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Profiling on rail vs mesh conveyors

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Profiling on rail vs mesh conveyors | 14 December, 2009

I need to profile a single sided board thats width is less than the profiler. Is there a difference in profiles when one is completed using the rail conveyor versus just laying the board and profiler on the mesh conveyor?

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Profiling on rail vs mesh conveyors | 14 December, 2009

Yes, there will be a difference. When the board is on the rail conveyors it is closer to the top heaters and farther away from the bottom heaters than when on the mesh conveyor. That difference will create different temperatures on both sides of your board. How much difference I do not know. I have never profiled the same board on both. It might be a small enough difference that it falls within your tolerance window or it could be large enough to make a significant difference.

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Profiling on rail vs mesh conveyors | 15 December, 2009

I have moved golden boards from chains to mesh as I got tired of fishing t-couples under the chain rail. I saw a 3-5 deg. decrease on top-side parts peak temp. (all t-couples were on top side). I had to bump zones 6 and 7 a few degrees to make up for it. It's not the right way to verify-profile as you should duplicate your production process. I would speculate results vary from oven to oven as convection air speed will differ depending on air speed and chamber design. The paste process window should allow this moderate change but sometimes (as in my case) you are trying to quickly bump 225C to reflow lead-free terminations that are trouble at lower temps. so you need keep those 3-5 deg. in mind.

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Profiling on rail vs mesh conveyors | 18 December, 2009

jamm, As with the other answers you've received, I agree there will be a difference. The question is will the difference between the temperatures of the product profiled at the mesh belt put you out of spec when you run production on the rail? the key is you have to look at you process specs to see where you are within your process window when proifling on the mesh. If you assume that you are going to have 3-5 degrees C or even more delta between mesh and rail, then your goal would be to optimize your profile results/process at the mesh level so that you are far enough (center) within your process that you will still be in spec (compensate for the offset) when you ultimately run process at the rail level.

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