Wave soldering technology is a mature electronic assembly process

Wave soldering technology is a mature electronic assembly process,the process is loading plate,coating flux,preheating,wave soldering,hot air knife treatment,cooling and unloading plate.The wave crests have wide flat wave,turbulent wave and rotating wave,etc,and the high process requirements are double wave soldering.Secondary welding is a supplement to primary welding,which can effectively improve the welding quality. 8 common solder joint quality problems with virtual welding,resulting in virtual welding are caused by:the solder pin is subject to oxidation,the surface of the weldment pin is dirt,the soldering quality is poor,the welding quality is not good,the amount of soldering tin is too little,the temperature of the soldering iron is too low or too high,and the welding time is too long or too short,jitter of weldment before soldering during welding.

pairs of pins less parts of the direct use of soldering iron and tweezers,and pin many of the components are removed,it is best to use the suction tin tool,the hot air gun is used to disconnect the patch elements.0 Observe Figure 2-1-29,pointing out the reasons for the poor welding. 

Wave soldering boot operation note:

set switch time and tin furnace welding parameters;

Set the preheating temperature of the tin stove;

check the equipment power supply pressure before the boot is correct;

check whether the air pressure and the temperature of the tin stove reach the set value;

check the conveyor belt is normal operation,the transmission part of the foreign body. 

Second,the basic knowledge of wave soldering 

What is the wave soldering refers to the melting of the soft solder ( Pb-Sn alloy ), by the electric pump or electromagnetic pump jet into the design requirements the solder wave crests can also be formed by injecting human nitrogen into the solder pool,so that the PCB printed boards of the pre-inserted components are placed on the conveyor chain, through a certain angle and a certain depth of immersion,through the solder wave crests to achieve the process of solder joint welding.

Wave soldering process

wave soldering process 

the surface of the wave surface wave is covered by a layer of oxide film,which is almost static on the whole length direction of the surface of the solder wave,during the wave soldering process,the PCB contacts the surface of the tin wave,the oxide film ruptures, and the tin waves in front of the PCB are pushed forward,this shows that the whole oxide film moves at the same speed as the PCB. 

When the PCB enters the front end of the peak,the substrate and the pin are heated,and the whole PCB is immersed in the solder before leaving the peak surface,that is,the solder is bridged,but at the moment of leaving the peak,a small amount of solder is attached to the pad due to the effect of wetting force,and because of the surface tension,the lead will shrink to the minimum state,and the wetting force between the solder and the pad is greater than the solder between the two pads cohesion.Therefore, a full and round solder joint will be formed,leaving the excess solder at the tail end of the wave crest,which will fall back to the tin furnace due to the effect of gravity.

peak height

Peak height refers to the height of the PCB to eat tin in the wave soldering. The numerical control is 1 / 2 ~ 2 / 3 of the thickness of the PCB, which will cause the molten solder to flow to the surface of the PCB and form a " bridge connection "; too low, easy to cause air welding leakage welding. 

Preheating pre-heater definition : it is a heating box made of a high temperature resistant material, and the heating pipe is placed in the heating box ( Fig. 2 1 35 ). The PCB is heated by radiating heat from the reflecting disk. 

The main component of flux soldering flux is turpentine or rosin ( Fig. 2-1 36 ), the principle of which is that turpentine or rosin is vaporized at high temperature, vaporized turpentine or rosin is chemically reacted with the oxide layer of the metal, and the metal removed from the oxide layer is more favorable for welding.The flux density is ( 0.812 + 0.02 ) g / cm.