Soldering Iron - Printed Circuit Board Soldering Process
1. Preparation before welding
First of all, you must be familiar with the assembly drawing of the printed circuit board to be welded, and make ingredients according to the drawing. Check whether the component model, specification and quantity meet the requirements of the drawing, and make preparations such as component lead molding before assembly.
2. Welding sequence
The order of assembly and welding of components is: resistors, capacitors, diodes, transistors, integrated circuits, and high-power tubes. Other components are ordered from small to large.
3. Requirements for component welding
1) Resistor soldering
Install the resistor accurately into the specified position according to the diagram. It is required that the mark should be upward and the word direction should be consistent. After installing the same specification, install another specification, and try to make the resistors the same height. After soldering, cut off the excess pins exposed on the surface of the printed circuit board.
2) Capacitor welding
Install the capacitor in the specified position as shown in the figure, and pay attention to the fact that the "+" and "-" of polarized capacitors must not be connected incorrectly. The direction of the marking on the capacitor must be easily visible. Install glass glaze capacitors, organic dielectric capacitors, porcelain dielectric capacitors first, and finally electrolytic capacitors.
3) Diode welding
The following points should be paid attention to when welding diodes: first, pay attention to the polarity of the anode and cathode, and cannot install it wrong; second, the model mark must be easy to see; third, when welding vertical diodes, the welding time for the shortest lead should not exceed 2 seconds.
4) Transistor welding
Pay attention to the correct insertion position of the three leads e, b, and c; the welding time should be as short as possible. Use tweezers to clamp the lead pins during welding to facilitate heat dissipation. When welding high-power transistors, if a heat sink needs to be installed, the contact surface should be flat and smooth before tightening. If an insulating film is required, do not forget to add the film. When the pins need to be connected to the circuit board, plastic wires should be used.
5) Integrated circuit welding
First, check whether the model and pin position meet the requirements according to the drawing requirements. When welding, first weld the two pins on the edge to position them, and then weld them one by one from left to right and top to bottom.
All excess pins of capacitors, diodes, and transistors exposed on the printed circuit board must be cut off.
