Generally, the PCB copper foil with a nominal thickness of 105 μm or over is collectively referred to as a thick copper foil (including the surface-treated electrolytic copper foil and rolled copper foil). The PCB and copper foil manufacturing industry domestically and abroad are more accustomed to specifically divide the thick copper foil into three varieties based on its nominal thickness, the one with thickness of 105μm (≥ 3oz) ~ 240μm or over is called thick copper foil; the one with thickness of 300μm or over is called super-thick copper foil; the one with thickness of 600μm and above is referred to as super MAX copper foil.

The thick copper foil and super-thick copper foil belong to a kind of special PCB copper foil. In addition to its conventional electrolytic copper foil (or rolled copper foil) performance, it also has such special performance as the conducting layer of high current board or the inner core cooling metal layer of the high-current PCB, and other special performance requirements. These special performance requirements are to meet the application conditions, processing conditions and other aspects from its downstream products. The application performance requirements of it is mostly expressed in the characteristics that the conducting circuit of thick copper can stably carry high current, and can better distribute high heat generated by the loaded high current in a substrate.

In recent years, with the expansion of application field of heavy copper printed circuit board, and the increase of production and sales, the production and sales of thick copper foil has also been significantly improved. According to statistics, its production and sales have accounted for 5 ~ 6% of the world's production and sales of electronic copper foil, which is 17,000 ~ 20,000 tons / year.

Printed circuit boards made of heavy copper foil and super-thick copper foil can be called "heavy copper printed circuit boards". The conductive material (copper foil) and substrate material, production technology, application areas it used are different from conventional PCB, so it belongs to a special kind of PCB. The heavy copper PCB applications and demands have been rapidly expanded in recent years, making it become a kind of "hot" PCB variety with a very good market prospects.

The new development of new heavy copper PCB product also leads to a new industrial chain with the center of it. Its terminal electronics filed is also somewhat different from conventional PCB.

The heavy copper printed circuit boards are mostly the high-current substrates. There are two major application fields of large current substrate --- the power supply module (power module) and automotive electronic components. Some of its major terminal electronic product fields are the same as conventional PCB (such as portable electronic products, network products, base station equipment, etc.), and some are different from conventional PCB fields, such as automotive, industrial control, power modules, etc.

The high current substrate and conventional printed circuit board are somewhat different in function. At the very beginning, the main function of conventional PCB is to form the conductors (wiring) that transmit the signals. With the continuous development of PCB technology toward HDI board, the line width of such signal transmission conductor has become more and more thin, and the thickness of the conductor (thickness of PCB conducting layer) has become thinner and thinner too. The thickness of copper foil is changed from 35 micron to the thinner 18 μm, 12 μm, or even 9 μm and even more thinner. The main function of PCB substrate that carries power device and high current passing is to protect the carrying capacity of current and stabilize the power supply. The development trend of this kind of high-current PCB is to carry greater current and distribute the heat generated by a higher current and larger device, therefore, the current passed is higher and higher, and the PCB copper foil is also more and more thick. For example, the copper foil of 210 μm will be used conventionally for presently manufactured high-current substrate; further, the thickness of conductor layer of PCB for buses, robots, power supplies and other original busbar and wire harnesses have reached 400u m to 2000 um.

Since the advent of heavy copper PCB, the application field of PCB has stepped into a new field of industrial products - power electrons.

Power electron is also customarily known as power electronics, it is a kind of product supported by cross technologies that include many sub-disciplines such as electrical engineering, electronics, and control, etc. Power flows through the power electronics circuit and is controlled by the electronic device.

The difference comparison of power electronics technology and microelectronics technology: The function of microelectronics technology is information processing, that is, the amplification, operation and waveform transformation of small signals, it is mainly used for signal sensing and transmission; the main function of power electronics technology is power regulation or power processing, its essence is power conversion, that is, to converse the electrical energy of a certain voltage (or current, frequency, waveform) to the electrical energy of another voltage (or current, frequency, waveform), the power conversion includes AC-DC, inverting, frequency conversion, DC-DC and so on. The converted power current is greater than a few kA, the voltage exceeds tens of kV, the capacity reaches the megawatt level.

In recent years, the market of heavy copper PCB has been rapidly expanded and it is closely related to the improvement of design and manufacture of heavy copper PCB and the extension and expansion of application functions. The expansion of market is driven by the new expansion of application function, which mainly shows in the following aspects.

4.1 Making full use of the advantages of miniaturization, thinning and multi-layer of heavy copper PCB, quickening the pace of replacing the ceramic substrate

Organic resin heavy copper PCB has the advantages of realizing the trend of miniaturization, thinning and multilayer. In recent years, the high-power power supplies and current controllers (such as DC-DC converters), power switches, motor circuits, fuses, etc. used in electric vehicles, hybrid electric vehicles, robots and so on are trending to be miniaturized, which creates opportunities and speeds up the replacement of the commonly used ceramic PCBs.

High-current and organic resin heavy copper PCB are used in DC-DC converters for hybrid electric vehicles.

4.2 The progress in the design and manufacturing technology of heavy copper PCB has promoted the "integration" of the power circuit (loaded high current) and the control circuit.

In PCB design of automotive electronics, it is often that the PCB that carries the power device and the one that controls circuit are discretely set up. The ceramic PCB is used for carrying a high current power device. It is difficult to achieve the circuit wire layout of the control circuit on the ceramic PCB in the manufacturing process. Then the organic resin heavy copper PCB replaces the ceramic PCB that carries the power device, which realized the "integration" of the power circuit and the control circuit with high load current.