Morgan,
Thanks for your answer.
So ideally if you can design to have an annular ring of 8, great. But you
know if you ned to you are allowed to go down to 2 mil on the outer layers.
You therefore need to talk to you PCB manufacture to get their drill
tolerance to work out the minimum pad size. Ours PCB manufacture has a
drill tolerance of +/-2mil.
So if you have an 8mil via, you need 4mil annular ring to meet the minimum
of 2 mil for class 3.
OK I understand that.
Sorry I have another question and it is again to do with what you have said
, it is a conflict between the two specifications.
We need to use a micro BGA. Based on our PCB manufactures capabilities in
the BGA area we need to use a blind via drilled at 6mil with a 14mil pad to
guarantee a 2mil annular ring.
But IPC-2221 states that the smallest blind via is 8 mil. Table 9-4. This
is just another design guide v IPC-6012 issue?
Many thanks for your time,
Larry
-----Original Message-----
From: Morgan Viggers <[log in to unmask]>
Sent: Friday 22 May 2020 16:22
To: [log in to unmask]; 'TechNet E-Mail Forum' <[log in to unmask]>
Subject: RE: [TN] IPC Class 2 v 3
IPC-2221 is a design guide, and Table 9-1 is one of the factors used in the
minimum pad size calculation in section 9.1.1. This would be used if you
were working on a new design and trying to decide what size pads to use. My
reference to Class 2 vs Class 3 annular ring is based on IPC-6012, which is
the industry standard performance/acceptance spec. So you'd use IPC-2221 to
design your boards so that they can ultimately meet IPC-6012. There are
plenty of conflicts that can be found, but I don't see a conflict in Table
9-1. But I might be misunderstanding your question.
Morgan Viggers
Field Applications Engineer
ISU Petasys
503.675.3877
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Friday, May 22, 2020 6:54 AM
To: 'Morgan Viggers' <[log in to unmask]>; 'TechNet E-Mail Forum'
<[log in to unmask]>
Subject: RE: [TN] IPC Class 2 v 3
Morgan,
Thank you so much for answering. I agree with you.
However this seems to contradict IPC-2221 Section 9.1.1 Looking at Table
9-1 it is stating a minimum of 0.2mm or 7.874 mil
Am I missing something here?
Thanks,
Larry
-----Original Message-----
From: Morgan Viggers <[log in to unmask]>
Sent: Friday 15 May 2020 20:08
To: 'TechNet E-Mail Forum' <[log in to unmask]>; [log in to unmask]
Subject: RE: [TN] IPC Class 2 v 3
Larry - there are a few major differences, but the one that most commonly
requires design changes is the via/PTH pad size. Class 2 allows 90 degree
drill to pad breakout, but Class 3 requires 1 mil annular ring remaining, so
Class 3 designs will typically need larger pads. Many other Class 3 items
(like plating thickness) often do not require any layout changes. A lot of
the other Class 2 vs Class 3 differences are in the sample and inspection
plans. If the design is already done, I suggest to just sent it to your
fabricator and ask them to review. They will be sure to point out any
design issues that currently prevent it from being fabricated to Class 3 -
and they make even be able to make any needed design changes themselves.
Morgan Viggers
Field Applications Engineer
ISU Petasys
503.675.3877
-----Original Message-----
From: Larry Brophy [mailto:[log in to unmask]]
Sent: Friday, May 15, 2020 3:24 AM
To: [log in to unmask]
Subject: [TN] IPC Class 2 v 3
Quick question,
If a PCB is designed to IPC Class 2, can I get the PCB manufacture to make
it Class 3?
If not, what areas do I need to ask the PCB designer to look at to make it
possible to manufacture as Class 3?
Thanks,
Larry
|
