PCB Technical - ​How to deal with substrate problems caused by PCB design

The main problems arising from the substrate in the process of printed circuit board design are as follows:

1. Various soldering problems

The scene is a sign: there are blast holes in the cold solder joints or tin solder joints.

Introspection method: often analyze the holes before and after dipping soldering to find the center of copper stress. In addition, carry out incoming inspection of raw materials.

Reasons for being able to:

1. The blast hole or cold solder joint is seen after the soldering operation. In many cases, poor copper plating, followed by shrinkage during the soldering operation, causes cavities or blast holes in the walls of the metallized holes. If this happens during the wet processing process, the absorbed volatilization

The object is covered by the coating and then expelled under the heating of the dip soldering, which will cause a spout or a blast hole.

Approach:

1. Try to eliminate copper stress. The shrinkage of the laminate in the z-axis or thickness direction is usually related to the data. It can promote the fracture of metallized holes.

Deal with laminate manufacturers to get recommendations for data with less z-axis shrinkage.

Second, the problem of bonding strength

The scene is a sign: During the dip soldering process, the pad and the wire are separated.

Introspection method: During the incoming inspection, stop the full test and carefully control all the wet processing processes.

The cause of the problem:

1. The detachment of pads or wires during processing can be caused by electroplating solution, solvent etching, or copper stress during electroplating operations.

2. Punching, drilling or perforation will cause the pad to be partially detached, which will become clear during the hole metallization operation.

3. In the process of wave soldering or manual soldering, the detachment of the pad or wire is usually caused by improper soldering technology or excessive temperature. Sometimes, due to poor bonding of the laminate or low thermal peel strength, bonding pads or wire detachment are formed.

4. Sometimes the design and wiring of PCB multi-layer boards will cause the pads or wires to detach in the opposite center.

5. During the soldering operation, the retained absorption heat of the component will cause the pad to detach.

Approach:

1. Give the laminate manufacturer a complete list of solvents and solutions used, including the processing time and temperature of each step. Analyze whether the electroplating process can cause copper stress and excessive thermal shock.

2. Really abide by the recommended machining methods. Frequent analysis of metallized holes can control this result.

3. Most of the pads or wires are detached due to the lack of strict requirements for all operators. The temperature inspection of the solder bath is effective or the staying time in the solder bath is extended. In the manual soldering repair operation, the pad detachment is probably due to improper use of wattage

Electric ferrochrome, and the failure to stop professional process training. Nowadays, some laminate manufacturers have manufactured laminates with high peel strength levels at low temperatures for severe soldering applications.

4. If the design wiring of the printed board causes a detachment that occurs in the opposite center of each board; then this printed board must be redesigned. Usually, this does happen in the center of a thick copper foil or a right corner of a wire. Sometimes, a long wire will have such a scene; this is because

This is due to the different coefficients of thermal contraction.

5 Printed circuit board design time. If possible, remove heavy components from the entire printed circuit board, or install it after the dip soldering operation. Usually a low-wattage electric soldering iron is used for careful soldering. Compared with the component dip soldering, the continuous time of the substrate material being heated is shorter.

three. Excessive size change problem

Scenery symbol: The size of the substrate is out of tolerance or can not be aligned after processing or soldering.

Introspection method: adequately stop quality control in the process of processing.

Reasons for being able to:

1. The direction of the texture of the paper-based materials is not paid attention to, and the shrinkage in the forward direction is about half of the horizontal direction. Moreover, the substrate cannot be restored to its original size after cooling.

2. If part of the stress in the laminate is not released, it will sometimes cause irregular dimensional changes during processing.

Approach:

1. Instruct all consumers to cut the board in the opposite direction of the structure and texture. If the size change exceeds the allowable range, consider switching to a substrate.

2. Contact the PCB laminate manufacturer for advice on how to relieve the material stress before processing.