David,

The IPC-D-275 task group is working on its replacement (IPC-2221), infact the group met on July 14 & 15 and discussed just this topic.

Here is the change that is coming down the road:

"The nominal hole size for solderability testing shall be the diameter of the smallest, solder-coated hole on the board and the nominal land size shall be the diameter of the land used for that hole. For thermal stress, the nominal hole size shall be the diameter of the smallest hole and the nominal land size shall be the the diameter of the land used for that hole."


Lisa Williams
IPC


>>> David Tyler <[log in to unmask]> 08/06/97 11:51AM >>>
Hello Technet
I'm having discussions with some of our PCB suppliers concerning the IPC
"B" coupon spec. which requires the holes to be drilled with the smallest
hole size used on the associated PCB.  The problem is that hole sizes have
been decreasing and we no longer feel that the smallest hole is
representative of the board.  Not only that but we (the end user) are
finding it increasingly difficult to microsection these coupons for quality
assurance purposes.  It is very difficult to get to the center of holes
below .030 inches.  We are using a PC Met Jr. to fixture the coupons for
grinding and an Ecomet to do the grinding.  So the question is, should we
spec. the most numerous component holes to be drilled instead, is the IPC
considering a different spec. or should we consider other equipment?  If
there is anyone who has encountered (and overcome) this problem I would
appreciate the feedback.

Thanks
David Tyler
Inspection Services
Teradyne Inc.
179 Lincoln St.
Boston, MA 02111