King Sun PCB

PCB price

How To Calculate The PCB Price?

Each piece of PCB to sell are customized in PCB industry, therefore, PCB board quotation need to be cost calculation first, but also need to refer to the utilization ratio of material to make a comprehensive quote.

Many PCB purchasing people have no idea for the ever-changing PCB prices, even many years of experience, they may don’t understand the whole story. There are many factors that affect the price of the PCB circuit board: materials, production process, difficult technoloies, customer requirements, regional,term of payment, manufacturers and other factors caused PCB circuit board cost is different.

PCB circuit boards are made of different materials, resulting in price diversity

Talk about materials of double-sided PCB,base material generally are FR-4, CEM-3,etc,thickness from 0.6mm to 3.0mm,copper thickness ranging from H OZ to 6 OZ, the different sheets will cause the cost gap is huge, the solder resist ink, ordinary thermosetting oil and photosensitive oil also has a certain price difference, so the materials caused by different diversity price.

PCB adopted different production processes, resulting in price diversity

Different production processes can result in different costs. For example, gold plating and HASL, outline of milling and punching.the printing circuit and dry film circuit will lead to different costs, resulting in the diversity of the price.

the price diversity caused by the difficulty of PCB itself

Even if the material is the same, the process is the same, but the PCB itself is difficult, also cause different costs. If two circuit board has 1000 holes, one plate aperture is greater than 0.6mm and the other plate aperture is less than 0.6mm will form the drilling cost is different; such as the two circuit board the same, but different from the line width, a more than 0.2mm, a less than 0.2mm, also cause different cost of production, because the difficulty board rejection rate is higher, the inevitable costs increase, causing the price of diversity.

customer requirements will also lead to different prices

Customer requirements will directly affect the yield of PCB plant, such as a PCB by IPC-A-600E, the Class2 requires a 98% pass rate, but according to the requirements of class 3 may pass rate of only 90%, resulting in different plant costs, resulting in changeable price.

Process cost:

  • The density of PCB layout, if the circuit line width/space is smaller than 4/4mil, the cost will be increased.
  • If PCB board has BGA, so that the cost will rise relatively.
  • The surface finishing,the common surface included: HASL,OSP, Immersion Tin, Immersion Silver,ENIG,ENEPIG,Gold plating. The surface process is different, the price will be different. in general the cost is like : HASL<OSP<Immersion Tin,Immersion Sliver<ENIG<ENEPIG<Gold plating
  • Acceptance standards,we are commonly used IPC Class 2 level, but there are customer requirements will be higher, such as IPC Class 3, enterprise standards, military standards, etc., of course, the higher the standard, the higher the price will be.

PCB cost calculation is the most complex among all the industries,from cutting material, pressing,CNC,FQC, packaging, finished products, the need accounting for each process step by step based on the input material costs, labor costs, manufacturing costs, according to the order number in total cost.And different types of products, the standard rate of their processes will be different. For some products, such as blind PCB, gold plating and copper plate, some special calculation methods must be adopted because of the particularity of the process or all the materials. Similarly, the size of drilling holes used in drilling operations will also affect the cost of products, which directly affect the calculation and evaluation of WIP costs and scrap costs.

In addition, a PCB buyer should pay attention to the choice of PCB board manufacturers, not just from the price point of choice, but compare the strength of manufacturers, supply support, and services etc..

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FLEX PCB

What Is Flexible PCB Board?

Flex PCB is Flexible Printed Circuit Board, abbreviated FPC, also known as flexible circuit board, or flexible board.According to the definition of IPC, flexible printed circuit board is a printed circuit designed and manufactured on flexible substrate.

Flexible circuit board is one of the important varieties of PCB.

FPC board is generally range into single layer, double-sided, multilayer layer, Its characteristics are specific:

  • Flexible circuit boards are small in size and light in weight.
  • Flexible circuit boards can be moved, bent or twisted.
  • Flexible circuit board has excellent electrical and dielectric properties and heat resistance.
  • The flexible circuit board has high assembly reliability and assembly operation.
  • Flexible circuit boards can be installed with three bit connections.
  • Flexible circuit boards are favorable for thermal dissipation.
  • Low cost.
  • Continuity of processing.

The flexible circuit board has the advantages of small size, light weight, greatly reduce the device size, suitable for electronic products to high density, miniaturization, lightweight, thin, high reliable direction. With a high degree of flexibility, free bending, torsion, winding, folding, stereo wiring, in accordance with the requirements of any space layout arrange, change shape, and move and expansion in the three-dimensional space, so as to achieve the integration of assembly and wire connection.

The flexible circuit board has excellent electrical properties, high temperature resistance, flame resistance. Chemical stability, good stability, high reliability. The assembly has higher reliability, which provides convenience for the circuit design, and can greatly reduce the workload of the assembly, and to guarantee the performance of the circuit, so the cost is reduced by using. The method to increase the strength of reinforced material, in order to obtain additional mechanical stability. The design of hardware and software combination also make up the flexible substrate in the component bearing the limitations slightly in a certain extent.

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electric soldering iron

How To Use Electric Soldering Iron?

Electric soldering iron is the most common welding tool used by electronic engineers.Good at use of electric irons will save us a lot of time. This article will detail the use of electric soldering irons through preparation, welding and soldering techniques, and, of course, key welding techniques.

The preparatory work

Electric soldering iron start-up preparation

Use finesand paper to polish the iron head and heat the electricity before using the new iron, After dipping the rosin, contact the solder wire with the head edge of the soldering iron to make the iron head evenly coated with tin.In this way, it is easy to weld and prevent the surface of the iron head from oxidation. If the old iron head is blackened by severe oxidation, the steel can be depressed and removed to the surface oxide, so that it can be plated again after being exposed to the metallic luster.

Electric iron to use 220V AC power, user should pay special attention to safety. The following should be conscientiously done:

  • Plug the electric iron preferably with a three pole plug. Make sure the casing is properly earthed.
  • Before use, should carefully check the power plug, power cord damage. And check if the iron head is loose.
  • The electric iron can not be struck with force. To prevent falling. When the soldering iron is too long, wipe it with cloth. Don’t throw it away in case it burns others.
  • In the process of welding, soldering iron can not be everywhere. When stopsoldering, it should be placed on the iron rack. Note that the power cord can not be attached to the iron head, in order to prevent burning insulation and accidents.
  • Should promptly cut off the powerafter using, unplug the power plug,then return the electric iron to the tool box after cooling.

Soldering and soldering flux

Soldering and soldering fluxes are needed for soldering

  • Soldering: welding electronic components, usually using rosin cored solder wire. The solder wire has lower melting point and contains rosin flux and is extremely convenient to use.
  • Flux: the commonly used flux is rosin or mineral spirits (rosin soluble in alcohol). The use of flux can help remove the metal surface oxides, easy for welding, and can protect the iron head. Solder paste can also be used for welding larger components or wires. But it is corrosive, and should be removed in time after welding.

Auxiliary tools

In order to facilitate the welding operation often used pliers, tweezers and partial knife as auxiliary tool. Proper use of these tools should be learned

Prewelding treatment

Before welding, Should take pre-treatment for the component pins or circuit boards.

Remove the oxide layer on the weld:

A knife can be made of broken saw blades. Scrape off the oxide layer on the surface of the metal lead so that the pin is exposed to metallic luster.

Use spinning paper polish the copper foil of printed circuit board and coated with a layer of rosin alcohol solution.

Components tin

Tin plated on a scraped lead wire. After the wire is dipped in the rosin alcohol solution, the hot iron tip with tin is pressed on the lead and the lead is turned. A thin layer of tin can be uniformly plated on the leads. Before the wire is welded, the insulating skin should be stripped off, and then treated by the above two items before welding. If multiple strands of wire wire, after polishing should be screwed together, and then tin.

A layer of tin is uniformly coated on the scraped oxide layer.

Welding technology

After welding is done, the welding can be carried out formally.

Welding method

Welding,checking, short cut

  • Right hand holding electric iron. The left hand use pliers or forceps clamping elements or wire. Before soldering, the electric iron should be fully preheated. Soldering tin on the edge of the iron head, with a certain amount of solder.
  • Press the edge of iron head on the spot. The electric iron is approximately 60 degrees from the horizontal plane facilitate tin is melted flows to solder joint from iron head,the time that the soldering iron stays at the solder joint is controlled for 2~3 seconds.
  • Lift the soldering iron head. Left hand still holds the component,loosen hand till the tin at the solder joint cooled and solidified.
  • Turn the lead with tweezers, make sure it is not loose, then cut out the excess lead with a side pliers.

Welding quality

  • When welding, make sure that each solder joint is well welded and in good contact. Welding quality must be guaranteed.
  • Good solder joints should be bright tin points, smooth without burrs and moderate tin. Tin and welded joints are fused firmly. There should be no missing welding and false welding.
  • Missing welding means only a small amount of solder joints, causing poor connection, on and off working. Fake welding means that the surface is soldered, but it is not soldered. Sometimes the wire can be drawn out of the solder joint by hand. These two situations will bring great difficulties to the debugging and maintenance of electronic manufacture. Only through a large number of serious welding practice can we avoid these two situations.
  • When soldering a circuit board, be sure to control the time. Too long, the circuit board will be burned or cause copper foil to fall off. When the component is removed from the circuit board, the electric iron head is attached to the solder joint and the component is drawn out after the tin on the solder joint is melted.
  • When welding flux (rosin and soldering paste is the key, fresh rosin) and non corrosive solder oil can help you complete a good welding, and can make the surface smooth beautiful, you can use a little more flux.

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PCB design checking

The Later Checking After PCB Layout Design

When we completed the layout of a circuit board, and checked there were no errors that the connectivity and spacing, then a PCB design really be finished? The answer of course no,many beginners also includes a number of experienced engineers often ignore the later check and get throught a thing carelessly because time is tight or impatient or too confident.As a result, there are some basic BUG, such as insufficient line width, component labels, screen printing on the through-hole, sockets too close, signal loop, and so on.Which leads to the electrical problems or process problems, to a serious waste. So, when a PCB completes layout and wiring, one of the most important steps is the later check.

The PCB check has a lot of detail elements. Here are some of the most basic and most error prone elements for later inspection.

Component package

  • Pad spacing. If it is a new device, it is necessary to draw the component package to ensure the proper spacing. The spacing between the pads directly affects the welding of the components.
  • Through-hole size (if available). For plug-in devices, the size of the hole should be retained enough margin, generally reserved not less than 0.2mm, more appropriate.
  • Silkscreen printing. The contour of screen printing is better larger than the actual size to ensure that the device can be installed smoothly.

Components allocation

  • IC should not be near the edge of the board.
  • The components of the same circuit should be placed close to. For example, decoupling capacitor should be close to the IC power pin, the components of the same functional circuit should be placed in an area, with distinct layers, and ensure the realization of the function.
  • Arrange the location of the socket according to the actual installation. Sockets are lead to other modules, according to the actual structure, in order to facilitate installation, generally use the nearest principle, arrange the location of the socket, and generally near the edge of the board.
  • Pay attention to the direction of the socket. If sockets are reverse direction, the wire will be rework. For flat plug sockets, the direction of the jack shall be toward the outside of the board.
  • There is no components in the Keep Out region.
  • The interference source is away from the sensitive circuit. High speed signals, high-speed clocks, or high current switching signals are all sources of interference and should be away from sensitive circuits, such as reset circuits and analog circuits,separate them through ground copper.

Layout

  • The line width should be selected by combining process and ampacity, and the minimum linewidth should not be less than the minimum line width of the PCB manufacturer. At the same time to ensure the carrying capacity of the current, 1mm/A is generally used to select the appropriate line width.
  • Differential signal line. For USB, the Ethernet arithmetic line, line length, pay attention to the same plane, parallel, spacing by impedance.
  • Pay attention the high-speed line return path. High speed lines are easy to generate electromagnetic radiation, and if the line path and the return path form too large area, a single turn coil will be formed to radiate electromagnetic interference.Therefore, the line should pay attention to the next side of the return path, the multilayer board with power and ground plane can effectively solve this problem.
  • Pay attention to analog signal line. Analog signal lines should be separated from digital signals, and the line should be taken as far as possible from interference sources (such as clock, DC-DC power), and the shorter the line, the better.

EMC and signal integrity

  • Termination resistance. A high speed line, or a higher frequency, and longer line digital signal line, it is best to string a matching resistor at the end.
  • Input the signal line and connect the small capacitance. The signal line input from the interface is preferably near the interface and connected to a small capacitor at the PI level. The size of the capacitor depends on the intensity and frequency of the signal. It can not be too large, otherwise it will affect the integrity of the signal.For low speed input signals, such as key inputs, a small capacitor of 330pF can be used.
  • Drive capability. For example, the driving current larger switch signal can add triode drive; for fan out a larger number of bus can add buffer (such as 74LS224) drive.

Silk screen

  • Board name, time, PN code.
  • Some of the interface (such as array) pin or key signal mark.
  • Component marking. Component labels should be placed to a suitable location, and dense component labels can be placed in groups. Be careful not to place them in the through hole.

Other

Fiducial mark. For PCB that requires machine soldering, you need to add two to three fiducial marks.

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PCB layout design

Tips Of PCB Layout Design

The PCB circuit board is a support component of components and devices in electronic products.Even schematic diagram is correct, but uncorrected PCB layout design will also effect the reliability of electronic products. In the design of printed circuit boards, attention should be paid to the correct method, to comply with the general principles of PCB design, and should meet the requirements of anti-interference design.

PCB circuit board layout design should follow the principles:

Consider the dimension of the PCB. When the dimension of the PCB is too large, the printed line is long, the impedance is increased, the noise resistance capacity is reduced, and the cost is increased; when PCB dimension is too small, heat dissipation is not good, and the adjacent lines are easily interfered. After determining the dimension of printed circuit board, the location of the special component is determined. Finally, according to the functional unit of the circuit, arrange all the components of the circuit board.

The following principles shall be observed when determining the location of a particular component:

  1. Shorten the connection between high frequency components as much as possible, and try to reduce their distribution parameters and electromagnetic interference. Vulnerable components should not be too close to each other, and input and output components should be kept as far away as possible.
  2. Some components or wires may have higher potential difference, should increase the distance between them, avoid discharge lead to unexpected short circuit. The components with high voltage shall be arranged as far as possible where the hand will not touched when debugging.
  3. Components weighing more than 15g shall be fixed with brackets and welded. Those large, heavy, and more heat components should not be installed on the printed board, but should be installed in the chassis of the whole machine chassis, and should consider the problem of heat dissipation. The heat sensitive element shall be away from the heating element.
  4. For potentiometers, adjustable inductors, coils, variable capacitors, micro switches and other adjustable components, should be consider the overall structure of the machine. If the machine is inside adjustment, the components places should be easy to adjust. If the machine is outside adjustment,its position should be adaptable to the knob in the box panel.
  5. Should keep the position for PCB tooling hole and fixed bracket.

The circuit components of the PCB layout, to meet the requirements of anti-interference design:

  1. Arrange the location of each functional circuit unit according to the circuit flow, so that the layout facilitates the flow of signals and keeps the signal in the same direction as possible.
  2. The core components of each functional circuit as the center, around it to layout. Components should be arranged evenly, neatly and compactly on the PCB. Minimize and shorten the lead and connection between components.
  3. In high frequency operation of the circuit, we should consider the distribution parameters between components. The general circuit should make the components arranged in parallel as much as possible. In this way, not only beautiful, but also easy to install welding, easy to mass production.
  4. located on the edge of the circuit board components, the distance is not less than 2mm from the edge to the circuit board. The best shape of the circuit board is rectangle. Long, wide, double, 3:2 or 4:3. The mechanical strength of the circuit board shall be considered when the circuit board dimension is larger than 200 * 150mm.

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PCB Layer stack-up design

Tips Of PCB Layer Stack-up Design

In PCB design, consider signal quality control factors, the general principles of PCB layer stack up should be follow below:

  1. The second planes adjacent to the component surfaceis ground plane, providing device shielding layer and referenceplane.
  2. All signal layers are adjacent to the ground plane as much as possible to ensure a complete return channel.
  3. Try to avoid two signal layer directly adjacent to reduce crosstalk.
  4. The main power supply is adjacent to ground plane as much as possible to form a planar capacitor to reduce the power level impedance.
  5. Considering the symmetry of laminated structure, it is beneficial to bow and twist control during PCB making.

Above is the principle of conventional laminated design, in the actual circuit board design, designers can increase the distance between the adjacent wiring layer, reduce the space between wiring layer to the corresponding reference plane, and then control the layer wiring crosstalk ratio under the premise, two signal layer can be directly adjacence.

For more cost oriented consumer products, you can weaken the power and ground plane adjacent to reduce the plane impedance, so minimize the wiring layer and reduce the cost of PCB. Of course, use this method will risk signal design quality.

For the Backplane or midplane stack design, in view of the common backplane is difficult to do the adjacent line perpendicular to each other, inevitably parallel long distance routing. For high-speed backplanes, the general layer stack up principle is as follows:

  1. Top plane and bottom surface are the complete horizon, and constitute the shielding cavity.
  2. No adjacent layer parallel wiring is used to reduce crosstalk, or the spacing between adjacent routing layers is great far than the reference plane spacing.
  3. All signal layers are adjacent to the ground plane as mush as possible to ensure a complete return channel.

In the particular PCB stack up setting, the PCB design should be flexibly applied to the above principles, and reasonable analysis is made according to the requirements of the actual single board.

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blind and buried via PCB

What Is Blind And Buried Via PCB?

Blind and buried via PCB came by high density and high precision electronic products requirement.

  • Buried via is interior vias between top layer and bottom layer,it can not see after pressing,so don’t have to occupy the outer layer area.
  • The blind via is non-drilled vias,it can be seen at one surface side but can’t be seen at another surface side.

Blind and buried via features:

  1. Eliminate large number of through hole design to improve routing density and package density.
  2. The design of interconnect structures can be diversification and complicated.
  3. Obviously improved the reliability of multilayer board and the electrical performance of electronic products.

There are three different ways to make the blind and buried via:

Mechanical fixed depth drilling

The process is traditional drilling of making multilayer PCB,set the depth of Z axis by using drilling machine after pressing.But there are several problems with this method:

a . Production efficiency is very low, only drill one panel one time.

b. Drilling machine table level requirements strict, each spindle drill depth settings to be consistent, otherwise it is difficult to control the depth of each hole

c. The hole plating is difficult, especially when via depth is bigger than via size, it is almost impossible to do hole plating.

The limitations of these processes have made this method less useful.

Sequential lamination

Taking 8 Layer PCB as an example, the blind hole can be produced simultaneously by successive pressing method. The first four sheets inner core by PTH double side way to make (or other combination; 6 Layer+ double sided, double double sided at top and bottom furface+ 4 Layer) and then pressure four sheets cores to 8 layer, produce by full hole. This process is long and cost much higher than others, so it is not common.

Build up Process

The extension of this method the lamination Sequential concept, a layer to the plate increases, and to drill the hole for interconnection between layers. There are mainly three kinds of way, as follows:

  • Photo Defind photo via using photosensitive resistance agent, is also a permanent dielectric layer, and then according to the specific position, to do the film exposure, developing action, to expose the bottom copper pad, a bowl shaped blind hole, with copper and copper plus comprehensive chemical. After etching, the outer line is connected with the Blind Via, or without copper plating, and the copper paste or silver paste is used to complete the conduction. By the same principle, add one layer at a time.
  • Laser Ablation laser hole burning laser hole burning can divided into three; a CO2 laser. One is Excimer laser, and the other is Nd:YAG laser. Some of the three laser hole burning methods are compared.
  • Plasma, Etching, this is the Dyconex company’s patent, the business name is DYCOSTRATE method.

The above three commonly used layer adding method in the non machine drilling type, three blind hole process should be clear. Wet chemical pitting isn’t be introduced here.

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50OHM Impedance PCB-feature

Why PCB Impedance Control Is 50 OHM Often?

Many newhands are curious Why the common single impedance controlled by 50 ohms instead of 40 ohms or 60 ohms?

First of all, 50 ohm has a certain historical origin, it must be mentioned from the standard cable. As we all know, a great part of modern electronic technology is derived from the army and gradually converted to civilian use. In the early days of microwave application, the choice of impedance was entirely dependent on the need for use during the Second World War.As technology advances, impedance standards need to be given to balance the economy and convenience. In the United States, the most used catheters are connected by existing rod and water pipes, 51.5 ohms are very common, but 50 ohms to 51.5 ohm to see and used in the adapter and converter.As the joint army and navy to solve these problems, an organization called JAN was established, which later became the DESC, especially by MIL development, considering the final choice of 50 ohms, and the catheter was created, and thus transformed into a variety of cable standard. This European standard is 60 ohms, soon after, in effect such as Hewlett-Packard in the industry of dominant firms, Europeans are forced to change, so the 50 ohm will eventually become a standard industry inherited, also become established, and all kinds of cable connections and PCB for impedance matching. The final is in accordance with the requirements of the standard impedance of 50 ohms.

Secondly, from the point of view of PCB fabrication, 50 ohm is more convenient to implement. The calculation formula of impedance from the front, low impedance to wide linewidth and thin dielectric (or larger dielectric constant), the present high density board space is difficult to meet the high impedance and linewidth; thin and medium thick (dielectric constant or smaller), is not conducive to the inhibition of EMI and crosstalk, and the reliability and production from the perspective of plate processing will be relatively poor; and 50 ohms in commonly used materials under the environment of ordinary width and medium thickness (4~6mil) that meets the design requirements (Figure 1, impedance calculation and convenient processing), slowly become the default option is be not at all surprising.

Third, from the point of view of loss, according to the basic physics, it can be proved that the 50 ohm impedance has the least skin effect and the least loss (from Howard Johnson, PhD’s reply). In general, the skin effect of the cable, the loss of L (in decibels), and the total skin effect resistance, R (unit length), are directly proportional to the characteristic impedance Z0. The total skin effect resistance R is the sum of the resistance of the shield layer and the intermediate conductor. The skin effect resistance of the shield is inversely proportional to its diameter D2 at high frequencies. The skin effect resistance of the internal conductor of a coaxial cable is inversely proportional to its diameter D1 at high frequencies. The total series resistance R is therefore proportional to (1/d2+1/d1). Combining these factors, given the dielectric constant Er of D2 and the corresponding isolation material, the skin loss effect can be minimized by using the following formula.

 impedance formula 1      formula 1

In any basic book on electromagnetic fields and microwaves, you can find that Z0 is a function of D2, D1, and Er.

 impedance formula 2      formula 2

Substituting formula 2 in Formula 1, the numerator denominator is multiplied by D2 at the same time

 impedance formula 3formula 3 

A constant term (/60) * (1/d2), valid item ((1+d2/d1) /ln (d2/d1)) is determined from the formula 3 to determine the minimum point. Check that the minimum point of formula 3 is controlled only by d2/d1, independent of Er and fixed value d2. Take d2/d1 as the parameter, do the graph for L, and display the minimum value when d2/d1=3.5911. Assuming that the dielectric constant of solid polyethylene is 2.25, the characteristic impedance of d2/d1=3.5911 is 51.1 ohms. A long time ago, radio engineers, for convenience, approximated the value to 50 ohms as the optimum value for coaxial cables. This proves that L is the smallest in the vicinity of 50 ohms.

Finally, from the point of view of electrical performance, the advantage of 50 ohms is considered as a compromise. For the pure performance from PCB line, low impedance transmission line is better, for a given width, and the closer the corresponding EMI will decrease, crosstalk will therefore decrease, but also less susceptible to capacitive load effects. But from the perspective of the path, but also need to consider a key factor driving ability, that is the chip, most of the early chip driving transmission lines not less than 50 ohm impedance, and high impedance transmission line due to achieve so inconvenience, using a 50 ohm impedance compromise.

To sum up: 50 ohms as the default value of the industry has its inherent advantages, but also the comprehensive consideration of the compromise, but not to say that we must use 50 ohm impedance, often depends on the matching interface, such as 75 ohm is still remote communication standard, some cable and antenna is the use of 75 ohms, then you need to match the impedance of PCB line. There are also some special chip chip driven by improving the ability to reduce the impedance of the transmission line, in order to get a better suppression of EMI and crosstalk effects, such as most of the requirements of Intel chip impedance control in 37 ohm, 42 ohm or less, and will not go.

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PCB design optimized

PCB Design Optimization

What are the basic principles of PCB design for whole board layout? How to optimize and analyze?

Reasonable layout directly affects the life of the product, stability, EMC (electromagnetic compatibility), must from the overall layout, circuit board wiring condition and PCB manufacturing, mechanical structure, heat dissipation, EMI (electromagnetic interference), integrated and reliability, signal considered.

In general, place the fixed position of the components related to the mechanical size first, and then place special and larger components, and finally placed small components. At the same time, need consider layout requirements, high-frequency components should be placed as tight as possible, the signal line wiring can be as short as possible, thereby reducing the signal line interference.

Placement of positioning pins in relation to mechanical dimensions:

The power socket, switch, interface between PCB, indicator light are all positioning pins related to machine size. Typically, the interface between the power source and the PCB is placed at the edge of the PCB, and the PCB edge is spaced from 3mm to 5mm;The light emitting diode should be accurately placed according to the needs; and some fine-tuning switch components, such as adjustable inductance, adjustable resistance should be placed near the edge of the PCB position, to facilitate adjustment and connection; the need for frequent replacement of components must be placed in a position to less devices, easy to replace.

Placement of special components:

High power tube, transformer, rectifier and other heating devices, make more heating in high frequency condition, so the layout should be consider ventilation and heat dissipation, the components are placed on the PCB with air circulation.Large power rectifier tubes and regulating tubes shall be provided with radiators and keep away from the transformer.Electrolytic capacitor such as heat element should be away from the heating device, otherwise the electrolyte will be dried, resulting in the increase of resistance, poor performance, influence the stability of the circuit.

Easy to break components, such as adjustment tubes, electrolytic capacitors, relays, etc.,also need consider the convenience of repair.For testing points that need to be measured frequently, it is important to ensure that the test rod can be conveniently contacted when arranging components.Since the 50Hz leakage magnetic field is generated inside the power supply device, when it is connected to some parts of the low frequency amplifier, it will cause interference to the low frequency amplifier. Therefore, they must be separated or shielded.

According to the principle of the best amplifier line form, so the method is of the advantages of various grounding current in the closed flow, does not affect other circuit work. The input and output stages should be kept as far away as possible to minimize parasitic coupling interference between them.

Considering the signal transmission relationship between each unit function circuit, low frequency circuit and high frequency circuit should be separated, analog circuit and digital circuit separate.

The integrated circuit should be placed in the center of the PCB, so that the wiring of each pin is connected with other devices.

Inductors, transformers and other devices with magnetic coupling should be placed orthogonal to each other to reduce magnetic coupling. In addition, they have a strong magnetic field, which should be properly surrounded by large space or magnetic shielding to minimize the impact on other circuits.

The key parts of PCB to configure the appropriate high frequency decoupling capacitor in the input terminal of a power supply should be PCB 10 F ~ 100 F electrolytic capacitor, near the power supply pin integrated circuit are connected with a ceramic capacitor of about 0.01pF.

Some circuits also have an appropriate high frequency or low frequency choke to minimize the effects of high and low frequency circuits. This should be considered in schematic design and drawing, otherwise it will affect the performance of the circuit.

When the components are arranged, the spacing should be appropriate, and the space between them should be considered whether there is any breakdown or sparking between them.

The amplifier with push-pull circuit and bridge circuit should pay attention to the symmetry of the electrical parameters of the component and the symmetry of the structure, so that the distribution parameters of the symmetrical components can be consistent as much as possible.

After the manual layout of the main components is completed, the component locking method shall be adopted so that the components will not move in the automatic layout. That is, the Edit change command is executed, or Locked can be locked and no longer moved by the Properties selection of the component.

Placement of common components:

For common components, such as resistors, capacitors, several common and convenient welding etc. from components arranged in neat, space size, routing, and uses the automatic layout mode.

PCB layout design, the first manual layout method to optimize the location of some components, combined with automatic layout to complete the overall design of PCB.

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save PCB cost

How To Reduce PCB Manufacturing Cost In PCB Design

When we design a project, we care more about layout and wiring, and often ignore the additional PCB manufacturing costs in the design. Here are some of the factors that affect PCB prices in the design and avoid increasing costs to customers.

PCB Layers number:layers good for layout, but the price increases with the number of plies, the higher of layers number, the price is doubled.

Vias size: As much as possible with more than 0.25mm, less than 0.25mm, most manufacturers have to charge extra fee.

Via in Pad plugging：the manufacturer usually increases the cost. Try not to use it unless the signal and layout are limited.

Back drilling: use in back board and other high-speed signal, otherwise do not use.

Line space and width: usually less than 4mil, manufacturers have to increase extra charges.

Materials: (high Tg, halogen free high frequency = unconventional material) will increase purchasing cycle and production cost. Some high-frequency materials can be mixed with ordinary sheets to reduce costs.

HDI and blind buried: the cost increase is very large, if the package is allowed, the best not to use. (0.65 or more BGA packages can be fan out via holes, and some 0.5bga packages can be fan out through vias, mainly to see packages pads and available pin).

Surface finishing: ENIG,Immersion Tin,Immersion Ag,Gold finger will increase the costs, which is mainly determined by the customer.

Copper thickness, PCB area, the number and type of holes, the surface treatment of gold layer thickness, and even the delivery time will affect the price of PCB.You need a lot of attention because some price control is very strict, as mentioned via in pad, backdrill,impedance, especially the selection of PCB materials,expect for some products that not particularly concerned about costs. Of course, in general, when we control costs, we must take into account its reliability, because sometimes the cost of PCB is actually not the most expensive (except for some high-end PCB).

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