When repairing equipment, it is often necessary to replace microcircuits. Microcircuits come in DIP packages - old samples and SMD - this is a modern planar package, smaller than DIP, for soldering directly to the tracks of the printed circuit board. It happens that the microcircuit is not soldered to the board, but inserted into a special socket. In this case, its replacement is very simple. But in most cases, the microcircuit is simply soldered with electrodes to the PCB tracks. In addition, microcircuits are of high power, for example, a 4-channel power amplifier for a car radio.
It is necessary
soldering iron, solder, soldering flux, new microcircuit, microcircuit guide, sewing needle
Instructions
Step 1
To replace a microcircuit, you first need to find out its brand. To do this, you need to read its designation on the case. There are times when a part of the case burns out from overload or overvoltage and it is impossible to read the name, then a diagram of this device is needed. If there is no circuit, on a sheet of paper draw a schematic diagram of the strapping of the electrodes of this microcircuit and, using the reference book, find a possible analogue.
Step 2
Now you need to remove the old microcircuit. If a powerful microcircuit attached to the heatsink is soldered, then before removing it from the board, you need to disconnect it from the heatsink. We note on which side the key was on the microcircuit in order to correctly install the new microcircuit. There are several ways to remove microcircuits from printed circuit boards:
-Being off all the electrodes with pliers.
-Solder each electrode separately, separating the electrode and the soldering pad with a syringe needle of a suitable diameter. In this case, first, the solder is melted with a soldering iron, and then a syringe needle is put on the electrode. By gently turning the needle, insert it into the mounting hole on the PCB. This is done with all electrodes of the microcircuit.
- Removing the solder with a desolder - a thick bundle of highly active thin wire. The desolder collects the solder in itself, leaving a minimum on the board and after that, you can forcefully remove the microcircuit from its mounting holes. This is the most popular method in most consumer electronics repair shops.
-Heating a section of the printed circuit board with a hot air gun to the melting temperature of the solder, usually 275 degrees.
-With the help of a special nozzle on the soldering iron, which allows you to heat all the electrodes at once. This method is not popular due to the very large assortment of microcircuits with different sizes.
Step 3
Having removed, in the most suitable way, the microcircuit, you must carefully inspect its strapping on the board. Perhaps some other part is out of order. There are frequent cases when, due to a burnt out small resistor, when turned on, a new microcircuit fails.
Step 4
After making sure that everything is in order, the power supply is giving out the correct supply voltage, the rest of the circuit is operational, you can mount a new microcircuit. To do this, you need to remove the remnants of the burning traces of the old microcircuit, if any. they are conductive with a cloth dipped in alcohol.
Step 5
Using a thin sewing needle, we check the patency of the holes. We heat the impassable holes with a soldering iron and use a needle to pierce a hole in the molten solder.
Step 6
We install the microcircuit on the board so that the key is on the right side. If the microcircuit is installed on a radiator, we bolt it to the radiator.
Step 7
We solder each electrode separately. In this case, it is necessary to warm up the soldering point well so that the solder takes hold of the electrode and the mounting pad and at the same time does not overheat the microcircuit. The optimal heating time for the solder electrode is 2 seconds. When soldering, it is advisable to use a rosin-based flux or rosin itself. You can use solder wire with flux applied to its surface.
