When using liquid metal pastes on laptops that are often transported or carried in backpacks often (e.g. for students or travelers), it is a good idea to have free insurance against liquid metal runoff escaping the CPU/heatsink/GPU areas, getting on the PCB and destroying your hardware. Do not allow conductive balls of doom to run amok in your laptops! You are STILL going to have to deal with possible dislodging or runoff even if you do use Super 33+ tape or decent Kapton tape. Tape won't prevent runoff at all. Runoff is spare traces of LM balls that escape from the housing, do NOT get trapped on insulated SMD resistors and slide ACROSS the CPU or GPU housing and off onto the motherboard, where it WILL eventually fry something by shorting. That's where barriers come in. A common barrier first used by an airline pilot over here (who takes his laptop with him, and who NEEDS a barrier) is highly compressible foam. The foam must be VERY porous and not dense at all and *MUST* compress to the width of a human hair, with your fingers, with MINIMAL resistance, with a cutout shape in the shape of the CPU or GPU, with a few millimeters to spare for proper clearance (you don't want the foam blocking the heatsink from touching the cores). THESE DAMS ARE NOT EVER, EVER TO BE USED IN SUBSTITUTION FOR NAIL POLISH INSULATION COATINGS, OR SUPER 33+/KAPTON TAPES, EVER, but in COMBINATION with them. The job of the foam is to catch any spare LM balls that escape the chips, and block them from going anywhere else. They will sit on the foam with nowhere to go. If you had a bad mount and the temps started skyrocketing, you will have saved your hardware. Suitable foam is best sourced locally so you can test it in person, rather than trying to find it online. Hardware stores or hobby shops are excellent places for finding foam. These foam materials are often used in packing sensitive objects. The cutout foam MUST be very thin. On high pressure heatsinks like desktop heatsinks or AIO's, if foam happens to be used, that is not important, just compressible. But laptop heatsinks have atrocious mounting pressure so ANY resistance from foam will decrease resistance even further and not give you desired temps--you want the temps with foam to be identical to without foam. So do your work. Let's say your foam is 3mm thick and highly compressible. You MAY get away with this, but to be safe, you should CUT the foam width in half to 1.5mm. This will be ideal. If you're good and OCD, or just plain pro, go for 1mm. Thinner is better. Just don't have it so thin that it breaks apart. Don't try to cut an 'uncut' (meaning: square shape of foam, that has not had the CPU or GPU layout trimmed from it yet to trim it, that will be too difficult. Instead cut out your shape first, trim the outside to the exact shape of the CPU and GPU housings, and THEN use extremely precise scissors like titanium scissors, and then start working around both the inside and the outside to trim some of the thickness away. Once you start this, you will see why the "cutout" is much easier to trim than an uncut block To secure the foam dams so they don't shift and move when applying the heatsinks, put a dab of transparent nail polish (the same stuff you used for insulating the SMD resistors) in each corner and secure it. Left image is original cutout foam dam, 3mm for BGA CPU. Right three images are trimmed 1mm cutout foam dams for BGA CPU and GPU's. Trying to use 3mm (or thicker) foam requires VERY low density. The thinner the better. Some substitutions for foam dams can possibly be thin compressed layers of silicone gasket sealer--the same stuff used for relidding IHS's, although this requires preparation--this MUST sit BELOW the level of the CPU or GPU as this otherwise adds resistance! There are ways to prep this, such as @Mr. Fox 's experiment,--and even extremely thick (VERY thick) pastes like that super old Radio shack thermal paste, or partially dried or old Arctic Ceramique (NOT dried out, just very hard to squeeze) will also work as barriers too, when used carefully around the silicon housings, although this will be messy, and a pain to clean up if you have to redo your LM application. A VERY big pain. Feel free to list tested foam dam alternatives which are safe and work well for you. Note that trying to use foam dams for LGA processors will require extra planning. Picture: 3mm cutout BGA foam dam, 1mm cutout CPU and 1mm GPU foam dams.