I would like to know why people don't use OSP - from a board shop's
viewpoint, it is the best finish to put on a board - why ? because it is
very simple chemistry, puts no thermal shock on the product, is applied on a
SHORT conveyor line, and can be easily reworked unlike ANY of the other
finishes. The assembly guys don't like it if they start assembling a product
and then stop because they don't have the parts to finish the job, but
anyone that puts a board into assembly without the ability to finish it
within 6 hours obviously knows nothing about world class manufacturing
practise. As for shelf life, if your stock is even 2 years old, send the
boards back to the board shop and for a small fee they just put them back
down the line again and you have a finish that is good as new, without
having undergone a vicious chemical attack to remove the finish.
Just my thoughts !
Dougal Stewart
email: [log in to unmask]
phone: +44 1896 822204
mob: +44 7984 629667
----- Original Message -----
From: "Jack C. Olson" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, April 17, 2002 4:22 PM
Subject: Re: [TN] Immersion Silver
> Hmmm,
>
> Well, at some point in EVERY new technology it was used by less
> than 3% of the world, eh? Guess I'm just a trailblazer....
>
> naw, just kiddin ya.
> I subscribed to a magazine called Circuitree, and the last issue
> came bundled with another publication called "The Board Authority"
> which has some very well written (and well researched!) articles
> on alternate finishes. I can't see any downside to using silver
> in our applications, and I've looked all through the archives for
> Technet, DesignerCouncil and PCDlist forums, still no show-stoppers,
> so we tried it for the first time on our last design. Yes, HASL and
> NiGold do work fine, but maybe we can get the same functionality
> for cheaper, and do our fab vendor a favor in the process, since
> they seem to prefer it (less steps? more reliable? not sure) maybe
> the fab guys can answer that one....
>
> Jack
>
>
>
>
>
> "WEEKES, MICHAEL HS-SNS" <[log in to unmask]>
> 17Apr2002 09:16 AM
>
>
> To: "'TechNet E-Mail Forum.'" <[log in to unmask]>
> "'Jack C. Olson'" <[log in to unmask]>
> cc:
>
> Subject: RE: [TN] Immersion Silver
> Retain Until: 05/17/2002 Retention Category: G90 - Information and Reports
> Caterpillar Confidential: Green
>
>
> There must be some reason why less than 3% of the world has moved toward
> immersion silver. Why doesn't HASL or NiGold work for your application?
>
> Mike
>
> -----Original Message-----
> From: Jack C. Olson [mailto:[log in to unmask]]
> Sent: Wednesday, April 17, 2002 7:39 AM
> To: [log in to unmask]
> Subject: Re: [TN] Immersion Silver
>
>
> The PCD magazine list went down before I could get an
> answer to this question, does anyone have experience
> with silver and contact switches?
>
> ==============================================
>
> Most sources say a silver surface will not be solderable
> after a month or so unprotected. (Even in a baggie it will
> be okay a year later?)
> Anyway, you say it is good for switches, which would solve
> some of our hard gold plating problems.
>
> But I would think the "unsolderability" of the aged silver
> surface (unprotected in the unit and tarnished?) would
> affect the reliability of the switches, wouldn't it?
>
> Jack
>
>
>
>
>
>
> Rob Mongey <[log in to unmask]>@freelists.org
> 4Apr2002 06:08 AM
>
> Please respond to [log in to unmask]
>
> Sent by: [log in to unmask]
>
>
>
> To: [log in to unmask]
> cc:
>
> Subject: [pcdlist] Re: Immersion Silver
> Retain Until: 05/04/2002 Retention Category: G90 - Information and Reports
> Caterpillar Confidential: Green
>
>
>
> Hi all,
> Good to see Immersion Silver is starting to take off. We've been
using
> it
> in here for about two years, and it is now our prefered board finish (We
> get silver finish unless we specify differently.) More common useage will
> mean that maybe more Far Eastern shops will start supplying it.
>
> We started to use Silver because it is so adaptable to what we need
> our
> PCB surface finish to do, namely:
>
> 1. Good solderability. (Silver excels at this, ask any vendor).
> 2. Flatness for fine pitch SMT. (Silver is as flat, if not flatter than
> Gold)
> 3. Mechanical strength for carbon pill switch contacts / Elastomer
> contacts. ( Flash Gold is weak, and hard Gold gives SMT solderability
> problems)
> 4. Stability for compression power contacts. (We have power contacts on
our
> PCBs that mate to battery contacts via a spring compression. We found that
> the nickel under gold can cause problems with electrochemical migration
> toward our battery contact.)
>
> Immersion silver is the most suitable choice that can do all four. I'd use
> gold as an alternative, but we'd have to compromise our designs somewhat.
>
> We specify our Silver finish as 0.1 Microns Min to 0.2 Microns Max, over
> bare copper. Anyone else do it differently? Or do we trust our board
shops?
> :)
>
> Regards,
> Rob Mongey.
> CAD Technician.
>
> Robert Mongey <[log in to unmask]> Tel : +353 (0)91 774300
> Bio Medical Research Direct : +353 (0)91 774338
> BMR House, Fax : +353 (0)91 774302
> Parkmore Business Park West, Mobile : +353 (0)87 2485262
> Galway
> Rep of Ireland.
>
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