| | R&D is currently designing a board with smt components on both sides of the board. They are adding a 16 pin IC Gull wing. on the bottom side of the board. I have asked for only caps and resistors to be placed on the bottom side. Is there a recommended direction for the IC and will I have problems through the wave. If I want to use the reflow for the thru hole components what do I ask for at the stencil house. | Pat, | Have the design guys orient the part in the direction of travel through the wave, like Jerry said, and have them put extra pads (for a total of 18) on the trailing edge. Solder tends to bridge between the last two leads of SOIC's, so if there's an extra dummy pad on each side, the solder will bridge the last lead to it instead of bidging the last two active leads together. | If you want to reflow through-hole components, there are design guidelines for stencil apertures and pad geometries, but it will still take a few experiments on your part. Particularly with your printing process. It depends on the viscosity of your paste, the type of blades you're using, if you're okay with printing extra solder on mask or hesitant because of solderballs, how thick you can go with the stencil (how fine is your finest pitch) etc. Then you must consider what through-hole parts you are | stuffing, and how good is your insertion system (manual, odd-form placer, AI equipment, etc). And finally, how full do you wan the barrels - is 50% okay? 75%? 100%? Full topside fillets?. It's highly do-able, but seems like a longer critical path to take when there's just one IC on the bottomside of the board. | If I were you, I'd put theive pads behind the SOIC, use about six glue dots under it, and run it over the wave. | Good luck, | Chrys Pat, I agree with Chrys 100%. Send it over the wave. Intrusive soldering is difficult at best. You have to either hand stuff the parts or have a good and FORGIVING odd form placer. If your board has a dense surface architecture, it's extremely difficult to print. You would probably need to use odd form apertures and thus would be required to do a ridiculous amount of geometry problems. There's also the issue of whether or not to use solder preforms to make up some paste volume. Wave it.... Regards, Justin Medernach
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