Hi Luke --

Regarding the intrusive reflow process, I have found the following:

1.  This process involves either buying the component with solder
billets attached to the pins or using a special solder stencil
process, where paste is also deposited into the through hole.
2.  With regard to solder billets on the component itself, I've found a
company that supplies these items Teka - they call them SBL
(Solder/Flux Bearing Leads).
3.  With regard to the solder in hole technique,
there is apparently some debate over the most effective process to
use.  Some recommend a dual-stencil process (one for SMT and one for
through-hole); some recommend a specially designed single stencil.  In
addition to the two stencils, the dual-stencil process would require
two stencil printers.  The single stencil would appear to be the most
viable option, however further investigation is necessary to clear up
the design issues.  The biggest problem recognized so far appears to
be solder volume (or lack thereof).
4.  If the IR components were to stuffed automatically (P&P equipment),
attention would have to given to the prep of the parts (assuming lead
length would still need to be addressed) and feeding the parts to the
equipment.  I believe this is being addressed by P&P manufacturers
currently.  If the parts were to be manually stuffed, attention would
have to be given to the handling of the solder pasted boards.  The
workstation would need to be designed to allow access to the pasted
boards, assumable already fixtured pasted boards so as not to jar the
components out of place.
5.  Another concern is component compatibility.  Typical components
for this pocess are: connectors, PGA's, and sockets.  These components
may be distorted(and no longer sit flush) or stress cracked (due to their
manufacture incurred stresses cracking during reflow).
6.  Finally, and maybe most affecting at this stage, is the quality of the
solder joint created by IR.  This type of joint may need to be defined in
the IPC & J Standards.  The joint is somewhat different than typical joints in
cross-section.  This difference is mostly attributed to the amount and
manner of application of solder paste.  Also, there is a higher
likelihood of voids in the joint as the inherent gases of the process
are unable to escape easily due to the design of the typical component
(a connector, for example).  Some debate is going on as to whether the
voids strengthen or weaken the joint.   It is further suggested that
the IR joints be examined with X-ray equipment due to the non-standard
shape of the joint and the possibility of voids.

Hope some of that's helpful.

Regards,
Lainie Loveless
General Atronics Corp
Wyndmoor, PA
(215) 242-7336

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