6. Soldering of radio radio elements

1.6. Soldering of radio radio elements

When repairing the RG, it is necessary to properly solder the electronic components. Soldering is the process of welding two metals together. At the same time, metals melt and combine, creating a strong electrical and mechanical connection.

In the process of soldering, the essential parameters are its duration and temperature. A typical soldering operation can be completed in approximately 1 to 1.5 seconds, provided that the correct type of soldering iron and tip are selected. The optimum melting point of the solder is 182 ° C. The combination of solder metals and connected conductors occurs at temperatures between 260 ° C and 315 ° C.

The main effect of soldering is to combine copper and tin. It should be borne in mind that both of these metals are easily oxidized. A bad or non-soldered joint is obtained if the surfaces to be joined are dirty, so it is necessary to perform soldering with a good, cleaned flux. Flux prepares soldered surfaces for better metallization. First, the solder is treated with flux, and then the soldering surface, removing oxides and other contaminants. As a result, the metal is heated so that the solder melts, spreads, giving a good surface connection.

It should be noted that if the temperature of the tip is too low, it will get stuck on the surface of the soldering. If the temperature of the tip is very high, it can damage the surface of the board. The optimum temperature for soldering on the board is in the range of 260 ° C - 315 ° C.

When soldering, the tip of the soldering iron must be kept on one side of the ERE output, and the solder on the other side. As soon as the contact pad warms up, the tin-lead solder will melt and flood the contact pad along with the output of the ERE. At the same time, solder should be kept low and fairly even.

After soldering is completed, it is necessary to carefully inspect the contact pad, since a lot of solder could be put on the joint, or it was not enough from above or below. Large solder balls, or hills, may contain cold soldering where only partial contact is made. Such soldering can be a source of flickering faults.

Before soldering the ERE to the board, it is necessary to make sure that they are operational, then clean them from oxides and dirt. If during the soldering the printed circuit is interrupted or peeled off from the board, it is necessary to bridge the damaged area with tinned wire on both sides with a diameter of 0.2 - 0.3 mm. If the contact pad or track rises above the board, it is necessary to glue or overlap the track on the damaged area, then scrape the coating off the contact or on both sides of the track so that the new contact or track can solder well to the existing contact or track. After that, remove all the excess solder and drill again each hole that has become covered or clogged with solder residues.

Certain problems often arise when removing solder residues and discharging electrical radio elements from the printed circuit board. One way to remove solder residues is to use a hand-held vacuum pump with a spring-loaded piston to draw hot melted solder from the contacts of the module board. This process consists of the following operations:

1. Heat the old solder with a soldering iron until it melts.

2. Place a spring-loaded vacuum pump in hot solder.

3. Quickly remove the soldering iron, at the same time, release the spring of the vacuum pump and pump the solder into its storage chamber.

This method works well when watering bipolar transistors or microcircuits that do not have CMOS transistors in their structure. Since vacuum pumps generate static electricity, it is dangerous to unsolder CMOS transistors (microchips) because they can be put out of action.

A safer way to remove solder is as follows:

1. Attach the copper braid to the solder, then heat the braid in a place close to the solder.

2. Copper braid warms up quickly, transferring heat to the solder, which will melt and be absorbed into the braid due to the capillary effect.

3. After that, it is necessary to cut off and throw away a piece of braid impregnated with solder.

If some amount of solder remains in the board hole, it is necessary to heat a steel needle having a diameter slightly smaller than the board hole. The needle will leave the hole open so that you can insert and solder another conductor.

When using this solder removal method, you must ensure that the soldering iron is well grounded. In some cases, solder residues can be removed by drilling a hole with a thin drill. After drilling the hole, you must make sure that all chips, residues and solder pieces from the board are removed. When evacuating the ERE from the module board, you must be careful not to overheat it, since the printed conductors (tracks) may become detached if the board overheats.

When repairing an RIP an important role is played by the tool with which the repair is made. First of all, it is necessary to have several different-capacity soldering irons with different stings, depending on what kind of soldering they produce. In addition, you must have a variety of screwdrivers from crosswise to flat, of various sizes, up to a set of watch screwdrivers. It is necessary to have several different sizes of tweezers, nippers, side cutters, pliers and other devices.