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SMT electronics assembly manufacturing forum.


soldering issues with MELFs

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#55225

soldering issues with MELFs | 26 June, 2008

Hello, we are having issues with two assemblies where the Melfs will lift or not solder on one end of the components. Has anyone had issues with this in the past? What can be done to help this? Thanks

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#55227

soldering issues with MELFs | 26 June, 2008

Depends on a few variables. Could be the part, your profile, your paste, your stencils..... many things affect it.

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#55228

soldering issues with MELFs | 26 June, 2008

Check your pad spacing on the board. Look at the IPC specs for pad design.

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#55230

soldering issues with MELFs | 26 June, 2008

The pad size is okay. I have also requested the manufacturer's recommend reflow profile. I have seen some issues with 0402 caps that we run also but for the most part solder paste does okay. I think the cap issues is stencil related. Still trying to work that out. All the components are from the same manufacturer. Would slowing the reflow oven down help?

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#55233

soldering issues with MELFs | 26 June, 2008

Yes, try slowing it down. It will indicate if your ramp up is too fast.

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#55235

soldering issues with MELFs | 26 June, 2008

Hello Mark,

I would recommend to look again on the pads. in many cases board design is causing these issues. Check

1. Is pad size good for the part 2. Are both pads the same size 3. traces connected to the pads should be same size 4. vias connecte to mentioned above. Sometimes a small via can take enough solder paste to make troubles 5. solder mask

I hope you get it soon

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#55236

soldering issues with MELFs | 26 June, 2008

Hi Mark, Are these lead free parts on a leaded process? If so, that could be your problem. We had the same issue in my place a while back.

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