LED aluminum substrate design choice
LED circuit design In order to better solve the heat dissipation problem, LED and some high-power ICs need to use aluminum-based circuit boards.
The aluminum substrate pcb is composed of a circuit layer (copper foil layer), a thermally conductive insulating layer, and a metal base layer. The circuit layer is required to have a large current carrying capacity, so thick copper foil should be used, and the thickness is generally 35μm~280μm; the thermal conductive insulating layer is the core technology of the PCB aluminum substrate, which is generally a special polymer filled with special ceramics. It has small thermal resistance, excellent viscoelasticity, anti-heat aging ability, and can withstand mechanical and thermal stress. The thermal insulation layer of high-performance PCB aluminum substrate such as IMS-H01, IMS-H02 and LED-0601 uses this technology to make it have excellent thermal conductivity and high-insulation electrical insulation properties; the metal substrate is aluminum substrate. The supporting members are required to have high thermal conductivity, generally aluminum plates, or copper plates (where copper plates can provide better thermal conductivity), and are suitable for conventional machining such as drilling, punching and cutting. Process requirements are: gold plating, spray tin, osp anti-oxidation, immersion gold, lead-free ROHS process.
Substrate: Aluminum substrate Features: Thin insulation layer, low thermal resistance; non-magnetic; good heat dissipation; high mechanical strength Product standard thickness: 0.8, 1.0, 1.2, 1.5, 2.0, 2.5, 3.0mm Copper foil thickness: 1.8um35um70um105um140um : It has high heat dissipation, electromagnetic shielding, high mechanical strength and excellent processing performance. Uses: LED dedicated power hybrid IC (HIC).
The aluminum substrate is used to carry the heat conduction of the LED and the device. The heat dissipation mainly depends on the area. The concentrated heat conduction can select the plate with high thermal conductivity, such as the American Begs plate; the slow heat conduction or heat dissipation can be used for general materials. The price difference is relatively large. It takes about 4,000 square meters for the production of the finished products of Bergs plate, and the domestically produced materials are more than 1,000 square meters. LED general use voltage is not very high, choose 1mil thickness insulation layer withstand voltage greater than 2000V.
Thermal reference design method:
Why do you want to design a heat?
The effect of high temperature on electronic products: degradation of insulation performance; damage to components; thermal aging of materials; cracking of low-melting welds and shedding of solder joints.
The influence of temperature on the components: Generally speaking, the temperature rises the resistance value of the resistor; the high temperature reduces the service life of the capacitor; the high temperature causes the performance of the transformer and the choke insulation material to decrease, and the allowable temperature of the general transformer and the choke coil It should be lower than 95C; if the temperature is too high, it will cause the change of the alloy structure of the solder joint—the IMC is thickened, the solder joint becomes brittle, and the mechanical strength is lowered. The increase of the junction temperature causes the current amplification factor of the transistor to increase rapidly, resulting in the collector current. The increase, and the junction temperature is further increased, eventually leading to component failure.
Purpose of thermal design
Control the temperature of all electronic components inside the product so that it does not exceed the maximum temperature specified by the standards and specifications under the working environment. The calculation of the maximum allowable temperature shall be based on the stress analysis of the component and shall be consistent with the reliability requirements of the product and the failure rate assigned to each component.
LED heat dissipation design is generally based on fluid dynamics software simulation and basic design.
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