Hints on Soldering Inspection Techniques:
Terminology used in Soldering as defined in NASA-STD 8739.3:
Article- A unit of hardware or any portion thereof required by the contract.
Assembly- A functional subdivision of a component, consisting of parts or subassemblies that perform functions necessary for the operation of the component as a whole.
Axial lead- Lead wire extending from a component or module body along its longitudinal axis.
Bifurcated (split) Terminal- A terminal with a slot or split opening in which conductors are placed before soldering.
Birdcage- A defect in stranded wire where the strands in the stripped portion between the covering of an insulated conductor and a soldered connection (or an end-tinned lead) have separated from the normal lay of the strands.
Blister- Raised areas on the surface of the laminate caused by the pressure of volatile substances entrapped within the laminate.
Blow Hole- A cavity in the solder surface whose opening has an irregular and jagged form, without a smooth surface.
Bridging- A buildup of solder between components, conductors, and/or base substrate forming an undesired conductive path.
Certification- The act of verifying and documenting that personnel have completed required training and have demonstrated specified proficiency and have met other specified requirements.
Circumferential Separation- A crack or void in the plating extending around the entire circumference of a PTH, or in the solder fillet around the conductor, in the solder fillet around an eyelet, or at the interface between a solder fillet and a land.
Cold Flow- Movement of insulation (e.g. Teflon) caused by pressure.
Cold Solder Connection- A solder connection exhibiting poor wetting and a grayish, porous appearance due to insufficient heat, inadequate cleaning before to soldering, or excessive impurities in the solder.
Component- A functional subdivision of a system, generally a self-contained combination of assemblies performing a function necessary for the system's operation.
Conduction Soldering- Method of soldering which employs a soldering iron for transfer of heat to the soldering area.
Conductor- A lead, solid or stranded, or printed wiring path serving as an electrical connection.
Conformal Coating- A thin electrically nonconductive protective coating that conforms to the configuration of the covered assembly.
Connection- An electrical termination that was soldered. A solder joint.
Construction Analysis- The process of destructively disassembling, testing, and inspecting a device for the purpose of determining conformance with applicable design, process, and workmanship requirements. This process is also known as Destructive Physical Analysis (DPA).
Contaminant- An impurity or foreign substance present in a material that affects one or more properties of the material. A contaminant may be either ionic or nonionic. An ionic, or polar compound, forms free ions when dissolved in water, making the water a more conductive path. A non-ionic substance does not form free ions, nor increase the water's conductivity. Ionic contaminants are usually processing residue such as flux activators, finger prints, and etching or plating salts.
Crazing- An internal condition occurring in the laminate base material in which the glass fibers are separated from the resin.
Cup Terminal- A hollow, cylindrical terminal to accommodate one or more conductors.
Delamination- A separation between plies within a base material or any planar separation within a multilayer PWB.
Deviation- A specific authorization, granted before the fact, to depart from a particular requirement of specifications or related documents.
Dewetting- The condition in a soldered area in which the liquid solder has not adhered intimately, but has receded, characterized by an abrupt boundary between solder and conductor, or solder and terminal/termination area leaving irregularly shaped mounds of solder separated by areas covered with a thin solder film.
Disturbed Solder Joint- Unsatisfactory connection resulting from relative motion between the conductor and termination during solidification of the solder.
Dross- Oxide and other contaminants that form on the surface of molten solder.
Egress- An opening that provides a pathway from the interior of an enclosed space.
Encapsulating Compound- An electrically nonconductive compound used to completely enclose and fill in voids between electrical components or parts.
Excessive Solder Joint- Unsatisfactory solder connection wherein the solder obscures the configuration of the connection.
Eyelet- A hollow tube inserted in a terminal or PWB to provide mechanical support for component leads or for electrical connection.
Flatpack- A part with two straight rows of leads (normally on 0.050 inch centers) that are parallel to the part body.
Fillet- A smooth concave buildup of material between two surfaces; e.g., a fillet of solder between a conductor and a solder pad or terminal.
Flux- A chemically-active compound which, when heated, removes minor surface oxidation, minimizes oxidation of the basis metal, and promotes the formation of an intermetallic layer between solder and basis metal.
Fractured Solder Joint- A joint showing evidence of cracking, resulting from movement between the conductor and termination, after solidification of the solder.
Haloing- Mechanically-induced fracturing or delaminating on or below the surface of the base.
PWB material- it is usually exhibited by a light area around holes, other machined areas, or both.
Hook Terminal- A terminal formed in a hook shape.
Insufficient Solder Connection- A solder connection characterized by incomplete coverage of one or more of the metal surfaces being joined or by incomplete solder fillets.
Interfacial Connection- A conductor that connects conductive patterns between opposite sides of a PWB.
Interlayer Connection- An electrical connection between conductive patterns in different layers of a PWB.
Joint- A solder joint; a termination.
Lifted Land- A land that has lifted or separated from the base material, whether or not any resin is lifted with the land.
Mission Essential Support Equipment- Equipment used in a closed loop with the system, where failure of this equipment would degrade the mission or imperil personnel. This category includes items of ground support equipment whose functions are necessary to support the count down phase and those items of ground support equipment used in pre-count down phases whose problems can create a safety hazard, cause damage to flight hardware, or inability to detect a problem on the flight hardware.
Measling- Discrete white spots below the surface of the base material, usually caused by moisture, pressure, and/or thermally induced stress.
Nick- A cut or notch on a conductor.
Nonwetting- A condition whereby a surface has contacted molten solder, but the solder has not adhered to all of the surface; basis metal remains exposed.
Offgassing- The release of volatile parts from a substance when placed in a vacuum environment that may affect crew members.
Outgassing- The release of volatile parts from a substance when placed in a vacuum environment.
Overheated Joint- An unsatisfactory solder joint, characterized by rough solder surface; dull, chalky, grainy, porous or pitted.
Pad- A portion of a conductive pattern used as a soldering area. Also called a land.
Part- An element of a component, assembly, or subassembly that is not normally subject to further subdivision or disassembly without destruction of designed use.
Part Lead- The solid conductor attached to a part.
Pierced (Perforated) Terminal- A terminal containing a hole through which conductors are placed before soldering.
Pinhole- A solder connection with a small hole penetrating from the surface of the solder to a void of indeterminate size within the solder connection.
Pit- A relatively small recess in the solder surface, the bottom of which is visible from all angles of vision.
Plated-Through-Hole- A plated-through hole is one formed by a deposition of metal on the inside surface of a through-hole. Also known as a supported hole. The configuration is used to provide additional mechanical strength to the soldered termination or to provide an electrical interconnection on a multilayer PWB.
Porous Solder Joint- A joint having a grainy or gritty surface.
Potting Compound- An electrically nonconductive compound used to partially encapsulate or for a filler between parts, conductors, or assemblies.
Printed Wiring Assembly- The PWA consists of the PWB, components, and associated hardware and materials.
Printed Wiring Board- A pattern of conductors printed (screened) onto the surface of an insulating base to provide interconnection for parts.
Radial Lead- Lead wire extending from a component or module body along its latitudinal axis.
Radial Split- A crack or other separation in the flange of an eyelet or other circular connector, which extends outward from the center. Such cracking is usually the result of swaging or other setting process as the item is embraced in a printed wiring board.
Repair- Operations performed on a nonconforming article to place it in usable condition. Repair is distinguished from rework in that alternate processes rather than reprocessing are employed.
Resistance Soldering- Method of soldering by passing a current between two electrodes through the area to be soldered.
Rework- The reprocessing of articles or material that will make it conform to drawings, specifications, and contract.
Rosin Solder Joint- Unsatisfactory connection that has entrapped rosin flux. This entrapment is usually due to insufficient heat or insufficient time at soldering temperature, or both, not enabling the rosin to rise to the surface of the solder. This results in insufficient bonding and/or high electrical resistance.
Solder- A nonferrous, fusible metallic alloy used to join metallic surfaces.
Solderability- The property of a surface that allows it to be wetted by a molten solder.
Solder Connection- An electrical/mechanical connection that employs solder for the joining of two or more metal surfaces.
Solder Mask- Coating material used to mask or protect selected areas of a pattern from the action of an etchant, solder, or plating.
Solder Pad- Termination area on a printed wiring conductor.
Solder Spatter- Extraneous irregular-shape solder fragments.
Solder Spike- A cone shaped peak or sharp point of solder usually formed by the premature cooling and solidification of solder on removal of the heat source.
Soldering- The process of joining clean metallic surfaces through the use of solder without direct fusion of the base metals.
Staking Compound- An electrically nonconductive adhesive material used for additional support after a component has been attached by mechanical or soldering process.
Straight Pin Terminal- A round post-type smooth terminal, with no grooves.
Straight-Through Termination- A conductor termination extending through a PWB without subsequent forming of the lead.
Stress Relief- The formed portion of a conductor that provides sufficient length to minimize stress between terminations.
Stud Termination- An unbendable conductor termination extending through a PWB.
Supplier- In-house NASA, NASA contractors, and subtier contractors.
Surface Mounting- The electrical connection of components to the surface of a conductive pattern that does not utilize part holes.
Supportive Hole- A hole in a printed board that has its inside surface plated or otherwise reinforced.
Terminal- A tie point device used for making electrical connection.
Termination- The point at which electrical conductors are joined.
Termination Area- A conductive surface on a PWB used for making electrical connections (also referred to as a solder pad).
Thermal Shunt- A device with good heat dissipation characteristics used to conduct heat away from an article being soldered.
Tinning- The coating of a surface with a uniform layer of solder.
Tubelet- A tubular metal part. Its ends may or may not be flared.
Turret Terminal- A round post-type grooved stud around which conductors are fastened before soldering.
Unsupported Hole- A hole containing no plating or other type of conductive reinforcement.
Via- A PTH used as an interlayer connection, but in which there is no intention to insert a component or other reinforcing material.
Void- A space enclosed on all sides by the solder.
Wave Soldering- A process wherein PWAs are brought in contact with the surface of continuously flowing and circulating solder.
Wetting- Flow and adhesion of a liquid to a solid surface, characterized by smooth, even edges, and a low dihedral angle.
Wicking- A flow of molten solder, flux, or cleaning solution by capillary action.