PCB Reflow Guide

Setting up the board

Here is what we are going to need to set up the PCB board. The solder paste (White container), the PCB board, and the stencil. The stencil will fit on top of the PCB board where you want the solder paste to fit on. In this example, we will be avoiding putting the solder paste on the three big copper plates, which you will see later.

To learn how to make a stencil with the Protolaser check out this page.

The solder paste, called Chipquik NC191SNL50, is stored in a refrigerator and needs to sit out for at least 4 hours prior to use. Make sure you let the solder paste get to room temperature. 

Check further information using the datasheet.

http://www.chipquik.com/datasheets/NC191SNL50.pdf

Using the datasheet you will be able to see the heat path the oven will need to use. More on that later.

Take your PCB board and lay the stencil on top. You should be able to see the copper part of the PCB were you want the solder paste to stick to. 

In this case, the PCB board is set inside the copper plate to make the stencil flat along the PCB board. Adding the tape will allow a secure stencil in which the solder paste can easily be applied. 

Using a solder paste spreader, take some of the solder paste and put it on the stencil. This is a quick supply you will be able to use. 

Spread the solder paste flush against the stencil and onto the copper plating. The solder paste card makes it easy to flatten the paste down with the stencil. 

Remove the stencil carefully after completing the application of the paste. 

Here, the components are placed onto the solder paste in their respective positions. The red circle shows what the paste looks like without components (after taking the stencil off). 

The three big copper plates on the right were left untouched. This soldering will be done by hand. 

Here is a close-up of what the components look like on top of the solder paste. They were delicately put into their positions and is now ready for the heating process!

Starting up the machine

Start by finding the machine located at the back of the DCI Lab, here is what the ProtoFlow S4 machine looks like.

Find the power button on the back side of the machine.

Open the software titled "Oven Manager Pro (Version)". This is the software we are going to use to heat the oven. Here is what the software looks like. The graph will represent the heat path the oven will make. The lower left hand side of the picture shows the "Disconnected" status. 

To connect to the software, plug in the computer to the oven via the wire next to the oven. Press the lightning icon labeled "Connect".

Find the correct port by opening the "Settings" button on the top.

Here you can change the "Serial Port" to the correct one, in this case COM3. Press "OK" when done.

You should see the "Connected" status in the bottom left of the software.

Oven settings

Our next step is to set the heat path the oven will take to heat up the board. 

The datasheet for the solder paste shows us the heat path required to heat up the paste in the oven. The time is shown on the x-axis and temperature on the y-axis. We will plug these points into the software as shown below.

On the lower right side of the software, click "Add Point".

This is where we will plug in our points. The temperature should be set in Celsius by default, but if not, either change it to C or use Fahrenheit. 

Our first point starts at (0,0), so we will plug in 0 for both time and temperature. 

After clicking "OK", your time-temperature point should be shown in the top right of the software. To add another point, click "Add Point" again.

The next point will be 90sec, 150C, or (90,150). 

This is what the start of the heat path will look like with the first two points. 

*The software in this photo is "Disconnected"

And here is what the completed graph looks like using the rest of the temperatures found in the datasheet.

*The software in this photo is "Connected", hence the current temperature monitor.


Putting the board in the oven

Carefully place your board into the oven. Here is it set on the grill when you slide it out. 

And here is a close-up of the board in the oven, ready for the heating process. 

After placing the board, close the oven tight and head back to the software to start the process.

When ready, click "Start heating process" using the blue arrow icon at the top of the software.

Here is what the oven looks like as it heats up. Be careful around the oven, the outside will be hot to the touch. 



Here is what the software will look like as it goes through the heating process. The blue line is the desired heat path. The red line is the heat path the oven takes. 

As you can see it is not exact, but very similar.

The board is now ready for the battery holder.

The bottom three copper plates are where the holder goes. Time to solder!

Here is the completed board after soldering the battery holder onto the board. 

This piece is relatively large, which is why it was done by hand instead of going into the oven. It may work using the oven, but in this case hand-soldering was sufficient. 

Congratulations on completed the blinky board!