Wave soldering is a very large production link with process parameter windows, and it is very easy to expose the impact of PCB design on soldering quality. Good PCB design can simplify the manufacturing process, shorten the manufacturing cycle, reduce manufacturing costs, optimize quality control, enhance product competitiveness, and improve product durability.

1. PCB routing orientation

X-Y coordinate wiring uses the wiping effect between the liquid solder and the wire solder joint to reduce the bridging probability. The so-called X-Y coordinate wiring is to arrange all the wires of the PCB wave soldering surface parallel to one side of the PCB.

2. Arrangement of welding surface patches

There is an important factor in wave soldering that can cause virtual soldering, called the shadow effect. The so-called shadow effect is simply that the device blocks the pad in the transmission direction. To a certain extent, the wave soldering equipment can properly solve this problem by turning on the random wave, but the most fundamental thing is to solve this problem from the component layout.

In the shadow effect, you can turn on the random wave to solve it, but turning on the random wave means that the component is subject to two high temperatures. Therefore, devices such as chip resistors and capacitors are best to have a straight line formed by two pads in the layout direction is vertical. And the placement of the triode should not block the pad. When the two pads of the component are heated at the same time, soldering with the same teacher is very conducive to the quality of the solder and reduces the impact of high temperature on the performance of the component. However, in most cases, it is difficult to take into account both the circuit layout and the above wave soldering process, so there are many designs that use the overall layout to turn a 45-degree angle.

3. Concentricity of pads and holes

In a single-sided PCB, the concentricity of the pads and holes can almost completely cause defects such as uneven cavities, voids or solder joints. Effect of hole and line gap on wave soldering:
1) Lead diameter and pad mounting aperture directly affect the mechanical and electrical properties of the solder joint
2) Important factor in generating solder joint holes
3) The generation of holes has nothing to do with the size of the pad. The size of the pad can only affect the fullness of the solder joint.
4) Considering the capillary effect during welding, 0.05 ~ 0.2mm is recommended.

4. Leaving hole pad

For wave soldering of single-sided PCB boards, in order to facilitate supplementary components, the pads that expose the holes are called left-hole pads. The size of the left-hole is 0.5 ~ 0.6mm

5. The height of the pins protruding from the PCB

1) For PCBs without SMD components, when H <1.8mm, the possibility of bridging will be relatively reduced. The longer the component feet, the stronger the bridging.
2) Less than 1.2mm, the reliability and appearance of the solder joint will be greatly reduced
3) For SMD PCBs, considering that some component bodies are relatively high, it can be appropriately relaxed, but the maximum cannot exceed 2.4mm, so as not to affect the assembly

6. Setting of break away tab

1) The setting of break away tab first considers the linear arrangement of the solder joints
2) Secondly consider setting it on the long side, so that the PCB's deformation will be lower when subjected to high temperature

7. Solder mask

When the solder resist is applied in wave soldering, it will have some adverse effects:
1) The moisture content of the solder resist, preheating at a temperature that can meet the normal welding, can not evaporate the moisture in the adhesive before welding, it is easy to explode tin beads during welding
2) Manual application of solder resist, which is easy to spread to the SMD pads when some components are close to each other, causing false soldering.
3) During the soldering process of long feet, when cutting the component feet, the glue is easy to stick to the blade surface and attract dust, which affects the PCB board at the back.
4) Therefore, for non-through holes, you can avoid the glue by the design of the pad; but the through holes are different, and only the glue can be used.