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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


wave solder bridges

Jason

#3439

wave solder bridges | 27 July, 2000

Hello once again! I am having a problem with a 24 pin connector bridging on the wave. We use very similar connectors on other PCB with zero problems. This connector bridges in the same place on the same pins. It forms like a little block of four pins that bridge every time. I've tried all I can think of....more flux, wave height, lead clearence, conveyor speed...and the list goes on. I am very puzzled. It is mostly SMT with only a few through hole parts. The rest of the board is good and other than the 4 pins that bridge the rest of the connector is good. I need help...PLEASE!!!

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#3440

Re: wave solder bridges | 27 July, 2000

Hi Jason,

a couple of questions: What�s the pitch? Did you change direction the board is going through the wave and what happend? How about the design abnormalities for those 4 pins, thermalreliefpads or whatever? We had problems with 2mm pitch and to long leads always with the last row. We added solderthiefpads and it worked.

Good luck Wolfgang

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Jason

#3441

Re: wave solder bridges | 27 July, 2000

i've rotated the board with the same result. What are soldertheif pads. I'm new to wave soldering and this is another new one on me. What did you use? where do you put the pads? please explain as much as you care to...also my leads are 1mm and the pitch is 2mm.

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Jason

#3442

Re: wave solder bridges | 27 July, 2000

i've rotated the board with the same result. What are soldertheif pads. I'm new to wave soldering and this is another new one on me. What did you use? where do you put the pads? please explain as much as you care to...also my leads are 1mm and the pitch is 2mm.

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JohnW

#3443

Re: wave solder bridges | 27 July, 2000

Jason,

where on the board is your connector?, front / back / middle? and where it on the PCB that you don't have issues with?

Thief pad's are basically dummy pad's taht you have after the last set of pin's on the component are are used to draw the solder off o the lead's it tend's to work fairly well. Other things I've saw work are removal of resist under the connector and angling the PCB to the wave to increase th space between the pin's for the peel off.

John

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#3444

Re: wave solder bridges | 27 July, 2000

Hi Jason I think Wolfgang has this one nailed. If it's the same four pins every time and nothing changes this, even rotating the board 90 degrees, then you're probably going to find something like a ground plane connected to them. I don't think solder thieves will help you here (although you didn't say if the bridging group was on the trailing edge of the connector)but this could be tested with the little iron-on replacement pads from Pace and others. What is your pot temperature? Solder gets "lazy" at lower temperatures. When you adjusted your conveyor speed, did you try slower? Is your preheat sufficient? I'm assuming that this is a new design and bridged right from the start rather than something that started happening.good luck John Thorup

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#3445

Re: wave solder bridges | 27 July, 2000

Sounds like the problem is design realted - here's a cheesy trick if your product/process permits: (you know how I love my cheesey tricks!)

Put an adhesive dot between the pins that are bridging. If you're gluing bottomside SMT components to the board, just program an extra dot or two between the bridging pins. We know all too well how solder will not wet to adhesive. The dot will break the surface tension of the solder and eliminate the bridging.

I hope you are gluing B/S parts and have enough room between pins to try this. It really works well.

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K.T

#3446

Re: wave solder bridges | 28 July, 2000

God bless the Airknife!

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Tekguy2000

#3447

Re: wave solder bridges | 28 July, 2000

Yea you gotta love those airknives. It may not work in this application if the shorts are present at the trailing edge. I have several boards that are using conns with pins at .050" centers and they short. The protrusion is .030" to .040". The shorter the leads will decrease the opportunity to inhibit shorting. I've tried robber pads to no avail and am bending the last 2 leads slightly away from the previous to increase the spacing. It worked!! YEEEEESSSS!! Now if I can only get rid of my resistor pak shorts. I am going to try some of Bob Willis' recommendations.

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Jason

#3448

Re: wave solder bridges | 29 July, 2000

Thanks for all the ideas. I tried solder "thieves" by placing some desoldering wick behind the briging pins and it worked! I have yet to try Chrys' idea but I will first thing Monday. This is a new board that has had this problem from day one. I didn't see a ground plane on the bottom of the board and have still no idea as to why it bridges like it does. My pot temp. is 500F and I took the conveyor speed from our usual 4.0 to 3.50 to 5.50 with the same results. Once again thanks for all the ideas and suggestions. it's nice for a "rookie" like me to be able to get help from the pros!!!! Thanks all!!

PS chrys did you get my email??

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Ron Lasky

#3449

Re: wave solder bridges | 1 August, 2000

Jason, it looks like you have several options that have strong promise of working. I suggest you perform a designed experiment to find/optimize the best solution with these suggested approaches.

Ron

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