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Lead Free Delta T (reflow 7 zones)

Views: 3743


CGO

#40320

Lead Free Delta T (reflow 7 zones) | 9 March, 2006

Please advice how can we reduce a delta T of 40 degres between pads with a seven zones reflow for a LF Assy. max 255 min 215 board size 3x5 inches.

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RDR

#40321

Lead Free Delta T (reflow 7 zone) | 9 March, 2006

First make sure that ALL of your fans and heaters are working! 40 deg. is one hell of a delta.

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CGO

#40322

Lead Free Delta T (reflow 7 zones) | 9 March, 2006

Fans and Heaters are checked last week all o.k.Next step will be...

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#40324

Lead Free Delta T (reflow 7 zones) | 9 March, 2006

What type of profile are you using (soak or straight ramp)? You may need to reduce the ramp rate or increase the time at soak.

Jerry

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#40325

Lead Free Delta T (reflow 7 zones) | 9 March, 2006

CGO Assuming your system is performing well here are a few ideas to help out your profile.... - Pull the material spec and ensure you are meeting the requirements for times and temp. Many times the material will allow a mild soak of the board prior to liquidous. - Try a "reverse spike" (use the second to last heating zone to drive heat into the product, the last zone to soak the product above liquidous) - Try a "double spike" (last two zone set to the same, or near same temp)

Send me an email with your conact info if you want to talk. thanks marc

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CGO

#40327

Lead Free Delta T (reflow 7 zones) | 9 March, 2006

Ramp or Soak give us same Deta T (from 35 to 40).All probes are tested o.k.Should we pump in more heat upfront in order to warm up heavy loaded ICs like PLCC64 or Change blower speed? or Slow down line?

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Chunks

#40328

Lead Free Delta T (reflow 7 zones) | 9 March, 2006

What make of oven?

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CGO

#40329

Lead Free Delta T (reflow 7 zones) | 9 March, 2006

OMNIFLOW 7.

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RDR

#40331

Lead Free Delta T (reflow 7 zones) | 9 March, 2006

Is there a way that you could plot the data points of your profile into excel and post somewhere? Or can you give us some data on what your profile looks like?

What exactly does this board look like? thickness, size, copper weight?

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Chunks

#40343

Lead Free Delta T (reflow 7 zones) | 10 March, 2006

Ah, I have 3 of these ovens. Not bad ovens at all. You mentioned a PLCC 64. Is this part having the delta T problem? If so, that seems odd. Without knowing your exact set-points, you could pump in more heat up front. Change blower speeds to high (green). Slow down the line line. But only do one thing at a time so you know what is giving you the results.

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CGO

#40344

Lead Free Delta T (reflow 7 zones) | 10 March, 2006

Increase Soak time & Slow down line did reduced Delta T by 10+,Fans are at max - Both High -getting closer to target now.Great idea.still more to do .Thanks for advices.

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#40348

Lead Free Delta T (reflow 7 zones) | 10 March, 2006

I hate to ask an obvious question, but are you sure all of your thermocouples are attached properly? I just can't imagine a 3X5 board having such a large Delta T unless it has some really odd parts on it. You sound like you know what you're doing, but if one of the profile lines is fluctuating a lot more then the others, it's probably not attached correctly.

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CGO

#40376

Lead Free Delta T (reflow 7 zones) | 13 March, 2006

Yes, All six new (LF ready kit) thermocouples are tested good.I would like to say boards are populated on both side back to back with two heavy PLCC's side by side just like having heatsinks and ground plane.Some Odd design.Next try will be to have all components and pcb pre-heated.More Ideas or Advices are more than Welcome!

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Bob R.

#40381

Lead Free Delta T (reflow 7 zones) | 13 March, 2006

I would try swapping the hottest & coolest thermocouples where they go into the mole and see if temp readings follows the thermocouples or stays with the mole input. A 40 deg delta T on a board that small really sounds like a measurement issue.

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rp

#40385

Lead Free Delta T (reflow 7 zones) | 13 March, 2006

Wow, MOLE now sells "lead free" probes?

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Wave Master Larry

#40404

Lead Free Delta T (reflow 7 zones) | 14 March, 2006

Well Im more of a wave guy but we had an employee in the engineering department, he's left the company but he used these setpoints on the ovens in ai. 180, 170, 170, 190, 200, 225, 225 I heard they worke pretty well at those deltas

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Chunks In Cebu

#40457

Lead Free Delta T (reflow 7 zones) | 15 March, 2006

I can see why he left. Not knowing your board or paste, but I would tend to say your profile is on the cool side. Unless your boards are very small and your conveyor speed is slow, I'd say this is no good. It looks like you're using the old "ramp, soak, spike" approach as well. Most paste mfgers recommend a staight ramp with little or no "knee".

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