Your Professional PCB Layout & Design Supplier in China

Your Leading PCB Design and Layout Supplier in China

PCB design and editing resources produce schematics and computer-assisted design (CAD) printed circuit boards (PCBs).

They produce standard Gerber files for the industry and provide design and assembly diagrams showing board size, hole sizes, the durability of board, multi-story folding, and partial installation.

PCB design and planning services also set the feet or pads where the parts are sold onboard. Other PCB designs and editing services help customers to redesign, redesign or remodel existing boards to increase efficiency and reduce production costs.

Others offer faster prototyping or perform simulated tests. PCB design and services that make PCB molding are available. There are two basic methods of assembly.

Surface mount technology (SMT) vendors sell tracks or terminals in the upper part of the board. By using a technology hole (THT) to mount objects by inserting objects that lead to holes in the board and then fold the tracks along the other side of the board.

PCB design and layout services specifically for different types of computer boards.

PCB categories include one-sided boards, two-sided boards, multi-layer boards, flexible boards, and solid boards.

One-sided boards enclose items on only one side of the substrate. Double-sided boards enclose items on both sides.

Multi-layer boards have three or more layers of printed circuits divided into attached layers and connected by internal and external connections. Flexible PCBs are usually made of polyester or polyimide materials.

Flex circuits can be used to solve complex packaging problems and improve product appearance. Solid-flexible PCB boards with dynamic connections.

What is PCB Design and Layout?

Before fabricating the PCB, a layout is designed in specific software that determines how the end product is going to look like.

The design files contain the shape of the PCB and the placements for the components which will be later soldered on the PCB and the electrical connection between different pads and pins of the different components on the PCB.

The file required for fabricating a PCB is called Gerber file(or files).

Gerber files are open ASCII vector format files that contain information on each physical board layer of your PCB design.

Circuit board objects, like copper traces, vias, pads, solder masks, and silkscreen images, are all represented by a flash or draw code and defined by a series of vector coordinates.

The CAM engineering software used by the manufacturer to create the circuit boards utilize manufacturing data to create two-dimensional or three-dimensional designs of the PCB.

They receive all the information needed from the Gerber files in order to etch the copper layers, create the component pads and connection traces, drill all required holes, and profile the board to the required size.

The Gerber data is imported into these CAM systems to produce the designs for production.

Upon import, the files are labeled accordingly, set to 0,0 archived, and saved in the original format.

The engineer will manipulate the files for production-ready layout, singles, or within an array. Clean-up is critical to processing files correctly in production.

Design rule checks are set to parameters for the type of PCB being checked.

Manual and automated cleanup is performed on each layer during the cleanup the engineer will compare to the archived original files to be sure no electrical changes have occurred.

Engineers must refer to guidelines and references mentioned in the Gerber file while manipulating the data.

A Gerber file is developed such that it elaborates the requirements in each stage of the product development. These files are used for both processes: PCB fabrication and PCB assembly.

How to Choose PCB Design Software?

There are several programs available that range from simple and intuitive to highly sophisticated. They range from free or inexpensive to high-end/premium and come with basic features to advance feature packed.

All of the tools are different and unique in their own way. Ultimately, your needs and preferences should drive what CAD program you use.

That being said, there are three PCB design packages that tend to be the most popular and considered the best:

• Altium Designer
• Eagle
• KiCad

However, most hardware entrepreneurs, startups, and makers prefer a less well-known PCB design packaged called DipTrace.

So Who Exactly Needs PCB Design Software?

Let’s look at the types of people most likely to need a PCB design tool.

We’ll discuss four groups of people likely to use circuit design software, although there are several more:

Corporate engineers – Most established companies can easily afford to spend thousands of dollars on software.  Altium is probably the right choice for them.

Independent freelance engineers – For individual freelance engineers DipTrace is probably the best choice, unless one needs to collaborate with other engineers.

If collaborating with other engineers is critical then you’ll probably be better off with altium.

Engineer entrepreneurs – If you have prior experience designing electronics (or wish to learn how) then you may be better off designing your product yourself.  Or at least as much as possible.

DipTrace or KiCad is definitely the way to go for you.

Electronic hobbyists and makers– If you’re developing a circuit for fun or for small profits then eagle or KiCad could be your preferred choice as both of them has a free license available and has a large community of people to back you up with any difficulties you may face during working on these software

The Most Important Criteria for PCB Design Software

For most entrepreneurs and a majority of freelance engineers, there are five primary criteria that matter most when selecting a circuit design software package:

Must be intuitive to use – DipTrace is the clear winner when it comes to being intuitive to use.

Using DipTrace you’ll be able to begin designing your circuit almost immediately with a very minimal learning curve.

No need to waste hours reading a boring manual with DipTrace.

Must be reasonably priced – KiCad is the clear winner in this segment as it is both free and open-sourced.

Also, DipTrace is easily the most affordable PCB design package.  It is only half the price of Eagle, or only an eighth the price of Altium.

DipTrace also has a low barrier to entry because you can begin with their low-cost Starter version and upgrade your way up as needed.

Needs to have most of the useful and latest features  – There is no clear winner here, and it really depends on your needs.

But if you are really looking for some premium features Altium is the best option

Large libraries of components available  –  All four packages come with huge libraries of components. Large libraries are critical because creating new components can introduce errors that won’t be captured by any of the verification tools.

That being said, regardless of the package, you’ll eventually need to create some custom components yourself.

Because they are so popular, Altium and Eagle are probably the winners for this criteria because component manufacturers are more likely to provide a component library for one of these two packages.

Understand PCB Layout Design Rules

The PCB design guidelines set out best practices to reduce the cost of your boards and to minimize the risk of errors arising during manufacture.

Different boards have different rules especially in terms of spacing, traces size, and power isolation.

Manufacturers have different requirements; make sure you read their own guidelines before sending your design.

Naming and file formats also vary depending on the manufacturers.

PCB Layout

1. Group components together. For example, the resistors surrounding a transistor in your schematic will also be grouped together on the PCB.
2. The minimum drill size should be 15 mils.
3. The minimum annular ring size should be 7 mils.
4. 7 mil is the minimum size for traces. 8mil is acceptable. When possible try to keep the trace size to 10mil.
5. Use thicker traces for power lines. 12mil=100mA max, 16mil=500mA max etc.
6. 7mil between traces and space is reasonable.
7. Avoid 90-degree corners. Straight lines with 45-degree corners are preferable.
8. Where applicable use a ground pour on top/bottom layers.

Footprints

1. All footprints need a reference designator. If you come across a part on a board that doesn’t have this, you should change it and save the library. For parts requiring it, a pin one marker should be defined.
2. All footprints need silkscreen indicators showing mechanical sizes, dimensions, or anything weird about the part.
3. To prevent it from flaking off easily silkscreen within a footprint or board should not go over pads or metal that will be exposed.
4. The top component layer should be marked by a red center cross.
5. Package outline layers should outline the actual package size.
6. The Top Courtyard layer should include all of the pins.
7. When adding a footprint make sure you add a solder mask.
8. Make sure every new footprint and part will have a schematic layout

How to Create a PCB Layout from Schematic?

The schematic is the very first part of this PCB designing process.

It’s a pictorial representation, either written or on a computer, that utilizes agreed-upon symbols to describe circuit connections.

It also indicates the components that will be used and how they are connected. The actual design and layout will be based upon this schematic.

Having a proper schematic is necessary for every PCB design and it is particularly useful during the assembly process.

The schematic also helps to identify defects or faults within the circuit and it makes troubleshooting much easier and faster.

Board Outline:

The board outline determines the physical shape of the PCB. It can be done at the very beginning of the designing process or at the very end.

A PCB can have a proper geometric shape such as rectangular or circular. Or can be asymmetrically shaped.

In both cases, the outline will become the border of the PCB. In most cases, the shape is predetermined and it is based upon the housing or the enclosure in which the PCB will be placed later on.

Hence the outline is fixed. But if that is not the case then the designer has the flexibility to make the outline of his own choice.

If the boards are required to fix on a position using screws then mounting holes for them are also placed on the specific position.

Component Placement:

Then the components are arranged within the board dimension.

Some components such as connectors, USB, and other ports need to be at the edge of the PCB so those parts are placed first.

Then rest of the components such as ICs and other peripheral components are placed. The components are generally placed in a group so that it makes the routing process easier.

Routing:

After that was done the routing process began. Here pads with the same nets are joined together using traces that will connect them electrically.

The width of the traces depends on the characteristics of the net that they are joining.

For example, thin traces used for joining signal traces and relatively thicker traces are used to join power rails.

The ground pins are not joined at this stage. If two traces cross each other then vias are used to reroute them to another layer of the PCB.

Copper Plane:

When the routing process is finished add a copper layer to the whole circuit filling the unused areas on the surface.

This Copper plane will be tied to the GND and act as a common GND plane for all the components.

There are several benefits of having a copper plane on a PCB. It reduces external interference, absorbs excess heat, etc.

Performing Quality Checks

Review the layout and physical position of components, as well as routing paths, and make adjustments as necessary to optimize the circuit within the context of all design constraints.

Verify that all sensitive circuits and nodes are shielded adequately from all noise sources, ensure that solder mask has been placed between pins and vias and that the silkscreen layer conveys the necessary detail clearly and concisely.

Gather feedback from other designers involved in the project and make sure that you maintain detailed lists of all changes implemented at each iteration.

Use a Design Rule Checker (DRC) as a framework to avoid errors in the design, as well as an Electrical Rules Checker (ERC) to verify that your design meets all constraints and specifications.

Design rules and electrical rules may vary and should be specific to your project.

Finally, once your DRC and ERC confirm that your design is error-free, you should run through your schematic, wire-by-wire, to verify the routing for every signal and ensure that nothing has been missed.

High-Speed PCB Design & Layout Features and Process

A PCB can be considered ‘High Speed’ when the signal switching occurs at frequencies of the order of megahertz or gigahertz.

In these cases, it is necessary to adopt specific rules for PCB design, which are added to the basic ones, common to all types of printed circuit boards:

• Contain the noise generated by the power distribution network (especially in the presence of switching power supplies);
• Reduce crosstalk phenomena between adjacent traces. When the signal frequency is high, capacitive crosstalk phenomena are easily generated as the induced currents have a capacitive impedance;
• Reduce the effects produced by the bounce of the ground reference (ground bounce). These effects, directly related to the signal integrity issue, are reduced by appropriately defining the PCB stack up and decoupling the various parts of the PCB (for example, the separation between logic and analog areas);
• Try to obtain the best possible impedance matching;
• Elimination of transient ringing, often caused by too narrow tracks;
• Provide the correct termination for each signal line. This aspect, together with the control of the input, load and transmission impedances, allows to eliminate the signal reflection;
• The high degree of immunity to electromagnetic interference (EMI), both conducted and radiated.

When laying out your high-speed and RF circuitry, make sure your placement follows the signal paths laid out in the schematic.

High-speed circuitry is dependent on short direct traces between pins within a signal path, and you don’t want these traces wandering around the board before they connect.

On the other hand, large data and memory busses will need to be equalized in length which often means that some of those lines will have to be lengthened.

In this case, you need to allocate enough room for tuning measured trace lengths to the correct values.

Another consideration is the correct layout of your power and ground networks.

Some components need to be placed within dedicated power or ground plane areas to isolate their noise from sensitive high-speed routing.

You also need to place bypass capacitors next to each supply pin of an IC and keep them as close as possible.

Another critical concern is to make sure that high-speed transmission lines are not routed across power and ground plane splits.

These traces need a contiguous plane for a return path, and a split will create a canyon that it can’t cross.

This can cause EMI problems that will ruin the design’s signal integrity performance.

RF routing will introduce a whole new set of requirements for how you create your traces.

Some of the trace topologies will be very different than what you are used to in order to create the correct size and shape.

You will also be adding additional vias for shielding and increasing widths and spaces, all of which will require more room.

Another aspect of both high speed and RF designs is in their layer stack up.

It is important to precisely configure the layers and materials in the stack up to support high speed and RF microstrip and stripline routing.

The success of your high-speed and RF PCB routing is dependent on many factors.

These include adherence to high-speed layout guidelines in order to correctly route high speed and RF PCB trace lengths.

How you plan ahead for your RF PCB routing is also important as well as simply designing the basic circuitry of your board such as how to connect a relay in a circuit.

Let’s take a closer look at some of these details.

Route high-speed signals over a solid ground plane

As a rule of thumb, it’s most beneficial to have a common ground plane below signal traces.

For best results, a designer should incorporate at least a four-layer PCB.

A four-layer PCB allows devoting one of the inner layers to a full ground plane.

A ground plane is a sheet of copper, forming one of the layers of the PCB and covering the entire area of one of the layers of the PCB.

This ensures minimal impedance between any two ground points in the PCB. This ground plane should never be broken by routing any tracks in it.

Keep 135⁰ trace bends while routing

The bends should be kept minimum while routing high-speed signals. If the bends are required, then 135° bends should be implemented instead of 90°. At 90 degrees, very high-speed sharp edges act as an antenna.

Increase the distance between the signals to reduce crosstalk

A minimum distance should be maintained between traces to minimize the crosstalk.

The crosstalk level depends on the length and the distance between the two traces.

In some areas, the routing of traces reaches a bottleneck where the traces are closer than desired.

In such situations, the distance between the signals outside the bottleneck should be increased.

Even if the minimum requirement is met, the spacing can be increased a little further.

The differential signal tracks should be routed in pairs

When routing high-speed differential pairs parallel to each other, a constant distance should be maintained between them.

This distance helps to achieve the specified differential impedance.

The designer should minimize the area in which the specified spacing is enlarged due to pad entries. The differential pairs should be routed symmetrically.

Incorporate Length Matching to Achieve Time Delay

The high-speed interfaces have additional requirements concerning the time of arrival at a destination known as clock skew between different traces and pairs of signals.

For instance, in a high-speed parallel bus, all data signals need to arrive within a time period in order to meet the setup and hold time requirements of the receiver.

The PCB designer should ensure that such permitted skew is not exceeded. To achieve this requirement, length matching is necessary.

Separate Analog and Digital Ground Planes to Reduce Noise

Defining separate Analog and Digital ground sections approach makes it easy in the schematic to determine which components and pins should be connected to the digital ground and which ones to the analog ground section. These kinds of designs can be routed by placing two different ground planes as reference. The two planes should be placed accurately.

Avoid hot spots by placing vias in a grid

The signal vias produce voids in the power and ground planes.

Improper positioning of vias can create plane areas in which the current density is increased.

These regions are called hot spots. These hot spots must be avoided. The best solution is to place the vias in a grid that leaves enough space between the vias for the power plane to pass.

As a thumb rule, place vias 15 miles apart wherever possible.

What to Pay Attention in PCB Design & Layout

Engineers tend to pay most attention to circuits, the latest components, and code as important parts of an electronics project, but sometimes a critical component of electronics, the PCB layout, is neglected. Poor PCB layout can cause function and reliability problems.

Component Arrangement

Sometimes, rotating your components is simply not enough. When that happens, it’s important to come at the situation with a bit of strategy in terms of the component arrangement.

Cascaded components play a vital role in many PCB design options.

However, they can be challenging to arrange correctly. Keep them near one another, and make sure that they are in sequence on the board. That will immediately remove the challenge of trying to route traces all across the board to connect cascaded components located in different areas.

Using PCB as Heatsink

Place extra copper around the surface mount component to provide extra surface area to dissipate heat more efficiently.

Some component datasheets(especially power diodes and power MOSFETs or voltage regulators) have guidelines for using PCB surface area as heatsinks.

Using Vias wisely

Vias can be used to move heat from one side of a PCB to the other.

This is especially useful when a PCB is mounted on a heatsink on a chassis that can further dissipate heat.

Large vias transfer heat more efficiently than small vias. Many vias transfer heat more efficiently than one via and lower the operating temperature of components. Lower operating temperatures contribute to higher reliability.

Keep the Noise Down

Signal noise can be problematic when it comes to some traces.

However, placing high-frequency signals carrying traces too close together can couple those signals, ratcheting up the noise and possibly creating problems with traces where no noise is desired.

Make sure that you keep noisy digital traces away from analog traces to avoid this problem.

What is a circuit schematic diagram?

A schematic diagram is a graphical representation of electronic circuits or systems connected together to convey the circuit’s function. The diagram displays important information such as electronic symbols, part numbers, connections, component values, and more.

What is a circuit simulator?

A circuit simulator allows you to test and analyze the behavior of your circuit for various conditions in a virtual environment. You can test the output, noise, bandwidth, and yield just to name a few. This helps you save on cost and development time.

Why do I need to design Break-away Rails (Break-away Tabs)?

If the clearance between the board’s edge and copper features is less than 3.5mm (138mil), or your boards need to be panelized for some reason, Break-away rails (Break-away tabs) must be added at the two longer paralleled edges of the boards to ensure that the boards can be assembled by the SMT machine.

Why do I need to penalize my boards?

Panelization is needed when your PCB dimension is smaller than 50mmx100mm, or when your PCB is of any shape (circular, or odd shape) other than rectangle, your boards must be panelized in an array for fabrication.

You can pre-panelize at your side, or we can also penalize you. In the latter case, we will send the panelization file back to you for your approval before fabrication begins. Panelization is a MUST if your PCBs will use surface mounting machines for assembly.

What influences the impedance?

Factors that influence impedance PCB tolerances include materials’ resin content and tolerance, and trace height and width at the top and bottom of the board.

How do I pick the thickness of the material?

When it comes to choosing materials, keep in mind that we calculate the final press-out thickness that we expect from the prepreg. This depends on the amount of resin in the prepreg, the amount of the copper area percentage, and the thickness of the adjoining copper layers.

What files do you need?

As a default, most manufacturers accept Gerber file RS-274X format. (Note: 274D format is not accepted) Some also accept the following layout files:*.ODB++, PROTEL *.PCB/ *.PCBDOC EAGLE *.BRD (IMPORTANT: please provide your Eagle Version to avoid conversion mistakes).

Conclusion :

As technology has progressed, the frequency of signals, including digital signals, has become blazing fast.

Understanding signal propagation has increasingly become a necessity for engineers.

Both analog and digital disciplines overlap very noticeably at high speeds, yet have been taught for several decades as separate worlds (at least to undergraduates).

Designing for a successful PCB layout can be straightforward (for a simple circuit), or an intense science covering several disciplines with potential for extreme complexity.

PCB layout can get complex when driven by product requirements (e.g., size), multiple layers, many and various components, and different types of signals (e.g., high-speed, low voltage, high voltage, digital, analog, etc.) that must successfully coexist on the same board.

Finally, regulations and environmental standards are also part of the PCB design process.

Creating well-behaved PCBs is both a science and an art.

This article barely scratches the surface, but perhaps it will equip you with an idea of areas that you need to investigate in-depth.