this post was submitted on 23 Nov 2024
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::: spoiler You can still lift pads on many double sided boards. The real key is to use the highest heat capacity iron tip that can fit into the task at hand. The highest heat capacity tip will allow you to lower the tip temperature and transfer that heat effectively. With experience, you'll also learn when to add supplemented heat due to ground planes and components.
If you ever get to the point of etching your own boards and then the extra even rarer step of attempting through hole plating. The biggest challenge is how to get the initial conductive bridge to form inside the hole itself. This usually involves something like a paint with graphite powder, or other chemical solution. Then the holes are electroplated with copper. The inside of these holes is not a particularly great surface to work with and has minor inconsistencies that are typical of a drill bit finish through a substrate like fiberglass. You're likely to have a composite of different materials like the glass fiber and resin or even a plastic core with CEM. It does not make a very consistent substrate to coat, and the surface is hard to build consistently.
I come from owning an auto body shop twice, so I know all too well: liquid paints always pull away from sharp edges where they will be thinnest. Also, absolutely every finish is only as good as the layer it is on top of. If you put a $10k job on top of a pealing $500 job, it will fall apart and be nothing but problems within a year.
The qualities of the base coating that is used to initially bridge the top and bottom layers is what will largely determine the durability of rework.
Overheating the region will have a big impact on the outcome. With many stations and tips you're likely to use too high of a temperature to compensate for tiny or the wrong tips. You need to get the lowest temperature possible and normalized on the whole connection quickly for rework. Preheating makes a big difference, as does eliminating any even small sources of moving air.
My favorite Hakko 900 series tip is the 900M-T-3.2D 4962615503139 (have it right beside me now in a sleeve of several). Genuine Hakko tips have far better plating that makes a difference too. I can do nearly every job with that tip turned in various orientations.
A hot air rework gun is helpful, just never cut off the cool down time prematurely. You can get a couple of the fake magic arm camera clamps for photography to make a handy holder for a cheap hot air rework setup. Use the counter clamp from the second arm to hold the gun.
A basic cheap hotplate from a thrift store is helpful for preheating too, even one that is only for warning with no temperature adjustment.
@j4k3 @grue
I have a roll of very low temperature solder that has high bismuth content. It is not to solder with instead you use it lower the melting point of solder then wick it up . Was used at EMR Telemetry and when they were sold I was given a roll. Like a big roll of chip quik.
It is valuable to desolder things like ESP32s. The odds of lifting pads are slim with it too.