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
>