using a 25W iron whose tip wasn’t heating up properly. Had to use its sides to get the solder to melt, which affected precision.

The tip was likely heating up just fine, what you encountered was probably thermodynamics.

Very common for novices to intuitively use the point of the tip. For anything but the smallest joints, it actually is the least effective part of the iron.

Soldering is a game of heat transfer. While you use the iron to transfer heat and try to wet the solder, that thermal energy is being dissipated into the rest of the project - circuit traces, components, and often the heftier ground plane. You’re essentially trying to beat the dissipation rate.

The point of the tip - and especially a conical tip - has a small surface area. Small surface area transfers a small amount of heat. The sides, conversely, have a larger surface area which results in more heat transfer. Most techs gravitate towards chisel or knife tips since they give a wide, flat surface to put into contact with the work.

Ultimately, your circuit works - yay! If you’d like to improve the quality of your joints:

• Add flux to help the solder reflow
• Keep a bead of solder on the tip to help with heat transfer
• Maximize the surface area of the tip that is in contact with both sides of the joint - the component and the pad.

For more stubborn projects, preheating the work with a heat gun can help combat thermal dissipation - just be mindful not to scorch your project!