The Technical Requirements and Circuit Fabrication of Aluminum PCB

First, the technical requirements of aluminum PCB  boards

 

The main technical requirements as bellow:

 

Dimensional requirements, including board dimensions and deviations, thickness and deviation, perpendicularity and warp; appearance, including cracks, scratches, burrs and delamination, aluminum oxide film, etc.; performance, including peel strength, surface resistivity , minimum breakdown voltage, dielectric constant, flammability and thermal resistance requirements.

 

 

The Technical Requirements and Circuit Fabrication of Aluminum PCB

 

 

Special inspection method for aluminum-based copper clad laminates:

 

1. The dielectric constant and dielectric loss factor measurement method. It is a variable-Q series resonance method. The principle of measuring the Q value of the series circuit by connecting the sample and the tuning capacitor in series to the high-frequency circuit;

 

2. The thermal resistance measurement method, which is calculated by the ratio of the temperature difference to the thermal conductivity between different temperature measurement points.

Second, aluminum PCB manufacturing 

 

1. Machine Machining: The aluminum substrate can be drilled, but no burrs are allowed on the edge of the hole in the hole after drilling, which will affect the withstand voltage test. Milling the shape is very difficult. The shape of the punch, the use of advanced molds, mold making is very skillful, as one of the difficulties of the aluminum substrate. After the shape is punched, the edge requirements are very neat, without any burrs, and do not hurt the solder mask on the edge of the board. Usually, the military model is used, the hole is punched from the circuit, the shape is punched from the aluminum surface, and the force is the upper shear drop when the circuit board is punched, and so on. After punching the shape, the board warp should be less than 0.5%.

 

2. The entire production process is not allowed to wipe the aluminum base surface: the aluminum base surface is touched by hand, or the surface is discolored and blackened by certain chemicals. This is absolutely unacceptable, and the aluminum base surface is re-polished. It is not acceptable, so the whole process does not hurt, and does not touch the aluminum base is one of the difficulties in producing aluminum substrates. Some enterprises use passivation technology, and some put protective films on the front and back of hot air leveling (HASL)... There are many small skills.

 

The Circuit Fabrication of Aluminum PCB

 

 

3. Over-voltage test: The communication power supply aluminum substrate requires 100% high-voltage test. Some customers require DC power, some require AC power, voltage requirements are 1500V, 1600V, time is 5 seconds, 10 seconds, 100% printed board is tested. Dirty objects, holes and aluminum-based edge burrs, circuitserrations, and any slight insulation on the board surface can cause high-voltage test fire, leakage, and breakdown. The pressure test panels were layered and foamed and rejected.

 

Third, aluminum PCB manufacturing specifications

 

1. Aluminum substrates are often used in power devices, and the power density is large, so the copper foil is relatively thick. If a copper foil of 3 oz or more is used, the etching process of the thick copper foil requires engineering line width compensation, otherwise, the line width after etching will be excessive.

 

2. The aluminum base of the aluminum substrate must be protected with a protective film in advance during the PCB processing. Otherwise, some chemicals will erode the aluminum base surface, resulting in damage to the appearance. Moreover, the protective film is easily scratched, causing a gap, which requires that the entire PCB processing process must be inserted.

 

3. The milling cutter used in the glass fiberboard raft is relatively hard, and the milling cutter used in the aluminum substrate has a high hardness. The production of glass fiberboard milling cutters during processing is fast, while the production of aluminum substrates is at least two-thirds slower.

 

4. Computer milling edge glass fiberboard is only using the heat dissipation system of the machine itself to heat, but the processing of aluminum substrate must be additional heat for the steamed bread