| We have to mount our SMD devices 0.1 to 0.4 mm off the pcb | PCb substrate to compensate for thermal stressing in a | Space enviroment. Has any one any ideas or contacts for | dissolvable pads. this only applies to leadless components We have applications in our facility in which we glue our components, (not only chips but also LCC's to pwa's) for wave solder. Within this process we: Stencil solder on the pads of the pwa, dispense glue for the components, place the components, then reflow the solder. When we do this the resulting component is spaced up off the pwa the height that it was depressed into the paste by the pick and place (varies by placement pressure). This happens because the glue cures prior to the solder reflowing, which does not allow the component to "settle" down to the pwa the way it normally would during reflow. I've never measured the resulting standoff of the component from the pwa, or it's repeatability, but depending on stencil thickness I'm sure you would get .1mm (.0039"). If you have an auto adhesive dispenser, this could be a very repeatable process. I think this method would work better than the dissolvable pad method because preapplying the pads before stencil printing would make printed difficult and applying them after stencil printing could lead to smudging your prints.
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