Flexible circuit board has the advantages of saving space, reducing weight and high flexibility. The global demand for flexible circuit board is increasing year by year.In view of the special nature of flexible circuit board materials, this paper introduces some problems that need to be considered when using laser to process high-density flexible circuit board and micro-via hole drilling.
High density flexible circuit board is a part of the whole flexible circuit board, which is generally defined as flexible circuit board with line spacing less than 200 PCB or micro via hole less than 250 PCB.High-density flexible circuit boards have a wide range of applications, such as telecommunications, computers, integrated circuits and medical devices.
The unique characteristic of flexible circuit board makes it become the alternative of rigid circuit board and traditional wiring scheme in many occasions, and it also promotes the development of many new fields.The fastest growing part of the flexible circuit board is the internal wiring of the computer hard drive (HDD).The magnetic head of the hard disk shall be scanned forward and backward on the rotating disk, and flexible circuit can be used instead of wire to realize the connection between the moving magnetic head and the control circuit board.Hard disk manufacturers have increased production and reduced assembly costs with a technology called "flexible suspension" (FOS), as well as better shock resistance and reliability.Another high-density flexible circuit board used in the hard disk is the interposer flex, used between the suspension and the controller.
The second fastest growing field of flexible circuit board is new integrated circuit packaging.Chip package (CSP), multichip module (MCM) and the flexible circuit board chip packaging (COF package) are used, such as flexible lines, even inside the CSP line of market is especially huge, because it can be used in semiconductor devices and flash memory and is widely used in the PCMCIA card, disk drives, personal digital assistant (PDA), mobile phone, pager, digital camera and digital camera.In addition, liquid crystal display (LCD), polyester film switch and ink jet printer cartridge are the other three high growth applications of high density flexible circuit board.
The market potential of flexible line technology in portable devices such as mobile phones is very large, which is natural because these devices require small size and light weight to meet the needs of consumers.In addition, the latest applications of flexible technology include flat-panel displays and medical devices that designers can use to reduce the size and weight of products such as hearing AIDS and body implants.
The huge growth in these areas has led to an increase in global flexible circuit board production.For example, annual sales of hard disks are expected to reach 345 million units in 2004, almost double that of 1999. Conservative sales of mobile phones are also estimated to be 600 million units in 2005. As a result, the production of high-density flexible circuit boards is expected to increase by 35% annually to 3.5 million square meters by 2002.Such high production demand requires efficient and low-cost processing, and laser processing technology is one of them.
The laser has three main functions in the manufacturing process of flexible circuit board: processing molding (cutting and excision), slicing and drilling.As a kind of non-contact laser machining tools, can focus on a small (100 ~ 500 microns) on the high strength light/was (650 mw), the high energy can be used as materials for cutting, drilling, marking, welding, marking, and other various processing, processing speed and quality with the nature of processed materials and the laser characteristics such as wavelength, energy density, such as peak power, pulse width and frequency.The flexible circuit board USES ultraviolet (UV) and far-infrared (FIR) lasers, the former usually USES excimer or UV diode pumped solid-state (uv-dpss) lasers, while the latter USES sealed CO2 lasers.