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Wave soldering of PTH components with pitch 1.27mm

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Wave soldering of PTH components with pitch 1.27mm | 8 July, 2010


this is my first post in this forum, but sometimes I visit it to get some news. Now we have an issue and I need your advice.

Few months ago we were awarded with a project that use PTH components. We solder these components on Wave soldering process, but we have a lot of short circuits - more than 20%. This is not the first project with PTH components, but this is the first one with 1.27mm pitch between the leads of the components. Because Customer do not allow us to do rework, we have to scrap all the modules with this defect. Components has 4 leads with pitch 1.27mm between. the leads. We try a lot of different changes in process to reduce shorts, but without success - we have play with wave soldering process parameters, we shorten the length of the component's leads etc. I would like to ask you, if somebody has such kind of issue and already solve it to give me some advice how to proceed.

Thank you Best Regards, Bozhidar

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Wave soldering of PTH components with pitch 1.27mm | 8 July, 2010

There are several things that can be done. Shortening the lead length should eliminate bridging between lead. We had done a project several years ago where the customer had shortened the leads to almost flush to the board, preventing any chance of component bridging. Another possibility is adding solder thieves to the board, preventing the bridge.

If you are gluing any component on the bottom side of the board, you can add glue dots in between the leads you are attempting to solder. Because solder won’t stick to the glue and it will help to break the bridges.

Last but not least, we are a fixture fabricator and one the project with the short leads, we actually had to bow the board down to assure complete solder fill. On a different project, we were actually able to eliminate the bridging with thin webs of material in between the leads, preventing the bridge.

In addition to leaving the material between the lead to break the bridge, we can also mask test points that can some times pick up solder and cause shorts.

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