What are the differences between wave soldering and manual soldering?

Date：2022-11-17 15:57:59Views：507

In PCBA processing, the welding methods mainly include reflow welding, wave soldering and manual welding. What is the difference between wave soldering and manual soldering? Now, what are the differences between wave soldering and manual soldering in PCBA processing?

Manual welding

1. The temperature of the soldering head is difficult to control accurately, which is the most fundamental problem. If the temperature of the soldering iron tip is too low, it is easy to cause the welding temperature to be lower than the lower limit of the process window, resulting in cold welding or faulty welding; At the same time, due to the limited thermal recovery of the soldering iron, it is very easy to lead to poor tin penetration in the metallized through-hole. If the temperature of the soldering iron tip is too high, it is easy to make the welding temperature higher than the upper limit of the process window and form an excessively thick intermetallic compound layer, which will cause the solder joint to become brittle and the strength to drop, and may cause the pad to fall off and the circuit board to be scrapped;

2. The quality of solder joints is often affected by the knowledge, skills and emotions of operators, which is difficult to control;

3. The cost advantage of labor over machinery and equipment is gradually lost.

Wave soldering

1. Different solder joints on the same PCB may require different welding parameters due to their different characteristics (such as heat capacity, pin spacing, tin penetration requirements, etc.). However, wave soldering is characterized by that all the solder joints on the whole PCB can be welded under the same set parameters, so different solder joints need to "accommodate" each other, which makes it difficult for wave soldering to fully meet the welding requirements of high-quality PCB;

2. The following problems are easy to occur in practical applications:

When the thermal shock is too large, it is easy to cause the deformation of the whole circuit board, thus opening the component solder joints on the top of the circuit board

The surface mounted devices welded on the double-sided mixed circuit board may have secondary melting

Welded thermal sensors (capacitors, LEDs, etc.) are easy to be damaged due to high temperature

The tooling and fixtures used to prevent the above situations are easy to form welding shadows and thus cause cold welding

3. The operation cost is high. In the practical application of wave soldering, the whole plate spraying of flux and the production of tin slag have brought high operating costs; Especially in lead-free soldering, because the price of lead-free solder is more than 3 times that of lead solder, the increase in operating costs caused by the production of tin slag is amazing. In addition, the lead-free solder continuously melts the copper on the bonding pad, which will change the solder composition in the tin cylinder over a long period of time. This needs to be solved by adding pure tin and expensive silver regularly;

4. The maintenance is troublesome. The residual flux in the production will be left in the wave soldering transmission system, and the generated tin slag needs to be removed regularly, which will bring users more complicated equipment maintenance;

5. Poor PCB design brings certain difficulties to production. When some circuit boards are welded, because the designer has not considered the actual production situation, no matter what wave soldering parameters we set and various fixtures are used, the welding effect is always difficult to be fully satisfied (for example, some key parts always have defects such as poor tin penetration or bridging). After wave soldering, repair welding has to be carried out, thus reducing the long-term reliability of the product.

From the comparison between selective wave soldering and manual soldering, we can easily find that selective wave soldering has many advantages such as good welding quality, high efficiency, strong flexibility, low error rate, less pollution and diversified welding components. The essential difference between wave soldering and manual soldering is that in the preheating area, impurities in the flux on the PCB board in the preheating area will be effectively volatilized, thus improving the quality of product tin bath. Again, its working efficiency will be much higher than that of manual soldering, and the board surface will be cleaner than that of manual soldering! The wave soldering efficiency is high and the quality is stable. The quality of hand soldering cloth is not well controlled, and there are too many personnel factors.