>Dear all,
>
>I am a student currently doing research in SMT.  One question concerning
>the trend of reflow oven came into my mind:  Which type of oven is most
>popular used in industries nowadays?  Force Air Convection?

Yes. These machines are dominant in the market today; have been for several
years.

>Does anyone still keep and use the pure IR oven for daily production?
>Why?  Or does this type of oven has already obsoleted for a long time that I
>cannot even find one as scrap?

Yes, but probably 5-7 years ago, most of the furnace manufacturers adopted
the forced convection design. Prior to that you would see "convection/IR"
designs, and claims that the  various IR designs heated convectively.

Keep in mind, the older panel emitter IR designs do heat "convectively" in
that the heat transfer is partially direct, and partially a result of the
IR heating the internal parts of the oven which heat air, which heats the
work.

You would have no difficulty finding an older IR oven in use. We have two,
you see used equipment brokers listing them all the time. The reason we do
is that our older equipment can still do the job, and it would be difficult
to justify replacement of the machines.

Most people agree that the forced air convection heating is more efficient,
i.e. heats the work more quickly and more evenly than the direct radiation
heaters. The 5 zone forced convection ovens can give as nice a profile as a
much longer IR furnace. There are, however; disadvantages.

The forced convection units require fans to move extremely hot air. This
becomes a design challenge to develop reliable blowers capable of
continuous operation in a very hot environment. The passive IR units had
many fewer moving parts, and therefore were pretty reliable. The convection
machines use more energy. It also becomes more difficult to design a
furnace with forced "air" for an inert environment as compared to the
conventional IR design - simply a problem of preventing infiltration of
outside air.


regards,

Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com/


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