It seems that a lot of companies in today’s market are buying specialized ovens for curing. Did you know that most SMT reflow ovens can be modified by the manufacturer (and quite easily too) for curing applications? In most cases, these ovens will also still work for SMT reflow, eliminating the need to waste precious floor space on a second oven.
Typically, when converting a reflow oven for curing, manufacturers simply replace gearing. This allows the oven’s belt to run slowly enough for the long profile required in most curing applications. Some oven manufacturers do not even charge, or have minimal charges, for these types of changes.
Granted, you will still need a separate oven for curing if your SMT line is at maximum capacity. Depending on volumes, you can go with a smaller, more compact oven to save floor space. For example, some freestanding four-zone ovens are only about 80 inches in length. With custom gearing, they can have belt speeds that allow a product to be in the oven for anywhere from 7 to 30 minutes or even longer.
Now, imagine if you have a very high-volume line for curing. Here, you could go with a two-in-one solution like a 10-zone reflow oven that is about 220 inches in length. This gives you the flexibility to run a longer profile in the close-to-90-minute range when required, and you would still have a 30-minute tunnel time available and get three times the volume of the four-zone oven.
There are also conformal coating applications that can be used in standard ovens. The only caveat is you need to use a heat-cured conformal coat rather than UV-cured. Changing to a heat-cured conformal coat eliminates the need for expensive UV ovens, which do not handle any applications other than conformal coat curing. Again, this allows you to maximize your investment in a single piece of equipment while reducing capital expenditures. A lot of people still buy ovens as separate, standalone units for heat-cured conformal coatings due to the “messiness” of conformal coating. In a lot of these cases, I have seen the mesh belts totally eliminated since almost all conformal coating applications require just the edge rail, which supports the product by its edges to ensure an even coating and curing.
Other options for custom ovens can be for photo optics, component manufacturers, etc. Typically, for some of these applications, it is as simple as removing edge rails for double-sided SMT and changing the belts to a finer diamond mesh belt versus the standard mesh belt. Clearance heights can also be changed to accommodate taller items. I have seen applications where a tunnel opening greater than 5 inches is required. In the case of most manufacturers, the oven can easily be modified for items like this.
Most ovens come with or can implement a SMEMA interface, which is a standard form of communication between machines that sends “board available” and “machine ready” signals back and forth, so the machine knows when to release another board to the reflow oven. This also ensures the line will stop in the case of any down situations.
As you can see, standard SMT reflow ovens can be adjusted to accommodate a number of multifunction situation, at a much lower price and within a smaller footprint than an expensive specialty oven.
Chris Ellis is a sales manager/engineer for Manncorp Inc.
This article was initially published in the August 2019 issue of SMT007 Magazine.