Some time ago I bought I BETA reflow controller to control a convection (fan assisted) oven I was building. I'd read about this controller on the internet I was keen to give it a try. Although not the most sophisticated controller in the world, I did find it gives consistent results when configured correctly. When reflowing, consistent results is the holy grail!
Before using the controller, it has to learn a little about your oven - this is to prevent it overshooting your set times (pre-heat, soak, reflow and dwell). You can then program the controller via the RS232 interface to actually configure the controller unit.
There are, however, a number of problems: How do you know if the oven can actually reach these set values? How do you monitor actual temperature when the controller is running? Has the oven hit reflow temperature and if so, for how long?
In short, the controller needed a graphical user interface (GUI) to (a) configure the unit for a given solder profile and (b) monitor the whole reflow process in real time, matching the desired profile against actual temperature measurements.
Please note that I cannot take any responsibility for loss or damage caused by using this software. However, I would add I use it all the time when great results. I would strongly suggest you close down and then restart the software after each reflow cycle. I have found that the controller RS232 interface can sometime get stuck and this ensures a clean reset every time.
Configuration is done using a small *.ini file called "reflow.ini". This should be held in the same folder as "reflow.exe". You can easily edit this *.ini file by clicking on the main screen, which will open the configuration window as shown here:
If using Win7 or higher, make sure the folder with "reflow.ini" can be written to, else your changes cannot be saved! When the application is started or when the "apply" configuration button is pressed, the configuration options are sent to the controller via the RS232 connection.
Here is a quick summary of the configurations options available
- com - the com port used to communicate with the controller
- showlabels - display labels in the GUI showing each set point
- starttemp - to give 100% repeatable results, the controller cycle should start at the same oven temperature every time. Trust me on this, the controller will work much better if the oven is "warmed" to a set temperature before the pre-heat cycle begins. A top tip when using this controller.
- name - the solder profile name displayed in the title bar
- phttemp - pre-heat temperature set point
- phttime - time in pre-heat
- phtpwr - amount of power sent to oven heaters during pre-heat
- soaktemp - soak temperature set point
- soaktime = time in soak
- soakpwr = amount of power sent to the oven heaters during soak
- reflowtemp - reflow temperature set point
- reflowtime - time in reflow
- reflowpwr- amount of power sent to the oven heaters during reflow
- dwelltemp - dwell temperature set point
- dwelltime - time in dwell
- dwellpwr - amount of power sent to the oven heaters during dwell
- liquidus - display a line on the graph to show the point when the solder turns liquid. The time spent when the temperature exceeds this value (reflow) is displayed on the LED readout marked REFLOW TIME.
- degps - Just used for graphing, 3 is usually a good value.
Here is a collection of images I collected during the whole reflow process.
Application at the start of the reflow process.
This shows the oven during "warm up", which gets the oven to a set temperature before pre-heat.
This shows the oven during pre-heat.
Now the oven is in the soak cycle.
The oven has now entered the reflow cycle. Note the REFLOW TIME LED display showing "time above liquidus"
This shows the oven during dwell.
The reflow process has finished. The door has been slowly opened to start cooling. You don't want the temperature to drop too fast, nor do you want to bake everything! The curve above is a nice 3 degC per second drop in temperature before falling well below the solder liquid state.
Here are a few images of the oven I use. It's a large convector, with a fan that pushes air to the side which then circulates in the oven. Two heaters at the top and bottom provide a total output of about 3.3 kW
The controller is rated at only 1.5 kW. Inspecting the controller internals shows that the components can handle more power, but not the heatsink - so a mod was required:
Note that modding your controller will invalidate your warranty! This is the inside of the oven with a stainless steel fan diffuser at the back and also a stainless steel mesh tied to the oven rack. This is really worth doing as it (a) reduces hotspots on your PCB and (b) stops the boards falling through the rack!
The temperature of this oven is so well balanced that you can place boards at the back, sides and front and they will all reflow correctly. The 3.3 kW power ensures very quick ramp times and using non IR heaters reduces the problems normally associated with uneven heat distribution on components.