From PCB World
3 High heat and heat dissipation requirements
With the miniaturization, high functionality, and high heat generation of electronic equipment, the thermal management requirements of electronic equipment continue to increase, and one of the solutions chosen is to develop thermally conductive printed circuit boards. The primary condition for heat-resistant and heat-dissipating PCBs is the heat-resistant and heat-dissipating properties of the substrate. At present, the improvement of the base material and the addition of fillers have improved the heat-resistant and heat-dissipating properties to a certain extent, but the improvement in thermal conductivity is very limited. Typically, a metal substrate (IMS) or metal core printed circuit board is used to dissipate the heat of the heating component, which reduces the volume and cost compared with the traditional radiator and fan cooling.
Aluminum is a very attractive material. It has abundant resources, low cost, good thermal conductivity and strength, and is environmentally friendly. At present, most metal substrates or metal cores are metal aluminum. The advantages of aluminum-based circuit boards are simple and economical, reliable electronic connections, high thermal conductivity and strength, solder-free and lead-free environmental protection, etc., and can be designed and applied from consumer products to automobiles, military products and aerospace. There is no doubt about the thermal conductivity and heat resistance of the metal substrate. The key lies in the performance of the insulating adhesive between the metal plate and the circuit layer.
At present, the driving force of thermal management is focused on LEDs. Nearly 80% of the input power of LEDs is converted into heat. Therefore, the issue of thermal management of LEDs is highly valued, and the focus is on the heat dissipation of the LED substrate. The composition of high heat-resistant and environmentally friendly heat dissipation insulating layer materials lays the foundation for entering the high-brightness LED lighting market.
4 Flexible and printed electronics and other requirements
4.1 Flexible board requirements
The miniaturization and thinning of electronic equipment will inevitably use a large number of flexible printed circuit boards (FPCB) and rigid-flex printed circuit boards (R-FPCB). The global FPCB market is currently estimated to be about 13 billion U.S. dollars, and the annual growth rate is expected to be higher than that of rigid PCBs.
With the expansion of the application, in addition to the increase in the number, there will be many new performance requirements. Polyimide films are available in colorless and transparent, white, black, and yellow, and have high heat resistance and low CTE properties, which are suitable for different occasions. Cost-effective polyester film substrates are also available in the market. New performance challenges include high elasticity, dimensional stability, film surface quality, and film photoelectric coupling and environmental resistance to meet the ever-changing requirements of end users.
FPCB and rigid HDI boards must meet the requirements of high-speed and high-frequency signal transmission. The dielectric constant and dielectric loss of flexible substrates must also be paid attention to. Polytetrafluoroethylene and advanced polyimide substrates can be used to form flexibility. Circuit. Adding inorganic powder and carbon fiber filler to the polyimide resin can produce a three-layer structure of flexible thermally conductive substrate. The inorganic fillers used are aluminum nitride (AlN), aluminum oxide (Al2O3) and hexagonal boron nitride (HBN). The substrate has 1.51W/mK thermal conductivity and can withstand 2.5kV withstand voltage and 180 degree bending test.
FPCB application markets, such as smart phones, wearable devices, medical equipment, robots, etc., put forward new requirements on the performance structure of FPCB, and developed new FPCB products. Such as ultra-thin flexible multilayer board, four-layer FPCB is reduced from the conventional 0.4mm to about 0.2mm; high-speed transmission flexible board, using low-Dk and low-Df polyimide substrate, reaching 5Gbps transmission speed requirements; large The power flexible board uses a conductor above 100μm to meet the needs of high-power and high-current circuits; the high heat dissipation metal-based flexible board is an R-FPCB that uses a metal plate substrate partially; the tactile flexible board is pressure-sensed The membrane and the electrode are sandwiched between two polyimide films to form a flexible tactile sensor; a stretchable flexible board or a rigid-flex board, the flexible substrate is an elastomer, and the shape of the metal wire pattern is improved to be stretchable . Of course, these special FPCBs require unconventional substrates.
4.2 Printed electronics requirements
Printed electronics has gained momentum in recent years, and it is predicted that by the mid-2020s, printed electronics will have a market of more than 300 billion U.S. dollars. The application of printed electronics technology to the printed circuit industry is a part of the printed circuit technology, which has become a consensus in the industry. Printed electronics technology is the closest to FPCB. Now PCB manufacturers have invested in printed electronics. They started with flexible boards and replaced printed circuit boards (PCB) with printed electronic circuits (PEC). At present, there are many substrates and ink materials, and once there are breakthroughs in performance and cost, they will be widely used. PCB manufacturers should not miss the opportunity.
The current key application of printed electronics is the manufacture of low-cost radio frequency identification (RFID) tags, which can be printed in rolls. The potential is in the areas of printed displays, lighting, and organic photovoltaics. The wearable technology market is currently a favorable market emerging. Various products of wearable technology, such as smart clothing and smart sports glasses, activity monitors, sleep sensors, smart watches, enhanced realistic headsets, navigation compasses, etc. Flexible electronic circuits are indispensable for wearable technology devices, which will drive the development of flexible printed electronic circuits.
An important aspect of printed electronics technology is materials, including substrates and functional inks. Flexible substrates are not only suitable for existing FPCBs, but also higher performance substrates. Currently, there are high-dielectric substrate materials composed of a mixture of ceramics and polymer resins, as well as high-temperature substrates, low-temperature substrates and colorless transparent substrates. , Yellow substrate, etc.
4 Flexible and printed electronics and other requirements
4.1 Flexible board requirements
The miniaturization and thinning of electronic equipment will inevitably use a large number of flexible printed circuit boards (FPCB) and rigid-flex printed circuit boards (R-FPCB). The global FPCB market is currently estimated to be about 13 billion US dollars, and the annual growth rate is expected to be higher than that of rigid PCBs.
With the expansion of the application, in addition to the increase in the number, there will be many new performance requirements. Polyimide films are available in colorless and transparent, white, black, and yellow, and have high heat resistance and low CTE properties, which are suitable for different occasions. Cost-effective polyester film substrates are also available in the market. New performance challenges include high elasticity, dimensional stability, film surface quality, and film photoelectric coupling and environmental resistance to meet the ever-changing requirements of end users.
FPCB and rigid HDI boards must meet the requirements of high-speed and high-frequency signal transmission. The dielectric constant and dielectric loss of flexible substrates must also be paid attention to. Polytetrafluoroethylene and advanced polyimide substrates can be used to form flexibility. Circuit. Adding inorganic powder and carbon fiber filler to the polyimide resin can produce a three-layer structure of flexible thermally conductive substrate. The inorganic fillers used are aluminum nitride (AlN), aluminum oxide (Al2O3) and hexagonal boron nitride (HBN). The substrate has 1.51W/mK thermal conductivity and can withstand 2.5kV withstand voltage and 180 degree bending test.
FPCB application markets, such as smart phones, wearable devices, medical equipment, robots, etc., put forward new requirements on the performance structure of FPCB, and developed new FPCB products. Such as ultra-thin flexible multilayer board, four-layer FPCB is reduced from the conventional 0.4mm to about 0.2mm; high-speed transmission flexible board, using low-Dk and low-Df polyimide substrate, reaching 5Gbps transmission speed requirements; large The power flexible board uses a conductor above 100μm to meet the needs of high-power and high-current circuits; the high heat dissipation metal-based flexible board is an R-FPCB that uses a metal plate substrate partially; the tactile flexible board is pressure-sensed The membrane and the electrode are sandwiched between two polyimide films to form a flexible tactile sensor; a stretchable flexible board or a rigid-flex board, the flexible substrate is an elastomer, and the shape of the metal wire pattern is improved to be stretchable. Of course, these special FPCBs require unconventional substrates.
4.2 Printed electronics requirements
Printed electronics has gained momentum in recent years, and it is predicted that by the mid-2020s, printed electronics will have a market of more than 300 billion US dollars. The application of printed electronics technology to the printed circuit industry is a part of the printed circuit technology, which has become a consensus in the industry. Printed electronics technology is the closest to FPCB. Now PCB manufacturers have invested in printed electronics. They started with flexible boards and replaced printed circuit boards (PCB) with printed electronic circuits (PEC ). At present, there are many substrates and ink materials, and once there are breakthroughs in performance and cost, they will be widely used. PCB manufacturers should not miss the opportunity.
The current key application of printed electronics is the manufacture of low-cost radio frequency identification (RFID) tags, which can be printed in rolls. The potential is in the areas of printed displays, lighting, and organic photovoltaics. The wearable technology market is Currently a favorable market emerging. Various products of wearable technology, such as smart clothing and smart sports glasses, activity monitors, sleep sensors, smart watches, enhanced realistic headsets, navigation compasses, etc. Flexible electronic circuits are indispensable for wearable technology devices, which will drive the development of flexible printed electronic circuits.
An important aspect of printed electronics technology is materials, including substrates and functional inks. Flexible substrates are not only suitable for existing FPCBs, but also higher performance substrates. Currently, there are high-dielectric substrate materials composed of a mixture of ceramics and polymer resins , as well as high-temperature substrates, low-temperature substrates and colorless transparent substrates., Yellow substrate, etc.