The metal base copper clad laminate is generally composed of a metal substrate, an insulating dielectric layer and a conductive layer (usually copper foil). That is, one or both sides of the metal substrate with the surface treated are covered with insulating medium and copper foil, and then composited by hot pressing .
(1) Classification of metal-based copper clad laminates. Divided from the structure of the metal substrate, there are three common ones, namely, the metal substrate, the clad metal substrate and the metal core substrate. The metal substrate is based on metal (aluminum, copper, iron, molybdenum, etc.), and the substrate is covered with an insulating dielectric layer and a conductive layer (copper foil); the coated metal substrate is covered on six sides of the metal plate A layer of glaze is sintered to form an integral base substrate, on which the conductor circuit diagram is made by screen printing and sintering; the metal core substrate is generally made of metal Invar (iron-nickel alloy) core material, coated on its surface Lay a layer of organic polymer insulating dielectric layer, or compound it on a prepreg or PET film, and cover it with a conductive foil (some use the additive method to directly form a conductive pattern). Among them, the metal substrate is the most common and the most used Kind of.
Metal substrates are classified from their composition and can be divided into: aluminum-based copper clad laminates, iron-based copper clad laminates, copper-based copper clad laminates, and molybdenum-based copper clad laminates. Metal-based copper clad laminates are classified in terms of characteristics and can be divided into: general metal-based copper clad laminates, flame-retardant metal-based copper clad laminates, high heat-resistant metal-based copper clad laminates, high thermal conductivity metal-based copper clad laminates, and ultra-high thermal conductivity metal Base copper clad laminate, high frequency, microwave type metal base copper clad laminate and multilayer metal base copper clad laminate.
(2) The main characteristics of metal-based copper clad laminates. The characteristics of metal-based copper clad laminates are mainly determined by the performance of the metal plate that occupies most of the thickness of the board.
①Excellent heat dissipation performance. The metal base copper clad laminate has excellent heat dissipation performance, which is the most prominent feature of this type of board. The PCB made with it can prevent the working temperature of the components and substrates loaded on the PCB from rising, and can also quickly dissipate the heat generated by the power amplifier components, high-power components, large-circuit power switches and other components. Among different types of metal substrates, the metal substrate with copper as the base material has the best heat dissipation. However, if the copper plate and the aluminum plate use the same volume ratio, the price of copper is high, and the density is high, which is not suitable for the development of lightweight substrate materials. Not widely adopted. Only a small amount of copper plates are used when manufacturing high heat dissipation metal substrates. Aluminum plate has better heat dissipation than iron plate.
②Good mechanical processing performance. Metal-based copper clad laminates have high mechanical strength and toughness, which are much better than rigid resin-based copper clad laminates and ceramic substrates, so large-area printed boards can be manufactured on metal substrates. Heavier components can be mounted on this type of substrate. In addition, the metal substrate also has good flatness, and can be assembled and processed on the substrate such as hammering and riveting. On the PCB made of it, the non-wiring parts can also be subjected to mechanical processing such as bending and twisting.
③Excellent dimensional stability. For various copper clad laminates, there are thermal expansion (dimensional stability) problems, especially the thermal expansion in the thickness direction (Z axis), which affects the quality of metallized holes and circuits. The linear expansion coefficient of iron and aluminum substrates is much smaller than that of ordinary resin-based substrates, and is closer to the linear expansion coefficient of copper, which helps to ensure the quality and reliability of the printed circuit.
④Electromagnetic shielding. In order to ensure the performance of electronic circuits, some components in electronic products must prevent the radiation and interference of electromagnetic waves, and the metal substrate can act as a shielding plate to shield electromagnetic waves.
⑤Electromagnetic characteristics. The substrate material of the iron-based copper clad laminate is an alloy with magnetic properties of iron-based elements (such as silicon steel plate, low-carbon steel, galvanized cold-rolled steel plate, etc.). Use its characteristics to apply it to tape recorders (VTR) and floppy disks Drives (FDD), servo motors and other small precision motors. This metal-based copper clad laminate not only functions as a PCB, but also functions as a stator substrate for a small motor.
(3) Application of metal-based copper clad laminates. Iron-based copper clad laminates and silicon steel copper clad laminates have excellent electrical properties, magnetic permeability and pressure resistance, and high substrate strength. Mainly used in brushless DC motors, tape recorders, radio recorders, spindle motors and intelligent drives, etc.
Aluminum-based copper clad laminates have excellent electrical properties, heat dissipation, electromagnetic shielding, high withstand voltage and bending performance, and are mainly used in automobiles, motorcycles, computers, home appliances, communication electronic products, and power electronic products. Among the metal PCB substrates, aluminum-based copper clad laminates have the largest market consumption.
Copper-based copper clad laminates have the basic performance of aluminum-based copper clad laminates, and their heat dissipation is better than aluminum-based copper clad laminates. This type of substrate can carry large currents and is used to manufacture PCBs for high-power circuits such as power electronics and automotive electronics. However, the density of copper substrates Large, high value, easy to oxidize, so that its application is restricted, and the amount is much lower than that of aluminum-based copper clad laminate.
