2022-12-13
Introduction to technical requirements and manufacturing steps of pcb for aluminum substrate
1、 Technical requirements for aluminum substrate
Main technical requirements include:
Dimensional requirements, including panel size and deviation, thickness and deviation, perpendicularity and warpage; Appearance, including crack, scratch, burr, delamination, aluminum oxide film and other requirements; Performance, including peel strength, surface resistivity, minimum breakdown voltage, dielectric constant, flammability and thermal resistance.
Special test methods for aluminum based copper clad laminate:
The first is the measurement method of dielectric constant and dielectric loss factor. It is the variable Q value series resonance method. The sample and tuning capacitor are connected to the high-frequency circuit in series to measure the Q value of the series circuit;
The other is the thermal resistance measurement method, which is calculated by the ratio of temperature difference and thermal conductivity between different temperature measuring points.
2、 Fabrication of aluminum substrate circuit
(1) Machining: It is OK to drill aluminum substrate, but no burr is allowed on the hole edge after drilling, which will affect the withstand voltage test. Milling the profile is very difficult. The shape stamping requires the use of advanced molds. The mold making is very skilled, which is one of the difficulties of aluminum substrate. After the appearance is punched, the edges shall be very neat without any burr, and the welding resistance layer at the plate edge shall not be damaged. Usually, the drill die is used. The hole is punched from the line, and the shape is punched from the aluminum surface. When the circuit board is punched, the force is cut up and pulled down. These are all skills. After punching the shape, the warpage of the board shall be less than 0.5%.
(2) The entire production process is not allowed to scratch the aluminum base surface: the aluminum base surface will change color and become black when touched by hand or by some chemicals, which is absolutely unacceptable, and some customers will not accept the re polishing of the aluminum base surface, so one of the difficulties in the production of aluminum base plate is not to bump or touch the aluminum base surface in the whole process. Some enterprises adopt passivation process, and some have many tips for pasting protective film before and after hot air leveling (tin spraying).
(3) Overvoltage test: the aluminum substrate of communication power supply requires 100% high-voltage test. Some customers require DC power, some require AC power, and the voltage requires 1500V, 1600V for 5 seconds, 10 seconds. 100% of the printed boards are tested. Dirt, holes and aluminum base edge burrs on the board surface, wire sawtooth, and damage to any small point of insulation layer will lead to fire, electric leakage and breakdown in the high voltage resistance test. The pressure test board shall be rejected for delamination and blistering.
3、 Specification for fabrication of aluminum substrate pcb
1. Aluminum substrate is often used for power devices, with high power density, so the copper foil is relatively thick. If more than 3oz copper foil is used, the etching process of thick copper foil requires engineering design line width compensation, otherwise, the line width will exceed the tolerance after etching.
2. The aluminum base surface of aluminum substrate must be protected with protective film in advance during PCB processing, otherwise, some chemicals will etch the aluminum base surface, causing damage to the appearance. Moreover, the protective film is very easy to be bruised, causing gaps, which requires that the whole PCB processing process must be inserted.
3. The hardness of milling cutter used for fiberglass gongs is relatively small, while the hardness of milling cutter used for aluminum substrate is large. In the process of processing, the milling cutter for fiberglass board production is fast, while the production of aluminum substrate is at least two thirds slow.
4. The computer edge milling fiberglass board can only use the heat dissipation system of the machine itself to dissipate heat, but the processing of aluminum substrate requires additional heat dissipation by adding alcohol to the gongs.
Main technical requirements include:
Dimensional requirements, including panel size and deviation, thickness and deviation, perpendicularity and warpage; Appearance, including crack, scratch, burr, delamination, aluminum oxide film and other requirements; Performance, including peel strength, surface resistivity, minimum breakdown voltage, dielectric constant, flammability and thermal resistance.
Special test methods for aluminum based copper clad laminate:
The first is the measurement method of dielectric constant and dielectric loss factor. It is the variable Q value series resonance method. The sample and tuning capacitor are connected to the high-frequency circuit in series to measure the Q value of the series circuit;
The other is the thermal resistance measurement method, which is calculated by the ratio of temperature difference and thermal conductivity between different temperature measuring points.
2、 Fabrication of aluminum substrate circuit
(1) Machining: It is OK to drill aluminum substrate, but no burr is allowed on the hole edge after drilling, which will affect the withstand voltage test. Milling the profile is very difficult. The shape stamping requires the use of advanced molds. The mold making is very skilled, which is one of the difficulties of aluminum substrate. After the appearance is punched, the edges shall be very neat without any burr, and the welding resistance layer at the plate edge shall not be damaged. Usually, the drill die is used. The hole is punched from the line, and the shape is punched from the aluminum surface. When the circuit board is punched, the force is cut up and pulled down. These are all skills. After punching the shape, the warpage of the board shall be less than 0.5%.
(2) The entire production process is not allowed to scratch the aluminum base surface: the aluminum base surface will change color and become black when touched by hand or by some chemicals, which is absolutely unacceptable, and some customers will not accept the re polishing of the aluminum base surface, so one of the difficulties in the production of aluminum base plate is not to bump or touch the aluminum base surface in the whole process. Some enterprises adopt passivation process, and some have many tips for pasting protective film before and after hot air leveling (tin spraying).
(3) Overvoltage test: the aluminum substrate of communication power supply requires 100% high-voltage test. Some customers require DC power, some require AC power, and the voltage requires 1500V, 1600V for 5 seconds, 10 seconds. 100% of the printed boards are tested. Dirt, holes and aluminum base edge burrs on the board surface, wire sawtooth, and damage to any small point of insulation layer will lead to fire, electric leakage and breakdown in the high voltage resistance test. The pressure test board shall be rejected for delamination and blistering.
3、 Specification for fabrication of aluminum substrate pcb
1. Aluminum substrate is often used for power devices, with high power density, so the copper foil is relatively thick. If more than 3oz copper foil is used, the etching process of thick copper foil requires engineering design line width compensation, otherwise, the line width will exceed the tolerance after etching.
2. The aluminum base surface of aluminum substrate must be protected with protective film in advance during PCB processing, otherwise, some chemicals will etch the aluminum base surface, causing damage to the appearance. Moreover, the protective film is very easy to be bruised, causing gaps, which requires that the whole PCB processing process must be inserted.
3. The hardness of milling cutter used for fiberglass gongs is relatively small, while the hardness of milling cutter used for aluminum substrate is large. In the process of processing, the milling cutter for fiberglass board production is fast, while the production of aluminum substrate is at least two thirds slow.
4. The computer edge milling fiberglass board can only use the heat dissipation system of the machine itself to dissipate heat, but the processing of aluminum substrate requires additional heat dissipation by adding alcohol to the gongs.
