What is the reason for wave soldering tin? How to reduce wave soldering tin

Wave soldering is to make the soldering surface of the board directly contact with the high-temperature liquid tin to achieve the purpose of welding. The high-temperature liquid tin maintains a slope, and the liquid tin forms a wave-like phenomenon by a special device, so it is called “wave soldering” and its The main material is solder bar. This article mainly introduces the content of wave soldering and tin soldering. We first introduced the phenomena of wave soldering and tinning. Secondly, we introduced the causes of wave soldering and tinning. Finally, we explained the technology of removing tin by wave soldering and how to reduce the number of solder tin solders. .

1. When the circuit board is over-stretched when the component pins are too long during wave soldering, pay attention to the pre-processing of the component's cutting legs: the extension length of the general component's pin is 1.5-2mm, which is not higher than this height. There will be no phenomenon

2. Because the circuit board process design is becoming more and more complicated, the lead pin pitch is getting denser and the wave soldering phenomenon occurs after soldering. Changing the pad design is the solution. If you reduce the pad size, increase the length of the pad exit wave side, increase the flux activity / reduce the lead extension length is also a solution.

3. Soldering tin after solder wave soldering infiltrates to the surface of the circuit board. The main reason for this phenomenon is that the inner diameter of the pad is too large, or the pin diameter of the component is too small.

4, the dense foot components formed in a region of the wave peak formed after soldering components connected tin

5, due to the pad size is too large and formed by the wave soldering tin

6, due to poor solderability of component pins formed after the wave soldering component pin Sn phenomenon

1, flux activity is not enough.

2. The flux does not wet enough.

3. The amount of flux applied is too small.

4, uneven flux coating.

5, the circuit board can not be coated with flux.

6, no regional tin board tin.

7, part of the pad or soldering feet serious oxidation.

8, circuit board wiring is not reasonable (unreasonable distribution of parts).

9, take the board in the wrong direction.

10, tin content is not enough, or copper exceeds the standard; [impurity exceeds the standard caused by tin liquid melting point (liquidus) is increased]

11. Blocking of the foaming pipe causes uneven foaming, resulting in non-uniform coating of the flux on the circuit board.

12, wind knife set is not reasonable (flux is not blown uniform).

13, take the board speed and warm up with bad.

14, hand dip tin when the method of operation is not proper.

15. The chain inclination is irrational.

16, uneven peaks.

There are many advanced supplemental options in various machine types. For example, a patented hot-air knife-to-bridge technology was provided to remove bridging and solder joint damage. The air knife is located at the exit of the weld slot and shoots 0.4572mm narrow hot air toward the solder joint at an angle of 40° to 90° from the horizontal. It can refill all of the through-holes that were not well-welded for the very first time with air, without affecting the normal solder joints. It must be noted, however, that in order to achieve a significant increase in the quality of solder joints, there is no need to set more options on wave soldering equipment. And for all production equipment, it is also very important to check the true accuracy of each engineering data. A good method is to run the board first before buying.

1. Design according to the PCB design specification. The long axis of the two tip Chips is perpendicular to the welding direction, and the long axis of the SOT and SOP should be parallel to the welding direction. Widen the pad on the rear pin of the SOP (designed to steal a solder pad)

2. The pins of the inserted components should be formed according to the hole pitch and assembly requirements of the printed circuit board. For example, when using the short plug welding process, the surface of the soldered component exposes the surface of the printed board by 0.8 to 3 mm. The component body is required for the insertion. correct.

3, according to the size of the PCB, whether the multilayer board, the number of components, there are placement components such as preheating temperature

4, tin wave temperature of 250 ± 5 °C, welding time 3 ~ 5s. At slightly lower temperatures, the belt speed should be adjusted slower.

5, replace the flux.