Jim,
        You mention at the bottom of your post that ANSI & IPC are
currently under revision. How would one go about submitting revision
suggestions to the committees? As a contract manufacturer, we see a
variety of situations that current standards can leave open to broad
interpretation both internally and externally.

Mike McMonagle
K*Tec Electronics

> -----Original Message-----
> From: [log in to unmask] [SMTP:[log in to unmask]]
> Sent: Thursday, July 02, 1998 8:54 AM
> To:   [log in to unmask]
> Subject:      [TN] ReDewetting
>
> 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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