how many 600 to 1200 pin .4mm CSPs and 01005s do you place per
day? If the answer is "lots and lots" it tends to affect your level
of concern concern with surface finish as a variable in SMT yields.
ENIG is much like our form of government. It's the most problematic
system we know of, except for anything we've tried. Those high
volume producers with historical (hysterical?) concerns about black
pad will often specify selective OSP on their BGA's and ENIG on the
remainder of the board.
At 10:30 AM 6/2/2011, Robert Kondner wrote:
>Scott,
>
> Is Black Pad worse than bad HASL?
>
> My point is comparing one finish when it is done poorly to another finish
>when it is done correct is a silly comparison.
>
> Now way down there at .4mm pitch is another ball park all together, I don't
>want to even tread there when "Finish Flatness" was the starting issue.
>
> And yes, I am overstating the case for HASL, I admit that. But I really
>want to flush out the reasons why folks move to different finishes. I can
>see some flatness issues for stencil printing though that problem has not
>shown up in my environments. I stay at or above .5mm pitch and 0402 just to
>keep things easy.
>
>Bob K.
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Post, Scott E
>Sent: Thursday, June 02, 2011 12:33 PM
>To: [log in to unmask]
>Subject: Re: [TN] Best Board Finish - beyond gold
>
>It can be really difficult to get solder paste to release consistently on
>very fine features with HASL. Also, the domed shape of HASL can cause poor
>stencil gasketing that leads to solder squeezing down the sides of the land
>and bridging. Every company seems to have a different threshold where they
>won't use HASL. I know some people won't use it on boards that have 0402s
>and 0.5 mm pitch QFPs. I personally think HASL is OK for those feature
>sizes but below that causes too much grief. In fact, last month I ran an
>experiment using a board design with 0.4 mm pitch QFPs and BGAs as well as
>some resistor arrays with very fine apertures. I had the same board design
>with OSP and SN100 HASL. The difference in print quality was dramatic even
>though the HASL boards had what I consider very good HASL. I'd hate to
>think how bad the print quality would have been with some of the variation
>we see in Pb free HASL quality.
>
>Scott Post
>Staff Manufacturing Engineer
>P.O.U. 0000-001E-0CTC
>2151 E. Lincoln Road
>Kokomo, Indiana 46904-9005
>765-451-2983 (Phone)
>765-451-0287 (FAX)
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
>Sent: Thursday, June 02, 2011 11:37 AM
>To: [log in to unmask]
>Subject: Re: [TN] Best Board Finish - beyond gold
>
>Bob,
>
> As for flatness: once a PCB has paste printed can you even tell what the
>finish is? I have never been able to figure out this flatness thing.
>
> As for reliability I think solderability wins every time. Are you telling
>me these other finishes have better solderability than, well solder, as
>found only in a HASL finish? Has anyone ever seen "Black Pad" with HASL?
>There is no Ni so the P cannot be wrong, ever. Right?
>
> I fell like a stick in the mud on my bias towards HASL, I am open to ideas
>here.
>
>Bob K.
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob METCALF
>Sent: Thursday, June 02, 2011 11:18 AM
>To: [log in to unmask]
>Subject: Re: [TN] Best Board Finish - beyond gold
>
>When considering finishes, if the ultimate in reliability and surface
>flatness are key considerations, you must give electroless nickel,
>electroless palladium, immersion gold (ENEPIG) some consideration.
>
>Regards,
>
>Bob Metcalf
>Western Regional Manager
>
>Atotech USA Inc
>1750 Overview Drive
>Rock Hill, South Carolina 29730 USA
>
>Mobile: 714-334-7667
>e-mail: [log in to unmask]
>Internet: www.atotech.com
>
>Managing Director: Kuldip Johal
>
>This e-mail and any attachments hereto are business documents of Atotech USA
>Inc. and may contain CONFIDENTIAL OR PROPRIETARY BUSINESS INFORMATION.
> Unauthorized disclosure and/or use of information contained in this e-mail
>are prohibited. If you are not the intended recipient, you should dispose
>of it and not use, disseminate or copy this message or any other files
>transmitted with it.
>
>
>
>.
>
>
>
>
>
>
>
>
>
>
>
>
>From: "Stadem, Richard D." <[log in to unmask]>
>To: <[log in to unmask]>
>Date: 06/02/2011 07:46 AM
>Subject: Re: [TN] Best Board Finish - beyond gold
>Sent by: TechNet <[log in to unmask]>
>
>
>
>I agree with everything you say, Barbara. It sounds like you are now on your
>way to making the correct choice.
>Stay away from immersion tin.
>If you choose immersion silver, refer to both IPC 1601 and IPC 4553 for
>storage and handling considerations. They can be managed.
>The double-sided process can leave a slight reduction of solderability with
>immersion silver PWBs by the time you are ready to hand solder any PTH
>parts, making that more difficult to do, sometimes.
>That is why I asked.
>Also, if you select Immersion Silver, make sure that your PWB fabricator
>has a good plating product, a well controlled process and some experience
>with it.
>Ditto with ENIG. Especially with ENIG.
>Regarding immersion silver, it is susceptible to environments that are heavy
>in sulfides, such as automotive exhaust, rubber processing, or paper
>processing. Keep some of these things in mind both from an end-use
>environment standpoint and from a storage standpoint. Do not store in areas
>where there are open containers of soaps, fluxes, etc., nearby.
>
>From: Barbara Burcham [mailto:[log in to unmask]]
>Sent: Thursday, June 02, 2011 9:22 AM
>To: Stadem, Richard D.
>Cc: TechNet E-Mail Forum
>Subject: Re: [TN] Best Board Finish - beyond gold
>
>Thanks everyone for you imput. What a great group of people!
>
>Richard,
>The application will be double sided, fine pitch array components, some
>through hole components and going into a shock environment.
>I will need to connect with the assemblers to check on flux and paste
>compounds. Does this information help? You make an excellent point. Must
>have the total picture. I do not know, yet, how long boards will sit on the
>shelf before moving into assembly, either. I do know that shelf life will
>also impact this decision.
>I do not think that I want to use tin...that hairy growth stuff.
>Barbara
>
>
>
>On Thu, Jun 2, 2011 at 8:01 AM, Stadem, Richard D. <[log in to unmask]<
>mailto:[log in to unmask]>> wrote:
>Barbara,
>What is the application, board type, component types, etc?
>Immersion silver is my personal favorite, but that is completely irrelevant.
>You should choose a board finish dependent upon the application of the CCA,
>whether it has fine-pitch array components, including CSPs, whether it is
>double-sided with PTH parts or hand-soldered components, the environment the
>CCA will be used in, the flux type to be used, the alloy that is required,
>and several other factors that go into the decision.
>Without complete knowledge of all these factors, it is hard for anyone to
>answer that question. I can tell you that IAg beats ENIG in cost, but each
>finish has strengths and weaknesses. Some definitely have more or less than
>others.
>
>
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]<mailto:[log in to unmask]>] On Behalf Of
>Barbara Burcham
>Sent: Wednesday, June 01, 2011 8:17 PM
>To: [log in to unmask]<mailto:[log in to unmask]>
>Subject: [TN] Best Board Finish - beyond gold Hey Y'all, I am looking for a
>reliable bare board finish that beats the cost of gold.
>What experience is out there?
>What would you recommend?
>Thanks,
>Barbara Burcham
>pcb Trace Design
>[log in to unmask]<mailto:[log in to unmask]>
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