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Glossary

Glossary

Array - Do you know the difference between an array and a panel? An array is a group of elements or circuits (or circuit boards) arranged in rows and columns on a base material. A production panel may be several arrays on a rectangular sheet of base material or metal-clad material of predetermined size that is used for the processing of PCBs.

Bare Board Test - A bare board is electrically tested to ensure that it reflects the original design as intended. The test is typically a series of continuity and insulation tests.

Copper Thickness - For many decades we have been measuring the copper thickness on a printed circuit board in ounces (oz). This is the resulting thickness when 1 oz of copper is pressed flat and spread evenly over a one square foot area. This works out at 1.37 mils (1.37 thousandths of an inch). For those who prefer metric measurements, 0.00137 inch equals 0.0347mm or 34.79 microns. Most PCBs are made to 1 ounce copper thickness. At BPC Electronics, if we are not given sepecific information, we will assume 1 oz when quoting and building your design.

Deburring - Process of removing burrs after PCB drilling.

ENIG - Stands for Electroless Nickel Immersion Gold. Approximately 100-150μ” of nickel is applied directly to the bare copper on the PCB. 2-5μ”of gold is then applied on top of the nickel via a chemical process. Because the gold bonds to the nickel by replacing the outer nickel molecules, the resulting finish is extremely flat and cannot be plated any thicker than approximately 5-6μ”.                                      Like all gold finishes, 100-200μ” of nickel is used as a barrier to prevent the copper from migrating into the gold. Because the finish is plated using current rather than chemicals, the surface is relatively rough. There are hardeners added to the chemistry making the finish very durable. It is generally used for edge fingers or keypad based applications where high durabilty is desired. Typical gold thicknesses for this finish range between 7 to 50μ”. The end result is excellent solderability, a non tarnish finish, but at a higher cost.

FR4 - Is a Flame Retardant laminate made from woven glass fibre material impregnated with epoxy resin.

Ground Plane - A conductor layer, or portion of a conductor layer, used as a common reference point for circuit returns, shielding or heat sinking.

Hot Air Solder Levelling (HASL) - This is where the PCB is typically dipped into a bath of molten solder such that all exposed copper surfaces are covered by solder. Excess solder is removed by scraping the PCB with hot air knives. At BPC Electronics, we use lead free solder to comply with RoHS regulations.

Interstitial Via Hole - This is a plated through-hole which connects two or more conducting layers in a multilayer PCB, but not extending fully through all of the layers of base material comprising the board. (See Via Below).

Keying Slot - Also known as a polarising slot, is a slot in a PCB which polarizes it, thereby permitting it to be plugged into its mating receptacle with pins properly aligned, but preventing it from being reversed or plugged into any other receptacle.

Legend - Not the Will Smith film or an old soccer star, but a format of lettering or symbols on the printed circuit board; e.g. part number, serial number, component locations. Different colours tell you where the different components sit on the board.

Metal Core PCBs (MCPCB) - BPC Electronics offer a full range of LED products through their lighting division, EVL Design. Standard FR4 material is not suitable for LED products because of the problems of hea dissipation. The solution is metal core PCBs. BPC Electronics LLP manufacture metal backed circuit boards by bonding a metal plate of various thicknesses to a range of high thermally dissipating dielectrics, allowing the heat to be spread across the entire area of the PCB and through to the metal base efficiently and without locking heat into isolated areas. With metal core PCB materials you can increase the life of your LEDs with better heat dissipation.

NC Drill - NC stands for numeric control. Our NC drill machines are used to drill holes at exact locations on the PCB specified in the NC Drill File.

Organic Solderability Preservative (OSP) - This is a method for coating printed circuit boards. It uses a water-based organic compound that selectively bonds to copper and provides an organometallic layer that protects the copper during soldering.

Plated Through Hole (PTH) - Through holes become plated-through holes (PTH) in order for the components to make contact with the required conductive layers. Plated-through holes are no longer required with SMT boards for making the component connections, but are still used for making interconnections between the layers and in this role are more usually called vias (see below).

Quick Turnaround - Involves exceptional delivery times, 48 to 72 hours being the most common.

Resist - This is the coating material used to mask or to protect selected areas of a pattern from the action of, solder, an etchant or plating. So a solder resist is a coating which masks and insulates portions of a PCB where solder is not required.

Single sided PCBs have been around since the late 1950s and still dominate the world market in terms of quantities produced. They are easily designed and manufactured, and are generally regarded as the most cost effective PCB in the electronics industry.

Tooling Holes - Have you ever wondered what those round holes on the edges of a PCB are for?These are tooling holes, which are holes placed on a PCB or a panel of PCBs for registration and hold-down purposes during the manufacturing process.

UL - This is the abbreviation for Underwriters Laboratory, a standards agency, whose approvals are recognised worldwide.

Via - This is a conductive surface hole that connects an outer layer with an inner layer of a multi layer board without penetrating the entire board. It's a plated-through hole used as a through connection, but in which there is no intention to insert a component lead or other reinforcing material.

Wave Soldering - This is an automated process in which PCBs are loaded into a conveyor which moves over a vat of molten solder. As the conveyor belt moves, a wave is created with a pump. The bottom of the board hits the "crest" of the wave, and the solder sticks by means of capillary action.

X Axis - The horizontal measurement on a PCB.

Y Axis - The vertical measurement on a PCB.

Z Axis Drive - PCB milling uses a two or three-axis mechanical milling system to mill away the copper foil from the substrate. A PCB milling machine receives commands from the host software that controls the position of the milling head in the x, y, and z axis. The relevant data is extracted from files generated in the PCB design software and stored in Gerber file format.

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