Common Problems in PCB Design, Manufacturing, Assembly Stages

Common PCB Manufacturing Defects

PCB Short Circuit Problem

Short circuits are a common pcb defect. Customers often confuse a short circuit with an open circuit. An open circuit refers to the disconnection of the connected line due to a break in the middle of the line. A short circuit is when excess copper or other impurities appear between lines that should have a distance, causing the lines to fail to transmit properly. In short, an open circuit is a little less “thing” and a short circuit is a little more “thing”. Here are a few reasons for short circuit problems:

Short circuit due to scratches

1. Improper operation during alignment will cause scratches on the film surface. In order to avoid this situation, the operator should control the spacing between the boards, use both hands during the whole process, and strictly implement the alignment operation specifications.

2. The failure of the connecting board of the developing machine causes the collision and scratches between the board and the board. The PCB manufacturing factory should adjust the spacing distance of the board according to the operator’s ability, and the board should not be placed when there is no one to connect the board at the exit port.

3. Improper removal of the plate during electroplating, improper operation when placing the splint, etc., resulting in scratches. Enterprises should remind employees to pay attention to operating specifications when electroplating, and avoid laminating two boards together for splinting.

Short circuit caused by film

1. The anti-coating layer is too thin, and the coating exceeds the thickness of the film during electroplating, forming a sandwich. The thickness of the plating resist needs to be increased, and if wet film is used, the thickness can be increased by multiple printings.

2. The distribution of the lines is uneven. During the pattern plating process of the isolated lines, due to the high potential, the coating exceeds the film thickness and forms a sandwich. In order to avoid this situation, FS technology generally reduces the current, using a current of 1.7~2.4A, can make the plating height on the isolated area exceed the film thickness.

Short circuit caused by tin loss

1. Due to improper operation, the loss of tin in the stripping potion tank is caused. When this happens, it is necessary to control the concentration, temperature, and soaking time of the potion according to the needs. Isolate the boards with a board rack.

2. The stacking of the stripped boards causes the loss of tin. The PCB factory needs to dry the stripping solution in time after stripping and check it carefully.

The influence of temperature and humidity

This is a common PCB problem. Due to the structure of the PCB itself, it is relatively fragile, and it is very easy to damage the circuit board when it is in an extreme environment (high temperature, large temperature difference, and large humidity). When in a high temperature environment: the solder joints of the circuit board are easily damaged, causing the circuit board to be deformed and bent, and in severe cases, the copper wire will be broken. When in a humid environment: The metal substances on the surface of the circuit board (copper traces, pads, component leads) are oxidized and rusted, resulting in overheating and performance degradation of the PCB during operation.

Poor welding

1. Destruction of solder joints: Before the solder joints solidify, they are easily affected by external factors and cause the solder joints to move. This is relatively common, and it is only necessary to reheat the solder joint, fuse and correct it.

2. Cold welding: Due to insufficient solder fusion, the surface is rough and the connection is not firm. When this problem occurs it is necessary to reheat the joint to remove excess solder.

3. Welding bridge: When the two leads are welded together and the current is greater than the rated voltage, it is easy to cause the components to be burned or the wires to be burned. After the PCB manufacturer receives the order, it reviews the manufacturing process and controls the amount of solder when soldering.

Dark or small grained contacts on the board

The main cause of this problem is that the solder is contaminated, or the tin contains too much oxide. Contamination of the solder can change its composition, and when this is found, a large amount of pure tin needs to be added or the solder replaced. Too much oxide in tin can make the solder joint structure more fragile, requiring higher tin content and lower preheat and soldering temperatures.

Discoloration of solder joints

The color of the solder joints is generally silver-gray, but occasionally some gold solder joints appear. The reason for this phenomenon may be that the temperature of the tin furnace is too high because the frequency of using the tin furnace is too high.

Copper is oxidized and corroded

Solder mask protects copper from oxidation and corrosion, and prevents gaps and bridges from forming between electronic components. As a commonly used material in the electronics industry, copper has natural advantages in current transmission, but its ability to resist corrosion and oxidation is extremely poor. Common pcb defects occur when copper oxidizes and corrodes. Some PCB manufacturers use solder mask that is too thin, or wears out from prolonged use, which can easily expose wires.

Human Error

In the PCB manufacturing process, it is not uncommon for workers not to operate in accordance with the company’s code of conduct, resulting in circuit board problems. The probability of this human error leading to a product defect is as high as 31%. In order to avoid this situation, FS Technology has formulated strict quality control standards and incorporated workers’ operating norms into performance appraisals.

Common Problems in Designing Circuits

Printed circuit board common problems not only occur on bare PCB boards, but also often during the design process. As the first step in PCB production, in order to ensure that the manufactured circuit board is error-free, designers need to strictly enforce the design specifications.

The copper wire is too close to the edge of the board

After designing the circuit, the designer carefully checks the distance between the copper wire and the edge of the base layer and separates the components. Copper spacing issues are often the result of incorrect PCB design for manufacturing (DFM) specifications. This layout risk is minimized due to strict adherence to design specifications.

Misuse of the Graphics Layer

1. Too many useless connections make the circuit board more complicated. Only six layers are required to complete the PCB design, but many more are used.

2. Speed over quality. In order to save trouble, the designer uses the Board layer to draw the lines on each layer, and uses the Board layer to mark the lines, which may cause the Board layer to be missed, and the connection will be missed and the circuit will be broken.

Design without guidance

A foolproof design solution and a high-quality turnkey PCB assembly service standard are the lifelong pursuit of FS Technology. As an EMS company that includes mechanical assembly, PBC manufacturing, and PCB assembly, we do not blindly assemble components, stack components together, and start welding. We have a first-class sales team, expert-level PCB designers, and top-notch PCB component procurement capabilities. When you place an order at FS Technology, our service begins, from guiding design, to production and assembly, to delivery, in one go, complete the perfect order with the fastest speed.

Common PCBA Problem

Components are loose or misaligned

When the PCB assembly is in the reflow stage, small parts can float on the solder, causing the target solder joints to fall off. At this time, the factory needs to strengthen the support force of the circuit board and design the procedure of the reflow oven according to the specification.

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