I really like the modules that Electroinks has designed. They are easy to place onto drawn circuits, they are pretty sturdy, and the spherical magnets in their spring-loaded feet make connecting things simpler than using a breadboard.
However, most of the modules cannot be stacked because of the plastic snaps that hold the feet to the PCB.
I thought about placing some tiny neodymium disk magnets on top of the connecting pads, but I didn't have any. So the solution? Put a bead of solder on the pad!
Let's get started!
Step 1: Place a Module in a Helping Hands Tool
You will want to place the module you're going to modify into some sort of clamp, like these Helping Hands.
When I first started, I intended to solder flat on the surface of my table without anything holding it. Big mistake! Remember, these contacts are connected to a magnet, and they will stick to your soldering iron.
Step 2: Place Your Soldering Iron Carefully
We don't want to accidentally melt the snaps on the feet, so be sure to place your soldering iron tip between them, and flat on the contact.
NOTE: Don't touch the solder to the tip! Touch the solder to the contact pad, and let the pad heat up. Your solder will melt and flow over the pad.
I used about a 1.5 - 2.0 inch length of solder for each contact. I didn't measure though, so keep an eye on how much you're feeding onto the pad. You want the bead to be level with the plastic snaps.
As long as the pad is thoroughly heated, the solder will flow over it, and form a nice, rounded bead.
NOTE TWO: One other thing I wish I did for all my LED modules is to place the feet of the module flat on my table, with the Helping Hand simply keeping the module from sticking to my soldering iron. This way, the magnet and spring assembly inside the foot isn't able to push against the snaps of the feet. Because the PCB and foot will be warm, the plastic will stretch, which will deform the foot.
When soldering, I kept downward pressure with the soldering iron, and when the solder finished melting, I applied pressure with my hand until the plastic cooled.
I did this with my 9-volt battery connector and it worked great!
Step 3: Stack Your Modules and Light Them Up!