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Looking for trays to lay boards on in reflow oven

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In our reflow oven it has pins which move at the predetermin... - Jun 09, 2019 by Don J  

#82746

Looking for trays to lay boards on in reflow oven | 9 June, 2019

In our reflow oven it has pins which move at the predetermined speed to move the pcb through the various zones in the oven. The forward row of pins is fixed along the front of the oven. The rear set of pins is adjustable per the width of the pcb.

We have a project which incorporates a module which has considerable thermal mass. We have problems with this module properly soldering to the board. We have had to increase the temperature and rotate the board so that the module is closer to the center of the oven, but we still can not get it anywhere close to the center of the oven, which we would like to do.

I'd like to source or fabricate some trays to lay the pcb's on while going through the reflow oven such that we can lay the pcb on the tray with the module centered in the heating zones.

Can anyone advise where to source these trays or what material to fabricate them out of?

Thanks very much. Don J

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#82747

Looking for trays to lay boards on in reflow oven | 10 June, 2019

Hello! Don,

I heard from SMT factory that the fixture for oven they use is durostone material, I don't if durostone is correct name translated, it is synthetic stone made of carbon fiber sheet.

Best Regards Clare PCB Connect China

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#82748

Looking for trays to lay boards on in reflow oven | 10 June, 2019

Thank you Clare.

After doing some more research, I found they are known in the industry as "Carriers".

I did look into that durostone material. They prices are beyond reasonable. My trek now is seeking a material to make planks out of to lay the boards on, such material having a higher specific heat than the pcb. There must be something out there.

I did find one company making carriers out of stainless but I'm concerned about the temperature of the stainless relative to the temperature of the pcb as they exit the oven.

Does anyone know of a suitable material for this purpose?

Thanks.

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#82750

Looking for trays to lay boards on in reflow oven | 10 June, 2019

Hello! Don,

Yes, if the carrier is steel/stainless, it would be very hot when it comes out from oven. I heard that durostone (synthetic stone) carrier can meet your requirement, it can stand high temperature with low thermal transmission. So when it comes out from oven, it would be not hot. Maybe you can do a research there. But I don't know if cost for this kind of durostone is high or not.

Best Regards Clare sales01@pcbconnectchina.com Wechat: clare13590287251

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#82751

Looking for trays to lay boards on in reflow oven | 10 June, 2019

What is the year, make and model of your oven? Are you running it with Upstream and Downstream (pre-reflow, post-reflow) conveyors? Is the qty of the product low, medium or high? What is the max process width of the oven? what is the max board with of the product? Is your facility exhaust at the correct CFM per the Oven OEM guidelines? Have you considered re-configuring the oven to better suite this particular product? (Add a mesh belt or change the position of the fixed rail and re-position the oven if you are using upstream/downstream inline equipment).

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#82752

Looking for trays to lay boards on in reflow oven | 10 June, 2019

We started getting better reflow after rotating the pcb to locate the greater mass closer to the center of the oven. However we still leave space between panels on the conveyor to achieve a better reflow. This costs us production time.

I'm simply looking for a material to effectively turn my pin conveyor into a mesh conveyor without paying bank to the manufacturer of the oven.

The rest of the questions are moot.

What material is out there which has demonstrated effective in making carriers or simply making planks to lay pcbs on during reflow? I've seen it done before but I don't know what the material is/ was.

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#82754

Looking for trays to lay boards on in reflow oven | 10 June, 2019

The only material I've ever heard of for these applications is the one that you have already rejected (Durostone).

There is a similar material called Durapol, and if memory serves me correctly it is somewhat cheaper than Durostone.

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#82755

Looking for trays to lay boards on in reflow oven | 10 June, 2019

Thank you. Maybe I'll just order some oversized thick boards from the board house with no traces. There has to be a lower cost way than paying that kind of money they are asking for those products.

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#82756

Looking for trays to lay boards on in reflow oven | 10 June, 2019

How wide is this board?

I ask because if it's not terribly wide, you might just be better off attacking the problem with the profile rather than attacking the board conveyor design.

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#82757

Looking for trays to lay boards on in reflow oven | 10 June, 2019

First thing we did was visit the profile and we have it adjusted as far as we're willing to take it.

I'm just going to make a carrier design in cad and have the board house produce some in their thickest substrate to see how it works out.

Thanks.

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#82773

Looking for trays to lay boards on in reflow oven | 11 June, 2019

If the board is just not reaching the temps you need, you could place them in an oven to "preheat" them. When I was building a rather thick board with a copper core I had to do this. Since we were only doing small runs it was feasible, I don't know your product requirements.

You may need to verify that all components can "handle the heat", some may have to be hand-soldered post reflow.

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#82774

Looking for trays to lay boards on in reflow oven | 11 June, 2019

&gt; If the board is just not reaching the temps you <BR> &gt; need, you could place them in an oven to <BR> &gt; &quot;preheat&quot; them. When I was building a <BR> &gt; rather thick board with a copper core I had to do <BR> &gt; this. Since we were only doing small runs it was <BR> &gt; feasible, I don't know your product <BR> &gt; requirements.

You may need to verify that all <BR> &gt; components can &quot;handle the heat&quot;, some <BR> &gt; may have to be hand-soldered post reflow. <BR> <BR>

Thanks for the suggestions. We've modified the profile as far as we're willing to push it while keeping to the specs of the paste & components. Preheating may be something we visit after trying to do a better job centering the panels.

If anyone remembers from physics & calculus classes, all areas within an oven are not the same temperature. Now consider it's open at both ends with negative air pressure vented to the outside.

When we rotated the panel to locate the components with the high thermal mass away from the front wall of the oven and more towards the center, that helped. But I still have a 300mm wide oven and those heavy mass components are no where near the center.

Seems getting the panels centered is the next logical step. We need (want) to be able to run this particular build at full production speed.

Thanks to all for the input.

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#82775

Looking for trays to lay boards on in reflow oven | 11 June, 2019

Consider an adjustable (or fixed) process carrier then. It could offset the board so that your component is better centered. I have used Pentagon EMS for such carriers in the past. They are pricey, but last forever. We were a contract house, so the customer picked up the cost for us.

I am not sure if he still works there, but Desi Silva was our account rep. Top-knotch guy.

https://www.pentagon-ems.com/universal-process-carriers/

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#82787

Looking for trays to lay boards on in reflow oven | 12 June, 2019

We just use scrap PCBs for Oven carriers. You could probably contact your board house and as for just sheets of FR4 to use.

I've also used a binder clip at each corner to lift a board off of the mesh belt in a pinch.

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#82816

Looking for trays to lay boards on in reflow oven | 13 June, 2019

Problem is I don't have a mesh belt (lesson learned). Our conveyor is pins.

If I laid some scrap pcb's spanning the conveyor pins on the long dimension of the board, I'm confident it would sag. We get a bit of sag today in our 1.6mm thick boards while spanning the narrow dimension (just a little bit of sag but there is some).

If sag causes the carrier to fall off the conveyor pins in the oven it's a disaster.

I just ordered a slab of .125" FR4 (about 3mm).

I'm going to cut that to max width of conveyor (minus a tiny fraction) and run it through the oven repeatedly with some weight on it and see if we get any sag out of it. If the amount of sag is tolerable, I'll put a populated pcb on it and see if it helps with even reflow across the board. This means I get an answer to my question for the $26 landed cost for the FR4. If it works, from there we'll decide whether we want to use that for production or get some carriers made up.

Many thanks to all for the input.

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#82819

Looking for trays to lay boards on in reflow oven | 13 June, 2019

Reach out to me Don, I build this type of tooling on a daily basis. these are known as Pallet carrier trays, custom Matrix trays, etc, etc... Very common in this day & age.

ETM SOLDER PALLET DUDE.

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DWL

#82820

Looking for trays to lay boards on in reflow oven | 13 June, 2019

A couple of caveats; The FR4 will degrade with successive reflows and will eventually need to be replaced. Not a big deal for low volume, but something to be aware of.

The bigger concern is that a sheet of .125" large enough to position your assembly in the center of your oven is going to add a lot of thermal mass and will require a significant change to your reflow profile.

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#82821

Looking for trays to lay boards on in reflow oven | 13 June, 2019

&gt; A couple of caveats; The FR4 will degrade with <BR> &gt; successive reflows and will eventually need to be <BR> &gt; replaced. Not a big deal for low volume, but <BR> &gt; something to be aware of.

The bigger concern is <BR> &gt; that a sheet of .125&quot; large enough to <BR> &gt; position your assembly in the center of your oven <BR> &gt; is going to add a lot of thermal mass and will <BR> &gt; require a significant change to your reflow <BR> &gt; profile. <BR> <BR>

That's all under consideration. Thank you.

It affords us the opportunity to do a test.

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