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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Wavesoldering

Adam

#5859

Wavesoldering | 4 April, 2001

Guys

Is it possible to completely eliminate random solder/microsolderballs from No-Clean products that go over the wave. The Assembly is a mixed technology product which is HASL finished. All profile types have been exhausted, 3 flux vendors have been trailled, Nitrogen has been switched off, yet they still exists. Would a VOC Free flux help ? How much is the solder resist having a bearing on this ?

Any help would be appreciated.

Adam

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#5860

Wavesoldering | 4 April, 2001

These solder balls are where [top / bottom]?

Describe the breadth and degree of this problem across all assemblies.

Finally, describe your wave solder machine, a common profile for this board, and the board [beyond that it's mixed tech, like are there SMD on the second side?]

Yes, solder mask finish and cure affect solder balling. Wuddya got?

A VOC / Non-VOC NC in itself may not help. It's possible that your low-solids, no-clean flux cannot withstand an extended dwell time in solder ... your flux may be exhaused before it leaves the wave.

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Adam

#5872

Wavesoldering | 5 April, 2001

The Solderballs are on the botton side of the board.The solderballs are concentrated around through hole edge connectors, which have a Tin/lead finish and have lead pitch of 2.5mm, on top of this, random solderballs are occuring around test points. The boards are flowed with the edge connectors perpendicular to the wave. The colour of resist on these range of boards vary from a dark rough surface to a light gloss surface, and even though I get fewer solderballs on the former surface the problem is still evident. The boards also range in complexity, from single sided reflowed boards which are then sat in WSC and the bottom side fully exposed to the wave, to double-sided reflowed boards which is selective soldered over the wave. The machine settings are as follows : Ramping upto between 95-105deg at less than 2deg/sec, achieving this temp between 70-90 seconds, at a conveyor speed of 1-1.2 m/min. With a dwell time of 1.5-3.0 secs(as recommended by the flux supplier)Running with Nitrogen and HAK switched off.Running with a single lambda wave, with the chip wave turned off. Various combinations of preheat settings have been tryed together with inert soldering but with no luck.Just out of curiosity we have some boards that have no solderballs at all that run on the same machine.So I tried running the problem boards on that profile, and yes you guessed.......Solderballs.

Adam.

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#5883

Wavesoldering | 5 April, 2001

I think your solder mask is a partial cause of your solder balling.

Additionally, adjusting some machine set-up parameters may also help.

1 If we were talking about a single assembly problem, we�d be thinking about the laminate, but since you say the problem is broad-based across multiple assemblies, consider the following machine parameters: 1a Crank-up preheat time / temperature to drive off flux solvent. 1b Check / adjust high flux specific gravity 1c Perform machine maintenance on pump or wave level control 1d Turn-down conveyor speed 1e Check if tinning oil is loaded with water

Next, I'd like to a structured approach to setting-up your wave, similar to the approach described on Bob Willis' site. Finally, I like to see a design of experiments approach to adjusting wave set-up parameters for particularly troublesome boards.

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