§01 Desoldering Resistors and Capacitors
When we are desoldering small surface-mounted resistors (such as 1206, 0805, 0603, etc.), since resistors are heat-resistant, a horseshoe-shaped soldering iron tip can be used for desoldering directly.
▲ Figure 1.1 Using a horseshoe-shaped soldering iron tip to desolder a 0805 surface-mounted resistor
If we are desoldering the components in the middle of a very dense resistor array, the horseshoe-shaped soldering iron tip may touch the surrounding components. Now, an insulating transparent paper, just like the antibacterial cloth on an operating table, is used to perform a targeted removal of the components.
▲ Figure 1.2 Using insulating paper with cutouts for protection in a dense resistor matrix
For heat-sensitive LEDs, a knife-shaped soldering iron can be used to heat the two solder pads simultaneously from the side of the component, so that the surface-mounted LED can be removed.
▲ Figure 1.3 Using a knife-shaped soldering iron to desolder a surface-mounted LED
The knife-shaped soldering iron has a wider heating surface, which can quickly remove small two-pin components such as resistors, capacitors, and LEDs in the open areas of the circuit board.
▲ Figure 1.4 Using a knife-shaped soldering iron to desolder surface-mounted resistors and capacitors
For resistors and capacitors located in the narrow areas between integrated circuits, we need the help of flux and the molten tin on the soldering iron surface, the components can be removed. There are two points in this process:
1. Pre-coat the knife-shaped soldering iron with solder;
2. it is easier for the solder to wet the component pins with flux.
▲ Figure 1.5 Using a knife-shaped soldering iron to desolder the capacitor between chips
§02 Desoldering Integrated Circuits
When we are desoldering integrated circuits, the main problem is that there are more circuit pins and a wider distribution.
Small IC circuits can be directly removed using a horseshoe-shaped soldering iron.
▲ Figure 2.1 Using a horseshoe-shaped soldering iron to desolder a micro integrated circuit
If the horseshoe-shaped soldering iron is not wide enough, a knife-shaped soldering iron can be used to remove it, but need to put more solder.
▲ Figure 2.2 Using a knife-shaped soldering iron to desolder a wider IC device
For SOP-8 integrated circuits, more solder needs to be applied and the heating time should be longer.
▲ Figure 2.3 Using a knife-shaped soldering iron + solder to desolder an SOP8 chip
After disassembly, the excess solder needs to be removedwith a soldering iron tip.
▲ Figure 2.4 Removing the remaining solder with a soldering iron
This method can also be used for some wide tantalum capacitors.
▲ Figure 2.5 Using a knife-shaped soldering iron to desolder a wider tantalum capacitor
§03 Desoldering with Heat-conducting Copper Wires
If we are desoldering a wider components,absolutely,a soldering iron tip plus solder can not heat all of the pins simultaneously. we can use the conducting copper wires, it can play the role of widening the soldering iron tip.
The following process shows the disassembly of a Mini USB socket. This requires heating the pins of the USB socket from three sides.
▲ Figure 3.1 Using heat-conducting copper wires to desolder a Mini USB socket
For this power MOSFET, the use of heat-conducting copper wires can also achieve the purpose.
▲ Figure 3.2 Using heat-conducting copper wires to desolder a power MOSFET
What about wider components? Just use longer heat-conducting copper wires. Of course, in addition to heat-conducting copper wires, applying more solder is also necessary.
▲ Figure 3.3 For larger SOP chips, use longer heat-conducting copper wires
The disassembly process is a contest between the heating of the soldering iron and the heat dissipation of the circuit board. If the soldering iron tip has low power,the heating process will be very long. Therefore, using a high-power soldering iron tip helps to shorten the disassembly time.
▲ Figure 3.4 Using a soldering iron to heat the heat-conducting copper wires to melt the solder on the IC pins
Yes. With a high-power soldering iron tip , no matter how large the chip is, it will be easy to be desoldered.
▲ Figure 3.5 Desoldering a TQFP100 chip
Add heat-conducting copper wires around it, and then use solder to add a molten tin "apron" to the component. Finally, the component will be removed from the circuit board obediently.
▲ Figure 3.6 With patient heating, the TQPF chip is finally removed
Yes,we have to break something to make something new. Only by mastering the desoldering technique then we can handle the desoldering any difficult components.
