halide-free flux Flux that does not contain halides.

halides A compound containing fluorine, chlorine, bromine, iodine, or astatine. In soldering, these materials may be part of the flux system, mostly the activator. The residues of ionic halides are considered dangerous, and must be washed.

halo effect Minor delamination of substrate material, resist, or laminate around holes.

halogenated hydrocarbon An organic compound in which some, or all, of the hydrogen atoms linked to the carbon atoms are replaced by atoms of the halogen family. One of the largest uses for these compounds is as solvents.

halogens A group of elements similar in their properties and chemical activities. These elements, in order of decreasing activity, are fluorine, chlorine, bromine, and iodine.

haloing A condition existing in the base laminate of a PCB in the form of a light area around plated through holes or other machined areas on or below the surface of the laminate. It is localized delamination.

hard solder A high melting solder with a melting point above 1100°F.

hard water Water containing calcium carbonate, and other ions such as magnesium and iron that tend to form insoluble deposits. These minerals may collect on the inside of cleaning equipment, causing a scale that can clog piping.

hardener A catalyst added to a thermoset plastic to hasten curing. Also referred to as a curing agent.

hardware Shells, guide pins, polarizing pins, strain relief clamps, mounting screws, etc. that are attached to the PCB.

heat and pull Desoldering method using a soldering iron with a heater block attached, a solder pot or solder fountain, or a device that grasps, heats, and pulls the component leads to be removed.

heat management PCB design philosophy that ensures adequate heat dissipation. Also known as thermal design.

heat sink A method of conducting heat away from an area, usually a component die. May be internally or externally mounted to a package.

heated collet A method of soldering surface-mounted components using an electrically heated collet positioned over the component terminals so that solder under the terminals melts.

heaters, IR panels Radiant energy emitters that emit IR energy in the middle to far infrared region from a plane surface.

heel crack A crack in the solder fillet across the lead bond width in the heel area.

hermetic Sealing to be gas tight. The test for hermeticity is to observe leak rates when the object is filled with a gas, typically helium, and placed in a vacuum. A plastic encapsulation cannot be hermetic by definition because it allows gases to permeate.

hi rel A contraction of high reliability. Refers to products that are assembled and inspected under rigid standards, given extra testing and conditioning, and typically used in a military, space, or medical application.

high speed digital functional testing A test of microprocessor-based boards that incorporates a data compression method called signature analysis. The board itself can be used running at speed to provide the test stimulus. Each device is exercised and its response, or signature, is then compared to a known good board. This test method is most effective for bus oriented boards.

high reliability soldering A soldering technique whereby the probability of obtaining perfect metallic joining, product cleanliness, and optimum electrical conductivity without damage to components or equipment has been statistically proven.

high voltage testing Testing conducted at 40V or more.

hole breakout A condition in which a hole is not completely surrounded by the land.

hot air (solder) leveling (HASL) A process used in solder dipping of bare copper circuitry in which high-velocity air is used to blow solder clear from plated-through holes and to minimize solder thickness.

hot cracking A cracking of a metal or alloy upon freezing. In relation to solder, this can occur as a result of stresses developed in the solder joint by uneven cooling.

hot short Brittleness in a solder joint due to elevated temperature.

hot spot A small area on a circuit that is unable to dissipate the generated heat and therefore operates at an elevated temperature above the surrounding area.

hot tinning The application of a solderable coating by a molten solder/wetting process. Tinning is not limited to the application of pure tin, but can be achieved with any solder alloy.

hot vapor soldering Reflow soldering method using condensation inert heating as the heat transfer medium.

hot zone The part of a continuous furnace or kiln that is held at maximum temperature. Other zones are the preheat zone and cooling zone.

hybrid circuit A microcircuit consisting of elements that are fabricated directly on the substrate material in combination with discrete add-on components. Also known as hybrid assembly.

hydrocarbon Organic chemical compounds containing only hydrogen and carbon atoms.

hydroscopic A material that is capable of absorbing moisture from the air.