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Precautions when designing PCB imposition

In order to facilitate production, PCB circuit board imposition generally needs to design Mark points, V-grooves, and process edges.

First, the imposition shape

1. The outer frame (clamping edge) of the PCB panel should adopt a closed-loop design to ensure that the PCB panel will not be deformed after it is fixed on the fixture.

2, PCB board width ≤ 260mm (SIEMENS line) or ≤ 300mm (FUJI line); if you need automatic dispensing, PCB board width & TImes; length ≤ 125 mm & TImes; 180 mm.

3, PCB layout as close to the square as possible, it is recommended to use 2 & TImes; 2, 3 & TImes; 3, ... puzzle; but do not spell into a yin and yang;


Second, V-shaped groove

1. After opening the V-groove, the remaining thickness X should be (1/4 to 1/3) plate thickness L, but the minimum thickness X must be ≥ 0.4 mm. The upper limit of the board with heavier load can be taken, and the lower limit can be taken for the board with lighter load.

2. The misalignment S of the upper and lower sides of the V-shaped groove should be less than 0.1mm; due to the limitation of the minimum effective thickness, the V-grooved plate method should not be adopted for the plate with the thickness less than 1.2mm.


Third, Mark points

1. When setting the reference positioning point, usually leave a non-resistance area 1.5 mm larger than the positioning point.

2, used to help the optical positioning of the placement machine PCB board with a patch device at least two asymmetric reference points diagonally (http:// copyright) the entire PCB optical positioning reference point is generally in the whole PCB Diagonal corresponding position; the reference point for optical positioning of the block PCB is generally at the corresponding position of the diagonal PCB circuit board.

3. For QFP (square flat package) with lead pitch ≤ 0.5mm and BGA (ball grid array package) with ball pitch ≤ 0.8mm, in order to improve the placement accuracy, it is required to set the reference point at two diagonals of the IC.


Fourth, the craft side

1. There should be no large devices or protruding devices near the connection point between the outer frame of the panel and the inner small plate, small plate and small plate, and the space between the components and the PCB circuit board should be more than 0.5mm. To ensure the normal operation of the cutting tool.

Five, the board positioning hole

1. The whole board positioning for PCB circuit board and the reference symbol for fine pitch device positioning. In principle, the QFP with a pitch less than 0.65mm should be set at its diagonal position; the positioning reference symbol for the imposition PCB sub-board should be Used in pairs, placed at the opposite corner of the positioning feature.

2, large components should be left with positioning posts or positioning holes, such as I / O interface, microphone, battery interface, micro switch, headphone interface, motor and so on.

A good PCB designer should consider the factors of production when making imposition design, so as to facilitate processing, improve production efficiency and reduce production cost.


PCB board component layout requirements

The rational layout of PCB circuit board components in chip processing is the basic premise for designing high quality PCB drawings. The requirements for component layout mainly include five aspects of installation, stress, heat, signal and appearance.

1, installation

Refers to a series of basic requirements for the installation of the board into the chassis, the enclosure, and the slot in a specific application without causing interference such as space interference or short circuit, and placing the specified connector in a specified position on the chassis or the casing. Claim.

2, stressed

The circuit board in the chip processing should be able to withstand various external forces and vibrations during installation and operation. For this reason, the circuit board should have a reasonable shape, and the positions of various holes (screw holes, shaped holes) on the board should be reasonably arranged. Generally, the distance between the hole and the edge of the plate is at least greater than the diameter of the hole. At the same time, it should be noted that the weakest section of the plate caused by the shaped hole should also have sufficient bending strength. The connector that directly “extends” the device from the board should be reasonably fixed to ensure the reliability of long-term use.

3, heated

For high-power, severely heated devices, besides ensuring heat dissipation conditions, be careful to place them in the proper position. Especially in sophisticated analog systems, special attention should be paid to the adverse effects of the temperature field generated by these devices on the fragile preamplifier circuit. Generally, the part with very large power should be made into a single module and take certain thermal isolation measures from the signal processing circuit.

4, the signal

Signal interference is the most important factor to consider in PCB board layout design. The most basic aspects are: weak signal circuit and strong signal circuit are separated or even isolated; AC part is separated from DC part; high frequency part is separated from low frequency part; pay attention to the direction of signal line; ground line arrangement; proper shielding and filtering And other measures.

5, beautiful

Not only must we consider the neatness of the placement of components, but also consider the graceful flow of the traces. Since the average layman sometimes emphasizes the former, to evaluate the advantages and disadvantages of the circuit design one-sidedly, for the image of the product, the former should be given priority when the performance requirements are not critical. However, in high-performance applications, if you have to use a double-panel, and the board is also packaged inside, you can't see it normally, you should give priority to the aesthetics of the trace.

What software can PCB draw in addition to DXP?

The first on our list is the ZentiPCB platform from Mirko Bruno Sortini, which offers a range of free software to help users design their own PCBs. ZentiCapture allows users to quickly and easily design schematics using a simple tool set that allows users to place parts (component symbols) through orthogonal locking and pin snapping. Once the schematics (in the form of a chart) are completed, they can be ported to ZentiPCb.


ZentiPCB is a CAD-based program that allows users to import netlist files and visualize their charts. The layout editor provides the ability to import components directly from the library using cursors, supporting single-sided and dual-panel depending on the requirements.


TinyCAD

TinyCAD comes from SourceForge users beuscher, don_lucas and mattpyne. Don't underestimate the software because of the name of the software. This software provides all the features of PCB design and layout design. The software contains 42 libraries with a total of 755 symbols, including digital logic gates, electromechanical components and even microcontrollers. And each of these components can be edited, and users can even add their own component symbols. TinyCAD supports a variety of netlist formats (Eagle SCR, PADS-PCB, XML, etc.), as well as SPICE netlists.


CometCAD

CometCAD is an excellent example of another free software platform that provides an electronic schematic editor and a PCB layout editor. Only this software only supports the Windows platform. The CometCAD electronic schematic editor supports multi-page schematics, symbol rotation, parts lists and netlist schematic outputs. The PCB Layout Editor provides almost all of the functions mentioned previously (component libraries, double-sided PCBs, etc.), as well as the ability to output CAM files, as well as the ability to design rectangular multi-PCB boards.


BSch3V

Those who don't want unnecessary functionality and only need the most basic functions can try Suigyodo's BSch3V schematic capture package (where BSch stands for Basic Schematic basic schematic). The PCB editor allows users to design single-layer, double-layer, or even four-layer PCB boards with a design area of 30 square millimeters. It also has a component library, a component list generator, and a netlist generator. Users can also use the other two software to enhance the BSch3V's capabilities, including SmdICpad (for QFP, PLCC, SOP data) and POLYGON (copper-placed area).


Designer

PCWeb's Designer is one of the most feature-rich editors on the web and is free to use. The software has an impressive lineup of tools including Schematic Capture (placement components, routing/networking, annotations, etc.), PCB (placement components, routing, design rule checking, etc.) and Part Editor (create/definition components, add Symbols, etc.), in addition to the BOM function, the BOM Manager integrates Digi-Key, allowing users to assign a number to each individual component on their PCB, which will be displayed through the BOM to facilitate procurement. . This software is a software that is efficient for efficient production.


Fritzing

The Fritzing platform is more than just a simple PCB editor, but its purpose is to actually create its own designs for makers and hackers. It is designed to allow users to implement their own Arduino-based microcontroller design and create PCB layouts that can be used for production. Once the user has designed an actual circuit on the breadboard, it can then be transferred to the editor, which contains three different project perspectives. The breadboard perspective allows the user to drag and place virtual electronic components on a virtual breadboard. The schematic view is the formal expression of the schematic, which is the correspondence of the circuits on the virtual breadboard, but the user can also edit as needed. Finally, the PCB viewing angle allows the user to place the component on a virtual printed circuit board and then use it for production.


KiCAD

One of the most popular PCB free editors on the Internet is KiCAD, an EDA tool similar to Fritzing above. The software provides the functionality of a virtual environment at every stage of the design process. Among the components included are Eeschema (schematic editor), Pcbnew (printed circuit board editor), Gerbview (Gerber file viewer), and Cvpcb (for component association path selector). There is also a built-in BOM manager that allows users to tag bills of materials and easily calculate costs.


DesignSpark

DesignSpark's PCB platform is another PCB editing tool for widely used EDA applications. Similar to the two tools mentioned above, DesignSpark PCB provides schematic editing, while PCB Wizard is used to complete the schematic, and Autorouter can automate the routing between components. However, the software does have some points to pay attention to. For example, this software is very resource-intensive. If the project does not exist on the same computer, problems may occur. In addition, some functions must be registered before the user can be unlocked, and the worst is The software also displays ads.


gEDA

Despite the fact that most of the PCB software runs on Windows-based computers, some are designed for Linux users, including Ales Hvezda's gEDA project, which provides a collaborative open source EDA tool. The collaborative part refers to the continuous efforts of developers working together to develop and update the gEDA toolkit, including gEDA schematic capture and circuit design for the netlist platform, PCB layout design and optimization, and Icarus Verilog (a type of simulation Hardware description language for electronic systems). It also includes ngspice/ngucap SPICE/simulator, gerbv Gerber viewer and GTKWave digital waveform viewer.


Osmand PCB

A PCB editor for Mac comes from Osmand PCB, which allows the user to do PCB designs of almost any size, shape, and how many layers to make. The software can be designed for wiring up to 10 nanometers in spatial resolution and at any angle, and supports both imperial and metric units. Osmand also allows users to move and relocate components, connect/route/modify paths, and design PCB labels using the libraries they contain. The software also supports scripting support for the Lua language, which can generate Gerber (RS-274X) files and Excellon presentation files. This is a luxury configuration for a free software.