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October 2009

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From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Thu, 1 Oct 2009 07:30:27 -0500
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Hi Denny - my experience is with SnPb HASL and not Pbfree HASL so I don't 
have any use experience in that arena. There have been a number of good 
technical papers released this last year on Pbfree HASL. My "guess" is 
that the complexities of the Pbfree solder alloys may make Pbfree HASL 
have a tighter processing window but how that would translate into 
assembly surface finish properties/characteristics is still being 
developed/refined/defined in real time.

Dave



[log in to unmask] 
09/30/2009 05:41 PM

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Subject
Re: [TN] ENIG / HASL CO-PLANARITY






One question - are we talking about lead-free HASL for the world, or 
eutectic solder HASL for the USA?  Wouldn't lead-free HASL start to have 
the same copper erosion issues as lead-free re-work with solder fountains? 
 Or are we already talking about the newer lead-free SnCu+X alloys that 
have lower erosion potential?
 
Denny Fritz


-----Original Message-----
From: David D. Hillman <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, Sep 30, 2009 6:17 pm
Subject: Re: [TN] ENIG / HASL CO-PLANARITY

Hi Bob - The two disadvantages of HASL surface finishes are coplanarity 
and solderability - both due to improper processing of the HASL finish. 
Typically the pwb fabricator gets too aggressive with the hot air process 
parameter settings causing a thin HASL deposit that also becomes very 
"bumped" in terms of surface topography.  As you detailed, the advantages 
of HASL are great wetting and processability if properly applied. HASL 
also has very good use environmental resistance in comparison to either 
immersion tin or immersion silver.  We just need someone to figure out how 

to apply Unattainium to our pwbs and all our surface finish issues would 
go away.        : - )

Dave



"Robert Kondner" <[log in to unmask]> 
09/30/2009 04:50 PM
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Subject
RE: [TN] ENIG / HASL CO-PLANARITY






Dave,

  Since we stencil print the boards, and machine place onto the stencil
printed paste coplanarity does not seem like a issue.

  Other than coplanarity are there any other problems with a HASL finish?

Thanks,
Bob Kondner

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Wednesday, September 30, 2009 4:29 PM
To: [log in to unmask]
Subject: Re: [TN] ENIG / HASL CO-PLANARITY

Hi Paul - the reason the coplanarity issue comes up is that many folks 
have issues with getting consistent and reproducible HASL finish 
coplanarity. All of the pwb surface finishes have advantages/disadvantages 


and HASL is no exception. HASL surface finishes were the primary finish of 


choice for our surface mount lines for many years and as you detailed, we 
also ran a very successful process. However, the inherent coplanarity of 
the immersion surface finish family (ImAg, ImSn, and ENIG) is better than 
HASL for our approved group of pwb fabricators. I have little doubt that 
if I had more control over pwb fabricator selection, I would share your 
experience but I have found that the immersion surface finish family 
provides me an expanded process window for BGAs/CSPs and many of the new 
Bottom Terminated Component styles (such as QFNs, ). HASL is still one of 
our approved finishes but we now include the immersion surface finish 
family as additional options in our "tool box".

Dave Hillman
Rockwell Collins
[log in to unmask]




Paul Edwards <[log in to unmask]> 
09/30/2009 12:27 PM

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Subject
RE: [TN] ENIG / HASL CO-PLANARITY






Why does this always come up?

With everything that is said about the real and potential metallurgical 
problems with ENIG, how can ENIG be considered a good replacement for a 
HASLed PCB, unless you are considering only the PCB fabrication of RoHS 
boards or the bulk buying PCB materials ?

Look at the flatness numbers for HASLed PCBs...Unless you have huge pads 
and a very bad PCB fabricator the HASL thickness variation is typically no 


more than 0.0007" on standard part pads... That is better than the 
planarity on everything but LCCs and QFN type structures and well within 
the solder paste print height tolerances of most systems...

Besides the last time I checked we all put solder paste on pads before we 
stuck parts to the PCB so there is at least 0.004" of solder compliance to 


compensate for any bumping of the HASL...

Have built a lot of high-density high-rel PCAs and over a lot of years and 


I will take a HASLed PCA over any other kind of surface finish...

Paul

Paul Edwards
Surface Art Engineering


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Wednesday, September 30, 2009 7:54 AM
To: [log in to unmask]
Subject: Re: [TN] ENIG / HASL CO-PLANARITY

Hi Lee - You might try another approach with the customer. Image that you
have a very large, nonflexible beach ball and you are trying to balance it
on your local parking lot speed bump - if you are using a HASL finish and
processing BGAs or CSPs you are doing the same procedure. Sometimes having
a visual reference is worth a pound of tolerance measurements. Good Luck.

Dave Hillman
Rockwell Collins
[log in to unmask]




Lee Whiteman <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
09/25/2009 09:09 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
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Subject
[TN] ENIG / HASL CO-PLANARITY






Happy Friday.

Does anyone have a reference on comparing the co-planarity between ENIG
and HASL (SnPb)? I know that ENIG is more planar than HASL, but by how
much (quantifying the argument). I'm anticipating a question from my
customer on why I want to use ENIG instead of HASL for fine pitch
applications.

Thanks.

Lee Whiteman, PMP
Senior Member Engineering Staff
L-3 Communications East
Telephone: (856) 338-3508
FAX: (856) 338-2906
E-Mail: [log in to unmask]

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