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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


solder ball

jasonfang

#20190

solder ball | 4 June, 2002

Does anyone knows root cause of solderball after reflow? Thanks

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jasonfang

#20191

solder ball | 4 June, 2002

Does anyone knows root cause of solderball after reflow? Thanks

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RDR

#20208

solder ball | 4 June, 2002

Where are they at, and what size?

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jasonfang

#20211

solder ball | 4 June, 2002

I found solderballs are around chip components (on one side of middle area), I checked gerber data, solder paste of aperture on the stencil for these chip components have 5% reduction to solder land on PCB, shape of solder land are square, not home plate design, the size of components are 0805 and 1206. I think I should rebuild new stencil with home plate design but I am wendoring any other reasons caused solderball such as reflow profile.

Thanks anyway

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RDR

#20219

solder ball | 4 June, 2002

Jason, Excessive thermal ramp rates, misprints, improper pad design, paste type, placement pressure, all can cause solderballs.

Do the pads on this board meet IPC 782 criterias? I have found that too much pad underneath component can cause this. A home plate design in the stencil can and usually does correct solderballs for this condition.

What type of paste are you using? Make sure that your profile matches their recommendations. No-cleans used to be and maybe they still are prone to "midship" solderballs. the homeplate can also correct this.

Is your print registration good?

how do you clean your stencil? If solvent is left on the underside bad things can happen like this.

A few of my thoughts

Russ

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#20223

solder ball | 4 June, 2002

Solder balls are one of the most popular topics here on SMTnet. Search the fine SMTnet Archives for background.

We like to wash solder balls from the board in our cleaner.

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Hussman69

#20257

solder ball | 6 June, 2002

Sure do, it's from the paste that gets squeezed under your R's and C's. This paste is now on your mask and during reflow, wants to move off the mask. Unfortunatly, it follows the flux residue to the side of your component.

An easy fix is to use the homeplate design. No need to change anything but your stencils. AND IT WORKS.

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#20265

solder ball | 6 June, 2002

I agree with the others and experienced the problem myself this week. Solderballs at the side of the chips. I looked at the board and found that the chip is pressing the paste away too much. This in combination with our quite big pads(and stencilapertures)probably causes the balls. Remarkable is that we did not have this too much before. I lowered the placentmachine's force and asked the printing operator to stirr very well before pasteprinting, and now our problem is gone. It is quite warm enviroment now, and I suspect that the viscosity plays a role during placement too.

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