Doug,
What you have is a self-inflicted design issue, not a supplier
quality issue. The supplier is doing the best job possible within the
restrictions that your design has imposed upon him. But as an OEM, you also
have the power to waive this particular workmanship specification outlined
in IPC-A-610. If you feel that the resulting products meets your
requirements for fit/form/function quality until the design can be
corrected.
In the event that you do attempt to have the supplier provide greater
barrel fill, remember that you may do more harm than good. Trying to add
additional fill from the bottom will require enormous amounts of heat to
allow flow of additional solder, potentially causing barrel and laminate
damage. Trying to add it from the top will do the same, and probably just
cover the upper surface of the barrel and trap flux inside the connection.
Having been there and done that before, even if you could wave the board
and part you would have quite a challenge in getting good (read: IPC-A-610)
barrel fill. Try performing cross sections of the existing joints to assure
that you have good overall joint integrity with what fill you have, and pull
tests to assure that the fill that is there provides adequate physical
strength. You will most likely find that the lead will break or the entire
barrel pull out before the joint itself fails.
Mike McMonagle
Senior SMT Engineer
Telxon Corporation
(713) 307-2443 Phone
(713) 307-2581 Fax
www.telxon.com
' Innovative Solutions for
Mobile Information and
Wireless Communications'
-----Original Message-----
From: Doug Smith (EWU) [mailto:[log in to unmask]]
Sent: Thursday, November 30, 2000 12:08 PM
To: [log in to unmask]
Subject: [TN] IPC-A-610 Barrel Vertical Fill Interpretation
To all TechNet members,
I am requesting assistance with the intent interpretation of the barrel
vertical fill requirement with ground plane exception in section 4.1 of the
IPC-A-610 revision B.
History:
I have a board design with two 1.0 oz ground planes at layers 4 and 8 in a
12 layer board. The engineer designed an ineffective thermal relief pad to
connect a leaded component's ground through-hole to the ground plane. Also
the component involved can not be wave solder due to thermal restrictions of
it's design. To make the situation worse, the component's ground lead,
which causing all the problems, is connected directly to the steal shielding
measuring 2x2x1. Our contract manufacture is not able to solder past the
first ground plane which leaves a 30% vertical fill. Our requirement is
Class 2, 75% vertical fill except when there is a thermal plane. We are in
the process of redoing the design but I need assistance with defending the
supplier.
Question:
Figure 4-2 shows the vertical fill stopping at the Metal
Core/Thermal/Heatsink plane half way through the board. The paragraph
following states that the vertical fill has to be 50% when there is a
thermal heat sink plane. Our design uses the ground plains as
thermal/heatsinks. Is the intent of the picture and the text to state that
it is allowable for the solder not to pass the thermal plane. With my
design, would it be acceptable to have a vertical fill of 30%.
Please reply with your opinions to my question,
Thank You,
Doug Smith
Supplier Quality Engineer.
[log in to unmask]
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