Circuit board {PCB circuit board}, also known as printed circuit board, is the supplier of electrical connection of electronic components. Its development has a history of more than 100 years; Its design is mainly layout design; The main advantage of using PCB is to greatly reduce wiring and assembly errors, improve the level of automation and production labor rate.

According to the circuit board layer number can be divided into single panel, double panel, four boards, six boards and other multilayer circuit board.

Printed circuit board is not a general terminal product, so the definition of the name is a little confused, for example: the PC used by the motherboard, called the motherboard, but not directly called the circuit board, although there are circuit boards in the motherboard, but not the same, so the industry evaluation of the two related but not the same. Another example: the news media call it an IC board because there are integrated circuit parts mounted on the circuit board, but it is not the same as a printed circuit board. When we talk about printed circuit boards, we usually mean bare boards – circuit boards that don’t have components on them.


Single panel

On a basic PCB, parts are concentrated on one side and wires on the other. The PCB is called single-sided because the conductor appears on only one side. Because single panels have many strict restrictions on the design of circuits (because there is only one side, the wiring cannot cross and must go around a separate path), only early circuits used such boards.

Double panel

This circuit board has wiring on both sides, but to use both sides of the wire, there must be a proper circuit connection between the two sides. The “bridge” between these circuits is called a guide hole (via). A guide hole is a small, metal-filled hole in a PCB that can be connected to a wire on both sides. Because the area of the double panel is twice as large as that of the single panel, the double panel solves the problem of interlaced wiring in the single panel (it can be passed through the guide hole to the other side) and is more suitable for use in more complicated circuits than the single panel.

A multilayer

In order to increase the area that can be wired, multilayer board used more single or double-sided wiring board. With a double lining, two one-way for outer layer or two double lining, two blocks of single outer layer of the printed circuit board, through the positioning system and alternate insulation adhesive materials and conductive graphics interconnection according to design requirement of printed circuit board becomes four, six layer printed circuit board, also known as multilayer printed circuit board. The number of layers on the board does not mean that there are several independent wiring layers. In special cases, empty layers will be added to control the thickness of the board. Usually, the number of layers is even, and it contains the two outermost layers. Most motherboards have 4 to 8 layers of structure, but technically it is possible to have nearly 100 layers of PCB. Most large supercomputers use fairly multi-layered mainframe boards, but because such computers can be replaced by clusters of many ordinary computers, the use of super-multilayered boards has become obsolete. Because each layer in the PCB is closely combined, it is not easy to see the actual number, but if you carefully look at the motherboard, you can still see.


Current circuit board, mainly by the following composition

Circuit and Pattern: circuit is used as a communication tool between the original elements. In the design, a large copper surface will be designed as the grounding and power layer. The line and the surface are made at the same time.

Dielectric layer (Dielectric) : used to keep the lines and insulation between the layers, known as base material.

Hole (Through hole/via) : Through hole allows two or more layers of wires to pass Through each other. The larger Through hole is used as part plug-in. In addition, non-through hole (nPTH) is usually used for surface mount positioning and assembly fixing screws.

Solder resistant /Solder Mask: not all copper surfaces should be on tin. Therefore, in the areas where the Solder is not eaten, a layer of material (usually epoxy resin) will be printed to prevent the Solder from eating on the copper surface, so as to avoid short circuit between the non-solder routes. According to different process, divided into green oil, red oil, blue oil.

Legend /Marking/Silk screen: this is not necessary. The main function is to mark the name and position box of each part on the circuit board, which is convenient for maintenance and identification after assembly.

Surface Finish: due to the fact that the copper Surface is easily oxidized in the general environment, it is unable to be tin covered. Therefore, it will be protected on the copper Surface where the tin is to be eaten. The way of protection has spray Tin (HASL), gold (ENIG), Silver (Immersion), Tin (Immersion), organic solder (OSP), the method has advantages and disadvantages, collectively known as surface treatment.


Printed Board is also known as Printed Wiring Board (PWB). The substrate of the board itself is made of insulating and non-bending materials. The thin circuit material that can be seen on the surface is copper foil. Originally, the copper foil was covered on the whole board, but part of the middle part of the manufacturing process was etched away, and the remaining part became network thin circuit. These lines are called conductor patterns, or wiring, and are used to provide electrical connections to components on the PCB.

The color of the PCB is usually green or brown, which is the color of solder mask. It is an insulating layer that can protect copper wire, prevent short circuit caused by wave welding, and save the amount of solder. In the welding resistance layer will also be printed on a layer of silk screen. Words and symbols (mostly white) are usually printed on the board to indicate where the parts are on the board. The screen printing surface is also known as legend.

Integrated circuits, transistors, diodes, passive components (resistors, capacitors, connectors, etc.) and various other electronic components are installed on the final product. Through wire connection, electronic signals can be formed and function.


The main advantages of using PCB are:

A. because the graphics have repeatability (reproducibility) and consistency, reduce wiring and assembly errors, saving equipment maintenance, debugging and inspection time;

2 design can be standardized, conducive to exchange; 3. High wiring density, small size, light weight, conducive to the miniaturization of electronic equipment;

It is beneficial to mechanization and automation production, which improves labor productivity and reduces the cost of electronic equipment.

The manufacturing methods of printed boards can be divided into two major categories: subtraction (subtraction) and addition (addition). At present, large – scale industrial production is still to reduce the corrosion of copper foil method.

(summary picture)

⒌ especially FPC soft plate bending resistance, precision, better application on high precision instruments. (camera, cell phone. Cameras, etc.)


Base material

Base material is made with the insulation part of base board commonly classification, common raw material is electric board, glass fiber board, and all sorts of plastic board. PCB manufacturers typically use a glass fiber, fabric, and resin insulation, then epoxy resin and copper foil pressed into a “prepreg.”

Xgs game circuit design and common substrate and main components are:

Fr-1 – phenolic cotton paper, commonly known as electric wood (more economical than fr-2)

Fr-2 – phenolic cotton paper,

Fr-3 — Cotton paper, epoxy resin

Fr-4 ─ Woven glass, epoxy resin

Fr-5 – glass cloth, epoxy resin

Fr-6 ─ wool face glass, polyester

G-10 — glass cloth, epoxy resin

Cem-1 — cotton paper, epoxy resin (flame retardant)

Cem-2 – cotton paper, epoxy resin (non-flame retardant)

Cem-3 – glass cloth, epoxy resin

Cem-4 — glass cloth, epoxy resin

Cem-5 – glass cloth, polyester

AIN — aluminum nitride

SIC – silicon carbide

Metal coating

In addition to wiring on the substrate, the metal coating is where the substrate wiring is welded to the electronics. In addition, because different metal price is different, affect the cost of production directly accordingly. In addition, each metal has different weldability, contact, resistance, etc., which will directly affect the performance of the components.

Commonly used metal coatings are copper, tin (usually 5 to 15 microns thick), lead-tin alloy (or tin-copper alloy, that is, solder, usually 5 to 25 microns thick, about 63 percent tin), gold (usually only plated at the interface), and silver (generally plated at the interface, or as a whole silver alloy).

Circuit design

The design of printed circuit board is based on the circuit principle diagram to realize the functions needed by circuit users. PCB design mainly refers to layout design, which requires the layout of internal electronic components, metal wiring, through-hole and external connection, electromagnetic protection, heat dissipation, cross talk and other factors. Excellent circuit design can save production cost and achieve good circuit performance and heat dissipation performance. Simple layout design can be realized by hand, but complex circuit design generally requires the help of computer-aided design (CAD). Famous design software includes OrCAD, Pads (i.e. PowerPCB), Altium designer (i.e. Protel), FreePCB, CAM350, etc

The basic production

Depending on the technology, the process can be divided into elimination and addition.

Subtract method

Subtractive, or Subtractive, is the use of chemicals or machinery to remove unwanted parts of a blank circuit board (that is, one that is covered with a whole piece of foil) and leave the circuit where it is needed.

Screen printing: good upfront design circuit diagrams are made into silk screen mask, silk screen don’t need the circuit on part will be covered by wax or waterproof materials, and then put the silk mask in blank on the circuit board, and will not be on screen in oil corrosion protective agent, put circuit board in the corrosive liquid, without being protective cover the part will be corrosion, finally, the clear protective agent.

Plate: the designed circuit TuZhi in advance on the pervious to light film mask (the simplest approach is to use the printer printed slides), printed with should be part of the need in opaque color, then coated with light-sensitive pigment on blank PCB, will prepare a good film mask on PCB irradiation light for a few minutes, remove the mask after use developer to display circuit board design, finally like with silk screen printing method into the circuit.

Engraving: use a milling machine or laser engraving machine to directly remove unwanted parts of the blank line.

Addition process

(i.e. the addition method), is now widespread in a thin plating on copper substrate, in advance to cover the photoresist (D/F), through uv light exposure and development, put the need to show, and then using the official line on the PCB plating copper thick thickening to the required specifications, the plating layer etching resistance agent resistance again – metal coke, finally get rid of the photoresist (this process is called to film), then put the photoresist layer of copper foil etching.

Horizon method

Lamination is one of the methods of making multilayer printed circuit board. The outer layer is wrapped after the inner layer is made, and then the outer layer is processed by subtraction or addition. Repeat the action of the multilayer method repeatedly, can get more multilayer printed circuit board is the sequential multilayer method.

1. Inner layer production

2. Layering (i.e. the act of bonding different layers)

3. The lamination is completed (minus the outer layer of the method containing metal foil film; Addition method)

4. The drilling

The Panel method

1. Electroplate the whole PCB

2. Resist the surface to be retained.

3. The etching

4. Remove the blocking layer

The Pattern method

1. Apply a blocking layer where the surface is not to be retained

2. The surface required for electroplating shall reach a certain thickness

3. Remove the blocking layer

4. Etch until the unwanted foil film disappears

Complete addition

1. Apply a blocking layer where no conductor is needed

2. The circuit is composed of no electrolytic copper

Partial addition

1. Cover the whole PCB with no electrolytic copper

2. Apply a blocking layer where no conductor is needed

3. Electroplating copper

4. Remove the blocking layer

5. Etch until no electrolytic copper disappears under the original blocking layer


ALIVH (Any Layer Interstitial Via Hole, Any Layer IVA) is a Layer addition technology developed by panasonic in Japan. This is based on an aromatic polyamide (Aramid) fabric.

1. Dip the fabric in an epoxy resin to make a “prepreg”

2. Laser drilling

Fill the hole with conductive paste

4. Glue copper foil on the outer layer

5. Make circuit pattern by etching on copper foil

6. Glue the semi-finished products completed in step 2 onto the copper foil

7. Stratification

8. Keep repeating steps 5 to 7 until completed


B2it (Buried Bump Interconnection Technology) is a layered Technology developed by Toshiba.

1. Make a double panel or multilayer

2. Print conical silver paste on copper foil

3. Place the adhesive film on the paste and run the paste through the paste

4. Attach the previous adhesive to the first step plate

5. The copper foil of the adhesive sheet is etched into a circuit pattern

6. Repeat steps 2 to 4 until completed

A functional test

Denser PCBS, higher bus speeds, and simulated RF circuits pose unprecedented challenges to testing in an environment that requires careful design, thoughtful testing methods, and appropriate tools to deliver reliable test results.

Keep these issues in mind when dealing with fixture vendors, as well as thinking about where the product will be made, which is an area that many test engineers overlook. For example, let’s assume that the test engineer is based in California and the product is manufactured in Thailand. The test engineer will argue that the product requires expensive automation fixtures because the California plant is expensive, requires as little testing as possible, and USES automation fixtures to reduce the need to hire highly skilled and highly paid operators. But in Thailand, neither problem exists. It is cheaper to solve these problems manually, because labor costs are very low and land prices are very cheap. Large factories are not a problem. So sometimes top-notch equipment may not be popular in some countries.

The technical level

In high density UUT, if needs calibration or diagnosis may need to be done by manual detection, this is because the needle bed contact is restricted, and testing faster (UUT test with a probe can be quickly collected data rather than the information feedback to the edge of the connector) wait for a reason, so required by the operator to probe on the UUT test points. Wherever you are, make sure that the test site is clearly marked.

Probe types and general operators should also note that issues to be considered include:

A probe is greater than