TECHNET Archives

May 2005

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:
Terry Kozlyk <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Terry Kozlyk <[log in to unmask]>
Date:
Tue, 10 May 2005 08:01:57 -0600
Content-Type:
text/plain
Parts/Attachments:
text/plain (222 lines)
Also, I have heard from a previous discussion on wether keeping
non-functional pads on inner layers also adds to the drill inaccuracy as the
drill is more probable of wandering off-centre going thru the copper. Though
keeping the inner non-functional pad adds to the strength of the PTH. A
typical PCB trade-off.

Regards
TDK



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Roger Stoops
Sent: Thursday, May 05, 2005 11:36 AM
To: [log in to unmask]
Subject: Re: [TN] Through hole drill accuracy


Good point and well taken, hadn't thought of that...

That must be why I'm in design and not in fabrication.  And those poor
fabricators that see my designs...ah, well.

Regards,
Roger

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jeffrey Bush
Sent: Thursday, May 05, 2005 1:13 PM
To: [log in to unmask]
Subject: Re: [TN] Through hole drill accuracy

Well, lets consider a tooling pin that is undersized in a tooling hole or
drill bed bushing that is oversized.  As you drill the panels will be moving
randomly and you will see variations hole to hole based on this tolerance
relationship.  Sometimes the mismatch will be in your favor and sometimes
you will see the extent of the gap.  This however cannot be ignored in the
consideration of capability for drilling as these frequencies will be seen
at one point or another in the resulting
products.

Jeffrey Bush
Director, Quality Assurance and Technical Support

VERMONT CIRCUITS INCORPORATED
  76 Technology Drive - POB 1890
    Brattleboro, Vermont 05302
      Voice: 802.257.4571.21 Fax: 802.257.0011
           http://www.vtcircuits.com


-----Original Message-----
From: Roger Stoops [mailto:[log in to unmask]]
Sent: Thursday, May 05, 2005 10:33 AM
To: [log in to unmask]
Subject: Re: [TN] Through hole drill accuracy

Thanks for the clarification.  However, for a given pattern or grouping of
plated holes on a board, pin tolerances would have little if any effect,
would they?  The only effect they would have is when moving a board stack
from one machine to another, correct?

If a particular press-fit connector required both plated and non-plated
holes, the additional tolerances added by the use of pins could become a
real concern.  But those new-fangled drill machines with vision capability
could help negate that, yes?  Excellon has some purdy machines...

Regards,
Roger

-----Original Message-----
From: Jeffrey Bush [mailto:[log in to unmask]]
Sent: Thursday, May 05, 2005 10:09 AM
To: TechNet E-Mail Forum; Roger Stoops
Subject: RE: [TN] Through hole drill accuracy

What about other factors in drilling beyond machine accuracy - pin
tolerance, pin to tooling tolerance, and pin to bed tolerance.  These
factors are also constituents in the overall drill accuracy beyond the
machine tolerances native to the process.

Jeffrey Bush
Director, Quality Assurance and Technical Support

VERMONT CIRCUITS INCORPORATED
  76 Technology Drive - POB 1890
    Brattleboro, Vermont 05302
      Voice: 802.257.4571.21 Fax: 802.257.0011
           http://www.vtcircuits.com


-----Original Message-----
From: Roger Stoops [mailto:[log in to unmask]]
Sent: Thursday, May 05, 2005 9:30 AM
To: [log in to unmask]
Subject: Re: [TN] Through hole drill accuracy

If the alignment is off by 2mils or more, sounds like your fab house needs
to check their drilling machine, or else use a better, more accurate one
than typically used.  The issue is one of positional accuracy plus
repeatability.  If a machine has a drilling accuracy of
+/-.001, positional accuracy of +/-.0005, and repeatability of +/-.0005,
then the total accumulated tolerance can be as large as +/-.002.

Sound like you need to specify a location tolerance (true position) of
+/-.0015 (or better) for the holes in question.  The wider the tolerance
for hole diameter, the narrower the tolerance for location accuracy, and
vice versa, for press-fit connectors.  IPC-2221 9.2.2 says you can expect
+/-.002 for fabs built to level B. Asking for Level C would give you
+/-.0015 tolerance. (If I'm missing something, somebody *please* set me on
the straight and narrow...)

Use of GD&T (IPC-2615) would help in specifying what you really want,
because tolerance zones with GD&T are round, not square as in the
(unfortunately) typical drawing practice.

All said and done: it's up to you to specify hole size, tolerance, *and*
accuracy for your design.  If you don't specify accuracy, the board vendor
may provide you with what's easy for them to make, to the widest tolerances
possible.


Best Regards,
Roger

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Scott Lefebvre
Sent: Wednesday, May 04, 2005 6:10 PM
To: [log in to unmask]
Subject: [TN] Through hole drill accuracy

I have looked profusely at IPC-6012 for a specification I could not find.  I
need to know if there is a specification for PTH drill accuracy and
repeatability.  We have a press-fit connector we are having problems with.
The component manufacturer tested one of our boards and said the alignment
is off 2 mils or more in some locations.  I could not find what is the spec
in IPC to reference to, could someone please point me to the correct
document I should look at.

Sincerely,

SCOTT L



---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or
(re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet
NOMAIL or (MAIL) To receive ONE mailing per day of all the
posts: send e-mail to [log in to unmask]: SET Technet Digest Search the
archives of previous posts at: http://listserv.ipc.org/archives Please visit
IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100
ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or
(re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per
day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or
(re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per
day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16
for additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or
(re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet
NOMAIL or (MAIL) To receive ONE mailing per day of all the
posts: send e-mail to [log in to unmask]: SET Technet Digest Search the
archives of previous posts at: http://listserv.ipc.org/archives Please visit
IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100
ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 or
(re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet
NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send
e-mail to [log in to unmask]: SET Technet Digest Search the archives of
previous posts at: http://listserv.ipc.org/archives Please visit IPC web
site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100
ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------

ATOM RSS1 RSS2