Copper clad laminate (CCL) is the raw material of the electronic industry. The structure of copper clad laminate includes substrate, copper foil, copper clad adhesive and so on. It is made of wood pulp paper or glass fiber cloth as reinforcing material. It is dipped into resin and covered with copper foil on one side or double sides. It is a product of hot pressing. CCL by carving method, manual drawing method, mapping method, mimeograph method, hot melt plastic film plate, pre coated photosensitive laminate and thermal transfer method for circuit board.
1. Substrate: insulating board composed of macromolecule synthetic resin and reinforcing material can be used as the base plate of copper clad laminate. A wide variety of synthetic resins, commonly used phenolic resin, epoxy resin, PTFE and so on. Reinforced materials generally have two kinds of paper and cloth, which determines the mechanical properties of the substrate, such as solder resistance, flexural strength etc..
2 copper foil: it is the key material for making copper clad laminate. It must have high conductivity and good weldability. Requirements of copper foil surface should not have scratches, blisters and wrinkles, metal purity not less than 99.8%, the thickness error is no more than 5um. According to the standards issued by the Ministry, the nominal series of copper foil thickness are 18, 25, 35, 70 and 105um.
3. Copper clad adhesive: adhesive is an important factor in whether copper foil can be firmly covered on the substrate. The scratch strength of copper clad laminates mainly depends on the properties of the adhesive.
1, according to the mechanical rigidity of copper clad laminate, can be divided into rigid copper clad laminate (Rigid Copper Clad Laminate) and flexible copper clad laminate (Flexible Copper Clad Laminate).
2, according to different insulation materials, structures can be divided into organic resin, copper clad laminate, metal based copper clad laminate and copper clad laminate of Tao Ciji.
3, according to the thickness of the copper plate can be divided into thick plate (plate thickness range of 0.8 to 3.2mm (including Cu)), sheet (plate thickness range of less than 0.78mm (excluding Cu)).
4, according to the CCL reinforced material is divided into glass cloth CCL, paper base copper clad laminate and composite base copper clad laminate (CME-1, CME-2).
5, according to the classification of flame retardant and non flame retardant flame retardant plate plate: in accordance with the UL standard (UL94, UL746E), division of CCL flame retardant grade, can be divided into four kinds of rigid CCL flame retardant grade: UL-94V0; UL-94V1; UL-94V2 and UL-94HB.
Grade separation of copper clad laminate:
1, FR-4A1 grade CCL: this level is mainly used in military, communications, computers, digital circuits, industrial instrumentation, automotive circuits and other electronic products.
2, FR-4A2 grade copper clad laminate: this level is mainly used in ordinary computers, instruments and meters, advanced household electrical appliances and general electronic products. This series of copper clad laminates are widely used, and all the performance indexes meet the needs of general industrial electronic products.
3, FR-4A3 grade copper clad laminate: This grade CCL is specially developed for the household electrical appliance industry, computer peripheral products and ordinary electronic products (such as toys, calculators, game consoles, etc.) FR-4 products. Its characteristic is that the performance meets the requirements of the premise, the price has a competitive advantage.
4, FR-4AB grade copper clad laminate: this class of sheet metal is a unique low-grade products. However, the performance indicators can still meet the needs of ordinary household appliances, computers and general electronic products, the price is most competitive, and the performance price ratio is also quite good.
5, FR-4B grade copper clad laminate: this class of sheet metal is secondary quality, sheet quality stability is poor, not applicable to the larger area of circuit board products, generally applicable size of 100mmX200mm products. Its price is the lowest, but customers should pay attention to choose to use.
Quality index of copper clad laminate
The quality of CCL affects the quality of PCB directly. The main non - electrical technical standards for measuring the quality of copper deposits are the following
1, copper index - anti stripping strength: stripping strength is the width of the unit width of copper foil peeling substrate required minimum force, unit kg / cm. This index is used to measure the bonding strength between copper foil and substrate. This indicator depends mainly on the properties and manufacturing processes of the adhesive.
2, copper index - warpage: warpage refers to the length of the warping value, measuring copper plate relative to the flatness of the roughness index, depending on the substrate material and thickness.
3, copper index - bending strength: bending strength shows that copper can withstand bending ability, the unit is kg / cm.. This indicator depends mainly on the base material of the copper clad laminate. This indicator shall be taken into account when determining the thickness of the printed circuit board.
4, the index of copper - solder resistance: solder resistance refers to the time of the molten solder copper clad plate in a certain temperature (usually 10s), can withstand the anti stripping capacity of copper foil. General requirements of copper foil plate is not blistering, not layered. If the dip is poor, after several printed circuit board welding, welding wire and plate will be off. This indicator has a great impact on the quality of printed circuit boards, depending mainly on boards and adhesives.
In addition, the technical specifications of copper foil are surface smoothness, smoothness, pit depth, dielectric properties, surface resistance, cyanide resistance and so on.