The amount of copper on a circuit pad between the edge of the drilled hole and the edge of the pad.

A via that connects an outer (surface) layer to one or more inner layers, but does not go all the way through the board.

A via that connects inner layers only and does not reach either surface of the board.

Plated or non-plated half-holes along the edge of the board, made by drilling a row of holes and then routing through their centers. Often used to solder one board directly onto another.

IPC Class 3 covers high-reliability electronic products where continued operation or performance on demand is critical (e.g., flight controls or life support). Building boards to this standard adds cost.

A process for drilling only partway through the thickness of the board.

A specified thickness for the insulating layers between a signal layer and a power or ground plane.

Matching material properties with trace dimensions and locations to create a specific electrical impedance for a signal. Impedance is also affected by the dielectric (the distance between layers).

The copper thickness required on inner layer cores, typically 1 oz.

The ounces of copper per square foot on the outer layers. Specify this as “finished” copper weight, typically 1 oz.

A flat-bottomed cylindrical recess machined around a hole so a screw head sits flush with the surface. Can be plated or non-plated.

A cone-shaped (beveled) recess machined around a hole so a flat-head screw sits flush with the surface. Can be plated or non-plated.

A code added to the PCB to identify when the board was manufactured.

Design Rule Check (DRC) is a software check of the design against a set of rules, to help ensure the finished board will function properly and can be manufactured.

A process that reduces the thickness of the material along the board edges. Typically used when a thicker board needs to slide into card guides.

Plating the edges of the board itself with copper and a surface finish such as ENIG.

Testing the circuitry for shorts and opens to ensure the PCB matches the net list (circuitry) in the Gerber data you supplied.

Electroless Nickel Immersion Gold (ENIG) is a RoHS-compliant surface finish with a thin layer of gold over nickel. A good choice for HDI PCBs, and the standard finish at Eagle Tech.

A document or print that provides all the details needed to manufacture the PCB, such as board size, drill sizes, solder mask and silkscreen type and color, laminate type, and overall board thickness.

A filled via has material applied into the hole with the intent of fully penetrating and encapsulating the hole. A plugged via has material applied with the intent of only partially penetrating the hole, from one or both sides of the board.

The total thickness of the board, including all plating and final finishes. Typical tolerance for a .062" board is ±.006".

Software files generated during PCB layout that are needed to build the board. Eagle Tech prefers Gerber RS-274X format with Excellon drill files.

Selective hard gold plating on the fingers where surface contact makes the electrical connection, typically along the board edge on both top and bottom. Eagle Tech bevels gold fingers unless otherwise specified, and does not bevel solder fingers unless the customer specifies it. Our standard bevel is 30 degrees, leaving a .030" edge (±.005") on a .062" board.

Hot Air Solder Leveling (HASL) is a surface finish that applies 63/37 tin/lead solder to the board.

High Density Interconnect (HDI) boards are complex enough to require small features such as fine lines, buried, blind or micro vias, and high layer counts.

The base material the PCB is built on. FR4 is the most common.

A small, laser-drilled blind or buried via. IPC defines it by an aspect ratio of 1:1 or less and a depth of .010" (0.25 mm) or less; it is still commonly described as a hole .006" or less in diameter. A costly process, so use it only when your design requires it.

The minimum distance between pad centers. Used to determine the cost and technology needed for SMT components.

The list of connections on a PCB, derived from its schematic. Used to electrically test the PCB and ensure it matches the intended circuit pattern.

Non-Recurring Engineering (NRE), also known as tooling, covers the industry-standard charges for initial setup and for making the tools and files to run your PCB. Eagle Tech never charges NRE or tooling.

Conductive metal on the surface or inner layers of a PCB, often with a drilled hole for connections between layers or for inserting through-hole components.

The industry-standard amount of copper plated in holes is .001" (25.4 µm).

Elongated holes, used for component placement, plated with copper and a surface finish such as ENIG.

RoHS (Restriction of Hazardous Substances) is a directive developed to protect the environment. Its main effect on PCB processing is eliminating lead on boards that must meet the standard.

A way to supply several PCBs connected by breakaway tabs instead of as single boards. Assembly is more efficient because components can be loaded on more than one board at a time. Boards are separated after assembly using route-and-retain tabs or scoring (a V-groove cut).

A diagram that shows the design of a PCB: the circuit, all the components used on the board, and all the connections between them.

A V-groove cut into both the top and bottom of the board so boards can be snapped apart after assembly.

Printed reference characters that show part locations. Also known as legend or component designators. White is the industry standard and lowest cost; black, yellow and red are also available.

The smallest hole on the board after plating, in mils. Also known as minimum finished hole size.

Liquid Photo-Imageable (LPI) solder mask is the protective coating over the copper circuitry that prevents solder bridges.

The color of the solder mask covering the PCB. Green is the industry standard and lowest cost; red, black, blue and clear are also available.

The final coating on exposed copper. Options include:

• ENIG — 3–10 micro-inches of immersion gold over electroless nickel. The standard surface finish at Eagle Tech.
• HASL — Hot Air Solder Leveling with 63/37 tin/lead solder.
• Immersion Silver — 12–15 micro-inches of silver plated directly over copper.
• Hard Gold — electrolytic gold plating.
• Soft Gold — 99.9% pure, 30–100 micro-inches of gold (wire-bondable gold).

The width and spacing of the metal circuitry on a PCB. Also known as trace and air gap.

Underwriters Laboratories (UL) provides safety ratings for PCBs. Eagle Tech holds a UL 94V-0 flammability rating, UL file number E90190.

A plated hole that makes an electrical connection between different layers of the board.

Via-in-pad (VIP) is a via (through, blind or buried) that is drilled, copper plated, then filled with a non-conductive epoxy (typically San-Ei Kagaku PHP-900 or Peters PP2795) and cured. The fill is planarized to create a flat surface and then plated over with copper. After this, the final through holes are drilled or further laminations (blind/buried vias) are done. These “invisible” holes are mostly used as solderable pads for SMT and BGA parts in HDI designs.