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PCB Prototyping

PCB Prototyping- Best Practices for Fast and Accurate Results

When designing a printed circuit board the prototyping process is one of the most important steps. It’s essential to get it right the first time so that the end product meets all of your specifications. To ensure fast and accurate results in this case, you must follow certain best practices. From choosing the right design software to properly testing the boards, we’ll cover everything you need to know to get the most out of your PCB prototyping projects.

Use the Correct Board Material

When it comes to PCB prototyping, selecting the right board material is crucial. The type of material you choose can impact the board’s durability, and performance. Some materials are more prone to overheating or warping, while others may be more conductive or have better insulating properties.

One popular option for PCB prototyping is fiberglass. It is a relatively low-cost material and can provide good insulation properties. It is also ideal for single-sided boards. However, it may not be the best option for more complex designs.

For multi-layered boards, you may want to consider a material like FR4. This type of material is more expensive but provides better durability and stability, which is critical for high-performance circuit boards.

Before selecting your board material, you must consider the specifications of your design, including the application, environment, and electrical properties you require. Don’t be afraid to consult with PC Board experts to help determine which material is the best fit for your project.

Using the right board material is just one of the many best practices to consider when it comes to PCB prototyping. By following these tips, you can achieve faster, more accurate outcomes and set yourself up for success in your PCB design projects.

Invest in Quality Components

When it comes to circuit board prototyping, investing in high-quality components is crucial to achieving fast and accurate results. While it may be tempting to cut costs by using cheaper parts, this can lead to several issues down the line, from malfunctioning circuits to reduced durability.

Using quality components ensures that your circuit board will function properly and last longer, saving you time and money in the long run. You must find the components that have been tested and verified to meet industry standards and specifications.

Another benefit of using high-quality components is that they are less likely to fail during testing, reducing the need for repairs or replacements. This not only saves you time but also minimizes the risk of damaging other components or causing additional issues with the circuit board.

Make Sure Your Board Design is Complete and Accurate

Before starting your PCB prototyping project, you must ensure that your board design is complete and accurate. This step may seem obvious, but it is often overlooked, resulting in errors and the waste of time and money.

Start by double-checking your PCB design for errors, missing connections, or any other issues. Use reliable design software and go over your schematic and layout files thoroughly. Get a second pair of eyes to review your design before moving forward with prototyping.

Another best practice is to perform a Design Rule Check (DRC). This automated check ensures that your board meets the minimum manufacturing requirements. A DRC can identify potential errors, such as overlapping pads, inconsistent track widths, or drill holes that are too small or too close to each other.

If your board design has multiple layers, it is crucial to verify that your stack-up is correct and that the signal integrity is maintained. You can use a simulation tool to predict and optimize the electrical performance of your board.

Follow the Data Sheet

Following the datasheet is essential to achieving accurate and reliable results while PCB prototyping. The data sheet contains crucial information about the board’s electrical characteristics, material properties, and manufacturing specifications.

The data sheet typically contains the following information:

  • PCB layer stack-up and dimensions
  • Minimum and maximum board thickness
  • Trace and via size, spacing, and clearance
  • Impedance requirements
  • Material composition and properties
  • Surface finish options
  • Solder mask and silkscreen specifications
  • Thermal management guidelines

Such a practice can ensure that your PCB prototype meets the manufacturer’s specifications, as well as any relevant industry standards. Failure to follow the datasheet can result in design flaws, manufacturing errors, and functionality issues.

Moreover, you should communicate with your PCB manufacturer if you have any questions or concerns about the datasheet. A reputable manufacturer has a team of experts who can guide you throughout the prototyping process. So, following the datasheet is the best practice for fast and accurate PCB prototyping.

Make Test Points Accessible

Make sure that the test points are easily accessible. This helps have easy testing and debugging of the PCB during the prototype stage.

Test points are small metal points on the board where you can attach the testing equipment to measure the voltage. You can find them near components to be tested. By making them easily accessible, you can avoid having to take the board apart or maneuver equipment to access them. You should consider this factor during the design phase. Ideally, you should choose unobstructed areas. You should also consider adding extra test points to ensure thorough testing of the entire board.

Moreover, you should consider the size and type of test points to use. Small test points can be difficult to use, while larger test points can take up more space on the board. You should also consider the technology, such as surface mount or through-hole.

By making test points accessible during the prototyping phase, you can save time and ensure accurate results. It can also help to identify any issues with the board early on in the development process, helping in easier debugging and revisions.

Consider Your Assembly Options
After the PCB prototype process, comes the assembly. There are several assembly options available, and you should consider which one is best for your particular project.

One option is hand assembly, which involves soldering components to the board by hand. This method is cost-effective and works well for small-scale production runs, but it is time-consuming and may result in inconsistencies.

Another option is automated PCB assembly, which involves using machines to place components onto the board. This method is efficient and accurate, but it may be more expensive and more suitable for larger production runs.

You should also consider whether you want your board to be surface-mount or through-hole. Surface-mount components are smaller and lighter, making them ideal for compact designs. However, through-hole components can provide a stronger mechanical bond and are ideal for larger components or those that require high voltage.

Make sure to consider the assembly options before finalizing your PCB design and prototyping process. This will help ensure that the end product meets your expectations and requirements.

Don’t Forget the Silkscreen

When it comes to printed circuit board prototyping, people often overlook the importance of the silkscreen. The silkscreen is the layer of ink on top of the PCB that indicates component placement, orientation, and other important information. It may seem like a minor detail, but an accurate silkscreen can save a lot of time and confusion during the assembly process.

First and foremost, make sure your silkscreen is complete. This means double-checking that all component labels are correct and aligned properly with their respective pads. Make sure there are no overlapping labels or missing information.

Next, consider the size and color of the silkscreen. A too-small or too-light font may be difficult to read, especially for those with vision impairments. Conversely, a font that is too large or too dark can clutter the board.

Finally, be mindful of the placement of the silkscreen. It should not cover up any important traces or pads. Besides, it should not interfere with any assembly processes or inspection.

Final Thoughts

Prototyping printed circuit boards is a complex and time-consuming process, but with the right techniques, it doesn’t have to be. If you want to ensure fast and accurate results, you must follow best practices, in this case. Investing in quality components is an essential step in achieving fast and accurate PCB prototyping outcomes. Don’t compromise on quality to save a few bucks as it will end up costing you more in the long run. Also, make sure that your board design is complete and accurate, as it will save you time and money.

Before starting your PCB prototype, you should thoroughly review and understand the data sheet provided by the manufacturer. It ensures that your design meets the manufacturer’s specifications and industry standards, preventing errors and functionality issues. Also, don’t hesitate to consult with your prototype pcb manufacturer if you have any concerns about the datasheet.

Also, remember the importance of the silkscreen when prototyping your PCB. A well-designed silkscreen can improve the overall functionality and aesthetics of the PCB. Make sure to choose the right font and color, and be mindful of placement. A little attention to detail can go a long way in the success of your PCB prototyping project.

Would like to know more about PCB prototyping or printed circuit board assembly? Email us at sales@pnconline.com

PNC’s step by step guide to PCB Design component placement

A schematic is an abstraction, a representation of an ideal circuit. A PCB Assembly, on the other hand, is a complex mechanical assembly. All the components in the circuit design must fit within the physical boundary of the PCB. The designer must locate and place hundreds of components subject both to the mechanical constraints of the product design and the manufacturing process while not introducing electrical noise into the circuit.

It can seem overwhelming to someone new to the PCB layout process. Fortunately, there are some simple guidelines used by the designers at PNC that will help break the layout task into manageable pieces.

Initial component placement considerations

Start by identifying the mechanical constraints on the component location. The Printed Circuit Board size and shape will be defined by the overall product configuration. Typically, the product’s mechanical design will define the location of the connectors, the keep-out zones and the locations of the heat sinks. The initial mechanical layout of the PCB is often an iterative process defined during design and early prototyping.

One recommended keep-out area is the perimeter of the board. The perimeter should be kept free to give the manufacturer a place to grip the PCB during assembly process, and room to score smaller boards to allow them to be removed from a larger multi-arrayed panel.

PNC recommends that all components be kept .050” from the PCB edge. Taller and more fragile components like capacitors should be kept .125” from the edge if possible, to allow room for tooling access to prevent damage when the PC Board is routed or scored from the panel.

The next step is to divide the PCB into functional modules to simplify routing and grounding. This will help minimize noise between power components, high speed digital components and analog components. Switching power supplies are particularly noisy, so the power supplies and their associated components should be grouped together as far as possible from noise sensitive sections of the circuit. While defining the location of the modules, be aware that high power components will need heat sinks, which may limit placement options.

Locating active components

Once the edge components are placed and functional areas of the Printed Circuit Board are defined, the next step is to locate the BGAs, quad packs and other large high pin count components. The room needed to fan out their pin counts is going to drive the locations of all the components around them.

In general, try to align the active components ICs with the #1 pin or A1 pin in the same orientation. While this may not have any utility in the actual circuit, it will make inspection and debugging of the initial prototypes far less frustrating.

Locating passive components

As a follow on to locating the active components, the bypass or decoupling capacitors on the power pins should be located as close to the IC as practical to minimize the parasitic inductance. If more than one capacitor is being used PNC recommends that the lowest value capacitor should place closest to the power pin. If components will be located on both sides of the PC Board, the bypass capacitors are often located on the opposite side, directly under the power pin. If possible, each power pin should have its own bypass capacitor.

Polarized components such as electrolytic capacitors and diodes should be arranged so they are all facing the same way. During debugging, it is much easier to spot the one diode that is not like the others rather than having to look at the silkscreen of each diode to determine if it is installed correctly.

Pull-up resistors and other groups of identical components are often grouped and lined up to simplify layout, debugging and inspection. Consider using resistor arrays when possible to save board space and reduce component count.

Inductors break this placement guideline. Because inductors generate magnetic fields, placing them too close together, particularly end to end, can cause inductive coupling, changing the value of the inductors.

Layout of double-sided boards

Double sided PCBs, PCBs with components on both sides, are expensive to produce, but may be necessary when real estate on the PCB design is tight, and when the overall product form factor is more important than PCB cost. A double-sided PCB is more expensive because it will need to pass though the pick and place machine and reflow oven twice.
Since the double-sided PCB will need to pass through the reflow oven twice, PNC recommends that the lighter and more heat resistant components be placed on the bottom of the board. Larger components on the bottom of the board will be glued to keep them from falling off, the smaller passive components cannot be glued, but the surface tension of the solder will hold them in place during the second pass through the oven.

Schedule a Design Review with your PCBA manufacturer

These are some general guidelines to aid in component placement used by the PCB designers at PNC. However, they are just guidelines. The best way to ensure that the printed circuit board assembly can be manufactured reliably is to have the layout reviewed by the people who will manufacture it. PNC’s designers can review your design to help reduce production cost and improve yield and reliability. Contact PNC today to schedule a review.