wave soldering and solder bridge

First of all, more info is needed. Solder shorts can be caused by much more than flux. Is the solder short always in the same spot or all over the place? More detail please.

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I recently had the same problems, solder bridges on every thing I made, different customers boards, etc. I wave with no-clean flux. As I sorted out problems (pin holes, blow holes, splatter, etc.) I found a lot of variable factors.

I changed flux, went more aggresive. It improved solderability significantly.(even improved top solder where all other efforts failed. I found with parts on the shelf too long that oxidation occurred. I found that component tinning (under 50x microscope) was poor.(Supplier problem). I found solder tail lengths on connectors are too long, lead protrusion caused the same defect repeatably. There are generic parts made, one size fits all. That does not always work.

Use SPC defect data collection by assembly, location, defect type. Pareto results. Be sure to differentiate from SMT and through hole. I follow IPC-9261A and also IPC-7921A. They are both for DPMO (defects per million opportunities), you can trend chart PPM, also use collected data for Pareto (top ten defects per assembly).

Contact me for excel spread sheet format. I can help get you started if you do not collect data.

DaveF- chime in if I missed sumtin, I know you have much more. Happy Holidays to you and the wife. Got some Californy spill with your name on it if you ever get to Vegas.

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5 Steps to Eliminate Bridges:

1. Establish (wave) Parallelism First and foremost, you must establish board-to-wave parallelism. This is the prerequisite to any wave solder process control. For an understanding of the power of this approach go to http://www.WaveSoldering.com/WSO/Parallelism.htm. Remember, you must establish parallelism from -0.2 seconds to +0.2 seconds based on your left and right dwell times. Disparallelism causes bridging!

2. The Secret Technique of Marking Your Fingers All our best customers are using this simple technique. It eliminates your fingers as a variable in your board quality. Parallelism readings that are taken in the context of this technique are meaningful and helpful; parallelism readings taken outside of this framework are not reliable. Affix the special finger marking stickers to your wave machine today. Use them right away and call us if you have any questions. Full implementation of steps one and two can immediately reduce a significant amount of your bridging.

3. Control Immersion Depth For the significant amount of bridging that may remain, the next step is to measure and control immersion depth. Too deep an immersion depth causes bridging; too shallow causes insufficients. In general, for 62 mil thick boards you'll want an immersion depth reading from 36 to 48 mil. Remember, immersion depth is not wave height, lead clearance or pump speed. Also, immersion depth variation directly changes your dwell time. A shallower immersion depth produces a shorter dwell time while a deeper immersion depth produces a longer dwell time. To ensure repeatability, are you verifying your immersion depth by measuring it every shift and with every board changeover?

4. Optimize Dwell Time This is the single most powerful process technique in wave soldering! After steps 1, 2 and 3 you are ready to optimize your dwell times by board type. Too long a dwell time causes bridging. To reduce bridging, shorten your dwell time by increasing your conveyor speed. This is simple, quick and immediately makes your life easier. Go to http://www.WaveSoldering.com/WSO/DwellTime.htm for background and procedures. Dwell time is the time each lead is in your wave, not the amount of time a board is in the wave. And remember, your dwell time is directly determined not only by your conveyor speed, but also by your immersion depth, contact length and wave shape. Have you identified the best dwell time for each board type that you assemble, and do you verify optimal dwell times every shift?

5. Improve Solder Conditions Your solder conditions are a factor in your bridging. One condition is dross, which on its own can cause bridging. Another condition is the viscosity of your solder. Adjusting your solder temperature can reduce bridging. Your solder temperature should be independently measured every shift.

� Technology Information Corporation 2003 (240) 221-0590

Some others are:

1. Component orientation- DIP leads should hit wave parallel, not perpendicular 2. Flux deposit- not enough, not uniform 3. Excessive dross in wave 4. Contaminated of solder, PWBs or components 5. Solder temp too low 6. Preheaters too low or too high 7. Improper board handling 8. Conveyor angle- 5, 6 or 7 degree

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