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November 2009

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From:
Robert Kondner <[log in to unmask]>
Reply To:
Date:
Tue, 24 Nov 2009 22:11:33 -0500
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George,

  Thanks for the info and pictures.

 Flatness has not been an issue for me, with paste on the pad parts are held
in place well.

 I was trying to be open minded but I know I am biased by years of HASL
usage. 

  For my 6/6 rule, .5mm pitch parts HASL has worked fine. The thoughts of
doing a build with possibly defective finish, HASL or ENIG, is a horror
story I do not want to live. The pictures you sent with funny looking HASL
is something I can see. Having go out for XRF just seems like a pain.

 Thanks for the info.

Bob Kondner




-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
Sent: Tuesday, November 24, 2009 9:20 PM
To: [log in to unmask]
Subject: Re: [TN] solder fracture solderable?

Bob,



Going back many years in my previous company we used lots of HASL for many
telecommunications circuit packs.  We also had an extremely large captive
PCB board shop.  We also developed our own internal thickness specification
primarily because we felt the IPC "coverage and solderable" didn't provide a
useful specification.  It was easy to do incoming inspection on HASL boards.
If the copper features on the board were "covered" (i.e., the features
changed from copper color to tin color) that told us the boards had
"coverage".  To determine if the boards were "solderable" you would need to
do a destructive solderability test or actually solder the boards.  We felt
we needed a non-destructive test to know if features would be solderable
before we actually soldered to them.  We chose to use XRF as a non-contact,
non-destructive measurement tool.  We also used a Fischer XRF with a small
diameter (3mil dia.) collimator so that we could measure the HASL thickness
even on small size features.  Our internal SnPb HASL thickness specification
was:



Minimum: >/= 60u"

5th Percentile: >/= 100u"

95th Percentile: </= 1000u"

Maximum: </= 2400u"



This specification worked well for us for many years.  However, when our
products began to use lots of fine pitch surface mount components we had a
difficult time trying to keep the HASL surface both flat enough for fine
pitch and solderable enough.  We used to joke that HASL can be "flat or
solderable" the problem was you needed to pick which attribute you wanted
because you couldn't have both at the same time.  Joking a side, this
difficulty is the reason products began to migrate away from HASL to other
final surface finishes.  I've attached a file with four slides that
illustrate the type of thickness variation we saw on QFP features on SnPb
HASL boards.



You'll be able to see the file but since TN strips off attachments I've
copied Steve in case there are others on TN who might want to see the
slides.







Regards,



George



George M. Wenger



Andrew Wireless Solutions



Senior Principal FMA / Reliability Engineer



40 Technology Drive, Warren, NJ 07059



(908) 546-4531 [Office]  (732) 309-8964 [Mobile]



[log in to unmask]



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna
Sent: Tuesday, November 24, 2009 11:41 AM
To: [log in to unmask]
Subject: Re: [TN] solder fracture solderable?



Bob,

Right or wrong, HASL is a "coverage and solderable" finish.  Unless you're
Rockwell Collins you won't be able to enforce the thickness (poor RCPC).

Solderable HASL isn't necessarily measurable in cross section.  It depends
upon how flat the mount preparation is-- and it's hard to use the XRF where
the HASL usually gets thin (like the knees of a PTH).

Solderability (ideally including wetting balance) is your best bet.

Chris



Chris Mahanna

Robisan Laboratory



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner

Sent: Tuesday, November 24, 2009 11:04 AM

To: [log in to unmask]

Subject: Re: [TN] solder fracture solderable?



Dave,



 Thanks you.



 Any quick easy way for a lowly engineer to measure this thickness? Is it
obvious by eye and a simple lens or optical scope? Flatness is not an issue.



 Has anyone seen photos of Bad HASL that I can use for reference?



Thanks,

Bob Kondner



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman

Sent: Tuesday, November 24, 2009 10:55 AM

To: [log in to unmask]

Subject: Re: [TN] solder fracture solderable?



Hi Bob - we typically require 900 +/- 300 uinches for HASL thickness. Good
solderability life and reasonable flatness at those values.



Dave Hillman

Rockwell Collins

[log in to unmask]









Robert Kondner <[log in to unmask]> Sent by: TechNet
<[log in to unmask]>

11/24/2009 09:52 AM

Please respond to

[log in to unmask]





To

[log in to unmask]

cc



Subject

Re: [TN] solder fracture solderable?













Hi,



 Can anyone tell me what is involved to do a quick verification of HASL

solder coating thickness?



 Any number on minimal coating required to prevent under metal oxidation?



Thanks,

Bob Kondner







-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee Whiteman

Sent: Tuesday, November 24, 2009 10:26 AM

To: [log in to unmask]

Subject: Re: [TN] solder fracture solderable?



Blair,



Q1: How do those of us who purchase and use ENIG boards know that we are

getting good product? First, we clearly provide our requirements to our

board suppliers. Second, we inspect panels and coupons per IPC-6012. At

time, we would perform XRF analysis to confirm the thickness of the gold

and nickel layers.



Q2: Continual auditing of the supplier? We have performed off-site

(Incoming Inspection) and on-site audits of our suppliers.



Q3; SPC data for each shipment? While we don't require it, we have

access to their SPC data if there is a problem with the shipment.



Hope this helps. Good Luck.



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]



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair Hogg

Sent: Tuesday, November 24, 2009 10:00 AM

To: [log in to unmask]

Subject: Re: [TN] solder fracture solderable?



How do those of us who purchase and use ENIG boards know that we are

getting good product? Continual auditing of the supplier? SPC data for

each

shipment?



If you find a reliable source, how do you know they stay reliable? Or do

you

find a shipment comes in one day and you build a hundred boards with

high

failure rate?



Blair



On Mon, 23 Nov 2009 23:50:07 +0100, Inge <[log in to unmask]>

wrote:



>...and responsible operators....

>Inge

>

>

>----- Original Message -----

>From: "Joyce Koo" <[log in to unmask]>

>To: <[log in to unmask]>

>Sent: Monday, November 23, 2009 9:22 PM

>Subject: Re: [TN] solder fracture solderable?

>

>

>Bath chemistry and pH and temp.

>--------------------------

>Sent using BlackBerry

>

>

>----- Original Message -----

>From: TechNet <[log in to unmask]>

>To: [log in to unmask] <[log in to unmask]>

>Sent: Mon Nov 23 15:15:04 2009

>Subject: Re: [TN] solder fracture solderable?

>

>

> Hi Bob,

>No, you read it correctly, and put your finger squarely in the problem.

>Werner

>

>

>-----Original Message-----

>From: Robert Kondner <[log in to unmask]>

>To: [log in to unmask]

>Sent: Mon, Nov 23, 2009 3:10 pm

>Subject: Re: [TN] solder fracture solderable?

>

>

>Hi,

>

> The other week there was talk about ENIG vs HASL so I have been

searching

>around the web for ENIG info. I read a number of items.

>

> I recall reading that a phosphorus (in nickel) content of > 10% (I

think it

>was %) was required to control the Immersion Gold thickness and better

>control corrosion resistance. Wow, 10% sounds high but I guess that is

>right.

>

>  The photos show a P+ layer at the failed interface. Does that imply

>increasing P is a problem at making "Strong" soldered connections?

>

>  How does a lowly PCB user monitor this kind of parameter of

phosphorus so

>it is not too much or not too little?

>

>  Or did I misread the entire scenario?

>

>Thanks,

>Bob Kondner

>



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