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Solutions to PCB Short Circuit

PCB "line short circuit" is an issue that PCB manufacturers will face practically every day, but it is also a more difficult problem to address, the problem of improving good or poor, directly connected to cheap or high production costs, but also to the final product qualifying rate of the problem.

The reasons of the foregoing phenomenon, as well as strategies for improvement, are now given below.

Ⅰ. Short circuit caused by tin running on bms PCB

1. Running tin causes improper functioning in the demoulding potion tank.

2. It was re-film circuit board that was packed together due to tin running.

(1) high concentration of annealing solution, annealing time, anti-coating has long fallen off, can bms PCB is still soaked in a strong alkaline solution, part of the tin powder attached to the surface of the copper foil, etching a very thin layer of metal tin protect the copper surface, play a role in corrosion resistance, resulting in the copper to be removed is not clean, thus leading to a short circuit in the line.

Since a result, we must tightly manage the decalcifying solution concentration, temperature, decalcifying duration, and decalcifying with the insertion of the board frame, as the board and the board cannot be laminated together.

(2) The bms PCB has been de-film is not dried and stacked together, so part of the tin layer will dissolve attached to the copper foil surface, etching a very thin layer of metal tin protect the copper surface, play a role in resisting corrosion, resulting in the removal of copper is not clean, resulting in line short circuit.

Ⅱ. The bms PCB etching is not caused by a net short circuit.

1. Etching solution parameters have a direct impact on etching quality: excellent or terrible control.

PH value: If the PH value is too low, the solution will become viscous, the color will turn white, and the etching rate will slow down. This circumstance is easy to cause bms PCB side corrosion, and may be avoided by adding ammonia.

Chloride ions: Etching salts, which are made up of ammonium chloride and supplements, are primarily responsible for controlling the chloride ion level.

Controlling the copper ion concentration, which is normally kept between 145 and 155 g/L, is the principal way to manage the specific gravity. Every hour or so during production, design custom PCB is checked to verify that the specific gravity remains stable.

Temperature: maintain between 48°C and 52°C; if the temperature rises too high, ammonia evaporates quickly, causing the PH value to fluctuate; and because the majority of the etching machine's cylinder is made of PVC, the PVC temperature limit is 55°C; any temperature higher than this will easily cause the cylinder to deform, or even cause the etching machine to be scrapped; therefore, an automatic temperature controller must be installed to effectively monitor the temperature to ensure that it is within the control range.

Speed: Generally, select the proper speed according on the thickness of the bms PCB board plate backing.

Recommendation: To ensure stability and balance of the following parameters, an automatic filling machine should be set up to manage the chemical composition of the ionic solution, resulting in a more stable etching solution composition.

2. When copper is plated across the whole board, the thickness of the plating layer is uneven, resulting in smeared etching.

Methods of improvement include:

(1) When plating the entire board, strive for automatic line production while also adjusting the current density per unit area (1.5–2.0A/dm2) and keeping the plating time as consistent as possible to ensure full-load production, while increasing the cathode and anode baffles and developing a system for the use of "plating edge bars" to reduce the potential difference and the possible disparity.

(2) Full board plating: If the production line is manual, the bms PCB should be plated with double clamping sticks to maintain the current density per unit area as consistent as possible, while a timing alarm should be installed on the bms PCB to ensure plating time consistency and reduce potential differences.

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6th floor, Huachuangda YiJing Building, 45 District, Bao'an District, Shenzhen, China, 518101