Thank you all in helping me to understand more on the subject which highlight by internal staff observation (as highlight by one of you, lol). I will compile and share you all expert advice and share it to internal team.
BTW. Bev, normal others in the company will call me G.A.
Have A Great Day To Everyone!
Thank again!
-----Original Message-----
From: TechNet <[log in to unmask]> On Behalf Of David Hillman
Sent: Wednesday, 15 January 2020 4:39 AM
To: [log in to unmask]
Subject: Re: [TN] [External] Re: [TN] Need advice : sulphur level on Gloves/ESD mat and reference standards
Hi Mary - very valuable comment! We have "experienced" the very situation you detailed which is how we arrived at the gloves we use today. Always fun to explain to a buyer that "all gloves are NOT alike!".
Dave
On Tue, Jan 14, 2020 at 2:17 PM Mary Davis <[log in to unmask]>
wrote:
> My experience indicates that nitrile gloves vary greatly from brand to
> brand, grade to grade, etc., and testing should be performed to
> qualify them prior to use. I wasn't dealing with silver corrosion -
> but instead with transfer of residue that caused de-wetting of
> urethane conformal coating and cure inhibition of silicones. I was
> told by a rep from the glove company that the residue transfer was
> the result of residual un-reacted nitrile. That seems to make sense
> as nitriles are listed as a source of silicone cure inhibition.
>
> Some nitrile gloves are washed as part of their manufacture. Some
> nitrile gloves are certified as containing low ionic extractable
> content. The washed and low ionic extractable gloves are relatively
> expensive but performed the best and prevented costly quality issues.
> And, once you get a nitrile glove product that is confirmed
> acceptable, you need to lock in your choice. Otherwise, time goes by
> and a buyer changes to a less expensive glove - and the quality problems return.
>
> Regards,
>
> Mary Davis
> Retired Materials and Process Engineer
>
> -----Original Message-----
> From: TechNet <[log in to unmask]> On Behalf Of Joe Russeau
> Sent: Tuesday, January 14, 2020 8:53 AM
> To: [log in to unmask]
> Subject: Re: [TN] [External] Re: [TN] Need advice : sulphur level on
> Gloves/ESD mat and reference standards
>
> I would add to this conversation by saying that we have tested
> power-free nitrile and powder-free vinyl gloves using ion chromatography for "ionic"
> contaminates. We analyze the lots of gloves we use to handle customer
> product to ascertain the types and amounts of ionics that we may be
> contributing to the test results. We have typically found that gloves
> of those types have very low levels of ionic contaminates (less than
> 1.5 ppm total for a pair of gloves anions and cations combined).
> Couple low ionic levels with proper handling techniques and you can
> minimize the chance for transference to a product.
>
> That all said, I can't speak to the relative amounts of contaminates
> coming from ESD mats. Until this past year, ESD mats haven't really
> been on anyone's radar for being a corrosion contributor. Now there
> seems to be a lot of questions being asked about the levels of
> contaminates coming from mats and do those contaminates lead to
> corrosion products. To date, I am not personally aware of any
> standard that defines what contaminate levels ought to be for mats.
> Perhaps some guidance is needed. My 2 cents would when in doubt have
> those materials tested, if for nothing else but peace of mind.
>
> Best Regards,
>
> Joe Russeau
>
> PAL, Inc.
>
> On 2020-01-14 10:55, David Hillman wrote:
>
> > 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]:
> >
> > 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
>
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