A couple of comments regarding dewetting:
- Dewetting is a problem in ANY product, not just high reliability products.
- IMHO you should be looking for causative factors instead of looking for
references in the manufacturing standards (presumably to confirm/deny that
dewetting is a defect).
- Your questions didn't give a clue as to whether the problem is associated
with leaded components in pth, or with surface mount, so I'll try to cover
both briefly.  In answer to your questions, what standards apply and what
paragraphs of which standard can be applied to dewetting, the following
information, based on ANSI/J-STD-001B (Requirements for Soldered Electrical
and Electronic Assemblies) and IPC-A-610B (Acceptability of Electronic
Assemblies) is provided.
- For plated through holes:
1) ANSI/J-STD-001B.  Defect #  6 of Table 11-1 (Hardware Defects) refers to
par. 9.2.5.1 which says "The solder joint MUST provide evidence of good
wetting and plated through hole solder fill MUST meet the requirements of
Table 9-1 and Figure 9-3."   Table 9-1 and Figure 9-2 provide detailed
information regarding solder coverage and percent of wetting required.  Note
that when the word MUST is used it means that the requirement is mandatory for
all 3 Product classes.
2) IPC-A-610B.  Paragraph 4.1 includes Table 4-1 (comparable to Table 9-1 of
J-STD-001) which describes wetting requirements.  The text below Figure 4-3
requires an acceptable solder connection to have evidence of wetting and
adherence when the solder blends to the soldered surface or be considered a
Defect for all 3 Product classes.  Text below Figure 4-9 lists a solder
connection which has poor wetting as a Defect for all 3 Product classes.
A-610 includes multiple references to the effect that wetting is a required
attribute for a connection to be considered acceptable, but does not
specifically list dewetting as a Defect.
- For Surface Mount:
1) ANSI/J-STD-001B:  Wetting is not broadly or universally "required" for SMT
by the J-STD-001B.  Bear in mind that only the items listed as Hardware
Defects by Table 11-1 are actually considered "defects" (words in the text of
the document are essentially advisory in nature and failure to meet the
requirements of the text does not constitute a defect unless the condition is
listed in Table 11-1).    The solder connection criteria which can be applied
to SMT are in Table 11-1, Defect # 20 which references paragraph 9.2.4.1
(wetting is not a requirement of par. 9.2.4.1).  You can find some limited
requirements for wetting of SMT solder connections in the notes associated
with Tables 9-2 through 9-9 inclusive.
2) IPC-A-610B.  Par. 10.2.1 says (below Figure 10-9): "A properly wetted
fillet is not evident" is a Defect for all 3 Product classes.  Par. 10.2.2
says (below Figure 9-15): Dewetted or nonwetted joint is a Defect for all 3
Classes.  Also below Figure 10-22 absence of a properly wetted fillet is
defined as a Defect for all 3 Product classes.  The IPC-A-610B document
continues to require a properly wetted fillet for all classes of product
throughout Section 10 (Surface Mount Assemblies).
- Hope the above helps identify the source of the requirements.  Note that
both ANSI/J-STD-001B and IPC-A-610B are presently being revised.  One of the
goals of the revision committees is to clarify the requirements so that the
documents can be more easily understood and used.  If you can find time your
participation in the revision process would be welcomed.
Regards, Jim Moffitt, Moffitt Enterprises

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