Protel DXP is the first board-level design system that integrates all design tools. Electronic designers can plan their design from the initial project module to the final production data. Protel DXP runs on an optimized design browser platform with all of today’s advanced design features to handle complex PCB design processes. Protel DXP is a new circuit design software based on the previous version with the addition of many new features. The new customizable design environment features dual monitor support, fixed, floating, and pop-up panels, powerful filtering and object positioning capabilities, and an enhanced user interface. Protel DXP provides a comprehensive design solution through the design of input simulation, PCB rendering editing, automatic topology routing, signal integrity analysis, and design output.
PCB board design of the general principles includes circuit board selection, the circuit board size, component layout, wiring, pad, fill, jumper, etc. Manufacturers generally make the circuit board of copper laminates, board selection from the electrical performance, reliability, processing technology requirements, economic indicators, and other considerations. Standard copper laminates are copper phenolic paper laminates, copper-coated epoxy paper laminates, copper-coated epoxy glass cloth laminates, copper-clad epoxy phenolic glass cloth laminates, copper-coated polytetrafluoroethylene glass, cloth laminates and multilayer printed circuit boards with epoxy glass cloth, and so on.
Different materials of the laminate have other characteristics. Epoxy resin and copper foil have excellent adhesion, so the copper foil adhesion strength and operating temperature are high, which can be 260 ℃ in the melting tin does not blister. Epoxy resin-impregnated glass cloth laminates are less affected by moisture. The ultra-high frequency circuit board is the best-deposited glass cloth laminate, polystyrene copper.
In the requirements of flame-retardant electronic equipment, also need flame retardant circuit boards, these boards are immersed in the flame-retardant resin laminate. Technicians should determine the thickness of the circuit board according to the function of the circuit board. And the weight of the components installed, the specifications of the circuit board socket, the dimensions of the circuit board, and the mechanical load.
Mainly should ensure sufficient rigidity and strength. Typical circuit board thickness of 0.5mm, 1.0mm, 1.5mm, and 2.0mm. From the cost, copper wire length, and anti-noise ability considered, the smaller, the better the size of the circuit board. But the board size is too small, and the poor heat dissipation and adjacent wires quickly lead to interference. The production cost of the circuit board is related to the area of the circuit board. The larger the dimensions, the higher the price. The board’s size is limited by the size of the chassis when designing a circuit board with housing.
Be sure to determine the size of the chassis before deciding the board size. Otherwise, you cannot select the board size. In general, the wiring range specified in the forbidden wiring layer is the size of the board size. The best shape of the circuit board is rectangular. The aspect ratio is 3: 2 or 4: 3. When the circuit board size is more significant than 200mm × 150mm, you should consider the mechanical strength of the circuit board. In short, you should consider the pros and cons to determine the size of the circuit board.
Although the Protel DXP can automatically layout, the circuit board’s structure is almost done by hand.
To carry out the layout, generally follow the following rules:
1. The Layout of Particular Components
The layout of particular components from the following aspects:
1) High-frequency Components:
The connection between the high-frequency components is as short as possible. Try to reduce the distribution of the parameters and the electromagnetic interference between each other. Vulnerable parts can not be too close. The distance between the components belonging to the input and the elements belonging to the output should be as considerable as possible.
2) Components with a High Potential Difference:
The distance between the elements with a high potential difference and the connection should be increased to avoid damage to the components when an unexpected short circuit occurs. A 2000V potential difference between the copper film line distance should be greater than 2mm to prevent the creepage phenomenon. If there is a higher potential difference, the distance should also increase. High voltage devices should be arranged as far as possible when debugging challenging to reach the place.
3) Too many Weight Components:
Such components should have a fixed bracket, and for large and heavy, more heat and more parts should not be installed on the circuit board.
4) Heat and Thermal Components:
The heating element should be away from the thermal parts.
5) Can Adjust the Components:
The potentiometer, adjustable inductance coil, variable capacitor, micro switch, and other adjustable parts of the layout should consider the structural requirements of the machine. If the device is adjusted, it should be easy to adjust on the circuit board of the place. If the device is outside the adjustment, its position knob is in the chassis panel on the corresponding part.
6) Board Mounting Holes and Bracket Holes:
The mounting holes for the circuit board and the mounting holes of the brackets should be reserved. Because they can not be routed near the gaps and holes.
2. According to the Circuit Function Layout
Suppose there are no special requirements for Protel DXP layout , as far as possible. Following the schematic components of the arrangements for the layout of the elements. The signal from the left into the output and the top input to the bottom of production. Following the circuit process, the various functional circuit unit position is arranged so that the signal flows more smoothly and maintains the same direction.
With each active circuit as the core, around the core circuit layout, the component arrangement should be uniform, neat, and compact. The principle is to reduce and shorten the lead between the various components and connections. The digital circuit part should be separated from the analog circuit section.
3. The Distance of the Component from the Edge of the Board
All components should be placed within 3mm from the board’s edge. At least the distance from the edge of the board is equal to the thickness of the panel, which is due to the use of high-volume production line plug and wave soldering.
But also to prevent the deformation caused by the shape of the circuit board edge, causing copper film broken lead to waste. If the components on the circuit board are too much, then it has to be more than 3m. You can add the edge of the circuit board 3mm auxiliary side, in the different side to open V-shaped groove, in the production by hand breaking apart.
4. The Order in which the Components are Placed
First, place the fixed position with the structure in close contact with the components, such as power outlets, lights, switches, plug-ins, etc. And then place particular parts, such as heating elements, transformers, and integrated circuits. Finally, put small components, such as resistors, capacitors, diodes, etc.
The rules of wiring of Protel DXP are as follows:
1) Line Length
The copper film should be as short as possible, in the high-frequency circuit should be the case. The fillet should not be rounded or beveled. The right angle or sharp corners may affect electrical performance in the case of high-frequency circuits and high wiring densities.
When the double-panel wiring, the two sides of the wire should be perpendicular to each other, in oblique or curved alignment, to avoid parallel to each other and reduce the parasitic capacitance.
2) Line Width:
the width of the copper film should be able to meet the electrical characteristics of the requirements and be easy to produce as a criterion. Its minimum value depends on the current flowing through it but generally should not be less than 0.2mm. As long as the board area is large enough, copper wire width and spacing are the best choices of 0.3mm.
Under normal circumstances, 1 ~ 1.5mm line width allows the flow of 2A current. For example, the ground and power lines are best to use a line width greater than 1mm. When the two wires are between the integrated circuit board pads, the pad diameter is 50 mils, the line width and line spacing are ten mils. When the place is taken between a line, the pad diameter is 64 mils, line width and line spacing is 12mil. Note the conversion between metric and imperial, 100mil = 2.54mm.
3) Line Spacing:
the spacing between adjacent copper film lines should meet the electrical safety requirements, and the spacing should be as comprehensive as possible to facilitate the production. The minimum spacing can withstand at least the peak of the applied voltage. In the case of low wiring density, the spacing should be as large as possible.
4) Shield and Ground:
The public ground copper wire should be placed on the edge of the circuit board as much as possible. The circuit board should be as much as possible to retain the copper foil to do the ground to enhance the shielding capacity. In addition, technicians preferably make the shape of the ground wire into a loop or a grid. As a result of using inner power and ground particular layer, the multilayer circuit board can play a better shielding effect.
The diameter of the metal lead, the thickness of the solder layer, the thickness of the thin layer, the pore size tolerance, and the thickness of the hole metalized plating determine the size and diameter of the pad and gap of the disk. For example, the resistance of the metal pin diameter of 0.5mm, the pad hole diameter of 0.7mm, the pad diameter should be pad diameter plus 1.2mm.
The minimum should be pad diameter plus 1.0mm. When the pad diameter is 1.5 mm, the user may use a square pad to increase the peel strength of the place. For holes with a hole diameter less than 0.4 mm, the outer diameter of the pad/pad hole diameter is 0.5 to 3. For spots with a hole diameter greater than 2 mm, the pad diameter/pad hole diameter is 1.5 to 2.
Common Pad Size
Pad hole diameter / mm
0.4 0.5 0.6 0.8 1.0 1.2 1.6 2.0
Pad outer diameter / mm
1.5 1.5 2.0 2.0 2.5 3.0 3.5 4
Consider the following when designing the pad of Protel DXP:
1) The edge of the pad hole to the edge of the circuit board is greater than 1mm, which can avoid the processing leading to pad defects.
2) When the copper film is connected with the pad, the connection between the place and the copper film is designed as teardrop-like so that you can not easily peel the pad off. The link between the copper film and the buffer is not easy to disconnect.
3) adjacent pads to avoid an acute angle.
1) Large Area Filled
The large area on the circuit board is filled with two purposes; one is the heat, the other is to use the shield to reduce interference. The space is filled with a window, which serves the grid to avoid the heat generated when the circuit board is welding and produce no gas emissions leaving the copper film off. The use of copper can also achieve the purpose of anti-interference, and copper can automatically bypass the pad and be connected to the ground.
2) Jumper Wire
In the design of single-sided circuit boards, when some copper film can not be connected, the usual practice is to use the jumper. The length of the jumper should choose the following: 6mm, 8mm, and 10mm.
1. Ground impedance of the typical impedance of the circuit on the ground diagram of the board that the zero potential and used as a common reference point in the other pinpoints in the board in the actual panel due to the ground (copper film line) impedance exists.
Bring together a total impedance interference, so when wiring, can not be connected with the ground symbol of the points together, which may cause harmful coupling and affect the regular work of the circuit.
2. How to connect the ground is usually in an electronic system. The environment is divided systematically into chassis (shield), digital (logical), analog ground, etc. In the connection, you should pay attention to the following ground point:
1) Properly select single-point ground and multipoint ground. In the low-frequency circuit, the signal frequency is less than 1MHz. You can ignore wiring and components between the inductance. And ground circuit resistance generated by the voltage drop on the circuit has a more significant impact. It should be a single-point grounding method.
When the signal’s frequency is more potent than 10MHz, the effect of ground inductance, it is appropriate to use the nearest ground multipoint grounding method. When the signal frequency is between 1 ~ 10MHz, using a single-point grounding method, the ground length should not exceed the wavelength of 1/20 or multipoint grounding.
2) Digital ground and analog ground separately. The circuit board has both digital circuits and analog circuits, so technicians should separate them as much as possible. And the ground wire can not be muted and connected to the ground side of the power supply (preferably, the power supply terminals are also connected separately).
To maximize the area of the linear circuit. General digital circuit anti-interference ability, TTL circuit noise margin of 0.4 ~ 0.6V, CMOS digital circuit noise margin for the power supply voltage of 0.3 ~ 0.45 times, while the analog circuit, as long as the micro-level noise, Enough to make it work is not normal. So technicians should separate the two types of boards from the layout of PROTEL DXP and wiring.
3) As thick as possible. If the ground is excellent, the ground potential will change with the current changes, resulting in the interference of the electronic system signal, mainly the analog circuit part, so the ground should be as comprehensive as possible. Generally, more than 3mm is appropriate.
4) The ground wire forms a closed loop. When there is only a digital circuit on the circuit board, it should make the ground loop, significantly improving the anti-jamming capability. Because when the circuit board has a lot of integrated circuits, if the ground is excellent, it will cause a more considerable grounding the potential difference. And the ring ground can reduce the grounding resistance, thereby reducing the ground potential difference.
5) The same level of circuit grounding should be as close as possible, and technicians should also connect the tier of the power supply filter capacitor to the ground tier.
6) The connection of the ground line. The entire ground line must strictly follow the high frequency, intermediate frequency, and low-frequency order level from weak to strong electrical connection. High-frequency is part of the best use of large areas surrounded by ground to ensure a good shielding effect.
Electronic systems with microprocessors, anti-jamming, and electromagnetic compatibility are issues technicians must consider in the design process. Especially for systems with high clock rates and fast bus cycles; systems with high power, high current drive circuits; Signal and high-precision A / D conversion circuit systems. To increase the system’s anti-electromagnetic interference ability, should consider the following measures during the layout of PROTEL DXP:
1) Select the microprocessor with low clock frequency. As long as the controller performance meets the requirements, the lower the clock frequency, the better the clock can effectively reduce noise and improve the system’s anti-jamming capability. As the square wave contains various frequency components, the high-frequency components can quickly become a noise source. Under normal circumstances, the clock frequency of 3 times the high-frequency noise is the most dangerous.
2) To reduce the distortion in signal transmission. When the high-speed signal (high signal frequency = rising edge and falling edge of the fast signal) is in the copper film transmission, the motion will be distorted due to the copper film line inductance and capacitance. When the distortion is too significant, it will make the System work is unreliable. General requirements: the circuit board signal to spread the copper film as short as possible, the less the number of viable the better. Typical values: no more than 25cm in length, no more than two holes.
3) To reduce the cross-interference between signals. When a signal line has a pulse signal, it will interfere with another weak signal line with a high input impedance. In this case, it is necessary to isolate the soft signal line by adding a grounded contour to surround the weak signal, or Increasing the distance between lines, for different levels of interference can be used to increase the power and ground-level solution.
4) Reduce the noise from the power supply to the system while providing energy. Its noise added to the power supply system, the system reset, interrupt, and some other control signals are most vulnerable to external noise interference. So it should be appropriate to increase the capacitance to filter out these noises from the power supply.
5) Pay attention to the circuit board and components of the high-frequency characteristics. In the case of high frequency, the circuit board on the copper film, pads, vias, electricity
So these are the techniques and steps for Decrypting PROTEL DXP Software For PCB Design.