Hi team - I'll just add a couple of comments to the conversation. The
tarnish typically found on immersion silver board finishes is the result of
boards being wet/damp from processing which leads to a brown/black visual
tarnish due to reactions with the air. The majority of the time the tarnish
is cosmetic and does not impact the solderability of the board. If it is
not cosmetic then you will find the solderability is a problem pretty
easily.  The gloves we use are not sulfur free - they are Micro Grip
nitrile gloves from VWR International (part number 40101-350) and we
haven't seen an issue with them causing tarnishing. Of course, everyone
should be handling a board by its edges as much as possible too. I would
look at your board storage and handling practices as possible root cause
sources for the tarnishing. Good luck.

Dave Hillman
Collins Aerospace

On Tue, Jan 14, 2020 at 7:42 AM Douglas Pauls <
[log in to unmask]> wrote:

> "Last Century"?  Thanks for turning me from old to ancient Bev.
>
> As Bev indicated, there are no standards in our industry for this kind of
> thing.  The recommended ionic levels from Foresite, PAL, or other test labs
> are for circuit assemblies or bare circuit boards, not for amounts in
> gloves.  We use standard latex or nitrile gloves here and a lot of what we
> use is immersion silver.  We have not seen the need for special gloves.
>
> In terms of functional impact, if it is just tarnish, then there is no
> functional impact.  Silver oxide conducts as well as pure silver.  All you
> have is a cosmetic issue when people collectively lose their minds looking
> at tarnished silver.
>
> I suspect what happened is somebody somewhere thought "sulfur is bad for
> silver" (which it is), "so we need sulfur free gloves" (which you don't).
>
> *Douglas Pauls *| Principal Materials and Process Engr | Advanced
> Operations Engineering
>
> *COLLINS AEROSPACE*
>
> 400 Collins Road NE, MS 108-101, Cedar Rapids, IA  52498  USA
>
> *Tel:* +1 319 295 2109 | *Mobile: *+1 319 431 3773
>
> [log in to unmask]
>
> [log in to unmask] for all Export Compliant Items
>
>
> On Tue, Jan 14, 2020 at 7:31 AM Bev Christian <[log in to unmask]
> >
> wrote:
>
> > First, do you like to be call GA or Tan?
> > a) & b) There are no standards. Shoot, we don't have any "official"
> > standards for sodium, potassium, fluoride, chloride, bromide, nitrate,
> > nitrate, phosphate or sulfate; unless they are in IEC standards that I
> > don't
> > know about.  We have the suggestions of Doug and Terry from the last
> > century
> > and those from Delco and a couple of other sets.
> > Certainly the measurement of Doug Pauls, etc. are professionally carried
> > out.
> > c) Only cosmetic
> >
> > I have never heard anyone ask for sulfur free gloves. I am not aware of
> > what
> > is available. I would start with asking a VWR or Fisher rep (large
> chemical
> > suppliers with extensive catalogues) .
> >
> > Regards,
> > Bev
> >
> >
> > -----Original Message-----
> > From: TechNet <[log in to unmask]> On Behalf Of Tan Geok Ang
> > Sent: January 14, 2020 6:34 AM
> > To: [log in to unmask]
> > Subject: [TN] Need advice : sulphur level on Gloves/ESD mat and reference
> > standards
> >
> > Will really appreciate advice on the following;
> >
> > a) how much of sulphur/calcium, etc. on gloves/ESD Mat is acceptable and
> > what level is considered harmful in handling of PCBA/module with sliver
> > plated surface
> >
> >
> > b) whether there are any "standards" or references for "compliance" check
> > for sulphur, and is there such measurements professionally carried out
> >
> >
> > c) What will be the impacts on the PCBA when silver plating become
> tarnish?
> >
> >
> > There are sulphur free gloves but it is not easily accessible/available
> in
> > Singapore and it is expensive.
> >
> >
> > Thanks.
> >
> >
> > GA Tan
> >
>