omegameter An instrument used to measure ionic residues on the surface of PCB assemblies. The measurement is taken by immersing the assembly into a predetermined volume of a water-alcohol mixture with a known high resistivity. The instrument records and measures the drop of resistivity due to ionic residue over a specified period of time. Also see ionograph.

onsertion Colloquial expression referring to the placement of components on the surface of a circuit board, as in surface mount technology.

open A fault that causes two electrically connected points to become separated. It is an area of a bare PCB which, due either to over-etching or fabrication related problems, interrupts the intended design on the circuit. It also may be caused by insufficient solder from wicking or gross coplanarity of the lead at the point of connection between the PCB and SMC. Also referred to as an open joint.

organic Relates to the chemistry of carbon compounds. The majority of carbon-containing compounds fall into the organic chemistry class. An example of a carbon compound that is not considered organic is carbon dioxide gas.

organic halides Organic compounds containing halogens.

organic solder preservative (OSP) Layers of organic coatings applied to entire board surfaces to prevent oxidation and to retain solderability.

ounces of copper This refers to the thickness of copper foil on the surface of the laminate: ½ ounce copper, 1 ounce copper, and 2 ounce copper are common thicknesses. One ounce copper foil contains 1 ounce of copper per square foot of foil. The foil on the surface of laminate may be designated for the copper thickness on both sides by: 1/1 = 1 ounce, two sides; 2/2 = 2 ounces, two sides; and 2/1 = 2 ounces on one side and 1 ounce on the other side. ½ 0z. = 0.72 mil = 0.00072″; 1 0z. = 1.44 mils = 0.00144″; 2 0z. = 2.88 mils = 0.00288″.

outer lead bonding Process of bonding the terminations of a tape automated bond integrated circuit to a circuit board.

outgassing De-aeration or other gaseous emission from a PCB assembly (printed board, component, or connector) when exposed to a reduced pressure or heat, or both.

overhang (1) PCB: Increase in printed circuit conductor width caused by plating buildup or by undercutting during etching. (2) Assembly: Refers to a lead or leadless termination that extends beyond the pad of the PCB.

oxidation Oxidation can be considered in two senses. In the first and narrow sense, oxidation can be considered the simple addition of oxygen to a metal, e.g., the addition of atmospheric oxygen to iron to familiar rust. In the broader chemical sense, oxidation is any process where a metal loses electrons and is converted from metal with zero electrical charge, to a metallic ion with a positive charge.

oxygen analyzer An instrument that detects and calculates in ppm the amount of oxygen in a given volume.

oxygen inhibition An undesirable side reaction occurring when UV ink is irradiated (during UV curing processes) and the initiator breaks down into the reactive species needed to polymerize the ink binder.