SMT Printed Circuit Board Overview

766 Published by FASTPCBA 5月 09,2019

SMT Printed Circuit Board Overview

Early electronic products, such as tube radios, used thin iron plate brackets and mounted insulated ceramic bases on the brackets to assemble electronic products. With the advent of new types of high polymer insulation materials, especially after the invention of transistors in the 1940s, printed circuit boards emerged. The copper foil is adhered to the insulating substrate, and the conductor pattern and the component mounting hole are manufactured by means of printing, etching, drilling, etc., to form an electrical interconnection, and to ensure the reliability of electrical, thermal and mechanical properties of the electronic product, It is called Printed Circuit Board, or simply printed board or PCB. PCBs used in electronic products assembled with early through-hole components are also referred to as interposer printed boards or single panels.

With the advent of SMT, components are directly mounted on the PCB printed circuit board. Although the PCB does not need to be drilled into the pad, the SMD has a large area, a large number of pins, a tight pin pitch, and a dense PCB layout. So for PCB, both the selection of substrates and the design and manufacture of graphics have placed higher demands.

printed circuit board

Substrate material

There are many kinds of substrates for printed circuit board, but they are generally divided into two categories, namely organic substrate materials and inorganic substrate materials. The organic substrate material refers to a reinforcing material such as a glass fiber cloth (fiber paper, glass mat, etc.), impregnated with a resin binder, dried to a billet, and then covered with a copper foil, which is produced by high temperature and high pressure. This type of substrate, called Copper Clad Laminatos (CCL), commonly known as copper clad laminate, is the main material for manufacturing: PCB. The inorganic substrate is mainly a ceramic plate and an enamel coated steel substrate.

There are many varieties of CCL. According to the variety of reinforcing materials used, it can be divided into four categories: paper base, glass fiber cloth base, composite base (CEM) and metal base. According to the organic resin adhesive used, it can be divided into phenolic Resin (PE), epoxy resin (EP), polyimide resin (PI), polytetrafluoroethylene resin (TF), polyphenylene ether resin (PPO), etc.; If it is divided according to the rigidity of the substrate, it can be divided into rigid CCL. And flexible CCL.

The variety of CCLs brings great convenience to the printed circuit boardselection of various electronic products. Only when you are familiar with the performance and characteristics of CCL can the performance requirements of  printed circuit board and electronic products be close.

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