Toronto Module D

1. September 25 2015: Gluing of ABC 250 ASICs to Remaining ABC250 Hybrid ("Hybrid D")

While gluing the final ABC250 hybrid, we tested our methods for dispensing glue using the microlitre pipette. Recall that in gluing the earlier modules (A-C), we had issues with the glue leaking out of the sides of the ASICs and spreading onto the bond pads. After the production of those modules, we realized that the issue must have been in the way we dispensed the glue. Essentially, the plunger of a microlitre pipette has two points of resistance. Originally, we pressed down to the second point of resistance both when loading and dispensing glue. This method is incorrect. Here are the instructions for properly using a microlitre pipette:

  1. Push the plunger down to the first resistance. This is the load volume. The distance you have to push the plunger to reach the first resistance will change depending on what volume you have set the microlitre pipette to.
  2. While holding the plunger at the first resistence, immerse the tip in the glue (or whatever solution you are using). Do not touch the tip to the bottom of the container, just immerse it enough to cover the tip in the liquid.
  3. Slowly release the plunger, taking care to leave the tip inside the liquid until it has filled completely. Removing it too soon will cause bubbles, which will result in an inaccurate volume of liquid.
  4. Visually inspect the load to make sure there are no bubbles.
  5. Dispense of the glue by pressing the plunger to the second resistance. This second resistance is for completely expelling the liquid. Wait a moment while dispensing the glue, and remove the pipette without releasing the plunger.
For the final hybrid, we dispensed glue for two of the ASICs using our original method, and the rest of the ASICs were glued using the proper method.

In the first picture you can clearly see the difference in amount of glue (see the first photo). For the 4th and 6th ASICs in the back row, we dispensed the glue using the same method that we used for gluing hybrids A-C. For the rest of the ASICs, we dispensed the glue using the proper method described above. Just to note, for the some of the ASICs we had the pipette set to 3 microlitres instead of 2 microliters (2 is the correct amount), but this did not affect the end result of whether or not glue leaked onto the bond pads.

In the second photo, once the ASICs are glued in place, you can see that the edges around the back 4th and 6th ASICs are a different colour. This is because glue did leak out, which we can see in person.