A Little Something about Squink first...
Squink is capable of creating an Printed Circuit Board in minutes, printing traces, dispensing solder and pick-and-placing components rapidly. Unfortunately, there is no milling or drill-head for placing holes and through-hole components, mostly because that is an outdated technology but also because there is no way to automate it. Even if there were plated through-holes, you have to hand-solder them. Even today this is common.
However, it is possible to place through-hole components on Squink using a few techniques. This is the first one.
This here is an MQ-2 Air Sensor for a fire alarm design taken from a design found at Electronicshub.com. It's a neat sensor that can detect Hydrogen, Alcohol and even Methane. Easy to tell who cut the cheese perhaps? As awesome as this sensor is, the trouble is that it is a 6-pin through-hole part with no SMT equivalent. Even the sockets are through-hole.
However, all of the pins are of the same length which means that it can be connected to pads by creating solder pads for each 'hole' in the design and then placing the sensor by hand. If given a Gerber or KiCAD file (like a .gts or .gtp formatted file) or an image (.jpg or .png, even .tiff or .bmp) Squink will dispense glue onto those spots. We tried Pick-and-placing the sensor but the mesh wire head prevented the vacuum system from picking it up properly - fingers do well in a pinch!
We employ conductive glue in this situation because it provides high mechanical strength and durablity. Generally speaking, the silver traces are very thin and while they are well bonded to the surface, a soldered part will be bonded to the silver, not necessarily the substrate.* Conductive glue bonds the part to the pads and the substrate, improving the strength and longevity of your PCB.
And if you look at this picture, it's pretty strong - perhaps 300 grams of weight that is not only pulling the substrate down, but levering it down as well. I saw no cracks or damage to the pins. We don't have a proper forcemeter so this is mere back-of-the-envelop experimentation, but for a typical connector that is enough strength for most a large set of plugging/unplugging cycles. We'll be updating this blog as we continue to test various applications.