Many thanks for your insightful reply.

I think that the stresses involved with these parts are the same as other
butt joints, so I would just copy the criteria from those. That is what we
are going to begin doing on all of our assembly notes--adding that if the
vendor considers any parts to be in the "Special" category they are
required to propose criteria, and if there are any components with leads
which are edge soldered, they are to be considered "butt joints" and will
need to meet the criteria of the "through hole components modified for
surface mount": Unacceptable for Class 3 and must not have any overhang for
Class 2. My preference would be to also add more stringent fillet
requirements but that is definitely complicated!

I understand that it takes a lot of time to haggle around the specific
criteria, but it is better to have a standard which needs some tweaking
than no standard at all!

Wayne Thayer

On Tue, Mar 29, 2022 at 8:28 AM Hillman, David D Collins <
[log in to unmask]> wrote:

> Hi Wayne - one thing to consider is that the JSTD-001/610 committee
> receives numerous requests to "just add this component" to the
> specifications with no additional information provided. Since adding
> criteria to the JSTD-001/610 specification costs the industry money (i.e.
> training, education, documentation, etc.), the committee expects, at a
> minimum, to receive a proposed set of solder joint criteria for each of the
> classes and supporting reliability data reflecting those proposed
> criteria.  As you detailed, the proposed criteria needs to be of high
> quality to support being added to the industry standard. Unfortunately the
> majority of component submissions are not accepted due to a lack of data
> which is one reason the inclusion of new component styles/types is not a
> fast action.
>
> Dave Hillman
> Collins Aerospace
>
> -----Original Message-----
> From: TechNet <[log in to unmask]> On Behalf Of Wayne Thayer
> Sent: Tuesday, March 29, 2022 9:48 AM
> To: [log in to unmask]
> Subject: [External] Re: [TN] EXTERNAL: [TN] Specialized Connections
>
> Hi Ben-
>
> Well said.
>
> I see an epidemic of poorly designed systems using these types of joints.
>
> As these "special" connections are now commonplace, perhaps it is time for
> IPC to update the butt joint section to include them. Or perhaps include
> their own section called "highly stressed solder joints". After all, that's
> the predominant engineering challenge with these things: (Pin-to-pad
> contact area) / (potential lever arm) is relatively small, especially when
> compared to the pin stiffness.
>
> Wayne Thayer
>
> On Mon, Mar 28, 2022 at 12:27 PM Gumpert, Ben <[log in to unmask]>
> wrote:
>
> > Wayne,
> >
> > Since J-STD-001 and IPC-A-610 describe what has traditionally been
> > considered a butt-joint as PTH parts that have been trimmed to the
> > butt configuration, and mentions new "versions" of a butt joint such
> > as those used in solder-charged connections, I see the termination
> > shown in 8-180 as "different" from the butt joints that are not
> > permitted. So they are "special".
> >
> > I agree with you that "special" terminations need to have acceptance
> > criteria agreed to with the customer, so if that's done, then it
> > wouldn't matter if they were butt joints since that would imply that
> > they are documented in the engineering and therefore take precedence
> > over the J-STD-001/IPC-A-610. Unless you could convince yourself that
> > other criteria in the J-STD-001 is close enough to be applicable (they
> > are kind of butt-joints so that the butt joint criteria applies, but
> > not really butt-joints so the prohibition doesn't? lol)
> >
> >
> > Ben Gumpert
> >
> >
> > -----Original Message-----
> > From: TechNet <[log in to unmask]> On Behalf Of Wayne Thayer
> > Sent: Saturday, March 26, 2022 11:18 AM
> > To: [log in to unmask]
> > Subject: EXTERNAL: [TN] Specialized Connections
> >
> > Over the last 15 years there has been an explosion in the availability
> > of surface mount board-to-board connections. Some of these use
> > traditional folded pins, but more and more are using stamped pins with
> > no stress limiting bends in the connection.
> >
> > Photo 8-181 in IPC-A-610H Section 8.4 is an example of this.
> >
> > Can someone explain to me why IPC calls these "special" as opposed to
> > what they are: butt joints? I have a module supplier who claims the
> > butt joint requirements don't apply because they are "special". Thus,
> > whereas butt joints are dis-allowed in Class 3 and must not overhang
> > the pad for Class 2, this module supplier claims they are fine. No doubt
> the "butt joint"
> > section of 610 should be updated to explicitly show this type of
> > termination, but anyone who categorizes soldered interconnects would
> > have to label these as common butt joints (where the metal is sheared
> > out of whatever stock it is made from and then soldered with the
> > sheared side against the pad.
> >
> > If there were only a few of these types of connectors on the market,
> > or if they were seldom used, the "special" would be a valid term. But
> > today industrial PCBAs I see more commonly have these than not.
> >
> > (And yes, a supplier who uses the "special" clause still isn't out of
> > the "hot seat" because they are supposed to bring this up with the
> > customer when they accept the job.)
> >
> > By the way, another photograph in Section 8.4, 8-180, shows a standard
> > surface mount dual row header (which is made up of pins bent into an "L"
> > shape) with a surface mount to through hole adapter installed. What
> > makes that "special"? The fact it has something plugged into it? So if
> > it leaves the assembly plant without that adapter installed, it
> > wouldn't become "special" until a user plugged in that adapter socket?
> >
> > Thanks!
> >
> > Wayne Thayer
> >
>