TECHNET Archives

May 1998

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:
Andy Slade <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 19 May 1998 16:02:49 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (73 lines)
     Hi Paul,
     One possible solution to the problem is the use of "teardropping" or
     "snowman" pads that effectively increase the land area specifically at
     the circuit to pad interfaces with little or no effect on overall
     spacing.  This is fairly easily accomplished with most CAM/Tooling
     softwares these days and can be done by your board supplier.

     Hope this helps

     Andy Slade
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: [TN] FAB Land around via holes
Author:  Paul Gould <[log in to unmask]> at SMTPLink-Hadco
Date:    05/15/98 1:29 PM


Can anyone help with a query on land around via holes. I have a copy of
IPC-A-600 Rev E Aug 1995 which states for plated through holes the
minimum land between the track and pad and hole must not be less than
0.002" as a minimum standard. This means that misregistration towards
the track is not acceptable if the pad is reduced below 0.002" even if
there is no actual breakout. On the other hand, the hole is allowed to
break  out of the pad in any other direction by as much as half the
diameter. Clearly the two are incompatible with each other since with
registration that bad there is bound to be breakout towards tracks in
some areas.

Has there been a revision specifically for via holes only, or is there
any other specification relating to landless via holes as this criteria
is impossible to meet on some designs. The implications of meeting this
spec are to increase via pad size and/or reduce hole size which has
implications for design density and manufacturing cost.

Any views on this would be greatly appreciated. For production drilling
on large panels, what minimum land do you think would be needed at the
outset to guarantee minimum annular 0.002" on the finished panel taking
account of drill size and etch reduction also?

Best Regards
--
Paul Gould
[log in to unmask]
Isle of Wight,UK

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text
in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional
information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or
847-509-9700 ext.311
################################################################

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################


ATOM RSS1 RSS2