|
Saponifier:
An alkaline chemical added to water to improve its ability
to dissolve rosin flux residues.
Screen Printing:
The transfer of a pattern onto a surface by forcing a suitable
material through a screen with a squeegee.
Self-Alignment:
The tendency of certain slightly misaligned components (during
placement) to self-align with respect to their land patterns
during reflow soldering. It occurs due to the surface tension
of molten solder.
Self-Planarizing Head:
A mechanism integrated into the head of an outer lead bonder
that allows the bottom surface of the thermode blades to adjust
to the plane defined by the surface of the substrate.
Shadowing:
The failure of molten solder to wet the leads of surface mount
components due to their location on the board during wave
soldering or the cause for insufficient heating of surface
mount components due to their location on the board during
infrared reflow soldering.
Shear Strength:
The force required to shear apart adhesive-bonded and cured
materials and/or components.
Shipping Tube:
In reference to molded carrier ring or TAB components in slide
carriers, it is the tube in which components are vertically
stacked for shipping and feeding into excise and form feeders.
Short:
An unwanted connection between conductor paths.
Silver
chromate test:
A qualitative check for the presence of ionic halides in RMA
fluxes.
Single Layer TAB Tape:
Tape constructed with a single conductive metal layer, typically
70 micron thick copper. This type of tape is generally used
in low lead count applications, and is not commonly seen.
Single-Layer Board:
A printed circuit board that contains metallized conductors
on one side of the board only.
Slide Carrier:
A carrier for handling singulated TAB components. The
slide carrier looks and functions similarly to the outer ring
of a molded carrier ring component. It serves to facilitate
component test, burn-in, and mechanical registration in a
set of tooling. Slide carriers come in three basic sizes,
35mm, 48mm, and 70mm.
Slump:
A spreading of material (solder paste, adhesive,thick film,
etc.) after stencil printing (or dispence) but before curing.
Small Outline Integrated Circuit (SOIC):
An integrated circuit surface mount package with two parallel
rows of gull-wing leads.
Small Outline J-Leaded (SOJ):
An integrated circuit surface mount package with two parallel
rows of J-leads.
Small Outline Transistor (SOT):
Discrete surface mount transistors with a molded plastic outline
that serve small and medium power applications.
Snapback:
The return of a stencil to normal (flat plane) after its deflection
by a squeegee across its surface.
Solder Balls:
Small spheres of solder adhering to the laminate, mask, or
conductor surfaces usually after wave or reflow soldering.
Solder Bridging:
Solder paste or solder on two or more adjacent pads that come
into contact to form a conductive path (forming a bridge).
Solder Bumps:
Round solder balls bonded to the pads of components and subsequently
used for face-down bonding techniques.
Solder Connection:
The joining of two or more metal parts by means of an electrical
or mechanical connection.
Solder Mask:
A dielectric material used to cover the entire surface (except
where the joints are to be formed) of the PCB primarily to
protect the circuitry from environmental damage. Solder mask
also helps to reduce bridging.
Solder Paste:
A homogenous and kinetically stable mixture of minute spherical
solder particles, flux, solvents and binder that is screen
printed onto the printed circuit board and then reflowed to
form the solder joints.
Solder Powder:
The solder alloy in solder paste exists in the form of powder.
Solder powder is the major ingredient that affects the printability
of the paste and the quality of the solder joint.
Solder Thickness:
The amount of solder deposited on a pad for reflow. Optimum
thickness will vary with pad size and pitch, but must be consistent
across a single bonding site.
Solder Wicking:
The capillary movement of molten solder onto a pad or component
lead or between metal surfaces, such as strands of wire.
Solder:
A low melting point alloy, usually of lead (Pb) and tin (Sn),
that can wet copper, conduct current, and mechanically join
conductors.
Solderability:
The ability of a conductor to be wetted by solder and to form
a strong bond with the solder.
Soldering:
A process of joining metallic surfaces with solder, without
melting the base material.
Solids Content:
The metal powder content as a percentage of the mass of the
wet solder paste, or the percentage by weight of rosin in
a flux formulation.
Solvent Cleaning:
A cleaning method employing chlorinated and fluorinated hydrocarbon
liquids.
Solvent Extraction:
The removal of one or more components from a liquid mixture
by intimate contact with a secondary liquid that is nearly
insoluble in the first liquid and which dissolves the impurities
and not the substance to be purified.
Solvent:
A solution capable of dissolving a solute.
SPC:
The use of statistical techniques to analyze the outputs of
processes with the results guiding actions taken to adjust
and/or maintain a state of quality control.
Specific Heat:
The ratio of a material's thermal capacity to that of water
at 15ºC.
Spherically Compliant Suspension:
A patented mechanism based on a four-bar linkage that can
be integrated into an outer lead bonder to have self-planarization
of the thermode head to the substrate. This mechanism has
been developed and patented by Universal Instruments Corporation.
Splice:
A strip of material used to join two pieces of tape. Splices
are used to connect strips of TAB
tape when handled in continuous tape format.
Spread:
The distance a substance (e.g., an adhesive) moves after it
has been applied at ambient conditions.
Sprocket Holes:
Holes along both edges of TAB
tape used for handling, indexing, and in some cases, registration.
Sprocket Pitch:
The center to center distance of two adjacent sprocket holes.
Squeegee:
A rubber or metal blade used in printing to wipe solder paste
(or glue) across the stencil's face, forcing the material
through the patterned apertures and onto the PCB.
Static Flex:
Flex circuits that are bent during installation, but do not
undergo any further movement in an assembly.
Statistical
process control:
(see SPC)
Stencil Printing:
Deposition of a specific material, such as solder paste, using
a stencil.
Stencil:
A metal mask in which patterns or apertures matching the component
locations on the PCB are made so a suitable material can be
forced through the apertures by a squeegee onto a substrate.
Common materials are stainless steel and brass.
Storage
life:
The period that an adhesive can be stored and remain viable
for use.
Stress Corrosion:
The gradual deterioration of the mechanical properties of
a material, usually accompanied by crack propagation, and
caused by the acceleration of applied stress. This phenomenon
usually occurs under high humidity conditions.
Substrate Geometry:
Substrate dimensions, typically dimensions critical to implement
a successful bonding process, including the following: board
size, bonding pad layout and dimensions, solder thickness,
adjacent components, planarity, fiducial shape and dimensions,
and board thickness and construction.
Surface Insulation Resistance (SIR):
The electrical resistance of an insulating material between
a pair of contacts or conductors. SIR is determined under
specified environmental and electrical conditions.
Surface Mount Device (SMD):
An active or passive device designed to be soldered to the
surface of the printed circuit board.
Surface Mount Technology (SMT):
A method of assembling printed circuit boards where the components
are mounted onto the surface of the board rather than being
inserted into holes in the board.
Surface Tension:
An effect of the forces of attraction between the molecules
on the surface of a liquid. Surface tension is the reason
water beads up better on the hood of your car when waxed versus
unwaxed. The wax increases the surface tension of the water,
and thus it beads up more readily.
Surfactant:
A chemical added to any substance to lower its surface tension.
Surftape:
A punched carrier for tape and reel packaging of surface mount
devices. It features a flexible, pressure-sensitive adhesive
base, negating the need for cover tape.
Suspension Brake:
A pneumatic clamp on the spherically compliant suspension
which can be used to lock the head in a given orientation.
Syringe:
A container for adhesive dispensing via its narrow opening.
|
