In my old company I was the technical advisor for ou
Ioan,
In my old company I was the technical advisor for our surface finish specification document. For the most part this document specified the requirements sent by IPC and listed only exceptions to IPC specs. One exception we had was for SnPb HASL. As Dewey indicated without specifically stating a surface finish thickness the default requirement is 'coverage and solderable'. I always though the 'coverage and solderable' requirement was not very meaningful. We could look at a PCB and determine if the features were covered with solder but we couldn't determine if the PCB's were solderable unless we actually did soldering or ran IPC-JSTD-003, which is destructive. When fine pitch assembly began to be introduced we ran into many solderability issues with HASL PCBs because we want the HASL flat. If you don't blow hard during HASL we had issues with stencil printing on boards with fine pitch features. If we blew really hard during the HASL process we could get really flat features but unfortunately they weren't solderable because we didn't have any what I call 'fresh SnPb' on the features. All that was left on the features was copper-tin IMC that had oxidized and wasn't solderable. Many of our boards were too costly to sacrifice a sample for solderability testing. We therefore developed our own specification for non-destructive XRF measurement of HASL thickness. For our Class B boards the specification was Minimum >=60u", the minimum allowable thickness for the 5th percentile thickness (the thickness measurement that ranks in the 5 percentile of measurements) was >=100u", and maximum allowable thickness for the 95th percentile thickness (the thickness measurement that ranks in the 95th percentile of measurements was <-1000u" with and absolute maximum of 2400u".
If I had to use a PCB with a HASL surface finish (SnPb or Pb-Free) I know I wouldn't use 'coverage and solderable' but I think I'd still use the above require.
Regards,
George
George M. Wenger
Andrew Solutions
Senior Principal FMA / Reliability Engineer
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 [Office] (732) 309-8964 [Cell]
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey (EHCOE)
Sent: Wednesday, July 08, 2009 12:48 PM
To: [log in to unmask]
Subject: Re: [TN] PCB Solderability issues
Unless the requirement for a HASL surface finish thickness is specifically stated, the default requirement is coverage and solderable.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Wednesday, July 08, 2009 9:35 AM
To: [log in to unmask]
Subject: Re: [TN] PCB Solderability issues
Hi Ioan! You can assess the solderability of a HASL surface finish using
the IPC-JSTD-003 specification. The thickness of a surface finish has a
direct impact on the solderability and shelf life characteristics. The
JSTD-003 specification covers how to do the solderability testing. The
thickness requirement for a HASL surface finish would be in IPC-6012 or
per your internal requirements.
Dave Hillman
Rockwell Collins
[log in to unmask]
Ioan Tempea <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
07/08/2009 10:59 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Ioan Tempea <[log in to unmask]>
To
[log in to unmask]
cc
Subject
[TN] PCB Solderability issues
Dear Technos,
The PCB HASL wetting issues saga is not over. The PCB fab told me they are
doing XRF on the pads. Does this have anything in common with
solderability assessment?
What would be the methods of measuring solderability of HASL bare boards?
And what are the pass limits?
Thank you,
Ioan Tempea, ing.
Ingénieur Principal Fabrication / Sr. Manufacturing Engineer
30 ans déjà! - Already 30 years!
950 rue Bergar, Laval, Québec, H7L 5A1
t : 450-967-7100 ext : 244
Mtl : 514-990-5762
f : 450-967-7444
[log in to unmask] <mailto:[log in to unmask]>
www.digico.cc <http://www.digico.cc/>
P N'imprimer que si nécessaire - Print only if you must
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