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PCB Classification

There are many classification methods for PCBs. According to the number of conductive layers, bending toughness, assembly method, substrate, special function, wire forming process, presence or absence of core plates, and surface treatment, the following classifications can be made.

(1) According to the number of layers of conductive layers: single-panel, double-panel, multi-layer board. The multi-layer board can be classified into a general multi-layer board and a multi-layer board according to the number of laminations (the core is the position of the holes, and the position of the holes determines the number of laminations).

In a conventional multi-layer board, generally, 12 or more layers are referred to as a high-level board, and 16 or more layers, a hole diameter of more than 0.3 mm, and a thickness-to-diameter ratio of 8 or more are referred to as a back sheet.

Build-up multi-layer PCBs, also known as build-up multi-layer boards (often referred to in the industry as micro-via multi-layer and multi-layer boards) , in essence, basically the same), the typical product of laminated multi-layer board is HDI PCB, which is called High Density Interconnection. Generally, the minimum line width/space is 0.075/0.075mm and below, and the minimum aperture is 0.15mm and below. Conditions such as blind, buried holes, etc. are called HDI.

HDI includes first-order, second-order, and high-order (third-order and above. Currently, more applications are applied to terminal products, such as third-order and fourth-order, and fourth-order and above are basically converted to Any layer), Any layer (any order, or arbitrary). Layers, there are also companies called ELIC (Every Layer Interconnect) and SLP (Substrate Like PCB, class carrier board), currently used in high-end terminal products are more than 10, 12 layers of Any Layer and SLP.

(2) According to the bending toughness: Rigid Printed Circuit, flexible board (FPC, fully known as Flexible Printed Circuit, common hard board and soft board in the industry), rigid-flex board (Rigid) -Flexible Printed Circuit, or rigid-flexible integrated board, meaning to be combined, not simply put together), as shown in Figure 2 (Note: the physical map and schematic diagram in Figure 2 do not correspond; the same below, unless otherwise specified ). At present, the relatively high-end application on the terminal products is the rigid board area for HDI.

(3) According to the assembly method, it is divided into: PCB for through-hole insertion, PCB for surface mounting, and PCB for chip-level packaging. The chip for chip-scale packaging, commonly referred to as Substrate or IC Substrate (also known as IC Carrier), is translated into (chip-level) package carrier board. It is not recommended to use the package substrate as a confusing and inaccurate name; The view that Substrate does not belong to the PCB is not accurate).

Substrate generally consists of two types: FCBGA (Flip Chip Ball GridArray) and Strip Base BGA (Ball Grid Array).

The FCBGA is a single type, usually 4-16 layers (the difficulty of making is the most difficult of all PCB products). There are many types of BGAs, such as BOC (Board on Chip), PBGA (Plastic Ball Grid Array), CSP (Chip Scale Packaging), SiP (System in package), FCCSP (Flip Chip Ball Grid Array), etc. usually 1 -10 layers

(4) According to the substrate, it is divided into: phenolic paper base, epoxy glass fiber cloth, PI (polyimide), BT (bismaleimide triazine resin), PTFE (polytetrafluoroethylene), ceramic base, metal base, etc.

(5) According to the special functions, it is divided into: embedded component board (internal embedded passive components or special materials for surface to realize passive components, and internal embedded active components), carbon fiber substrate, photoelectric printed board, etc.

(6) According to the wire forming process, it is divided into: Subtractive (or Tenting, subtraction method, the core is formed by thickening on conventional copper), MSAP/MSA+ (Modified Semi-Additive Process, modified semi-additive method, the core is The thickening of the line is formed on the thin copper, and the SAP (Semi-Additive Process, the core is thickened by plating the ultra-thin copper on the insulating substrate to form the line).

(7) According to the core board (Core): Cored (core board), Coreless (coreless board). Coreless can be further divided into ordinary Coreless, ETS (Embedded Trace Substrate, or EPP, Embedded Pattern Process, buried circuit board or flat board).

(8) According to the surface treatment method: tin plating, gold plating (with nickel gold, nickel palladium gold, also have hard gold and soft gold), silver plating, OSP, SOP (Solder On Pad, also known as Bump) and so on. SOP is actually a proprietary, main surface treatment method for FCCSP products mentioned above (the other is OSP, which is low in cost but less used). General FCCSP package, It is a more complex PoP package (Packaging on Packaging, usually two types of different chips are packaged in one module).

However, in practice, what is often seen is the hybrid classification method: single side, double sides, multi-layer board, HDI board, package carrier board, flexible board, rigid-flex board, special board, which is mainly based on the whole The output value of each segment of the PCB industry is divided.

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