Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


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Help!! | 5 November, 2005


We are having insufficient hole fill only at DIMM connector area(120 pin/row total two or 4 rows at that area) when we switch to lead free (SAC and Sn/Cu). The finish we using is immersion silver. Preheat on top side ~98-118oC. Rosin flux type.Solder temp. 265 & 273oC respectively.Solder contact time 4 sec.Selective wave by pallet sheilding. We did try some combination but when there is good hole fill then we found voids in hole. What should be take care when running board with DIMM connector?

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Help!! | 8 November, 2005

First, general comments about voiding in wave soldered connections are: * Causes of voids in solder connection are many: moisture, flux/paste volatiles, wave process, etc. * Impact on reliability of voids in a PTH solder connection is insignificant, unless the voids contain chemicals that attack the surrounding metal. Mechanically, the component lead provides excellent connectivity redundancy to the solder and hole wall. Electrically, the amount of metal in the solder, connector, and hole wall are more that sufficient. * Requirements are ideally, no voids, but we�re unaware of a specification.

Second, areas for investigation in resolving this voiding issue are: * Look at cross sections and focus on the board hole wall/plating [eg: glass fibers protruding into the hole, nodules, skip plating, plating folds, etc] as well as on the solder/component lead. * If this is localized to a few components, consider: if the hole size is proper, if the component body needs to stood-off, etc.

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Help!! | 9 November, 2005


Thank you for your opinions. If I need to look at my wave process, which area do I need to check?

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Help!! | 9 November, 2005

Mandy, you chicken. You should throw that xray machine in the lake!!!

Typical DOE Wave Process would include: Trial Number|| Conveyor Speed (m/min)|| Preheat Temp. (C)|| Soldering Temp. (C)

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Help!! | 9 November, 2005

Wetting with lead free at wave is a bit different. You may need to increase your flux parameter to gain top side wetting. May get rid of the voids too.

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