Neil,

Take a look at some of the surface mountable DIP switches on the market
(from Aries, C&K, etc.).  These are often no more than the through hole   
DIL version with the leads cropped and bent outwards.  It should be quite
easy to bend the leads of a DIL component and cut them to a suitable
length, thus forming a gull wing lead type rather than a butt lead.

There are, however, some issues to watch out for..

- The formed leads must be co-planar, i.e. all leads should contact the
board surface.  The effect of poor coplanarity is well understood and
relates more to fine pitch technology than this much larger pitch
situation, but don't forget about it.

- The DIL component may not be compatible with the reflow process. The 
plastic packages may be damaged by the high temperatures and soaks. 
Remember that these components normally sit on the top-side during wave
soldering and are thermally isolated from the heat source, (i.e. the solder
wave). 

- If you use a ceramic DIP package you may also have difficulty with reflow
soldering as the component will act as a mini heat-sink.  I know one
company where the board was designed for reflow soldering of the CERDIP
and they had so many soldering problems that they now hand solder these
components in place at end of line.

- The solder pad size that you use is, of course, pretty important.  The pad
size will depend on the shape of the formed lead.  You need to ensure that
there is space behind the lead for a good heel fillet.  You may want to do
some calculations on pad size versus solder paste volume to ensure that
there is enough solder to form the joint.  You may find that you need a
pretty thick stencil to get sufficient solder in each joint.

- As for reliability data on this type of joint we have done some
basic testing, but I suggest that you call some of the DIP switch
manufacturers and get them to convince you about the reliability of their
connections !

Hope this helps...  


Brendan Mc Cormack
Senior Interconnect Engineer
AMT Ireland
Electronics Manufacturing Centre
University of Limerick
Limerick
Ireland

Tel. +353 61 331588
Fax. +353 61 330316





On Thu, 24 Aug 1995, Neil Sellars wrote:

> Does anyone have any experiences or commemts on converting DIL
> components to a  surface mounting which they can share with me?  Our
> current in house workmanship standards donot allow butt joint  solder
> joints. I have noted that in IPC SM   780  it talks 
> about forming these parts to a SOIC leadform shape. I would      
> appreciate any information on footprint/ landpad design, leadform 
> profiles and  solder joint reliability that anybody can send to me. 

> Regards 
> Neil Sellars
> Principal Engineer 
> Radstone Technology PLC
> UK  
>