101 Tutorial on how to solder a mismatching SMD

The Problem

First of all, i have to de-solder the existing R_Prog on the TP4056 to lower the charging current from 1A to less than 400mA. The problem is that the SMD on the TP4056 follows a 0603 footprint pad, and I ordered a 0805 SMD. Well, Gemini told me it would be okay. Also if you think about it, I don't think I will be able to solder a 0603 SMD with my exisitng setup. I would definitely need a microscope and there is no way on Earth I can solder them without solder paste and heat gun.

The approach that actually worked

Well, first thing - I didn't have a flux cleaner with me, which actually made my first board messier and dirty. At first glance, you would find that to be a stupid reason but trust me its not. Keeping the pads and the board clean is as much as important. I got the steps right on the second day and soldered it within 30 minutes, only because I had a spare TP4056. The first one really got dirty. Here is how I would tackle this problem if I was given another chance.

1. Removing the R3 resistor is the easiest part. All you need to do is apply some flux in the area and push the SMD using the iron itself.
2. Next, I would remove any remaining solder on the pads - my guess is the solder used would be of higher temperature and mixing it with your solder makes it more messier. If you have a temperature controlled iron, remove the remaining solder using a wick.
3. Next apply fresh solder until it forms a blob.
4. Place the 0805 SMD next to the pads parallelly,. Heat up one pad and push the SMD, heat up the other pad as quickly as you can. During the whole process it would be preferrable if you have a light parallelly placed and tweezers.
5. Finally apply some more solder on the top portion, not too much and that should do the trick.

Verifying the connections

To verify the connections, the best way to check is to see the resistance between Pin 2 of the TP4056 chip and the ground, which would be either OUT- or BAT-. Another way to proof check is the check continuity across one end of the resistor and PIN 2, and the other end to the ground.