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Reply To: | TechNet E-Mail Forum. |
Date: | Sat, 11 May 2002 16:36:24 EDT |
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Carl, All Concerned:
- No conflict exists within IPC-A-610C regarding vertical fill of PTH's. For
Class 3 products: Table 6-2 requires the vertical fill to be a minimum of
75%; Figure 6-5 on page 6-6 restates that if the vertical fill of hole is
less than 75% it is a defect for both Class 2 and 3. Figure 6-7 on page 6-7
lists an exception that applies only to a Class 2 product. That exception is
that it is Acceptable for a Class 2 product if the vertical fill of the hole
is only 50% as long as the limited vertical fill is due to a PWB design that
results in thermal swamping of that particular PTH (note that adjacent PTH's
are required to meet the requirements of Table 6-2). The indication that the
50% vertical fill applies only to a Class 2 is found adjacent to Figure 6-7
where it says that: 1) no vertical fill requirement is specified for Class 1
(consistent with the requirement of Table 6-2), 2) 50% vertical fill is
acceptable for Class 2 ONLY when it is known to be caused by heat sinking of
that specific PTH, and 3) less than 50% vertical fill of the PTH is a Defect
for Class 3 (consistent with Table 6-2 and the Defect listed adjacent to
Figure 6-5.
Hope the above clarifies the intent of the requirements. By the way, the IPC
is preparing to publish a document called IPC-HDBK-610 (or something like
that). It is, as the name implies, a handbook that explains the rationale
behind, and reasons for, some of the requirements in IPC-A-610.
Regards, Jim Moffitt, Moffitt Consulting Services, Noblesville IN
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