How much do you know about the manual welding of monolithic ceramic capacitors? (II)

1. A method of soldering while preheating a circuit board and components of a correction portion using a heater

Solder paste on a single side pad

Apply flux to components and pads

Preheat the components on the hot plate

Preheat the board with a hot air blown circuit board

After the preheating temperature of the component and the board reaches the specified temperature, clamp the component with tweezers and quickly place it in the mounting position (the required warm-up time varies depending on the heat capacity of the board)

Solder the solder paste again with a soldering iron tip and solder the terminals at one end

Soldering the opposite side of the terminal while supplying the solder wire

2. Method of welding only using a heater

Solder paste on a single side pad

Apply flux to components and pads

Heating with a heater to solder the terminals on one side

Soldering the opposite side of the terminal while supplying the solder wire

By using hot air for welding, cracking can be suppressed without preheating the element. In addition, when soldering, the temperature of the board during soldering can be increased by blowing the board with hot air.

The principle of manual soldering leads to reduced bending resistance of the board

In terms of operation flow, the biggest difference between reflow soldering and manual soldering is the temperature of the board during soldering. This difference affects the board's bending resistance.

Solder, components, and boards shrink during the cooling process after soldering. The external electrode end (stress concentration part) is the starting point of the destruction of the component of the circuit board bending test. The shrinkage of the solder and the component can generate tensile stress on the part, and the shrinkage of the circuit board can be used as the force of the compression direction to alleviate other Tensile stress. The compressive stress generated by the board is determined by the board temperature at which the solder begins to solidify.

When reflow soldering is performed, the overall heating and cooling are relatively uniform, and when manual soldering is performed, the temperature of the board when the solder starts to solidify is low (50 to 70 ° C when the board is not preheated), and therefore, it is cooled to a normal temperature state. At the time of stress concentration, the residual stress in the tensile direction is increased, and the bending resistance of the hand-welded circuit board is lowered as compared with the reflow soldering.