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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