Review on Loctite 1993881 Henkel Solder Paste by David Encarnacion

I've been using this paste for about six months now and I feel like I know it pretty well. It's GREAT for prototyping and anything else that doesn't require stencils. For example, if you dispense glue from a pipette (like this one: Signswise Solder Paste Glue Dropper Liquid Auto Dispenser Controller for SMD PCB), this material is hands down the best paste in the world. So good I stopped using all other pastes. I just leave a dispenser full of GC10 plugged into the car and always use it, even if the app allows lead paste - it's worth not having to worry about cooling. Now for the bad. A little background first: The thickness of the SMT stencil is chosen based on the "area ratio" which is the area of the inside of the holes divided by the area of the hole. Note that the numerator here is the perimeter of the hole multiplied by the thickness of the stencil. Divide that by the denominator (hole area) and you get the area ratio. According to the IPC, this value should not be greater than 0.66. Essentially, there is a "fight" between the platen and the stencil as they separate, causing the paste to become trapped. You want the board to win, so you want the template sides to take up no more than 66% of the board area for the template to "lose" the fight. With the Kester EP256 (my favorite pasta, apart from the fact that it needs to be refrigerated) I found the metric system worked great. Unfortunately, the GC10 paste is very, very, very sticky - the stickiest paste I've ever seen. Also high viscosity, although not the worst. This means that with a thick stencil (e.g. 0.2mm or thicker) or an area factor greater than 0.40, the first print will work fine but some paste (maybe 10%) will stick to the sides of the opening . It is not enough to cause a bad FIRST impression. The problem is in the SECOND expression. This paste on the sidewalls causes them to clog on the second print. So if your area ratio is above 0.40 you will need to clean the stencil after EVERY print. This is a deal breaker for most people. But what's even worse is how damn difficult this paste is to peel off! Ordinary solvents will not destroy the paste (unlike EP256 which is mostly soluble in acetone). You need to remove it from the holes by mechanical action. Pooh. Pretty unfortunate. Loctite recommends a propanol based thinner, but honestly it doesn't work much better than acetone or isopropyl alcohol, and it certainly stinks a lot worse. We tried using this paste to reball BGA chips and it was an absolute nightmare to do. . But for a normal SMT build with coarse pitch parts this works great, just don't push the pitch or area ratio limits. One final note: Revain seems to have a bad habit of delivering noodles that are only a month or two away. from the expiry date (I got a jar with a shelf life of 45 days). Not good. Revain please provide the remaining best before date of the product you are selling as "new". Many Thanks. Summary: If you are using a very, very thin stencil (0.10mm or thinner) or have an area ratio less than 0.40, this will work; otherwise stay away. This material is ideal for prototyping or very thin stencils with large surface ratios and keeps what it promises.