What Is PCB IC Ic Substrate? (2022)

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Before the early PCB ic substrate appeared, the various components of electronic products were connected by wires to form a complete path. Later, in order to simplify the manufacturing process of electronic products and reduce the cost, the circuit was developed by printing, and the copper foil on the ic substrate was used to replace the original wire connection, thereby improving the production efficiency.

The various components are mainly connected through the metal copper foil circuits on the board. Through the design of each layer to connect and conduct related components, a complete product that operates effectively is achieved.

The traditional circuit board construction method uses printed resists to make circuit lines and drawings, so it is called a printed circuit board. Because the size of electronic products continues to be miniaturized and refined, most circuit boards are currently covered with etching resists (wet film or dry film), which are exposed and developed and then etched to remove the unwanted copper foil to make circuit boards.

PCB ic substrate

The base material is generally classified according to the insulation, material composition or flame resistance of the ic substrate. The common raw materials are bakelite, glass fiber, and various plastic boards. Manufacturers of PCB ic substrates generally use an insulating prepreg composed of glass fiber non-woven fabrics and epoxy resin resins, and then press them with copper foil to form a copper foil ic substrate for use.

The following are the more common types of PCB ic substrates:

FR-4: Glass fiber + epoxy resin. It is the most commonly used PCB material, but the Tg is only about 130. If the subsequent processing environment of the product or the operating environment temperature is high, High Tg FR-4 is recommended.

High Tg FR-4: Glass fiber + epoxy resin, the use is second only to FR-4. Tg above 150°C is High Tg .

CEM-1: The center is tissue paper, and the surface is covered with glass cloth + epoxy resin.

CEM-3: The center is glass non-woven cloth, and the surface is covered with glass cloth + epoxy resin.

Ceramic ic substrate (Ceramic PCB): ceramic powder + glass fiber.

Teflon PCB (Teflon PCB): Teflon + glass fiber.

5G Applicable Ic substrates

5G PCB products are suitable for ic substrates, please refer to this page for information: PCB 5G ic substrates - selection and application

PCB surface treatment

Since the copper surface of the PCB is easily oxidized in the environment, it must be reprocessed and covered with a layer of coating on the exposed area that is not covered with solder mask ink to protect the process from oxidation. In response to various subsequent processing needs, various surface treatment methods with different materials, prices, and different degrees of protection have been developed.

Common PCB surface treatments include the following:

Bare copper plate, spray tin plate, lead-free sprays tin plate, chemical gold plate, electroplating gold, chemical silver plate, OSP plate. Please click this page for various PCB surface treatment instructions.

Types of PCB structures

The printed circuit board (PCB) structure can be divided into the following three types

Single-Layer PCB:

Only one side of the circuit board has copper foil conductors, and the other side has no copper foil conductors at all. The circuits of early electronic products were simple, only one side was needed for connection and conduction, and parts could be placed on the other side without copper foil.

Double-Layer PCB:

 There are copper foil wires on both sides of the circuit board, and the paths on the front (Top layer) and the back (Bottom layer) can be connected to each other through vias. Since both sides can be wired, the usable area is twice that of a single panel, which is more suitable for products with complex circuits. The design is to place the part on the front, and the back is the welding surface of the part foot.

Multi-Layer PCB:

Multi-Layer PCB is made of multiple etched double-sided boards, an insulating layer (Prepreg) is stacked between the boards, and copper foil is laid on both sides of the outermost layer and then pressed together. Since multiple double-sided laminates are used, the number of layers is usually an even number.

The copper foil layer that is pressed inside can be a conduction layer, a signal layer, a power layer or a ground layer. The multi-layer board can theoretically reach more than 50 layers, but the practical application surface is currently up to about 30 layers.

pcb

PCB application - single panel, double panel

1. Single-sided board:

Using glass fiber covered with copper foil on one side as the bottom plate, integrated circuits (ICs) and other electronic components are concentrated on one side, and copper wires are concentrated on the other side. The number of copper conductors that can be made on a single panel is small, and only early circuit boards were used.

2. Double-sided board:

The glass fiber covered with double-sided copper foil is used as the bottom plate, and copper wires are made on the front and back surfaces of the bottom plate, and "vias" are drilled to allow the copper wires to pass through the board from the front to the back. The copper wires on the surface are connected to each other and are used in circuits that are more complicated than single-sided boards.

3. Material

For simpler and low-end electronic products, lower-priced FR-1 or FR-2 (phenolic tissue paper, commonly known as bakelite) may be selected as materials for cost considerations, but most of them still use the mainstream introduced above. Ic substrate FR-4, other common materials are:

(A) PTFE (Teflon ic substrate)

High Frequency (HF) PCB, high-frequency electronic equipment is today's development trend, especially in the wireless network environment. With the rapid development of satellite communication, communication products are also developing towards high speed and high frequency.

Therefore, the development of new products always requires the use of high-frequency ic substrates, satellite systems, mobile phone receiving base stations, etc. These communication products must use high-frequency PCBs. In general, high frequencies can be defined as frequencies above 1GHz. Currently, PTFE material is widely used in high frequency PCB manufacturing, also known as Teflon, and its frequency is usually higher than 5GHz.

 (B) Alumina (ceramic ic substrate)

Ceramic ic substrate is a kind of circuit board. Unlike traditional FR-4 or aluminum ic substrate, it has a thermal expansion coefficient close to that of semiconductors and high heat resistance. It is suitable for products with high heat generation (high brightness LED, solar energy). Weather-resistant properties are more suitable for harsher outdoor environments.

Generally speaking, ceramic ic substrates have sufficiently high mechanical strength, and can be used as support members in addition to mounting components; good workability, high dimensional accuracy, and easy multi-layering.

(C) Aluminum (aluminum ic substrate)

Aluminum ic substrate is a unique metal-based copper clad laminate with good thermal conductivity, electrical insulation properties and mechanical processing properties. Most used in LEDs and power conversion electronics, LEDs generate high heat when they emit strong light, and aluminum ic substrates dissipate the heat directly from the components.

 And the aluminum ic substrate can prolong the service life of LED components and provide higher stability. Aluminum ic substrates are typically found in street lights, parking lights, and lighting fixtures. It also allows power converters to change current and regulate electronics. Aluminum ic substrates are usually made single-sided, but also double-sided. Multilayer aluminum ic substrates are more difficult to manufacture.

2. Types & Uses

(A) 4-layer board

The ic substrate material is mainly epoxy glass fiber cloth. The main uses are personal computers, medical electronic equipment, measuring instruments, semiconductor testing machines, numerical control machines, electronic switches, communication machines, memory circuit boards, IC cards, etc.

(B) 6-8 layer board

The ic substrate material is still mainly epoxy resin glass fiber cloth. Most of them are used in electronic switches, semiconductor testing machines, mid-range personal computers, engineering workstations and other machines.

(C) 10 layers or more

The material is mainly glass benzene resin material, or epoxy resin is used as the multi-layer PCB ic substrate material. The application of this type of PCB is special, and it is used in large industrial computers, high-speed computers, defense machines, communication machines, etc.

Common unit conversions

Copper Foil Thickness-oz ounce, oz

The copper foil thickness commonly used in the PCB industry is ounces (oz), but ounces (oz) are obviously a unit of weight, why can it be changed to a unit of thickness?

Because the specification of PCB ic substrate copper foil is defined by how many ounces (oz) of copper per square foot (ft²) area. Since the heavier the copper on the fixed area, the thicker the copper foil thickness, the copper foil weight is proportional to the thickness, so convert the copper foil weight ounce (oz) to the thickness mil.

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