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October 12, 2009

Reflow Oven in a Class 1000 Cleanroom

What are the requirements for setting up a 7 zone reflow oven in a class 1000 cleanroom?

C. J.

Experts Comments

Sorry to answer your question with more questions there are some loose ends that would need to be tie up first as follows:

1) Is the oven already a class 1000 oven or is it a "standard" (non-cleanroom) oven that is now going to find a home in a class 1000 cleanroom?

Setting up a Cleanroom class 1000 prepared oven in a class 1000 cleanroom is pretty straightforward. Give it electricity, give it exhaust, nitrogen &water (if needed) and away we go.

Or is it a standard oven that is NOT class 1000 and the idea is to convert it to be class 1000 compatible?

The job of making an oven fully class 1000 compatible inside and out typically needs to be done WHILE THE OVEN IS BEING BUILT. So turning a standard oven into a Class 1000 after the fact is a BEAR. There are companies that quote such kind of retrofits but this job is time consuming and dollar consuming.

In other words, a retrofit can cost almost as much as a new machine so a new machine may be the best way to go. Suggest going back to the manufacturer of the oven for this type of quote as they will likely give you the best pricing -- for the retrofit OR for the trade in for a new machine!

2) Another thing that is important to know in cleanrooms is: class 1000 for the outside of the oven or class 1000 for the inside or both?

In other words, sometimes a cleanroom spec is more concerned that the oven doesn't contaminate the cleanroom. So the "outside" needs to comply with class 1000 and not spew forth particulates that might drive up the particle count in the room but particle count inside the oven tunnel is not so critical.

In many cases a Non-cleanroom oven CAN be put in a cleanroom if the parameter is only that the oven itself doesn't contaminate the room. Many standard or "stock" ovens can be run in cleanrooms without the risk of external or room contamination. (Years ago Motorola had several standard ovens running in their class 1000 cleanroom in China for about 5 years with no problem.)

In other cases, the particle count in the tunnel is the key. The product cannot have particles thrown on it during its ride through the oven so the "inside" needs to be class 1000. And as noted above, you then have to look at retrofitting or replacing the oven and the associated costs.

A side note on this. If we were talking about Class 10,000 instead of Class 1,000 many standard ovens CAN run at Class 10K inside and out without modification. The caveat here is that the wear rods that support the mesh belt will create dust and particulates and need daily wipedowns to keep the particle count down.

In many cases customers will say that particles created below product level are acceptable -- as in the case of the wear rods running under the conveyor belt. Although this is not a general rule.

Marc Peo
Heller Industries Inc.
Mr. Peo has been with Heller Industries for over 20 years and has been President for the past 8 years. Marc has authored several industry articles on Soldering, Flux collection, nitrogen use and Lead Free conversion.
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