SMT: Glossary Of Terms - Def Stage
Glossary of terms
Dewetting
A condition that occurs when molten solder has coated a surface and then receded, leaving irregularly shaped mounds of solder separated by areas covered with a thin solder film. Voids may also be seen in the dewetted areas. Dewetting is difficult to identity since solder can be wetted at some locations and base metal may be exposed at other locations.
DIP, Dual In-Line Package
A package intended for through-hole mounting that has two rows of leads extending at right angles from the base with standard spacing between leads and row.
Disturbed Solder Joint
A condition that results from motion between the joined members during solder solidification. Disturbed solder joints exhibit an irregular surface appearance although they may also lustrous.
Double sided assembly
A packaging and interconnection structure with components mounted on both the primary and secondary sides.
Drawbridging/ Tombstoning
A solder open condition during reflow in which chip resistors and capacitor resemble a draw bridge.
Dual-wave Soldering
A wave soldering process that uses a turbulent wave with a subsequent laminar wave. The turbulent wave ensures complete solder coverage in tight areas and the laminar wave removes bridges and icicles. Designed for soldering surface mount devices glues to the bottom of the board.
Eutectic
The alloy of two or more metals that has a lower melting point than either of its constituents. Eutectic alloys, when heated, transform directly from a solid to a liquid and do not show pasty regions.
Fault profile
A description of the type and frequency of electrical faults most likely to be found on a populated PCB.
Fillet
The configuration of solder around a component lead and land. A blending or rounding of interconnecting conductors or leads which eliminates sharp corners.
Fine Pitch Component Packages
Surface mount component packages with lead pitches less than 50 mil, more commonly 25 mils and under. fine pitch packages generally require vision system for accurate placement and lower solder paste prints than 50 mil pitch packages.
First Article
A part or assembly manufactured before the start of a production run to determine whether processes are capable of fulfilling end product requirement.
Flatpack
An integrated circuit package with gull wing or flat leads on two or four sides, normally on 0.050†centers, which are parallel to the component body. Lower pitches are generally referred to as fine pitch packages.
Flip-Chip Technology
A chip-on-board technology in which the silicon die is inverted and mounted directly to the printed wiring board. Solder is deposited on the bonding pads in vacuum. When inverted, they make contact with the corresponding board lands and the die rests directly above the board surface. It provides the ultimate in densification also known as C4, controlled collapse chip connection.
Flux
A chemically/physically active formation that is capable of enabling and promoting the wetting of metals with solder
Flux Residue
Particles of flux materials remaining on the PCB after soldering and cooling.
Flux solder connection
A solder joint characterized by entrapped flux that often causes high electrical resistance.
Flux, RMA
An organic acid of mildly activated rosin dissolved in isopropyl alcohol, which attacks and removes oxides from the metals to be soldered.
FPT, Fine pitch technology
The term used to describe the assembly technology for those IC packages having lead spacing of generally 0.65 mm(0.0256â€) or less .
Functional Test
An electrical test of an entire assembly that simulates the intended function of the product.
