Mike, things haven gotten a bit mixed up here, I think. Let me see if I can offer
some assistance.
(1) IPC has not issued any documentation I am aware of to state there there is an
error related to IPC-A-610B Figure 4-2. Something could have happened before my time,
but I can't find any records of it. This topic always invokes lively discussion
though.
(2) The words in 610B don't refer to PWBs attached to heat sinks; they refer to PWBs
with integral thermal challenges such as heavy internal layers (typically used for
power/ground/shields).
(3) There is no new standard/requirement with industry consensus, however several
industry ballots have already been conducted during development of the next revisions
to J-STD-001and IPC-A-160. There was no clear consensus to move away from the hole
fill requirements which have been in place for many years. Any user can take
exception to any part of any standard by putting their unique requirements or
acceptance criteria either on their drawings or in the contract. A note has been
proposed that also helps with understanding. Based on the two ballots conducted, IPC
considers that the hole-fill issue will be closed for this revision. It's been a long
and sometimes emotional discussion at quite a few meetings and as technology evolves
to the use of different solder alloys, future revision work will probably visit this
area again.
(4) I've quoted the words below from the proposed C Revision of 610. NOTE: THIS
REVISION HAS NOT YET BEEN BALLOTED FOR INDUSTRY CONSENSUS AND SHOULD NOT BE
CONSIDERED APPROVED. I'm shouting it because it's an important note.
(5) Less than 75% fill was a defect for 610B. The proposed wording in 610C still
shows it as a defect.
(6) The additional words proposed in 610C are for clarification of the original
intention.
(7) Experienced attendees at the committee meetings have stated many times that
normal processing should give 100% hole fill with good fillets both sides of the
board. Processes that are not fully optimized may result in less than 100% hole
fill.
(8) I suspect that our very knowledgable colleagues at MTTC (who are also actively
involved in the new standard development) were offering some words to help with
understanding the stated requirements of 610B. They may have been suggesting some
words that your customer could use in a contract to force a specific requirement.
They probably need to be involved directly in any further discussion when they are
being quoted.
From PROPOSED 610C:
"Class 1 Not Specified
Acceptable - Class 2
Defect - Class 3
As an exception to fill requirements on Table 6-2 on thermal heatsink planes plated
through holes, a 50% vertical fill of solder is permitted, but with solder extending
360º around the lead with 100% wetting from barrel walls to lead on the secondary
side, and surrounding PTHs meet requirements of Table 6-2.
Note: Less than 100% solder fill may not be acceptable in some applications (thermal
shock). The user is responsible for identifying these situations to the
manufacturer."
Hope this helps a bit in understanding, and please feel free to contact me directly
for more info. Jack
==========================================
APEX - the industry's premier trade show in Electronics
Manufacturing, March 12-16, 2000, Long Beach, California.
More information on website www.ipc.org/html/apex.htm
-----------
Jack Crawford, IPC Director of Assembly Standards and Technology
2215 Sanders Road, Northbrook IL 60062-6135
[log in to unmask]
847-790-5393
fax 847-509-9798
>>> Mike Meanor <[log in to unmask]> 06/09/99 03:24PM >>>
I have recently received a notification from a customer of mine that states:
"Clarification of heat sink/ground plane vertical fill of Solder requirements,
referenced in IPC-A-610B page 52 Figure 4-2 and associated paragraph."
In the notification the author writes that, per agreement with an IPC Master
Instructor at MTTC (Manufacturing Technology Training Center), there is an error in
the book.
IPC-A-610B page 52
Acceptable Class 1 & 2
Nonconforming Defect - Class 3
As an exception to fill requirements on Table 4-1 on thermal heat sink planes plated
through holes, a 50% vertical fill of solder is permitted, but with solder extending
360 degree around the lead with 100% wetting from barrel walls to lead on the solder
side.
The error is stated:
Because there is less solder allowed in the PTH for Class 1 & 2, what solder is there
must have 100% wetting to both barrel and lead as viewed from the primary side with
solder extending 360 degrees around the lead on the solder side.
New standard/requirement:
Class 2
All heat sink/ground plane holes must have 100% wetting of barrel to component lead
on the primary side.
Class 3
75% solder fill is required on PTH attached to heat sinks per Table 4-1.
My comment:
The changes proposed will be greater tolerances for assemblies with thermal heat sink
planes than that with out.
My understanding of the exception was to allow for the physical properties of the
thermal heat sink planes and the effects it has on normal processing of assemblies.
The changes suggested in this notification will make soldering of assemblies with
large thermal heat sink planes more difficult to achieve and actually has tighter
requirements than assemblies without the thermal planes.
Is this change really accurate, if so, please let me know the proposed changes to the
standard.
Michael Meanor
Director of Engineering
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