Design Principles Of High-Speed PCB

What is high speed? This is the basis for considering the high speed problem, and is also a problem among many hardware engineers. With the development of the times, electronic design engineers have slowly reached a consensus.

The edge rate of the signal is the key to determine the high-speed problem. When the signal's rise time and transmission delay can be compared, it is a high-speed circuit. Although there are various circuits on the PCB, there are always some general principles that can be observed for the design. Rigid PCB Manufacturersto explain.

1. Impedance matching principle

Impedance mismatch is the root cause of many high-speed problems caused by reflections. Conventionally, a high-speed problem cannot be discussed without an impedance match. From this design original. The following high-speed PCB board design requirements are derived:

(1) A reasonable layout for termination matching design. In PCB layout, first determine the position of electronic components on the PCB, then design the power line, ground line and high-speed signal line

After the design of ordinary signal lines.

(2) Less through holes, which will cause important impedance discontinuity.

(3) The stacking setting is reasonable to ensure that the impedance is consistent after the signal is changed, while taking into account the performance and price.

(4) Pay attention to the corners of the trace. 900 and acute angles will cause impedance discontinuities.

(5) The line width is equal, and the line width can be partially reduced in the range of BGA (PCB with ball grid array structure) and high-speed connectors. These areas are also impedance discontinuities.

(6) Differential wiring is equally spaced to control differential impedance.

(7) Pay attention to the signal cross-segmentation. In addition to the problem of backflow, the position of the cross-segmentation is also a point of impedance discontinuity.

High Speed PCB

2. Principle of suppressing interference

Interference includes the mutual interference of wiring and components inside the board, as well as the interference of the external electromagnetic environment.

(1) Route 3W principle to ensure line spacing.

(2) The 20H criterion suppresses signal radiation outside the board.

(3) When possible, minimize the distance between the signal layer and the reference plane.

(4) Pay attention to interlayer interference and avoid parallel wiring of adjacent layers.

(5) When possible, reduce the length of parallel wiring in the same layer, and you can optimize it after wiring.

(6) Pay attention to the signals with fast rising edges, such as Low volume PCB Manufacture and Double Sided PCB Wholesale.

What is the Difference Between a PCB And an Integrated Circuit?

PCB (Printed Circuit Board), Chinese name is printed circuit board, also known as printed circuit board. It is an important electronic component, a support for electronic components, and a carrier for electrical connection of electronic components. Because it is made using electronic printing, it is called a "printed" circuit board. An integrated circuit is a miniature electronic device or component. Adopt a certain process to interconnect transistors, resistors, capacitors, inductors and other components and wiring required in a circuit, make it on a small or several small semiconductor wafers or dielectric substrates, and then package them in a tube case Into a micro-structure with the required circuit function. Let's follow the rigid PCB manufacturer to understand the difference between the two.

The characteristics of China's multilayer PCB boards are: 1. Can be high density: For decades, the high density of printed boards can be developed with the integration of integrated circuits and advances in installation technology. 2. High reliability: Through a series of inspections, tests and aging tests, it can ensure that the PCB can work reliably for a long period of time (usually 20 years). 3. Designability: For the various performance (electrical, physical, chemical, mechanical, etc.) requirements of the PCB, printed board design can be achieved through design standardization, standardization, etc., with short time and high efficiency. 4. Producibility: Adopt modern management, can carry out standardization, scale (quantity), automation and other production, and ensure the consistency of product quality. 5.Testability: Established relatively complete test methods, test standards, various test equipment and instruments to test and identify the qualification and service life of PCB products. Assemblability: PCB products are not only convenient for standardized assembly of various components, but also can be automated and large-scale mass production. At the same time, PCBs and various component assembly components can be assembled to form larger components and systems, up to the entire machine. 6. Maintainability: Since PCB products and various component assembly components are standardized design and large-scale production, these components are also standardized. Therefore, once the system fails, it can be replaced quickly, easily and flexibly, and the system can be quickly resumed. Of course, you can give more examples. For example, the system can be miniaturized and lightened, and the signal transmission speed can be increased.

The characteristics of the integrated circuit are that the integrated circuit has the advantages of small size, light weight, fewer lead wires and solder joints, long life, high reliability, good performance, etc. At the same time, the low cost facilitates mass production. It is not only widely used in industrial and civilian electronic equipment such as radio cassette recorders, televisions, computers, etc., but also widely used in military, communications, remote control and other aspects. The use of integrated circuits to assemble electronic equipment can increase assembly density by several tens to thousands of times over transistors, and the stable working time of the equipment can be greatly improved.

The difference between a PCB board and an integrated circuit is that integrated circuits generally refer to the integration of chips. Like the Northbridge chip on the motherboard, the internal CPU is called an integrated circuit, and the original name is also called an integrated block. The printed circuit refers to the circuit board and the like that we usually see, and there is a solder chip printed on the circuit board.

The integrated circuit (IC) is soldered on the PCB; the PCB version is the carrier of the integrated circuit (IC). The PCB board is a printed circuit board (PCB). Printed circuit boards are found in almost every electronic device. If there are electronic parts in a certain kind of equipment, the printed circuit boards are mounted on PCBs of various sizes. In addition to fixing various small parts, the main function of the printed circuit board is to electrically connect the various parts on it.

To put it simply, integrated circuits are integrated with a common circuit on a chip, which is a whole. Once there is damage inside, the chip is also damaged, and the PCB can solder components by itself, and can be replaced if it is broken.

If interested, please contact us, we can provide small batch PCB manufacturing in a short time.

How to Judge a Good PCB?

With the rapid development of mobile phones, electronics, telecommunications and other industries. The printed circuit board industry continues to grow rapidly. At the same time, people are demanding more and more. About PCB quantity, weight, color, material, accuracy, reliability, etc. However, due to competition in the PCB market, PCB materials are also on the rise. Therefore, more and more manufacturers are trying to enhance their core competitiveness. Low prices are often used to monopolize the market.

However, behind these ultra-low costs is a reduction in material costs and production costs. This makes the PCB easy to crack, easy to scratch, unqualified and other comprehensive factors. It will seriously affect the solderability and reliability of the product. So how should we half-quality PCB? The following Rigid PCB manufacturer will come to tell you.

content:

1. Distinguish the quality of the circuit board from the appearance;

2.High-quality PCB board needs to meet the following requirements

Not sure for many electronics engineers and purchasers. In fact, there is no standard method of judgment. But you can make a preliminary judgment from the following points:

The first method is to distinguish them by appearance. The other is to judge the quality specifications from the PCB itself.

1. First, distinguish the quality of the circuit board from the appearance:

The first thing to distinguish is the material used for the plate. Then the ink discolored from the board, the copper was deposited, the surface was treated, and it smelled.

The materials are usually as follows:

The ordinary HB board 22F is the cheapest, and easily deformed and broken, and can only be used as a single panel. The surface of the module is dark yellow with irritating odor, rough copper and thinner color.

Single-sided 94V0 and CEM-1 boards cost more than cardboard but are cheaper than half-glass fiberboard. The component surface is light yellow and is mainly used for industrial boards and switchboards that require fire ratings.

FR4 glass fiber board has high cost but high strength. Basically, most double-sided and multilayer boards use this material, copper can be very accurate, and unit boards are relatively heavy.

Surface treatments include OSP boards, immersion gold boards, hot air solder leveling boards, and other processes. Everything requires that the surface of the PAD is not contaminated. Otherwise it will affect solderability.

In addition, consideration should be given to the size and thickness criteria, and the appearance of the weld. Because this may affect the soldering quality, such as 2 Sided Flexible Circuit Board Material.

Multilayer Flexible PCB 

2. Secondly, high-quality PCB boards need to meet the following requirements:

(1) Meet the electrical connection requirements;

(2) The width, thickness and distance of the line shall meet the requirements to avoid high temperature, breakage or short circuit.

(3) The copper surface should not be easily oxidized. Otherwise it will affect the installation speed and cannot be used for a long time after oxidation.

(4) No other electromagnetic radiation.

(5) The shape is not deformed. All of them are now mechanically installed. And the hole position of the circuit board and the deformation error of the design line should be within the allowable range.

(6) High temperature, high humidity and special environment resistance should also be considered.

(7) The mechanical properties of the surface should meet the installation requirements.

The above is the method for judging the high quality PCB introduced by Multilayer Flexible PCB Manufacturer.

Classification and Advantages of Flexible Circuit Boards

Flexible circuit boards are currently classified as: single-sided, double-sided, and multilayer flexible boards.

① The single-sided flexible board is the printed board with the lowest cost and low electrical performance requirements. For single-sided wiring, single-sided flexible boards should be used. It has a layer of chemically etched conductive pattern, and the conductive pattern layer on the surface of the flexible insulating substrate is a rolled copper foil. The insulating substrate may be polyimide, polyethylene terephthalate, aramid fiber ester, and polyvinyl chloride.

② 2 Sided Flexible Circuit Board Material is a conductive pattern made by etching one layer on each side of the insulating base film. The metallization holes connect the patterns on both sides of the insulating material to form conductive paths to meet the design and use functions of flexibility. The cover film protects single and double-sided wires and indicates where the component is placed.

③ Multi-layer flexible board is a single-sided or double-sided flexible circuit with 3 or more layers laminated together, forming metallized holes by drilling collar L, electroplating, and forming conductive paths between different layers. This eliminates the need for complicated welding processes. Multilayer circuits have huge functional differences in terms of higher reliability, better thermal conductivity, and easier assembly performance. When designing the layout, the interaction of assembly size, number of layers and flexibility should be considered.

2 Sided Flexible Circuit Board Material

First, the advantages of flexible circuit boards

1. Flexibility: A significant advantage of applying flexible circuit boards is that it can be more easily routed and connected in three-dimensional space, and can also be rolled or folded for use. As long as it is curled within the allowable radius of curvature, it can withstand thousands to tens of thousands of uses without damage.

2. Reduced volume: In the assembly of the module, the conductor cross section of the flexible circuit board is thin and flat compared to the use of cable, which reduces the size of the wire and can be formed along the casing, making the structure of the device more compact and reasonable. , Reducing the installation volume. Compared with rigid PCB, space can be saved by 60 ~ 90%.

3. Reduce weight: In the same volume, the ratio of flexible circuit board to wire and cable can be reduced by about 70% under the same current carrying capacity, compared with rigid PCB, the weight is reduced by about 90%.

4. Consistency of installation: Installation with flexible circuit boards eliminates errors when wiring with wires and cables. As long as the processing drawings are proofread, all the winding circuits produced in the future are the same. No misconnection will occur when connecting the cables.

5. Increased reliability: When the flexible circuit board is used for installation, because it can be wired on the three planes of X, Y, and Z, the number of transfer interconnections is reduced, which increases the reliability of the entire system and checks for failure Provides convenience.

6. Controllability of electrical parameter design: According to the requirements of use, designers can control capacitance, inductance, characteristic impedance, delay and attenuation when designing flexible circuit boards. Can be designed to have transmission line characteristics. Because these parameters are related to wire width, thickness, pitch, insulation layer thickness, dielectric constant, loss tangent, etc., this is difficult to achieve when using wire cables.

7. The entire end can be soldered: Like Rigid PCB, the flexible circuit board has terminal pads, which can eliminate the stripping and tinning of the wires, thereby saving costs. Terminal pads are connected to components, devices, and plugs. Manual soldering of each wire can be replaced by dip soldering or wave soldering.

8. Material usage is optional: Flexible circuit boards can be manufactured with different base materials according to different application requirements. For example, in assembly applications that require low cost, polyester films can be used. In demanding applications, excellent performance is required, and polyimide films can be used.

9. Low cost Installation with flexible circuit boards can reduce the total cost.

The above is the classification and advantages of flexible circuit boards introduced by PCB Board Factory.

What Are the Advantages of Rigid Flexible PCB?

Today Rigid Flex PCB Manufacturer will discuss with you what rigid flex PCBs are, the advantages of using them, and the rules for designing with them.

In electronics, we sometimes encounter seemingly new technologies that have their roots in the past. Rigid-flexible PCB technology dates back about 50 years and the wiring harnesses in the spacecraft need to be replaced. The first commercial mobile computer (weighing more than 25 pounds!) Used rigid and flexible technology.

What is a rigid flexible PCB? A rigid-flex PCB is used, and the flexible circuit substrate and the rigid circuit substrate are laminated together. Rigid and flexible PCBs cross the boundaries of traditional Rigid PCBs and the unique properties of flexible circuits. Conductive plating or rolled annealed copper conductors are photo-etched onto flexible insulating films.

Flexible circuits include laminated heat, acrylic adhesive and pressure laminated by flexible polyimide and copper.

Rigid Flex PCB Board

What are the advantages of rigid flexible PCB?

Rigid Flex PCB Board still exists in the panel after manufacturing. As with traditional PCBs, you can mount components on both sides of a rigid board. Due to the integration between rigid and flexible circuits, rigid-flex designs do not use connectors or connecting cables between parts. Instead, flex circuits electrically connect the systems together.

Missing connectors and connecting cables do the following:

1.Improve circuit transmission capacity without loss of signal;

2. Adapt to controlled impedance;

3. Eliminate connection problems such as cold junctions;

4. Reduce weight;

5. Make room for other components.

Each rigid-flex PCB is divided into areas with different materials and different layers. The rigid region may have more layers than the flexible region, and the material is transferred from FR-4 to polyimide in the transition region. Complex designs often change from rigid to flexible and again to rigid. When these intersections occur, the overlap of rigid and flexible materials requires keeping the hole away from the transition area to maintain integrity. In addition, many rigid-flex designs include stainless steel or aluminum stiffeners to provide additional support for connectors and components.

Flexible circuits always have bent wires that affect wiring. Due to possible material stresses, it is not possible to place components or vias near bend lines. Even when components are positioned correctly, flex flex circuits can cause repeated mechanical stress on surface mount pads and vias. Your team can alleviate these pressures by using through-hole plating and supporting the pad support with additional overlays to secure the pad.

When designing rigid-flex PCBs, consider the electromechanical factors that affect flexible circuits and rigid circuit boards. As you build your design, pay attention to the ratio of bend radius to thickness. For flexible circuits, narrowing or increasing the thickness of the bend area increases the likelihood of failure. The manufacturer recommends keeping the bend radius at least ten times the thickness of the flexible circuit material.

Avoid flexing the flexible circuit along its outside or compressing the flexible circuit along its inside. Increasing the bending angle beyond 90°increases tension at one point and compression at another point on the flexible circuit.

Another key issue with rigid flexible reliability is the thickness and type of conductor in the flexed area. You can reduce thickness and mechanical stress by reducing the amount of plating on the conductor and using only pads. The use of heavy copper, gold or nickel plating reduces the flexibility of bends and allows mechanical stress and fracture to occur.

Advantages of Flexible Circuit Boards

The flexible circuit board has the following advantages:

1: Flexible circuit board flexibility

A significant advantage of using FPC circuit boards is that they can be easily routed and connected in three dimensions, and can also be rolled or folded. As long as it is curled within the allowable radius of curvature, it can withstand thousands to tens of thousands of uses without damage.

2: Flexible PCB reduces volume

In assembly assembly, the conductor cross section of FPC flexible board is thin and flat as compared with the use of cable, which reduces the size of the wire and can be formed along the casing, which makes the structure of the device more compact and reasonable, reducing assembly volume. Compared with rigid PCB boards, space can be saved by 60 ~ 90%.

3: FPC circuit board can reduce weight

In the same volume, the weight of FPC flexible board and wire and cable can be reduced by about 70% at the same current carrying capacity, and compared with rigid PCB board, the weight is reduced by about 90%.

4: FPC circuit board installation and consistency

It is connected by FPC circuit board, which eliminates the errors when wiring with wire and cable. As long as the processing drawings are proofread, all the winding circuits produced in the future are the same. No misconnection will occur when connecting the cables.

Flexible PCB

5: FPC circuit board increases reliability

When the FPC flexible board is used for connection, since it can be wired on the three planes of X, Y, and Z, the number of transfer interconnections is reduced, the reliability of the entire system is increased, and the failure inspection is provided for convenience.

6: Controllability of electrical parameter design

According to the requirements of use, designers can control capacitance, inductance, characteristic impedance, delay and attenuation when designing flexible PCBs. Can be designed to have transmission line characteristics. Because these parameters are related to wire width, thickness, pitch, insulation layer thickness, dielectric constant, loss tangent, etc., this is difficult to achieve when using wire cables.

7: The end of the FPC flexible board can be soldered as a whole

Flexible PCBs, like Rigid PCBs, have terminal pads that eliminate stripping and tinning of the wires, thereby saving costs. Terminal pads are connected to components, devices, and plugs. Manual soldering of each wire can be replaced by dip soldering or wave soldering.

8: FPC circuit board materials can be selected

Flexible PCB can be manufactured with different base materials according to different application requirements. For example, in assembly applications that require low cost, polyester films can be used. In demanding applications, excellent performance is required, and polyimide films can be used.

9: FPC circuit board low cost

With a flexible PCB assembly, the total cost can be reduced. This is because:

a. Due to the consistency of various parameters of the flexible PCB wire; the implementation of the overall termination eliminates the errors and rework that often occur when the cable is connected, and the replacement of the flexible PCB is more convenient.

b. The application of FPC flexible board simplifies the structural design, it can be directly adhered to the component, reducing the clamp and its fixing parts.

c. For wires that require shielding, FPC circuit boards are less expensive.

10: Continuity of processing

Since FPC flexible boards can be continuously supplied in rolls, continuous production of flexible PCBs can be achieved. This also helps to reduce costs.

The above are the benefits of flexible circuit boards introduced by Rigid Flex PCB Manufacturer.