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EC-Stencil-Mate
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Re: EC-Stencil-Mate

by vincentp on Sat Sep 08, 2012 12:51 am

just to confirm, you purchased the EC stencil mate ?

which oven are you talking about ? I can't believe there's such a big difference of temp with a small offset with 3 heating bars, on the EC (plus moving air with the fan).
I reflowed a backplane board with a 90 pin BGA connector, the board was like 30 x 20, no issue, really. I'm also placing several panels in the tray, up to 4 currently and this occupies 80 of the tray space : reflow result is totally even with beautiful solder joints.

Also, the profile is the thing. I currently have a 235° reflow temp in the profile to guaranty I get the right temp *on the PCB*. I could attach the additional thermocouple for a better precision but I found that increasing a bit the peak temp just works fine and I had no component failure : the temp on the board itself will always be less than the air. When I watch the reflow phase, I see the solder changing at about 1/3rd of the reflow duration, one heavy / big part reflows later due to temp inertia, in the middle of the phase but overall the duration is just enough.

Reflow duration is 1 minute in my case, but the actual dwell is a bit less than that as the temp must first reach the peak temp, so it's probably more like 45-50 sec, still < 75 seconds indicated by the datasheet.
vincentp
 
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Re: EC-Stencil-Mate

by heli_linus on Sat Sep 08, 2012 2:16 am

hi,

yes, I purchased stencil-mate.

Well, I measured the temp, what can I say...

I use a K glued into a hole of a left over PCB, I use thermal compound/epoxy to glue it in.

This sensor is not calibrated but for detecting differences it will do just fine.

Cheers
Linus
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Re: EC-Stencil-Mate

by vincentp on Sat Sep 08, 2012 2:49 am

Linus,
measuring temperature *in* the PCB makes no sense to me. The PCB is by definition non homogeneous (ground planes, copper & traces density).

When I had my DIY oven setup, I had a spare piece of PCB with the thermocouple attached to it but the end of the K was 1 mm above the surface of the PCB. This way you measure the oven PCB, not the PCB itself.
While the PCB should heat up (of course, and that's one of the role of the preheating, along with flux soaking), that's at the end the ambient temperature that generates the reflow.
Not bullying at all, just trying to figure out with you.
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Re: EC-Stencil-Mate

by heli_linus on Sat Sep 08, 2012 3:02 pm

Hi

Nothing to say against, I use a different sensor configuration for soldering in my DIY, just, this sensor was only made to compare temp at different locations in the oven.

The idea was exactly not to measure the hot air instead how homogeneous the IR reaches and heat up the board. What you explain reg. sensor position is somehow exactly what I measured. The air transfers less energy to the board than the IR does. So I measure such big differences.

If the reflow process itself is affected I would assume depends now on the board and parts and where they are placed.

Well, maybe this is just common with all IR ovens and I can't get around.

... again, the overall impression was not bad for the oven. Software is OK, too.

Cheers
Linus
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Re: EC-Stencil-Mate

by heli_linus on Fri Sep 14, 2012 12:46 pm

Hey

we found out that the ventilation was not working properly on the oven so this explains the bad temperature distribution.

Cheers
Linus
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Re: EC-Stencil-Mate

by vincentp on Fri Sep 14, 2012 1:22 pm

*tempted to make a "fan" joke* :D

that's good news cause I freaked out a bit for my own oven despite the uber good results I got with it !

thank you for those details !
vincentp
 
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