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

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Skewing of parts


Skewing of parts | 20 July, 2004

We are having a problem with our Heller 1800W oven with certian parts skewing. It seems that some inductors and taller Can caps are shifting around in the oven. It seems it will solder fine and than all of a sudden just be off to one side or the other and cause rework. Is there anyone out there that has a solution or comment to this problem? Below I listed 1 of 3 profiles that we use in conjunction with our boards. The one listed below is basically used on 75% of our boards.

Medium Profile Zones top and bottom 1.)80 2.)110 3.)140 4.)155 5.)180 6.)220 7.)240 8.)270 and conveyor speed at 90. and some other information below: Soak: 79.6 Seconds Ramp 1.73 Degrees C/Sec. Time above Liquidous: 46.3 Seconds. Peak Temp: 219.3 Degrees C. Cooling ramp 3.9 Degrees C/Sec.

And paste placement and part placement before the heller is 100% dead-on. We also use NWS-4200-4H3 paste from Amtech.

Thanks in advance for any information.

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Skewing of parts | 22 July, 2004

how fast are your cooling fans and/or convection fans running?

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Skewing of parts | 23 July, 2004

100% Power on cooling fans. Cooling fan speed can be adjusted, but convection fans can�t.

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Skewing of parts | 23 July, 2004

For reflow, low soak time and low peak temperatures will help reduce the number of components skewing

Search the fine SMTnet Archives. For instance:

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Skewing of parts | 23 July, 2004

Make sure that your mesh conveyor drive chain is not jumping a sprocket tooth. This will cause the conveyor to "pop" and you will have skewed parts.

I seriously doubt that it is your profile causing skew. It is more than likely something mechanical.

Good luck.

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