The problem is that skin is porous (and this means more than containing
pores). Soap and chemicals in the paper towels enter into the skin and
NO amount of rinsing will remove it all. It exudes back out over time,
helped by perspiration. Furthermore, the skin cells die off continuously
and the slightest friction will remove them on to your assembly.
If washing your hands were as good as you pretend, CSI would be out of a
job because criminals would simply wash their hands before committing
their acts.
Still don't believe me? Wash, rinse and dry your hands. Then smell the
soap on them. As simple as that!
Brian
[log in to unmask] wrote:
>
>
> The difference between bacteria and germs that get past the protective
> barrier of the skin and the reliability of soldered circuit boards isn't
> even remotely similar.
>
> The hygenic lotion is washed off and the paper towels are dry and scrub
> your hands clean.
>
> Boards tested in the lab for Ionic contamination and SIR have also
> prooved that the boards are at no reliability risk, the etches are
> covered in solder mask and the joints are then filled or coverd with
> solder as a result wetting from fluxes that are thousands of time more
> acidic that any minute residue from a finger print.
>
> Boards are handled by the edges and most boards are panelized etc.
>
> I could never recommend gloves that pick up everything and aren't going
> to get washed 6-10 times a day as would a persons hands.
>
> This idea of needing gloves which are extremley dirty and not cost
> effective is simply not warranted.
>
>
> ----- Original Message -----
> From: "Brian Ellis" <[log in to unmask]>
> To: "TechNet E-Mail Forum" <[log in to unmask]>, [log in to unmask]
> Sent: Sunday, March 15, 2009 12:19:34 PM GMT -05:00 US/Canada Eastern
> Subject: Re: [TN] Gloved Hands / Fingerprints / Failure Articles
>
> And what do you do with the soap on the boards? And don't tell me it is
> rinsed off the hands, because it ain't. Plus, what kind of soap? How do
> they dry their hands after washing? On a dirty towel? On a paper towel,
> saturated with manufacturing chemicals? With a hot-air blower which not
> only causes the hand to sweat, but blows dust and the mist from flushing
> the toilets straight onto the hands? And what about the salts, urea and
> amino acids from the perspiration? If the handler is a lady, what about
> the sulfur compounds in the perspiration at "that time of the month"?
> And if the wicked bossman appears on the horizon, the perspiration
> levels are doubled. What about the squamous residues from the fingers?
> There is no such thing as a clean hand; it cannot exist.
>
> Surgeons scrub hands and arms for 5-10 mins before an operation,
> finishing with an antiseptic rinse. Then what do they do? they don
> sterile gloves because they know darn well that it is the only way to
> prevent contamination of the operating site.
>
> Brian
>
> John Goulet wrote:
> > The cleaner the person uses 6-10 times a day is hand soap and water
> which removes all the oils and food products.
> >
> > The aqueous cleaner therefore only has to remove the OA flux which it
> is designed to do.
> > ----- Original Message -----
> > From: "Joyce Koo" <[log in to unmask]>
> > To: [log in to unmask]
> > Sent: Wednesday, March 4, 2009 9:07:16 AM GMT -05:00 US/Canada Eastern
> > Subject: Re: [TN] Gloved Hands / Fingerprints / Failure Articles
> >
> > What is your cleaner? � Is it good to remove fry chicken oil, powder
> make up, drssing used on salad, etc. How about after wash? � The
> cleaner is designed to remove industry contaminant what ever used in
> your process, not universal cleaner. � Let me know if you have a
> universal cleaner in you neck of woods. � It could potentially a winner
> for the award from ipc ;-).
> > --------------------------
> > Sent using BlackBerry
> >
> >
> > ----- Original Message -----
> > From: TechNet <[log in to unmask]>
> > To: [log in to unmask] <[log in to unmask]>
> > Sent: Wed Mar 04 08:39:20 2009
> > Subject: Re: [TN] Gloved Hands / Fingerprints / Failure Articles
> >
> > If you have a ROSE Tester (Ionograph Omegameter etc) cycle a board,
> leave in
> > machine.
> > Ask recalcitrants to (with bare fingers) remove and immediately
> replace in
> > machine.
> > Re-test it and have them watch the numbers.
> >
> > Regards
> >
> >
> > Mike
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Glidden
> > Sent: Wednesday, March 04, 2009 1:27 PM
> > To: [log in to unmask]
> > Subject: [TN] Gloved Hands / Fingerprints / Failure Articles
> >
> > Hello everyone,
> >
> > We are in the midst of a proposal from myself and manufacturing
> engineering
> > to require use of gloves or finger cots throughout our PCB assembly
> process.
> > We had considered that it really would only be required after final
> > cleaning, but for uniformity would require it all steps including
> > population. � We have of course met with a real resistance,
> particularly from
> > the final assemblers who are stating it doesn't matter once the
> conformal
> > coat is on. � I can see at least some logic in that, and admittedly
> a large
> > portion of our argument is aesthetics (we don't want fingerprints on the
> > boards even after coating), but it would be really nice to have some
> sort of
> > scare tactic, like an article or something that related a PCB failure to
> > fingerprints or handling contamination. � Anyone have such a thing?
> >
> > Thanks!
> >
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