Here is my 2 cents,

I agree with Mike Green on having a hard number for inspection purposes.

Because: 
Quality Inspectors are at times hard pressed to quantify a percentage of
an coverage area.  A hard number would give a definitive inspection
criteria for both fabricator and user.

Scott Montgomery
Boeing-Anaheim
Manager & Chief Technical Engineer
Electronic Design Support Department  
Business Phone: 714-762-3066




-----Original Message-----
From: Green, Mike [mailto:[log in to unmask]] 
Sent: Tuesday, April 19, 2005 9:32 AM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] Proposed IPC-6012B Change for SnPb in SMOBC


We also take the following exceptions:

FINAL FINISH PLATING MAY EXTEND .010 INCH MAXIMUM UNDER THE EDGE OF THE
SOLDER MASK, BUT SOLDER MASK IS NOT PERMITTED ON TERMINATION AREAS.

Instead of:

3.5.4.7.2 Tin-Lead under SMOBC
Tin or Tin Lead under SMOBC on areas not to be soldered is permitted on
1% of the conductor surfaces for Class 3 and 5% of the conductor
surfaces for Class 1 and 2.

Because:

Solder is not the only finish that is affected.
Termination areas need to be excluded.
The issues are generally relegated to the edges of the solder mask.

Mike Green
Production Design Engineering
Lockheed Martin Space Systems
Sunnyvale, CA 94089
office  408-743-1635
Synergy works at LMC.  "Show me the data."
Won company, Juan team, One process, Un slogan, 1 badge, I goal, Ein
mind, Aleph idea

-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]]On Behalf Of John Perry
Sent: Tuesday, April 19, 2005 9:05 AM
To: [log in to unmask]
Subject: [IPC-600-6012] Proposed IPC-6012B Change for SnPb in SMOBC

Colleagues,

The IPC D-33a Rigid Board Performance Task Group is beginning the
development of an Amendment 1 to IPC-6012 Revision B.  Relative to this
is a request to modify and append text in section 3.5.4.7, Final Finish
Coverage (Areas not to be soldered).

Background on change request:

A printed board was found to have small amounts of Tin Lead under the
solder mask with reflow/SMOBC finish.  The part has been fabricated
using the selective solder strip process.  The customer rejected the
parts for small amounts of tin lead found on bare copper and under the
solder mask, claiming with Tin Lead, the part no longer was Solder Mask
over Bare Copper.  There is currently no IPC specification that
prohibits such Tin Lead on the bare copper.  However, at some point it
becomes a workmanship issue per IPC 6012B paragraph 3.3.9.

Rationale for change request:

This new accept/reject criteria provides a check and balance for the tin
lead strip process (i.e., the process is not capable of absolute ZERO
tin lead as there is always trace amounts on some circuits) and at the
same time we don't want to be throwing away printed boards that are
functionally fine.

Proposed Change within 3.5.4.7 of IPC-6012B:

3.5.4.7 Final Finish Coverage
Final finish shall meet the solderability requirements of J-STD-003.

3.5.4.7.1 Exposed Copper (Areas not to be soldered) Exposed copper on
areas not to be soldered is permitted on 1% of the conductor surfaces
for Class 3 and 5% of the conductor surfaces for Class 1 and Class 2.
Coverage does not apply to vertical conductor edges.

3.5.4.7.2 Tin-Lead under SMOBC
Tin or Tin Lead under SMOBC on areas not to be soldered is permitted on
1% of the conductor surfaces for Class 3 and 5% of the conductor
surfaces for Class 1 and 2.

If you approve the proposed change without comment, please send your
approval, by May 3rd, to [log in to unmask]  If there is a need to comment
on and discuss this within the task group, please respond through this
e-mail forum.

Thanks,

John Perry
Technical Project Manager
IPC
3000 Lakeside Drive # 309S
Bannockburn, IL 60015
[log in to unmask]
1-847-597-2818 (Phone)
1-847-615-7105 (Fax)
1-847-615-7100 (Main)