PCB Material Default Values

The choice of PCB material is crucial for the performance and reliability of your circuit. Most PCB Prototyping services offer a range of standard materials, each with its own set of default properties.

FR-4 Laminate

FR-4 is the most common PCB material and is the default choice for many prototyping services. It is a glass-reinforced epoxy laminate with the following default properties:

Property	Default Value
Dielectric Constant (Dk) @ 1 MHz	4.5
Dissipation Factor (Df) @ 1 MHz	0.02
Thermal Conductivity	0.3 W/mK
Tg (Glass Transition Temperature)	130°C
Td (Decomposition Temperature)	340°C
Flexural Strength	415 MPa

High-Frequency Materials

For high-frequency applications, such as RF and microwave circuits, specialized materials like Rogers laminates are often used. Some common default values for these materials include:

Material	Dk @ 10 GHz	Df @ 10 GHz	Thermal Conductivity
Rogers RO4003C	3.38	0.0027	0.71 W/mK
Rogers RO4350B	3.48	0.0037	0.62 W/mK
Rogers RT/duroid 5880	2.20	0.0009	0.20 W/mK

PCB Dimension Default Values

PCB prototyping services typically have default values for various dimensions, such as board thickness, copper weight, and minimum feature sizes.

Board Thickness

The default board thickness for most PCB prototyping services is 1.6 mm (0.063 in). However, other common thicknesses are also available:

Thickness (mm)	Thickness (in)
0.8	0.031
1.0	0.039
1.2	0.047
1.6	0.063
2.0	0.079

Copper Weight

Copper weight refers to the thickness of the copper layer on the PCB. The default copper weight is usually 1 oz/ft² (35 µm). Other common options include:

Copper Weight (oz/ft²)	Thickness (µm)
0.5	17.5
1.0	35
2.0	70
3.0	105

Minimum Feature Sizes

PCB prototyping services have default minimum feature sizes for various aspects of the design, such as trace width, spacing, and hole diameter.

Feature	Default Minimum Size
Trace/Space	0.15 mm (6 mil)
Via Diameter	0.4 mm (15.7 mil)
Via Drill Diameter	0.2 mm (7.9 mil)
Hole Diameter	0.3 mm (11.8 mil)
Silkscreen Width	0.15 mm (6 mil)

PCB tolerance Default Values

Tolerances are essential for ensuring the manufacturing feasibility and functionality of your PCB. Default tolerance values cover aspects such as hole size, conductor width, and spacing.

Hole Size Tolerance

The default hole size tolerance is typically ±0.1 mm (±3.9 mil). This applies to both drilled holes and vias.

Conductor Width and Spacing Tolerance

The default tolerance for conductor width and spacing is usually ±0.05 mm (±2 mil). This ensures that the manufactured PCB closely matches your design.

Board Outline Tolerance

The default board outline tolerance is ±0.2 mm (±7.9 mil). This allows for slight variations in the overall dimensions of the manufactured PCB.

PCB Surface Finish Default Values

The surface finish of a PCB protects the copper layer from oxidation and enhances solderability. The most common default surface finishes offered by PCB prototyping services include:

Hot Air Solder Leveling (HASL)

HASL is the default surface finish for many PCB prototyping services. It involves dipping the PCB in molten solder and then using hot air to remove excess solder, resulting in a flat, solderable surface.

Electroless Nickel Immersion Gold (ENIG)

ENIG is a popular choice for high-reliability applications. It consists of a layer of nickel plated onto the copper, followed by a thin layer of gold. The default thicknesses for ENIG are:

Layer	Default Thickness
Nickel	3-6 µm
Gold	0.05-0.1 µm

Immersion Silver (IAg)

Immersion silver is a cost-effective alternative to ENIG. It involves depositing a thin layer of silver onto the copper surface. The default thickness for immersion silver is 0.1-0.3 µm.

PCB Solder Mask Default Values

Solder mask is a protective coating applied to the PCB to prevent solder bridges and protect the copper traces from oxidation. The default solder mask color is green, but other colors like red, blue, and black are also available.

The default solder mask thickness is 0.01-0.03 mm (0.4-1.2 mil), and the minimum solder mask opening is typically 0.1 mm (3.9 mil).

PCB Silkscreen Default Values

Silkscreen is used to print text, logos, and component outlines on the PCB for easier assembly and identification. The default silkscreen color is white, but other colors, such as black and yellow, are also available.

The default silkscreen thickness is 0.01-0.02 mm (0.4-0.8 mil), and the minimum silkscreen line width is typically 0.15 mm (6 mil).

PCB Panelization Default Values

Panelization is the process of grouping multiple PCB designs into a single panel for more efficient manufacturing. Default values for panelization include:

Parameter	Default Value
Panel Size	100 x 100 mm (3.94 x 3.94 in)
Board Spacing	3 mm (0.12 in)
Tab Width	3 mm (0.12 in)
V-Score Width	0.2 mm (7.9 mil)
V-Score Depth	1/3 of board thickness

PCB Manufacturing Time Default Values

The default manufacturing time for PCB prototyping services varies depending on the complexity of the design and the chosen options. However, most services offer the following default turnaround times:

Service	Default Manufacturing Time
Standard	5-7 business days
Expedited	3-5 business days
Express	1-2 business days

Keep in mind that these are general default values, and actual manufacturing times may vary depending on the specific service provider and your design requirements.

Frequently Asked Questions (FAQ)

1. Can I request custom values for my PCB design?

Yes, most PCB prototyping services allow you to specify custom values for various aspects of your design, such as material, thickness, and surface finish. However, keep in mind that deviating from the default values may increase the cost and manufacturing time.

2. What if my design requires tighter tolerances than the default values?

If your design requires tighter tolerances, you can discuss your specific requirements with the PCB prototyping service. They may be able to accommodate your needs, but this may come at an additional cost and may require more time for manufacturing.

3. Are the default surface finishes suitable for all applications?

The default surface finishes, such as HASL and ENIG, are suitable for most general-purpose applications. However, for specific requirements, like high-frequency or high-reliability applications, you may need to choose a different surface finish. Consult with the PCB prototyping service to determine the best option for your project.

4. How do I ensure my design is compatible with the default manufacturing capabilities?

To ensure your design is compatible with the default manufacturing capabilities, follow the design guidelines provided by the PCB prototyping service. These guidelines will specify the minimum feature sizes, tolerances, and other design rules that your PCB must adhere to.

5. Can I specify a custom color for the solder mask or silkscreen?

Most PCB prototyping services offer a selection of standard colors for solder mask and silkscreen. If you require a custom color, you can inquire with the service provider. However, custom colors may incur additional costs and may not be available for small-quantity prototype orders.

By understanding the default values used by PCB prototyping services, you can design your PCBs to be compatible with their manufacturing capabilities. This knowledge will help you create designs that are cost-effective, reliable, and can be manufactured efficiently. Always consult with your chosen PCB prototyping service for their specific default values and design guidelines to ensure the best results for your project.