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Printed Circuit Boards (PCB) Glossary

This PCB printed circuit glossary is designed to give you definitions to some of the words and phrases you will come across in doing business with Sunstone Circuits. While not exhaustive, it provides useful information about PCB circuits, circuit board design, and circuit board construction.

Scroll down or choose the letter below to find your specific definition request.

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z

Aperture Information

This is a text file describing the size and shape of each element on the PCB printed circuit boards. These are also known as D-code lists. These lists are not necessary if your files are saved as Extended Gerber with embedded Apertures (RS274X).

Annular Rings

The copper pad area that remains after a hole is drilled through the pad, measured from edge of hole to edge of pad.

Your inner and outer layer pads should be at least 0.018" larger than the finish hole size (0.010" for vias). If your design has any pad to trace junction minimum requirement, add that to the above numbers [0.018" pad + 0.002" junction should have 0.020" pad]. This will provide a 9mil annular ring for component pins, 5mil annular ring for vias.

Designer tip: Try using teardrop shaped pads. They offer a more robust design to accommodate for drill registration and / or Image shift during manufacturing and will help keep a IPC–A-600 Class II compliant, = 0.002" not reducing trace width more than 20% at trace/pin junction.

Aspect Ratio

The ratio of the length or depth of a hole to its pre-plated diameter (Example. 0.062" thick board 0.0135" drill = aspect ratio of 4.59:1).

Maximum aspect ratio allowed for Sunstone Circuits manufacturing is 6:1.

Board Thickness
Smallest Drill Size







Designer tip: Minimizing the aspect ratio of the holes improves through hole plating quality and minimizes the chance of via failures.

Board Thickness

The standard base thickness is 1/16 inch (0.062"). The following thicknesses are also available through Full Feature Product: 0.031", 0.047", 0.093", and 0.125". Overall thickness tolerance is within +/- 10% of the given thickness (for 2 and 4 layer boards) and 14% for 6 layer boards.

Additional thicknesses available through Custom Quote or, choose "Design Review Plus" option and select the closest thickness on the dropdown menu. Include all layer thickness requirements on your drawing or "readme".

Technical information on our laminate materials.

Build time

The cutoff time for receiving orders and files for Full Feature Product is 2:00 pm (PST) Monday through Friday and noon (PST) for Quickturn Product . Some files have been known to take 45 minutes to navigate the web, so please allow for this. Build time starts the following business day, unless a "hold" occurs.


A clearance (or isolation) is a term used to describe the space from a power or ground layer to a plated through hole. To prevent shorting, ground and power layer clearances need to be a minimum over the finished hole size of 0.020" for Full Feature Multilayer PCB and 0.025" for PCBexpress quickturn printed circuits.

Component Side

In order to build your printed circuit board correctly, we must be able to identify the correct orientation of your design. Component, layer 1, or 'top' layer should read in facing up. All other layers should line up as though looking through the board. Please use layer designators, pass through marks, or correct reading layer text.

Continuous Outline

The outline or cut line for the printed circuit board made from a single continuous line. This line may not contain any broken/overlapping lines and/or improperly drawn arcs. The outline describes the shape of the board and is required for creating the route program.

Controlled Impedance

The electrical result of manufacturing a circuit board to meet characteristic impedance specifications. Combination of copper thickness and line width as well as the dielectric thickness and properties of the base material all contribute to the impedance value. The following is a good resource for calculation of impedance:

Characteristic impedance extends the concept of resistance to AC circuits, describing not only the relative amplitudes of the voltage and current, but also the relative phases. When the circuit is driven with direct current (DC) there is no distinction between impedance and resistance; the latter can be thought of as impedance with zero phase angle.

Copper (Finished Copper) Weight

This is total thickness of copper on the board surface. The value is determined from the copper foil thickness, plus plated copper, minus copper removed during surface preparation. Copper weight is measured in oz /sq foot. 1 oz = a minimum of 0.0012" thickness.

We offer finished copper weight of 1-oz., 1.5-oz., and 2.5-oz. If you need a different finished copper weight, please complete our Custom PCB Quote form.


The voltage which causes tracking after 50 drops of 0.1% ammonium chloride solution have fallen on the material. The results of testing at 3 mm thickness are considered representative of the material's performance in any thickness.

Tracking is an electrical breakdown on the surface of an insulating material. A large voltage difference gradually creates a conductive leakage path across the surface of the material by forming a carbonized track.

Performance Level Categories (PLC) were introduced to avoid excessive implied precision and bias.

Tracking Index (V)

600 and Greater

400 through 599

250 through 399

175 through 249

100 through 174



Cut Lines

The cut line will be used to program the router path and it represents the circuit board outside edge. The tolerance on route dimension is +/- 0.010". It is recommended to keep outer layer copper 0.010" and inner copper 0.020" from the cut line to avoid exposing copper at the board edge.

Date Code (Full-Featured)

Marking of products to indicate their date of manufacture. It can be etched in copper, or printed during the Silkscreen process (default).

Design Review

As part of the Full-Featured Service we conduct a 25 point pre-engineering design review with a personalized report listing any DFM violations. Sunstone will give you the option to proceed "as is" or upgrade to "Design Review Plus".

Design Review Plus

In addition to the 25 point Design Review , Sunstone's experienced pre-engineering and CAM team will work with you to resolve any non-conforming findings, and will make the necessary edits to meet manufacturing requirements. A copy of modified Gerber files will be sent to you for your records.

Document Retention

The standard retention of quality documents (evidence of test, and inspection) for our product lines is as follows:


Drawing or Print

Sunstone orders do not require drawings or prints. If a drawing is provided with the order, the order form will override any details or notes on the drawing that deviate from Sunstone Circuits online capabilities and inspection criteria. The order form placed with each order is the governing document for orders placed on the web site.

Drill File (aka. Excellon Drill File)

This is an example of an Excellon drill file. It will have X & Y coordinates with tool sizes viewable in any text editor. This is the file that governs your finished hole sizes and locations.

A Sample Excellon File:


Electrical Test

Continuity and Isolation testing of Circuit Boards. A netlist is created from the customer supplied gerber files and then electrically compared to the finished pcb. The soldermask layer acts as the mask to determine what can be tested. In general, endpoints of all of the nets are programmed for testing unless they are covered in soldermask. The standard testing parameters used are 100 Volts, Isolation Resistance of 10 M Ohms, Isolation Distance 0.050", and Continuity Resistance of 50 Ohms.

Sunstone Circuits employs two methods to conduct electrical test 1) flying probe (fixtureless) and 2) the bed of nails grid tester (requires a fixture). We may choose to test your boards either way. We recommend testing for all surface mount boards and multilayer orders.

It's not possible to accurately test boards that have silkscreen on pads. It is highly recommended that the silkscreen clip option be selected on electrically tested orders.

Embedded Traces

A trace that is surrounded by ground fill. These types of features have different manufacturing characteristics that do not behave as traces grouped in tight runs do. The etching of this type of feature is slower and as a result we request that a minimum of 0.010" spacing be used from trace to ground fill.

Excellon Drill File

See drill file

Files: Gerber

TThe Industry standard format for files used to generate artwork necessary for circuit board imaging. Sunstone's preferred Gerber format is RS274X, which places aperture information in the header of each gerber layer file (see Aperture information).

If files are not saved in RS274X, Sunstone will need one aperture list sent with the files.

When your software outputs more than one aperture list we may place your order on hold until we receive your instructions or correctly formatted files. It is recommended you download Pentalogix Viewmate, a file viewer that will allow you to preview your Gerber files as they are interpreted by our CAM software.

Files: Eagle

We can output the Gerber RS274X and Excellon Drill files from your Eagle.brd file at no additional charge. It is recommended you download Pentalogix Viewmate. It is a viewer that will allow you to preview the production files as interpreted by our plotting software.

Files: Protel

You can output the Gerber RS274X and Excellon Drill files from your Protel file at no additional charge. It is recommended you download Pentalogix Viewmate. It is a viewer that will allow you to preview the production files as interpreted by our plotting software.

File Submission

Files that are not specifically used in your design, and or an incomplete file set can add delays to your order. Insure that your submitted files are complete and do not contain extraneous files. When ordering a 4-layer board with Soldermask and one side Silkscreen, send in 7 gerber layers and an excellon drill file.


A patterned arrangement of printed circuitry and components that utilizes flexible base material with or without flexible cover lay.

Flexible circuit boards are often used as connectors in various applications where flexibility, space savings, or production constraints make the use of rigid circuit boards impossible. In addition to cameras, a common application of flexible circuits is in computer keyboard manufacturing; most keyboards made today use flex circuits for the switch matrix. Flexible circuits are available through the Custom Quote Service.

Gold Fingers (Linear Inches)

EEdge connectors electroplated with nickel (Ni) and gold (Au), good for wear type applications available for Full-Featured and Custom Quote Product. (Approx. 200 u" Ni / Min. 30 u" Au). Utilizing industry standard tie-bar plating protocol to allow electro plating of Ni and Au after etching. Price is calculated on the distance (linear inches) between the outside edges of the outermost connector contacts.

Individual Route

Cutting of the circuit board to match the outline layer provided. There must be a continuous board outline for our Quickturn product. Boards will NOT be delivered in a multi-board panel for automated assembly.

Internal Signal Layers

Routing layers composed of signal traces that are contained below the surface layers of your board. These layers are connected to the surface layers by plated through holes and/or vias.

We may remove any pads that are not connected to traces on your internal signal layers in order to expedite the imaging process on Full-Featured Orders. Many customers upload their files with these non-functional pads already removed, which expedites the tooling process. If for any reason, you do not wish these pads to be removed, please clarify this by listing it as a drawing note, or in a "readme" file.

Inspection Guidelines

Our inspections and conformance criteria are setup based upon "IPC-A-600 Class II." The inspection methods that we use to insure the quality of your orders can be accessed on our inspections guidelines page.

Manufacturing Capabilities

The limitations of a specific manufacturing process that is aimed at consistently producing product with a sufficiently high yield. These specific capabilities may be different at all manufacturing locations, please follow these in the design portion of your project to help avoid problems down the road.


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