VIII. Wave soldering machine furnace temperature debugging
Wave soldering machine furnace temperature is the key to the entire soldering system. Leaded solder can be wetted between 223 ° C - 245 ° C, while lead-free solder needs to be between 230 ° C - 260 ° C to wet. A tin temperature that is too low will result in poor wetting or poor fluidity, bridging or poor soldering. Too high a tin temperature will result in severe oxidation of the solder itself, poor fluidity, and serious damage to the copper foil on the surface of the component or PCB. Due to the differences between the set temperature of each place and the measured temperature of the PCB board surface, and soldering by the component surface temperature limitations, leaded soldering temperature is set at about 245 ℃, lead-free soldering temperature is set at about 250-260 ℃ between. At this temperature PCB solder joint brazing can achieve the above wetting conditions.
IX. PCB circuit board pad wave soldering before adjustment
PCB board pad design PCB board pad graphic design is good or bad is caused by welding in the pull tip, bridge, eat tin bad main factors.
1. The shape of the pad should generally be considered with the shape of the hole, and the shape of the hole generally corresponds to the shape of the component line. Common shapes are: tear drop, round, rectangular, oblong.
2. The pad and through-hole if not centered, easy to appear in the welding of air holes or uneven tin on the solder joints, the formation of the cause is the metal surface of the liquid solder adsorption force caused by different.
3. Component pin diameter and the size of the gap between the aperture seriously affects the electro-mechanical properties of the solder joints, welding solder is formed by capillary action rising to the surface of the PCB. Too small a gap between the solder is difficult to penetrate the aperture in the back of the copper foil wetting, too large a pitch will make the component pins and pads combined with the mechanical strength of the weak. Recommended value of 0.05-0.2mm; AI plug-ins can take the value of 0.3-0.4mm between the maximum value of the gap can not exceed 0.5mm or more.
4. The pad and through-hole diameter with improper, will affect the fullness of the shape of the welded joints, thus directly affecting the mechanical strength of the welded joints.
5. Line design requires a smooth and uniform wire, gradient transition can not become a right angle or acute angle of the sharp transition, to avoid welding at the sharp corners of the stress caused by the copper foil warping, peeling or fracture. In general, the line is designed to follow the principle of smooth flow of solder.
X. Wave soldering machine component adjustment
1. Components in the welding caused by bad mainly in the component pin surface oxidation or component pins too long. Component pin oxidation will lead to virtual welding, while the pin is too long will produce a bridge or solder joints on the tin is not full (solder surface liquid solder is dragged off the component pins).
2. Component pin surface plating is also a factor that affects the component welding.
3. Components installed on the PCB surface is an important part of the impact of welding, IC class packaging components and row of plug welding will directly lead to the generation of bridging. SOP class components towards the production or not will lead to empty welding. The essential reason for its formation is that the tin flow is not smooth and components of the shadow masking effect.
XI. Wave soldering transmission angle adjustment
Wave soldering transfer angle transfer angle refers to the inclination of the rail, welding caused by bad commonly found in the bridge connection. The fundamental nature of adjusting the angle is to avoid the possibility of two neighboring solder joints at the same time in the solder desoldering. Generally, bridging can be achieved by adjusting the angle or the amount of flux or the immersion time or the depth of PCB immersion and other relevant factors. In regulating the above factors, if only a certain part of the adjustment, will inevitably change the PCB immersion tin time, without affecting the state of the PCB surface cleanliness, try to give the amount of flux appropriate more to prevent the production of bridging (appropriate angle between 4-7 degrees, some companies are currently using roughly 5.5 degrees).
XII. PCB circuit board tin depth adjustment
PCB tin depth due to the solder in the process of infiltration of a large number of heat will be absorbed by the PCB, if the solder in the soldering process is now insufficient temperature will lead to the inability to penetrate the tin or due to the weakening of diffusivity caused by other bad, commonly found in the bridge or empty welding (flux high-boiling substances attached to the surface of the pad can not be volatilized), in order to obtain sufficient heat, according to the different PCB boards will be eaten by the depth of the tin to regulate the principle of the correspondence is roughly Corresponding principles are roughly as follows:
Single-panel for 1/3 board thickness
Double-sided board for 1/2 board thickness
Multilayer board for 2/3-3/4 board thickness.
XIII. Wave solder wave adjustment
Wave solder wave form components and PCB in the solder after welding, out of the wave when the wave needs to provide a relatively stable, no external interference in a balanced state. For a simple PCB, if there is no fine-pitch design components, the degree of stability of the wave surface will not adversely affect the welding. But for fine-pitch pin components, when the component pins out of the crest, by the capillary effect, the solder is pad and lead in "a relatively balanced point" separated from the solder wave, ("a relatively balanced point" refers to the instant the component is removed from the tin, the front flow and back flow of the wave crest. (The "point of relative equilibrium" refers to the moment when the component is removed from the solder, the front flow and back flow of the wave and the transportation speed is a set of balanced forces, and the surface of the wave is free of disturbances and cross-flow conditions.) The solder will be wetted on the surface to be soldered by the capillary function. We adjust different waveform shapes essentially to find this "balance point" to accommodate different customer needs. (This is what we often refer to as the "tin release point".) Generally speaking, simple PCBs do not require too much waveform, while complex PCBs have stringent requirements for waveforms. In terms of high-density mixed boards, T components require the first wave to provide a trapezoidal high-impact wave that can be soldered for 2 seconds to correspond to the masking effect; packages and plug-in components are required to provide a soldering time of 3-4 seconds of the "stable wave". Each type of components according to their own characteristics, basically also put forward the requirements of the solder wave, large heat capacity of the package and the row of plugs adapted to the stratospheric wave, while similar to the package of small heat easy to the row of plugs are adapted to the arc wave.
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