Solder Reflow Oven

Solder Reflow Oven Instructions

Quick Start

• turn on oven power with the switch on the back
• place PCBs into the oven
• turn on the oven with the power button on the front
• press run
• wait until the screen says done to remove boards (use tweezers or prongs, the metal is still hot)
• turn off machine with the power switch on the back
• wait until the machine is fully cooled (room temperature) before attempting another reflow
• test that your PCB is not shorted before plugging it into anything you care about

In Depth Instructions

The solder oven works by taking the solder paste to controlled temperatures for controlled amounts of time in order to properly melt the flux in the past and then the solder. Different solder pastes are made out of different combinations of elements and thus have different heating curves. The heating curve can be found in the data sheet for the solder paste. The machine should be set to work with a solder paste composition of 96.6% Sn, 3% AG, and 0.5% Au. This is the composition of the solder paste found in the Makerspace.

If you are setting the machine to work with a solder past of a different composition please note that the oven does not heat as quickly as the data sheet heating curve may call for. The machine will let you set temperatures for amounts of time it can not do. For example the oven will allow you to set it to raise the temperature 100c in 1sec, but it can not actually do this. I have found that for the solder past located in the makerspace that setting the times for 15-45sec longer than the data sheet called for at the proper temperatures is effective. For charts of the data sheet times and temperatures and the times and temperatures I use in practice see below.

The settings currently used for the 96.6% Sn, 3% AG, and 0.5% Au solder past are as follows

PREH: 150c 2:00min

HEAT 217c 2:45min

SLDR 249c 1:15min

KEEP 217c N/A

COOL 150c N/A

For an example of the need time offset mentioned above, the data sheet for the 96.6% Sn, 3% AG, and 0.5% Au solder paste calls for the following:

PREH 150c 1:30min

HEAT 217c 2:00min

SLDR 249c 0:30min

KEEP 217c N/A

COOL 150c N/A

THIS DOES NOT WORK, OUR OVEN CAN NOT DO THIS

Programing the heat curve

• Turn on oven power with the switch on the pack
• Turn of the oven with the button on the front
• Press the set button
• Use the arrow buttons the scroll between the phases (PREH, HEAT, SLDR, KEEP, and COOL)
• Press the set button once on a phase to set the temperature with the arrow keys, press the set button again to set the time, and press the set button a third time to save changes
• Press Run when finished
• Press Run again to Run the oven with the new settings.

In addition to the solder reflow feature this oven has a repair feature. The purpose of this feature is to re-reflow solder past in order to fix poor connections. This feature has never been used or tested. If you have any experince the repair feature please update this data sheet.

Questions/ possible concerns about the oven

I do not know if all of the oven drawer is heated evenly. I have always tried to put my PCBs as close to the center of the drawer as possible. In theory the whole drawer should be a uniform temperature. Feel free to test this and update this data sheet with the results.

I do not know if the temperature displayed on the machine is accurate. I have no reason to believe it is not, but given some of the other oddities of the machine I have no reason to believe it is accurate either. Furthermore I do not know where the temperature sensor for the machine is located or how the temperature is determined. If you find that the temperature displayed on the screen is not accurate please update this data sheet to reflect that, also please try to determine if there is a constant offset.

Problems/troubleshooting

The oven says it’s done but I can’t turn it off or start another run cycle

Once the oven finishes the cycle it seems to stop responding to button presses. If you try to turn if off or start over it will either do another or start displaying a message saying waiting. The only thing to do is to turn the oven off using the switch on the back and then turn it back on. You have to do this after every time you run a cycle with it.

The solder came out looking dark and matted

This is normally caused by heating the solder for too long, or at two high a temperature. If this happens you need to through the board out and try again. Make sure you put the PCB into the oven when the oven is at room temperature. Also consult the datasheet for the solder past you are using. Adjust the times and temperatures as needed using the method outlined above.

The solder came out looking weird some other way

Make sure that the solder past you are using is not expired. The solder paste should have an expiration date on it, and if we are significantly past that data the past is bad and should be thrown out. In general solder paste should last about 6 months if it is refrigerated.

Another possible reason that the past may come looking out weird is that it was heated for too long or not long enough. Make sure to consulate the data sheets and adjust the oven as needed

There are little tiny balls of solder on my board not near any solder points, how do I get rid of them?

You can clean the board using isopropyl alcohol and a soft brush or towel. It is best practice to clean every board after you reflow it to remove any excess solder or flux