SM Headers & Connectors

Is it just me, or does anybody else have problems with open connections on small surface mount headers and connectors? I am talking about small 20 to 40 pin devices, 25 to 50 mil pitch. We put these things on the board, the feet look like they are in the paste, and they come out of the oven with random placed opens. We use devices with retention pins for mechanical strength, but that doesn't seem to matter. Paste volume is consistent on the lands. Any ideas? Thanks, Bob

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| Is it just me, or does anybody else have problems with open connections on small surface mount headers and connectors? I am talking about small 20 to 40 pin devices, 25 to 50 mil pitch. We put these things on the board, the feet look like they are in the paste, and they come out of the oven with random placed opens. We use devices with retention pins for mechanical strength, but that doesn't seem to matter. Paste volume is consistent on the lands. Any ideas? | Thanks, | Bob Bob, Do we work in the same place? It's not just you. Surface mount connectors tend to exhibit what I call "floating syndrome." The component goes into the reflow oven nestled all nice and snug in the paste and comes out sitting on top. One thing you may do is check the material that the leads are "tinned" with. You may find they are coated with some sort of noble metal. there are a couple of things you can try. Jump up your temperature in your reflow zone by 10 or 15 degrees Celcius. Another more costly and time consuming step is to pre-tin the leads. If you have a volcanic solder fountain, you can do this. Flux the part, grip it with pliers, dip it in the solder fountain, and tap the excess solder off. Also, try to hand solder the part. If it wets readily with a hand soldering iron, odds are the former solution I offered will work. Best Regards, Justin Medernach Flextronics Int'l Westford, MA PIC

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Justin, Thanks for the response to my dilemma. For once it's not just me! The parts seem perfectly solderable, but I will try the modification to the profile you suggested. I wonder if the retention clips may be letting loose from the holes they are secured into as the holes expand from the oven heat or, if they come loose if the boards warps slightly in the oven? I did a little experiment (one sample) by cutting the retention tabs off and just letting the header sit on the paste like any other sm part. It came out fine as if it was able to seat itself without the interference from the pins. Of course, this doesn't really solve the problem since engineering wants the retention pins for mechanical strength (take the load off the joints as the mating connector is pugged on and off.) But it does provide food for thought. I'll keep working on this problem and let you know if I come up with anything. It really is becoming a serious rework issue. Bob

| | Is it just me, or does anybody else have problems with open connections on small surface mount headers and connectors? I am talking about small 20 to 40 pin devices, 25 to 50 mil pitch. We put these things on the board, the feet look like they are in the paste, and they come out of the oven with random placed opens. We use devices with retention pins for mechanical strength, but that doesn't seem to matter. Paste volume is consistent on the lands. Any ideas? | | Thanks, | | Bob | Bob, | Do we work in the same place? It's not just you. Surface mount connectors tend to exhibit what I call "floating syndrome." The component goes into the reflow oven nestled all nice and snug in the paste and comes out sitting on top. One thing you may do is check the material that the leads are "tinned" with. You may find they are coated with some sort of noble metal. there are a couple of things you can try. Jump up your temperature in your reflow zone by 10 or 15 degrees Celcius. Another more costly and time consuming step is to pre-tin the leads. If you have a volcanic solder fountain, you can do this. Flux the part, grip it with pliers, dip it in the solder fountain, and tap the excess solder off. Also, try to hand solder the part. If it wets readily with a hand soldering iron, odds are the former solution I offered will work. | Best Regards, | Justin Medernach | Flextronics Int'l | Westford, MA PIC

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