If the temperature is too low, the flux may not activate fully, allowing oxidization on the PCB pads and component leads to remain. If the soak period is too long, the flux will be consumed and parts may not solder well. The activation of the flux is quite critical when it comes to the time and temperature of the soak. The purpose of this stage is to continue the outgassing of volatile compounds from the solderpaste, to begin activation of the flux and to continue allowing all components to rise in temperature. As the figure above shows, the ramp rate should be less than 2.5 C / second. The goal of this ramp is to get the board heated up safely and to allow for the solder paste to outgas safely. The first, “Preheat”, is a steady ramp up to ~155 C. This will result in poor solder joints, where the flux has all burned off before the board even gets up to reflow temperatures.Īs mentioned previously, there are four different reflow zones. If the oven is not well insulated, it will never heat up quickly enough to complete the profile in time. This is why it is so important to have a controller AND to have a very well insulated oven. In addition, these all occur in under 5 minutes. If you look at the top of the figure, you will notice that there are four distinct zones to the reflow profile: “Preheat”, “Soak”, “Reflow”, and “Cool Down”.
The image shown above is a reflow profile for a popular leaded solder paste. The recommended reflow profile when using Kester EP256, a leaded solder paste. Some Background Information About Reflow Soldering Profiles We share our first 3 trials at the end of this post, along with some of the challenges we encountered. As each reflow oven is different (our first one is an old toaster oven, the building of which is detailed here), the reflow profile will likely need to be adjusted to get good results with your own oven. We will cover reflow profiles and briefly discuss their different aspects. In the picture above, solder paste has been applied to the circuit board and is awaiting part placement and reflow soldering.Īs mentioned in our last post detailing moisture sensitivity levels and the need to bake parts, this post dives into enabling reflow soldering using a Tiny Reflow Controller V2 by Rocket Scream. The automation possible as well as the overall quality of solder joints make it an easy choice for most electronics projects. Today, reflow soldering is what makes every cell phone and almost every consumer electronic device work.
Reflow soldering is a relatively recent addition to the electronics industry, ushered in to allow the usage of SMT (surface mount technology) parts. It was a bit light on the larger pads but volume was sufficient for good fillets.
The license for the spreadsheet is CC-BY-SA, meaning you can use it commercially as long as you retain the copyright notice.Solder paste applied to a micro USB footprint. If you need more interpolated times, be sure to extend columns E thru I, which are hidden for clarity.
So, I made a spreadsheet-you can download it for yourself. They only give a bullet every 25 seconds, and you even have to guess those temperatures! It’s difficult to “eyeball” the interpolated 10-second intervals here. Here’s an example from MG Chemical for their 4902P low-temp, lead-free paste: Unfortunately most solder paste datasheets don’t specify at 10-second intervals rather, they specify times and target temperatures. You specify a target temperature at 10-second intervals.
The main thing I did was install the replacement firmware written by Unified Engineering, and replace the masking tape (!) with kapton tape.Įither firmware allows you to configure two custom profiles. This is a reflow oven that can be bought fairly cheaply, but because the manufacturer cuts corners in several places, you have to do several modifications to make it usable. I am the proud owner of a new-to-me Puhui T-962.