Mark,

Hi!  In response to the email sent by Susan, I will clarify that my
intention is to use externals as well.  My reason is that normally we see
more laminate voids under the external pads than we see internally. If
internal layers (which may be designed much smaller) are only used to
determine the Zone B, then those voids under the external layers will be
nonconforming/rejectable.  As I stated in a previous response the military
and IPC-6013 use the layer extending furthest into the laminate (it does not
state to omit external layers).  IPC-6013 has a great picture representation
on page 16 showing the thermal zone boundaries.

Debora Obitz

-----Original Message-----
From: Susan Mansilla [mailto:[log in to unmask]]
Sent: Monday, January 27, 2003 4:55 PM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] Zone B Concept Clarification


Yea!  Hi Mark!  It is great to hear from you and to know that you are
continuing to chair both of these groups.  Having you cover both has been a
real
blessing and the thought that someone else might have to come in just as we
were making progress was a little scary.

The only clarification would be to number 2 - just make certain that we are
talking about internal lands and not external.

Susan

-----Original Message-----
From: IPC-600-6012 Mail Forum [mailto:[log in to unmask]]On Behalf Of
[log in to unmask]
Sent: Monday, January 27, 2003 1:15 PM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] Zone B Concept Clarification


Greetings to all;

Wow!  Judging by the volume of unread messages in my email que, it looks
like Susan has generated some excellent discussion for the 600-6012 Forum!
I apologize for my late entry into the discussion, especially after so many
people have provided excellent proposals/counterproposals and clarifications
to the existing Note 1 wording to IPC-6012A, Figure 3-5 and IPC-A-600F,
section 3.1.1.

If I understand the inputs correctly, these are the two differing inputs
that are being reviewed:

1.  Mike Hill provided a proposal that would add further clarification to
the existing Note 1 wording found in IPC-6012A.  An improved Figure 3-5
would be needed to accurately depict the "zigzag" or "staircase"
interpretation that Mike provided.  In the case of less than perfect inner
layer registration, you extend the vertical boundary for Zone B delineation
0.08mm beyond the end of each land  and then halfway down into the
dielectric spacing between that land and the next land  below it in the
stack up.

2.  Debora Obitz has provided a recommended proposal that would change the
IPC-6012A Note 1 wording to mirror what is currently found in IPC-A-600F.
This would result in the Zone B vertical boundary being extended 0.08mm
beyond the end of the land that extends the furthest into the laminate area.

If this is a correct summary of what has been proposed, please let me know.
I welcome additional inputs and feedback  from all members of this forum.

I agree with Randy Reed's comments that the 600-6012 email forum is the
correct means to discuss this issue as many committee members will not be
able to attend the interim meeting in Tempe or maybe not even the IPC Expo
in March.

After receiving additional feedback regarding this issue, I think that I
need John Perry's assistance in getting the proposals into the appropriate
format so that the forum can determine which proposal goes into the updated
drafts for IPC-6012B  and IPC-A-600G.

Thanks for your inputs / feedback regarding this topic.

Mark Buechner
Chairperson for 7-31a and D-33a Task Groups
Currently unemployed
Home phone  (603) 595-0075
email:      [log in to unmask]

***For those of you who were not aware, I was notified the week after
returning from the IPC annual meeting in New Orleans that I was included on
Teradyne's most recent layoff list.    I informed John Perry at the time
that I intended to continue on as the Chairperson for both the IPC-6012 and
IPC-A-600 committees during my job search.  If I do not land a future
position within the electronics industry, I will let John know immediately,
so that he can begin the search for a replacement.