Brief PCB design and routine of alicloud designer 10

Author: Instructor Lu,Hua Qing vision embedded college lecturer.

4. Brief PCB design

To compile the schematic diagram or the entire project, this step is to generate a network table and prepare for the work. Open it in project and project options.

4.1 DRC rules

In terms of electrical rules, I searched for some annotations on the Internet for reference:
Violations associated with buses various types of bus electrical errors (12 in total)
Bus indices out of range bus branch Index out of range
Bus range syntax errors syntax error for bus range
Invalid illegal bus range values bus range value
The bus defined by illegal bus definitions is invalid.
Mismatched bus label ordering bus branch network label wrong sorting
Mismatched bus/wire object on wire/bus/wrong connection wire/Bus
Mismatched bus widths bus width error
Mismatched bus section index ordering bus range value expression Error
Mismatched electrical types on bus wrong electrical type
Mismatched generics on bus (first index) bus range value first error
Mismatched generics on bus (second index) the last digit of the bus range value is incorrect.

D: violations associated with nets network electrical errors (19 in total)
The hidden network is displayed in the diagram of adding hidden net to sheet.
Adding Items from hidden net to net add objects to existing networks in the hidden network
Auto-assigned ports to device pins automatically allocate ports to device pins
Duplicate networks appear in duplicate nets schematic
Floating net labels schematic diagram contains floating network labels
The global power-objects scope changes global power symbol is incorrect.
Net parameters with no name is missing in the network attribute
Net parameters with no value missing assignment in the network attribute
Nets containing floating input pins network includes suspended input pins
Nets with multiple names multiple network names attached to the same network
No Drive Source in the nets with no driving source network
Nets with only one pin network is connected to only one pin
Nets with possible connection problems the network may have a connection Error
Signals with multiple drivers repeated driver signal
Sheets containing duplicate ports schematic contains duplicate ports
Signals with load signal No Load
Signals with drivers signal not driven
Unconnected objects in Net network element unconnected object
Unconnected wires has unconnected wires in the schematic.

E: violations associated with others various types of schematic errors (3 items)
1. No error
2. The object in the object not completely within sheet boundaries schematic diagram exceeds the drawing border.
3. The objects in the off-grid object diagram are not in the grid position.

F: violations associated with parameters different types of parameter errors
1. the same parameters of same parameter containing different types appear in different models.
2. Different values appear for parameters with the same parameter containing different values

Ii. Comparison of comparator rules
A: differences associated with components different from the PCB schematic (16 items in total)
◆ Changed channel class name
◆ Changed component class name
◆ Changed net Class Name Network Class Name
◆ Changed room definitions region Definition
◆ Changed Rule Design Rules
◆ The channel classes with extra members class contains redundant members.
◆ The component classes with extra members component class contains redundant members.
◆ Different descriptions of difference component Components
◆ Change of different designators component identifier
◆ Different library references different component reference libraries
◆ Different types standards
◆ Different footprints component encapsulation change
◆ Extra channel classes redundant channel classes
◆ Extra component classes redundant component classes
◆ Extra components of extra component
◆ Extra room definitions additional region Definitions

B: differences associated with nets schematic diagram is different from the relevant network on the PCB (6 items in total)
◆ Changed Net Name Network Name
◆ Extra Net classes redundant network classes
◆ Extra nets redundant networks
◆ Extra pins appear in the extra pins in nets Network
◆ Extra design rules appear in the extra rules Network
◆ Extra members appear in the net class with extra members Network

C: differences associated with parameters the schematic diagram has different parameters related to the PCB (three items in total)
◆ Changed parameter types parameter type
◆ Changed parameter value to change the parameter value
◆ Excessive parameters appear in the object with extra Parameter

These rule settings help you find problems when creating a schematic. We also recommend that you increase the level of necessary rules, for example, in the violations associated with nets project, the floating net labels schematic diagram contains a suspended network label. This is changed to error. When you place the network label on the electrical grid, an alarm is automatically triggered, this helps us to discover our mistakes.

For the rule part, you only need to constantly compile and check for errors. With the accumulation of experience, you will adjust the format that you think is complete.

The next step is to test the DRC of the schematic diagram. The shortcut key is C + C. Even if the first item in the project menu does not display the message content on the page, you can find the message in the lower right corner of the page, check the compilation information, import the data to the PCB environment after compilation, and execute updata PCB document to *** in the design option in the menu ***. pcbdoc, display

Compile process display

Hook only show error and display it, mainly because the J1 component is not encapsulated. Return to the schematic diagram, use the shortcut key J + C to find the component, double-click the component, and add the corresponding encapsulation in footprint,

4.3 compilation error, lack of encapsulation

Execute the updata PCB document to ***. Upload Doc again, and you can see that there is no errory in the figure.

4.4 Add encapsulation and re-import

The PCB will show that the corresponding components have been imported in different rooms. Next, set the rules in the pcbh environment.

4.5 import completed

Click the L key on the keyboard to bring up the dialog box. You can remove unnecessary display and modify the corresponding color, such as the drill guide layer display and the drill Drawing Layer display. The remove method is to remove the check mark corresponding to show.

4.6 Operation layer display

Set the border of the PCB Board. In this step, the original can be directly displayed in the center each time the ad10 software is started. I will mainly introduce shortcut key operations, E + O + S is the coordinate origin setting (the input method is switched to the English format), and the PCB layer is switched to the keep-out layer (the switching method, one is the * key in the keypad, the other is to click the keep-out layer in the work window with the mouse), and then draw the border. The shortcut key p + L is used up, and the dimension is finished. There are many ways to place the dimension labels. Here, the most direct method is the p + D shortcut key, which is then drawn from the border endpoint. Completed, for example,

4.7 settings of the work area

Then, use the shortcut key D + S + R to draw the PCB editing environment and draw the border line along the left origin. In this way, the black area is the area where the original and wiring will be placed in the future, of course, you can plot this area into any desired shape, and use Shift + space to control the boundary shape during the painting process. If you want to draw a circle and hollow out part of the PCB work area, the closed area is drawn directly on the working layer of the keep-out layer. In the future, when machining, the Closed Area of the PCB can be cut out, of course, it is more reasonable to do this in the mechanical layer, but many processing plants suggest drawing holes in the keep-out layer.
Gerber file generation can reduce the number of layers, reduce costs, and increase efficiency.

Move the room to the vicinity of the work area.

4.8 mobile room

Next, let's talk about the room. Some of the drawings will delete the room directly. I often enlarge the room to cover the editing area of the work and hide it, show it as needed, hide it from the room, press the shortcut key L, Click Show/hide, and then pop up (partial ). Commonly used such as polygons, strings, room, and

4.9 display and hide of Elements

4.10 The dragged room will be included in the editing area

When the original pin spacing is smaller than the default value, a green warning will appear, which leads to the problem of PCB layout and wiring rules.

4.11 electrical rule Error alert

PCB rule settings play an important role in PCB layout and wiring. Different industry rules are also very different. Although they are all electronic, for power supply design, the rules for designing high-frequency signals are also different.

Before layout and wiring, the PCB rules must be configured with specific rules and constraints on some designs, such as the spacing between components, wire width, and copper laying method.

4.12 electrical rule settings

4.2 wiring rule setting and Verification

Add the clearance_1 rule here. Right-click the method in clerance, click New rule, click advanced in the box on the right, and then click query helper. Locate isregion and add the rule. You can also enter the rule directly, this is to set the spacing between copper and the element and the wire. When the link is laid on the grid, isregion cannot be used as a constraint. You need to enter inpoly.

4.13 padding settings

When wiring, different signal lines have different widths and are also related to the thickness of the Board copper foil. Generally, the width is 0.5 ounces, and the current of 40mil is about 1A,

4.14 width range setting

Generally, the difference between the inner and outer diameters is not smaller than 8mil. If the size is too small, it is not conducive to processing. Generally, it is 12*20, 12*24, 16*32, 28*50, etc. If necessary, it can be larger,

4.15 pass setting

4.16 mechanical air setting

4.17 cross-hole copper connection, the selected dircet connnect

Silk Screen spacing of 4.18 Devices

Height between 4.19 Elements

The above are some basic settings. Of course, special settings are required for some special ones. For example, some pins need to be directly connected, or some networks need to maintain special spacing, in this case, you need to add special rules. In fact, these rules are only commands, such as adding Gnd to a direct connection, such as 4.20. We can make more flexible settings in a similar way.

4.20 add innet ('gnd ')

4.21 Save the settings and eliminate the warning.

Next, let's talk about global modification. This is also a very practical method. For example, we want to change the overall silk screen to the desired size, increase the size of a certain type of pad, or cover all the overholes with oil, in addition, this method is also practical and schematic design. If there is a mix of Gnd, agnd, and dgnd in the schematic design, if there is hidden, it can be displayed globally, in short, it is a very convenient operation. The following uses silk screen as an example.

Click silk screen, right-click, find similar objects,

4.22 texl height 60mil same

4.23 modify texl height 40mil width7mil,

Click Enter on the keyboard to complete the operation. If the screen printing is not modified, check whether the select matched option is missing during the operation.

4.24 select matched

When you place a component, sometimes both sides need to place the component, or when the direction needs to be changed, double-click the component. For details, see 4.25 modify layer, top layer or bottom layer, rotation, and component direction settings.

4.25 element direction, layer settings

4.26 after setting, pay attention to the position of the silk screen to be sorted

Before adjustment, 4.27 Shortcut Key A +

4.27 element location

4.28 set the direction to be aligned, bottom

4.29 bottom side alignment

After the layout is complete, it is cabling. Pay attention to the line width and the hole passing. You can use * to change the wiring layer and place the hole passing. During the placement process, press the tab key to change the line width and the hole passing size, some cabling rules will be detailed at the end

Add tear T + E

4.30 add tear

Shortcut Keys P + G show copper, copper solid copper and grid pass, when the Board is heated unevenly, with grid, commonly used is solid copper, grid can Prevent Uneven heating phenomenon, solid Object, hatched mesh, network name and layer, set the connection network as needed, conncet to net, and remove dead copper when connecting the same copper, pour over all same net objects select Remove dead copper,

4.31 Copper

Comparison before and after copper laying

4.32 copper layer display

4.3 about the inner electrical layer

Figure shows adding an inner electric Layer

Concept: the positive and negative parts are two different types of negative films.
Main film: Simply put, everything is visible on the negative film.
Negative slice: on the contrary, what you see is none. What you don't see is yes.
Main film: the advantage is what you see and there is a comprehensive DRC check.
Main plate: We generally talk about the pattern process. The liquid used for alkaline etching is the main plate. If the negative film shows that the line or copper surface is black, the other part is transparent, and after the line process is exposed, the transparent part is chemically hardened by the light of the dry film resistance agent, the subsequent development process will take away the non-hardened dry film, and then the process of tin-plated lead, plating the tin-lead on the copper surface washed out by the previous process (Development) Dry Film, then the film removal action (remove the dry film hardened by light) is ***, and in the next etching process, use an alkaline potion to bite the copper foil without the protection of tin and lead (transparent part of the negative ),
The rest is the line we want (the black part of the negative film )... --> Process
Negative slice: Generally we talk about the tenting process. The liquid is acidic etching. The negative slice is transparent to the line or copper after the negative slice is made, the other part is black. After the line process is exposed, the transparent part is chemically hardened by the light of the dry film resistance agent, in the subsequent development process, the unhardened dry film is washed out, so in the etching process, only the etching dry film is washed out of some copper foil (the black part of the negative film ), while the retained dry film is not flushed out of the line we want (the transparent part of the negative film )... --> Process

Use the shortcut key L to view the inner electric layer.

In actual wiring, the power supply layer uses a negative slice, which brings a lot of convenience, but some companies will require the power supply layer to use the positive slice for processing, because the logic of the negative slice is opposite to that of the normal wiring, if the negative slice network is not divided, copper may die, which may affect the signal of the whole board. In particular, multiple power supplies appear on the power supply layer. The entire board has a hybrid power supply of 1, 2 V, 2.5 V, 3.3 V, and 5 V, this can easily lead to incorrect Power Supply segmentation. P + L is used to divide different network areas.

4.4 3D: Try to observe. The Shortcut Keys enter 2 and 3 dimensions respectively, and switch between them.

4.33 3D images

The graphic method is used to check whether silk screen printing overlaps with the pad. Once the pad is overlapped, welding is affected after the screen is produced. The pgup key or scroll wheel is used to enlarge the screen,

4.34 zoom in on a 3D image

Click the L key during viewing to modify the layer color,

4.35 layer color modification

The shortcut key T + D + R design rule test is displayed after the test, indicating that the component connection is normal. If there is an error, You need to modify it. Note that this step can be performed before the screen preparation.

4.36 complete rule Testing

4.5 common knowledge of manual cabling

First, I would like to add some knowledge about the PCB hierarchy.

The following are taken from the network. The network is also a learning resource. Here we talk about protel99, and alicloud is just an upgraded version.

I. Signal layers (signal layer)
Protel99 provides 16 signal layers: Top (top layer), bottom (bottom layer), and Mid1-Mid14 (14 middle layers ).
The signal layer is the wiring layer used to complete the copper strip of printed circuit boards. When designing a dual-panel, only the top and bottom layers of bottom are generally used. When the number of layers of the printed circuit board exceeds four layers, the mid layer is used ).

2. Internal planes (internal power supply/ground connecting)
Protel99 offers a Plane1-Plane4 (4 internal power supplies/ ). The internal power supply/ground layer is mainly used for printed circuit boards with four or more layers as the dedicated wiring layers for power supply and grounding. The dual-Panel does not need to be used.

Iii. Mechanical Layers)
The mechanical layer is generally used to draw the border (Border) of the printed circuit board. Generally, only one mechanical layer is needed. There is metric-mec4( 4 mechanical layers ).

Iv. drkll Layers)
There are two layers: "Drill drawing" and "drill guide ". It is used to plot the positioning of the hole diameter and hole.

V. Solder Mask (Solder Mask)
There are two layers: top layer and bottom layer ). When drawn on the solder mask, the pad on the printed circuit board and the protection area around the pass hole.

Vi. paste mask (Solder Paste protection layer)
There are two layers: top layer and bottom layer ). The solder paste protection layer is mainly used for printed circuit boards with surface components. At this time, the installation process of the table post components is required. This layer is not required when no table post components are required.

7. silkscreen)
There are two layers: top layer and bottom layer ). The silk screen Screen Layer is mainly used to draw text instructions and graphical instructions, such as the Shape Contour, labels and parameters of components.

8. Other (other Layer)
There are eight layers: "Keep Out (disallow cabling layer)", "multi layer (set multi-level)", "Connect (connection layer)", and "DRC error (error layer) ", two" visible grid "," Pad holes ", and" via holes )". Some layers are used by the system itself, such as visible grid (visual grid layer), to facilitate the positioning of the designer during drawing. The keep put (do not use the cabling layer) is used for automatic cabling, and manual cabling is not required.

Top layers (top-layer copper foil wiring), bottom layers (bottom-layer copper foil wiring), and top silkscreen (top-layer Wire Guide) are the most commonly used for manually drawing double-sided printed circuit boards ). You can select a preferred color for each layer. Generally, the top layer is red, the bottom layer is blue, the text and symbols are green or white, and the pad and the overpasses are yellow.

For the entire circuit board, EMC and EMI are largely influenced by the layout of components. Large companies have dedicated playout engineers as common electronic engineers, in terms of layout and wiring, there are too many rules, different boards, high-speed signal RF boards, and High-Power Supply boards, as well as simulation boards, digital boards, and hybrid signal boards, there are big differences. There are a lot of summaries on the Internet in this regard, which is worth learning.

Processing of Power Supply
In order to reduce the impact of power noise, the power supply sometimes adds a difference mode suppression and common mode suppression throttling. Of course, TVs suppression and RC filtering are available. The layout is mostly close to the terminal, the wiring should be as wide as possible, while reducing the detour. When the margin is ensured at ordinary times, the current of 40 mil follows 1A. Of course, the standard line is estimated at 0.5 ounces/inch. The specific material must be referred to the actual design.

Power circuit problems
The signal transmission is divided into two paths, one is along the actual line and the other is radiation. When a circuit is formed, the signal is returned along the path with the lowest impedance, rather than the lowest resistance, while the impedance is the best, and the path is the shortest. In this way, the signal is sometimes bypassed, and when it is bypassed, it will interfere with other signals. If the bypass path is improper, it will also be disturbed by other signals, always EMC is a topic frequently discussed in PCB layout and wiring.

For line width and line spacing
For the line width, the first step is to understand the minimum width of the processing process to avoid the failure of the PCB designed by myself. Generally, 10mil is used, which is basically greater than 4mil, while the power supply part, A separate power supply layer can be used for design. An independent power supply layer provides a good return path for the signal. For wire recommendations, the general 3 W, 5 W principle, W refers to the wire width. 70% can reduce the crosstalk of adjacent signals by, and no tests have been conducted. Of course, there are still requirements for high-speed signals and line spacing,

For Differential Pair Signals
For the detection signal, it is sometimes necessary to control the impedance. In this way, the distance between the detection line width and the positive and negative signals can also be calculated by software. At the same time, the gap between differential pairs should also be greater than 3 times the gap between differential pairs. The difference pairs offset each other to reduce the interference of the differential mode, and the main external interference is the common mode.

Analog Digital Signal
Analog signals are sensitive signals, while digital signals have stronger anti-interference capabilities. When deployed on the same PCB, digital models are separated to reduce the interference of digital signals on analog signals, an isolation circuit is sometimes used to reduce the crosstalk between digital-analog signals.

In short, for high voltage, the circuit board needs to be slotted to increase the climbing distance. There are different requirements for PCB design in different industries. Here is just a class. If you are interested, you can search for relevant information on the Internet.

Source:Huaqing vision embedded College,Original article address:Http://www.embedu.org/Column/Column718.htm

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