineer
> >
> > Fluke Corp
> >
> > Everett WA
> >
> > 425-446-6076
> >
> >
> >
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]]On Behalf Of Fineline Circuits,
> > Inc
> > Sent: Friday, October 14, 2005 9:39 AM
> > To: [log in to unmask]
> > Subject: Re: [TN] Electrolytic Tin Plating
> >
> >
> > Colin:
> > 2-3 years back we ran an experiment with a tin vendor where we did
> > electrolytic tin plate, etch, and mask.Tin was supposed to be the final
> > finish per vendor.Vendor told us that he had customers that did this.
> > However the tin got tarnished and dark grey after cure and we just did
> not
> > like the look off the final finish. We did not pursue it further.
> > Sona
> >
> > ----- Original Message -----
> > From: "Colin McVean" <[log in to unmask]>
> > To: <[log in to unmask]>
> > Sent: Friday, October 14, 2005 10:33 AM
> > Subject: Re: [TN] Electrolytic Tin Plating
> >
> >
> > Are you suggesting that you use the tin plate as your final finish? I'm
> > no chemist, but I think that could spell trouble, with the open
> > structure of the electroplated tin giving rise to whiskers.
> > We use Electroplated tin, but only for the etch resist application - we
> > strip it off, solder mask, then final finish, either Immersion Silver,
> > Immersion Ni/Au, or lead free HASL dependant on customer requirements.
> >
> > Colin McVean M.Inst.C.T.
> > Production Manager
> > Artetch Circuits Limited
> > Main: 01903 725365
> > DD:    01903 712926
> > Email: [log in to unmask]
> > www.artetch.co.uk
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Fineline Circuits,
> > Inc
> > Sent: 14 October 2005 15:20
> > To: [log in to unmask]
> > Subject: [TN] Electrolytic Tin Plating
> >
> > Hi Technetters:
> > Now that Leadfree is here or close to, we would like to change the
> > electrolytic tinlead plating tank to electrolytic tin tank.
> > I would like to know if the other fab houses have done this and if so
> > which
> > vendors tin chemistry has a wider window of operation. Are they seeing
> > any
> > tin whiskers/sliver problems etc..especially if the boards are stored
> > for
> > few months.
> > Also it is my understanding that you can mask over this plated tin since
> > it
> > does not flow. In this case you can totally avoid stripping the tin and
> > tin
> > levelling.
> > We currently do offer other finishes including electroless tin ,
> > immersion
> > nickel/gold, silver....
> > If there are other consideration in making this change I would
> > appreciate
> > your input.
> > Franklin, like you I would like to see more fab houses participating but
> > I
> > would like to remain with technet.
> > Thanks
> >
> > Sona Sitapara
> > Fineline Circuits Inc.
> >
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