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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.




CONNECTOR ISSUE | 30 May, 2000

Problems with dry joints on a 184 pin Berg connector with locating pins.Using a 0.005"screen, on a n-tek finished board and using Nitrogen. The problem is really intermittent.We tryed using a variety of placement forces using our siemens F5. The component seems to be correctly located and there does not seem to be any obvius coplanarity issue, but once out of the reflow oven I'm getting dry joints. Under a x20 magnification it looks as though the locating pins are at a greater stand-off heigth before they inserted the oven, and the joints themselves look as though they have reflowed but the component leads just seem to be sitting on top. CAN ANYBODY HELP!!


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Re: CONNECTOR ISSUE | 30 May, 2000

Sal, I have seen this problem placing SMT connectors which exceed 60mm in length. Although I did not use siemens equipment at the time I am not sure if they will place enought force to seat the entire connector flush to the board. They have a maximun force of I believe 10 Newtons.( you might want to look that up though )This, along with the fact that you are probably placing the part with a nozzle that only covers the center of the connector. This causes the ends of the part to have a bowing affect when being snapped into the board. Here are some things you might want to look at: 1.Use a nozzle that is wide enough to distribute the force evenly along the components body.($$$) 2.Run the boards in fixtures which you can attach lock-down brackets to. These will insure correct placement entering the oven.($$$$$$) 3.Set up a nozzle as a component. You can then place force on the ends of the connector. You can figure out the locations of the connector that need extra force.(0) Any questions, feel free to e-mail!

That's just my opinion, I could be wrong!!!

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Re: CONNECTOR ISSUE | 30 May, 2000

Sal: JAX makes good points, but I�d like to think about this differently.

It sounds like the poorly soldered connection is lifting the whole connector, so that termination floats on top of the solder, rather than submit to the wetting force and be drawn down to the pad. As a result, the good terminations on the connector probably have a greater than expected spacing between the pad and the termination, producing weaker solder connections on all terminations on the connector, which is the reason you�re seeing an increased stand-off height of the locating pins after reflow.

Depending on visual inspection to catch soldering faults is a particularly dangerous situation, making you wonder: * What portion of these connectors are faulty and slip by the inspectors? * What portion of these solder terminations look good, but are really marginal?

Two things that you might consider: 1 Possibly: Flux is burnt-up before the solder connection can be made. 2 More Likely: Component (connector) has a level or a type of contamination that your flux can not remove.

How do you reflow these components during rework?

Good luck Dave F

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