1、 Scratch short circuit

1. Scratches on the film surface caused by improper alignment during wet film coating.

2. The outlet of the developing machine is too busy to connect the plates, resulting in collisions and scratches between the plates.

3. Improper removal of the plate during electroplating, improper operation during clamping, and improper operation during manual pre-treatment of the plate can cause scratches.

·The improvement method is as follows:

(1) Due to the simple formation of scratches during board insertion after coating with wet film, it is recommended to keep a longer distance between boards to ensure that there are no scratches on the board surface. When aligning, take and place the board with both hands, strictly prevent the boards from overlapping or conflicting with the alignment table, and prevent scratching the board surface.

(2) When developing, adjust the distance of the board placement according to the size of the board and the operating ability of the receiver. When there is no one receiving the board at the board outlet, the machine should not place the board at the board entry point. When receiving the board, use both hands to clamp the board to prevent collisions between boards and scratches on the board surface.

(3) When electroplating, use both hands to take and place the board to prevent two or more boards from being stacked together for clamping. When manually threading the board, prevent conflicts between the board and the table. Do not handle too many boards before manual threading. When passing over the board, clamp one by one to prevent collision.

2、 Short circuit of clamping film

1. The anti coating layer is too thin, and during electroplating, the coating exceeds the film thickness, forming a film gap, especially the smaller the line distance, the simpler it is to form a film gap short circuit.

2. The distribution of the board graphics is uneven, and isolated lines during the graphic electroplating process, due to high potential, the coating exceeds the film thickness, resulting in film clamping and short circuit.

The improvement method is as follows:

(1) Adding the thickness of the anti plating layer: Select a dry film with an appropriate thickness. If it is a wet film, it can be printed on a low mesh screen, or the film thickness can be added by printing the wet film twice.

(2) The distribution of the board graphics is uneven, and the current density (1.0~1.5A) can be appropriately reduced for electroplating. In daily production, due to the need to ensure output value, we usually control the electroplating time to be as short as possible. Therefore, the current density used is generally between 1.7 and 2.4A. In this way, the current density obtained in isolated areas will be 1.5 to 3.0 times that of normal areas. In places where the distance between isolated areas is small, the coating height will exceed the film thickness by a lot. After the film is removed, there will be incomplete film removal, and in severe cases, the anti coating film will be clamped at the edge of the circuit, and then a short circuit will be formed, which will result in a thinner solder mask thickness on the circuit.

3、 Short circuit caused by tin running

1. Improper operation in the film stripping solution tank caused tin leakage;

2. Stacking the already peeled plates together causes tin leakage.

·The improvement method is as follows:

(1) The concentration of the stripping solution is high, the stripping time is long, and the anti coating has already fallen off. However, the board is still immersed in a strong alkaline solution, and some tin powder adheres to the surface of the copper foil. During etching, there is a thin layer of metal tin protecting the surface of the copper, which plays a role in corrosion resistance, resulting in incomplete removal of the copper to be removed and causing a short circuit in the circuit. So we need to strictly control the concentration, temperature, and demoulding time of the demoulding solution. When demoulding together, use a board holder to insert it properly, and the boards cannot be stacked or bumped together.

(2) The boards that have already been stripped are stacked together without being dried, causing the tin between the boards to be immersed in the undried stripping solution. Some of the tin layer will dissolve and adhere to the surface of the copper foil. During etching, a thin layer of metallic tin protects the copper surface, providing corrosion resistance, resulting in incomplete removal of copper and causing a short circuit in the circuit.

Article source: PCB manufacturerhttp://www.yonghongpcb.com/