HDI-Multi-layer-PCB: HDI-Multi-layer-PCB

Wednesday, July 1, 2015

what is embedded system

An embedded system is a computer system with a dedicated function within a larger mechanical or electrical system, often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. Embedded systems control many devices in common use today.

Properties typical of embedded computers when compared with general-purpose ones are e.g. low power consumption, small size, rugged operating ranges and low per-unit cost. This comes at the price of limited processing resources, which make them significantly more difficult to program and to interface with. However, by building intelligence mechanisms on the top of the hardware, taking advantage of possible existing sensors and the existence of a network of embedded units, one can both optimally manage available resources at the unit and network levels as well as provide augmented functionalities, well beyond those available. For example, intelligent techniques can be designed to manage power consumption of embedded systems.

Modern embedded systems are often based on microcontrollers (i.e. CPUs with integrated memory or peripheral interfaces) but ordinary microprocessors (using external chips for memory and peripheral interface circuits) are also still common, especially in more complex systems. In either case, the processor(s) used may be types ranging from general purpose to those specialised in certain class of computations, or even custom designed for the application at hand. A common standard class of dedicated processors is the digital signal processor (DSP).

Since the embedded system is dedicated to specific tasks, design engineers can optimize it to reduce the size and cost of the product and increase the reliability and performance. Some embedded systems are mass-produced, benefiting from economies of scale.

Embedded systems range from portable devices such as digital watches and MP3 players, to large stationary installations like traffic lights, factory controllers, and largely complex systems like hybrid vehicles, MRI, and avionics. Complexity varies from low, with a single microcontroller chip, to very high with multiple units, peripherals and networks mounted inside a large chassis or enclosure.

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HDI-Multi-layer-PCB

HDI is the abbreviation for High Density Interconnector. HDI PCB is defined as a PCB with a higher wiring density per unit area than conventional PCB. They have finer lines and spaces, smaller vias and capture pads and higher connection pad density than employed in conventional PCB technology.

HDI PCB is used to reduce size and weight, as well as to enhance electrical performance of the
device. HDI PCB is made through Microvia and buried vias and sequential lamination with insulation materials and conductor wiring for higher density of routing. HDI PCB is the best alternative to high layer-countand expensive standard laminate or sequentially laminated boards.

Concerning the electrical requirements for high-speed signal, the PCB must possess some AC characteristics, such as impedance control, high-frequency transmission capability and reduce unnecessary radiation. Multi-layered design is necessary for the structure of Stripline and Microstrip. In order to lesson the quality issues of signal transmission, the insulating material with low dielectric factor and low attenuation ratio is applied. Duo to the miniaturization and arrays of the electronic components, the PCB must be improved in the density. Along with the outcome of the assembling methods of Ball Grid Array, Chip Scale Package and Direct Chip Attachment, the PCB is featured with unprecedented high-density. The hole with a diameter less than 150um is known as Microvia. It can improve the effectiveness of assembly and space utilization and so on. It’s also necessary for the miniaturization of electronic products.

There were a lot of different names for the PCB with such structures. For example, it was called SBU (Sequence Build up the Process) in European and American industry as the program production is in the constructive mode of sequence. It was called MVP (Microvia Process) in Japanese industry because the hole of such products is much smaller than the previous one. It was also called BUM (Build up Multilayer Board) because the traditional multilayer is known as MLB (Multilayer Board).In order to avoid confusion, IPC Printed Circuit Association proposed to call it HDI (High Density Interconnection Technology) as the common name, but it can not reflect the characteristics of the circuit board. So the majority in the PCB industry define such products as HDI PCB.

There are a lot of advantages with HDI PCB, such as small size, high speed and high frequency. It is the main components of personal computers, portable computers, mobile phones and personal digital assistants. At present, except mobile phones, HDI PCB is also widely used in a variety of other consumer products, such as game consoles and MP3, etc. In addition, the applying of HDI PCB in notebook computer is expected trend since 2006 is in the industry.