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Pin in Paste of screw terminals

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#59431

Pin in Paste of screw terminals | 1 August, 2009

I have been working on Pb-free assemblies of screw terminals (terminal blocks). Unlike, other pin-in-paste conducive components, these component has square headed leads. We have been facing issues with the solder dripping into the oven. We were able to do the same assembly with Sn-Pb. Any suggestions on what could have got different? What can be done to improve our chances? Any level of help is greatly appreciated.

Thanks, Abhinav

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#59446

Pin in Paste of screw terminals | 3 August, 2009

We know nothing about your: * Solder alloy * Materials of your board * Materials of your teminal block * Process setup of your wave * Wetting condition of the board or the terminal block

... but we'll take a guess anyhow. Tin-copper based solder alloys have lower wetting forces than tin-lead solder alloys. In production, this affects contact time and solder pot temperature. So to achieve proper hole-fill, contact time and pot temperature must increase.

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#59447

Pin in Paste of screw terminals | 3 August, 2009

Sounds like the Pin in Paste would be a reflow technique not involving a pot. I'm guessing however the same causes are in play, in that the poorer wetting of the Pb-free allow means it drops out of the joint before it can wet to the terminal. We use similar high current terminals and they require significant pre-heat energy to ensure good wetting.

GT

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#59675

Pin in Paste of screw terminals | 26 August, 2009

Hi, Just as DaveF said; please give us some more information. It could be a a´lot of things. For .ex. Do you by any chances solder with Ni/Au at the board?

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#59699

Pin in Paste of screw terminals | 28 August, 2009

Would suggest you have a re-look at your reflow profile. There could possibly be a higher thermal demand to solder the Pb-free version of these screw terminals considering that external plating has changed.

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