If you really need to use an oven, I cannot say enough good things about Shel Labs ovens. I have been purchasing and using them for 15 years, and the first one still works perfectly. The ones I have purchased all are run 24/7/365. There have been very little, if any, repairs or replacement parts needed. For the companies I work for, I'm required to characterize the oven chambers at different temperature settings as part of the qualification process, where I place a mass with a thermocouple attached at different parts of the oven to ensure there are no hot spots or cold spots (no significant delta Ts). In the chambers of these ovens, no matter where the mass is placed, the oven temperature varies by less than 2 degrees C over time. Typically the temperature delta is more like +-1 degree C. Excellent ovens, extremely competitive pricing. https://sheldonmanufacturing.com/shel-lab     I have also done this for many other oven brands that were quite good, but some not so reliable and others not as accurate.
Note; when qualifying any convection oven, please note that if you simply dangle a floating thermocouple inside an oven but it is not attached to any significant mass, you will never get an accurate temperature reading for two reasons, the first is that air movement inside ANY oven during normal operation and with doors opening/closing will cause some variation. The second reason is that ALL convention ovens that use heated elements also have a certain percentage of infrared energy, albeit a very small percentage. With a mass consisting of a cubic inch of steel, for example, your thermocouple will constantly read anywhere from 3 to 6 degrees higher in an "average" size (perhaps 8 ft.2 oven set at 105 deg. C, than the same exact thermocouple dangling inside the same oven but not connected to anything. The mass is required to measure the additional IR energy; a dangling welded bead TC will not pick it up.
So when characterizing an oven, you want your TC to be connected to some type of mass. It will not only provide a more accurate reading, but the mass sees the same temperature as a circuit board or other object, and it will be a much steadier or constant reading. That is why ovens are manufactured with the controller TC fastened to the inner wall or some other mass inside the oven. If it were dangling in air, the controller would be working overtime to keep the temperature the same, constantly overshooting either too cold or too hot. Whatever you put in an oven has a certain mass and is unaffected by an occasional door opening/closing for less than 30 seconds or so, and is also not affected by minor temperature variations from swirling air currents. You want a mass that is somewhat representative of the objects you are baking, that way your TC will see the same temperatures as the product being baked. The TC mass does not have to be exactly the same as the product. 

But I also wanted you to know that you can achieve a saturated moisture content of less than 10% (removal of 90% of total moisture under worst conditions) for reeled parts in a DR Storage drybox, any of the models that run at 5% RH or less. It takes about two weeks to achieve that level of dryness with no heat applied. DR Storage also makes heated dryboxes which I think would reduce the time, but I have never used or qualified one of those.  http://www.dr-storage.com/en/    I have been using these after using other brands for years and years, they are much better. Their desiccant containers and controllers are modular, so after about 15 years or so you may have to replace them, but you don't have to ship the whole drybox back to the manufacturer to do so, any maintenance person can service them right in your factory. Cheap and efficient. Better recovery times when doors are opened.

I purchase these through a distributor called www.salesjw.com. They have excellent service.
I have no monetary interest in any of these. It is simply that after working in this industry for 45 years I know a little bit about what works and, ahem, what else is out there.
Dean


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Vargas, Stephen M
Sent: Thursday, November 15, 2018 1:23 PM
To: [log in to unmask]
Subject: [TN] Drying Oven

Good afternoon:

     I am looking for an economical oven that will allow us to bake moisture sensitive parts at a low temperature (40 degrees C, </= 5% RH). This is for SMT parts that are not conducive to placing in a high temperature oven due to package considerations (T&R, etc.). Offline responses welcome. Thanks in advance.

Regards,
Steve Vargas

If you don't have time to do it right, when will you have time to do it over?
John Wooden

Lockheed Martin RMS-Rotary and Mission Systems
Polaris Contract Mfg.
15 Barnabas Rd
Marion, MA 02738
774-553-6192
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