TECHNET Archives

January 2002

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 15 Jan 2002 13:21:01 -0600
Content-Type:
text/plain
Parts/Attachments:
text/plain (242 lines)
Well drilling is not my thing either, but doing the mechanics the idea that
.0014" thick (1oz) typical, of copper can even affect the drilling is a stretch,
the total glass is about .060 thick and is stacked up many boards thick at a
time in drilling. Glass is harder and much more damaging to metal drills that
very thin copper films. Also the gumming of the epoxies loading the bits would
affect the drilling. All of this can be accounted for in the (hit count) on bits
and they are change automatically.

The amount of copper thickness provided by the inter layer planes is very little
compared to the other materials. However it does make for stress risers at their
intersection with the hole plating. Another place you can see the stress risers
starting cracks is on the "knee" if the PTH, there is a pad there with plating
flowing over it.

The thickness of 2 sided boards is relative and can be .015 to .125 easily the
same as MLBs.

Maybe Susan M. @ Robisan can way in, or Werner can set us all strait.








"Hinners Hans M Civ WRALC/LUGE" <[log in to unmask]> on 01/15/2002
11:43:34 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to
      "Hinners Hans M Civ WRALC/LUGE" <[log in to unmask]>








 To:       [log in to unmask]

 cc:       (bcc: Warren Crow/US/I-O INC)



 Subject:  Re: [TN] Remove unused "dead" pads on internal
           layers








Hey Warren,

Granted, Drill isn't my specialty but I've always heard that additional pads
in the drilled stack can help.  I'll hazard a guess, since Coombs isn't
readily available, the additional metal gives the bit something to dig into
being softer than the surrounding glass fiber & epoxy resin.   What would be
the benefit of softer layers in a drill stack?  Could that improve hole wall
quality?  Reduce drill wander/wobble?  I'm assuming the right feed, speed
and chip load have been used.  Somebody steer me in the right direction here
- I'm learning.

Obviously, a double sided board doesn't have inner layers and they tend to
be a bit thinner than the high layer count boards I'm used to processing.

Hans

Integrity First  -  Service Before Self  -  Excellence in All We Do
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hans M. Hinners
Electronics Engineer
Warner Robins - Air Logistics Center (WR-ALC/LUGE)
226 Cochran Street
Robins AFB GA 31098-1622

mailto:[log in to unmask]

Com: (478) 926 - 5224
Fax:   (478) 926 - 4911
DSN Prefix: 468


-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Tuesday, January 15, 2002 11:50 AM
To: TechNet E-Mail Forum.; Hinners Hans M Civ WRALC/LUGE
Subject: Re: [TN] Remove unused "dead" pads on internal layers




Actually the cracked vias I have witnessed in the inter barrell tend to
start at
the intersection of the copper planes. A corner or stress riser starts the
crack
during thermal shock tests. Don't understand how the extra non- connected
pads
could help barrell, if so then there is no hope for a 2 sided board.







"Hinners Hans M Civ WRALC/LUGE" <[log in to unmask]> on 01/15/2002
07:40:50 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
to
      "Hinners Hans M Civ WRALC/LUGE" <[log in to unmask]>











 To:       [log in to unmask]

 cc:       (bcc: Warren Crow/US/I-O INC)



 Subject:  Re: [TN] Remove unused "dead" pads on internal
           layers








Hi Patrick,

As others have said, I don't think the class of board matters for "unused"
pads.  It all depends on what your procurement documentation states, are you
building to drawing or is there a clause that says process improvements that
do not affect functionality are permissible.

"Are they really unused pads?"

They may be electrically nonfunctioning but they are there for a reason -
better lamination quality (avoiding low pressure areas or excessive prepreg
flow), better hole wall quality, better plating quality (esp. for any
isolated traces), reduced loading of your etch solution or better thermal
loading during assembly.

Hans

Integrity First  -  Service Before Self  -  Excellence in All We Do
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hans M. Hinners
Electronics Engineer
Warner Robins - Air Logistics Center (WR-ALC/LUGE)
226 Cochran Street
Robins AFB GA 31098-1622

mailto:[log in to unmask]

Com: (478) 926 - 5224
Fax:   (478) 926 - 4911
DSN Prefix: 468


-----Original Message-----
From: Patrick Lam [mailto:[log in to unmask]]
Sent: Friday, January 11, 2002 5:12 PM
To: [log in to unmask]
Subject: [TN] Remove unused "dead" pads on internal layers


Hi TechNetters,

For class 3 boards, is it acceptable to have unused pads removed on
interanal
layers.

Thanks,
Pat
This e-mail may contain SEL confidential information.  The opinions
expressed
are not necessarily those of SEL.  Any unauthorized disclosure, distribution
or
other use is prohibited.  If you received this e-mail in error, please
notify
the sender, permanently delete it, and destroy any printout.  Thank you.

----------------------------------------------------------------------------
-----

Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET
Technet NOMAIL
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search previous postings at: www.ipc.org > On-Line Resources & Databases >
E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
----------------------------------------------------------------------------
-----

---------------------------------------------------------------------------------

Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET
Technet NOMAIL
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search previous postings at: www.ipc.org > On-Line Resources & Databases >
E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
---------------------------------------------------------------------------------

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------

ATOM RSS1 RSS2