The Difference Between The Raw Materials of PCB

The PCB market is really "unbalanced" recently, and the wave of unrest has arisen again and again. Recently, the issue of sheet materials has raised a wave of topics. PCB is the core of electronic products, but the quality and price of raw materials are different. The use of low-priced raw materials to compete maliciously and disrupt the market is the fuse that causes dissatisfaction among other peers. Today, I will take you to understand the difference between the important raw material of PCB - copper clad laminate.

The copper clad laminate is the basic material in the production process of the circuit board. The reinforcing material is impregnated with resin adhesive, dried, cut and stacked into blanks, and then covered with copper foil. Made by high pressure lamination. The copper clad laminate mainly plays the four functions of conduction, insulation, support and signal transmission. In addition, it also plays the role of heat conduction and flame retardant.

If the CCL is classified according to the resin adhesive used in the board, it can be mainly divided into paper-based CCI, glass fiber cloth-based CCL, composite-based CEM and special material-based.

Common paper-based CCI types include phenolic resins (XPc, XxxPC, FR-1, FR-2, etc.), epoxy resins (FE-3) and other types.

Common glass fiber cloth based CCL has epoxy resin (FR-4), which is also the most widely used type.

Common composite matrix CEM types are CEM-1, CEM-3.

In addition, unlike FR-1, FR-2, and FR-4, FR-3 is a type between paper-based CCI and glass fiber cloth-based CCL. Foil is compounded, and CEM-1 CCL is improved on the basis of FR-3, which is why CEM is a compound base type.

The following mainly describes the FR-4 and CEM types.

FR-4 copper clad laminate: FR-4 is the abbreviation of glass fiber epoxy resin copper clad laminate. It is a kind of flame retardant substrate with epoxy resin as adhesive and electronic grade glass fiber cloth as reinforcing material. FR-4 sheet has the characteristics of high strength, good heat resistance, good dielectric properties, and metallizable through holes, and realizes electrical conduction between the conductive layers of double-sided and multi-layer circuit boards, so it is the best choice for all overlays. It is the most widely used and the largest type of copper plate. FR-4 sheet can be subdivided into different grades. Among them, grade A sheet is widely used in military industry, communication, computer, digital circuit, industrial instrumentation, automotive circuit and other industrial electronic fields. The performance indicators of FR-4 sheet are all It can meet the needs of general industrial electronic products.

CEM-1 copper clad laminate: CEM-1 is made of paper base impregnated with epoxy resin, then double-sided composite layer of glass fiber cloth, and copper foil composite hot pressing, CEM-1 is more structurally than FR-3 Two layers of glass fiber cloth, so the comprehensive properties of CEM-1, such as mechanical strength, moisture resistance, flatness, heat resistance and electrical properties, are superior to paper-based CCL. CEM-1 can therefore be used to make PCBs with high frequency characteristics, such as TV tuners, power switches, ultrasonic equipment, computer power supplies and keyboards, as well as TVs, tape recorders, radios, electronic equipment meters, office automation equipment, etc. All in all, the CEM-1 is an ideal replacement for the FR-3.

CEM-3 copper clad laminate: CEM-3 is improved from FR-4. In the structure, glass mat (also known as non-woven fabric) is used to impregnate epoxy resin, and glass fiber cloth is attached to both sides, and then compounded with copper foil. Press-molded. It differs from FR-4 in that CEM-3 replaces most of the glass fiber cloth with glass mat, which increases the degree of "cutting" in terms of mechanical properties. CEM-3 is usually directly made into double-sided copper clad laminate. Because glass mat is looser than glass fiber in structure, its processing convenience is higher than FR-4 in drilling process, and it is also better than FR-4 in punching process. The disadvantage of CEM-3 compared to FR-4 is that the thickness and accuracy of CEM-3 are not as good as FR4, and the degree of distortion after PCB soldering is also higher than that of FR-4.

Special material base types include BT, PI, PPO, MS, etc. In addition to being classified according to the resin adhesive used in the board, CCL has a variety of classification methods, such as classification according to flame retardant performance, CCL can be divided into There are two types of boards, flame-retardant (UL94-V0, UL94-V1 grade) and non-flame-retardant type (UL94-HB grade); the key bonding process is divided into two types: direct bonding method and adhesive lamination bonding method.

The performance of the sheet material directly affects the application effect of the PCB, such as FR-4 sheet, although its price is the most expensive, but its performance is also the best, so FR-4 can be widely used in high-end products and multi-layer board market. If the board is cut corners and shoddy, it will directly lead to the instability of the circuit board, affecting the service life and safety of the product.

Knowing the raw materials of PCB board is of great significance for users to choose PCB factories. Only high-quality board types can meet the requirements of higher product performance.