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June 2011

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From:
Robert Kondner <[log in to unmask]>
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Date:
Thu, 2 Jun 2011 13:20:33 -0400
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Joyce,

  No Depends About it. Once paste is applied all finishes look identical.

Bob K.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joyce Koo
Sent: Thursday, June 02, 2011 1:18 PM
To: [log in to unmask]
Subject: Re: [TN] Best Board Finish - beyond gold

It depends.  Some HASL are really flat.  It is all vendor dependent.  Want
HASL with super clean (no trapped oil, glycol, etc), low IMC, flat and
cheap, is hard to get.  
--------------------------
Sent using BlackBerry


----- Original Message -----
From: Post, Scott E [mailto:[log in to unmask]]
Sent: Thursday, June 02, 2011 12:33 PM
To: [log in to unmask] <[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
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.












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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