ACID
A hydrogen-containing substance which breaks down upon solution
in water to produce hydrogen ions. Acid strength is determined
by the quantity of hydrogen irons which are released into the
solution. The higher the concentration of hydrogen, the stronger
the acid.
ACTIVATED
The condition of a compound or mixture of compounds having
higher chemical activity than that normally found with the
compound or mixture.
An example
is the addition of an activator to rosin to increase fluxing
activity.
ALLOY
A combination of two or more metal elements. An example is
63% tin plus 37% lead, a solder alloy.
AUTO
IGNITION POINT
The temperature at which vapour from a material in air will
spontaneously burst into flame.
BOILING
POINT
The temperature of a liquid at which its vapour pressure is
equal to the pressure of the atmosphere surrounding the fluid.
BONDING
PAD
A metalized area at the end of a thin metal strip or on a
semiconductor to which the connection is made.
BRAZING
A group of joining processes wherein the filler metal is a
non ferrous metal or alloy whose melting point is typical
higher than 1000°F but lower than that of the metals or
alloys to be joined. At one extreme, brazing is similar to
soldering and is sometimes called hard soldering.
BURNOFF
Removal of electroless copper as a result of excessive current.
Usually occurs at edges of holes and causes plating failure
in the hole.
CAPILLARY
ACTION
The interaction between a liquid and a small diameter channel
or opening in a solid. Because of the physics involved, if
the liquid wets the sides of the solid channel, surface tension
will draw the liquid up into the capillary channel.
CATHODE
The negative pole of a plating cell. It is the physical entity
of the plating set-up at which positively charged ions leave
the plating solution. The cathode is normally the object of
the plating, i.e. a metal is deposited on the cathode.
CHEMICAL
STABILITY
That characteristic of a compound which describes its ability
to retain, without modification, its chemical properties over
a long period of time.
CIRCUIT
The interconnection of a number of devices in one or more
closed paths to perform a desired electrical or electronic
function.
COLD
SOLDER JOINT
Incorrectly made solder joint caused either by a soldering
iron with too low a tip temperature or by heating of the solder
rather than the metals to be joined.
COMPONENT
Any part placed on a printed circuit assembly i.e. resistor,
capacitor, diode.
COMPOUND
A homogenous pure substance composed of two or more essentially
different chemical elements, which are present in definite
proportions.
CONTAMINANT
An impurity or foreign substance present in a material or
on a surface which affects performance in the material or
circuit.
CORROSION
The most common kind of corrosion is that of rusting.This
is known as atmospheric corrosion wherein the oxygen of the
atmosphere reacts with the material in question. Most metals
with the exception of the noble metals such as gold, can be
oxidized by atmospheric oxygen.
CREEP
STRENGTH
A characteristic of a material which describes its strength
and resistance to elongation i.e. stretching at low loads.
This characteristic can be measured either as the load to
fracture the sample at a given temperature, or the load that
will produce a given percent of stretch, or elongation, at
a given temperature.
DEWETTING
A condition which results 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,
base metal is not exposed.
DIP
SOLDERING
The process of soldering all components on a board at one
time by dipping the board in a solder pot. The board is not
dipped deeply enough to immerse components.
DROSS
Metal oxides and other entrapped impurities which float in
or on the surface of a molten metal bath. In the case of solder,
it would include the oxides of lead and tin, in addition to
non-metallic impurities such as flux residues that were dragged
into the solder bath, and oxides of any metal impurities found
in the solder.
ELEMENT
A substance which cannot be decomposed or otherwise modified
by ordinary types of chemical processes. Neither can an element
be made by chemical union.
EUTECTIC
When applied to an alloy, eutectic refers to the composition
of an alloy which has the lowest melting pint of a series.
For example in the tin/lead system, Sn63/PB37 is the eutectic.
This is the alloy composition of all those in the Sn/Pb system
which has the lowest liquidus.
EVAPORATION
A physical process by which a liquid loses material to the
atmosphere surrounding it. Evaporation is caused by the motion
of the molecules of the liquid.
FLASH
POINT
Temperature at which a volatile liquid mixes with air in such
proportions as to produce flammable gaseous mixture. The mixture
will flash when exposed to a flame or spark but will not necessarily
continue to support combustion.
FLUX
As used in soldering, i.e. a material which cleans metal surfaces
of absorbed gases, oxide films and other tarnishes. The flux
also reduces the surface tension of the molten solder and
the metal to be soldering, so that the solder may flow and
wet the metal surface.
FREEZING
POINT
The temperature at which a previously molten material solidifies,
or becomes completely solid.
HOT
AIR LEVELLING
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 thicknesses.
ICICLING
The formation of solder spikes resulting from poor drain off
of liquid solder following wave or dip soldering of printed
circuit boards and assemblies. Poor solderability of the surfaces
to be soldered and contaminated solder is frequent causes
of icicling.
INORGANIC
When applied to chemistry, refers to the chemistry of those
compounds found in nature or synthesized by man which do not
depend essentially upon chemistry of carbon for their properties.
JUNCTION
A joining of two different semiconductors or of semiconductor
and a metal.
LEAKAGE
Loss of insulation between between conductors on a board.
May be due to improper cleaning procedures that leave conductive
residues.
LIQUIDUS
The temperature at which an alloy is completely molten.
METALURGY
The area concerned with the extraction of metals for their
orders and the refiring of these metals is known as the process
of metalurgy.
MOLECULE
The smallest quantity of matter which can exist by itself
and be recognizable as a particle of the original material.
A molecule retains all the properties of the bulk substance
from which it came.
ORGANIC
HALIDES
An organic compound containing halogens.
PAD
Area of copper surrounding a hole in a board to be used for
lead of component, or for insertion of interconnecting wire.
Provides area for solder bonding.
PCB
A printed circuit board, at almost any stage in production
from raw material to the finished assembly complete with components.
PICK
AND PLACE EQUIPMENT
The automated pick up and placement of discrete active and
passive devices on ceramic substrates.
PLASTIC
RANGE
Refers to a range of temperature in which metal or alloy can
be mechanically worked without danger or cracking of the material.
REFLOW
SOLDERING
A method in which a solder joint is made by melting the solder
coatings on them mating surfaces.
RESIN
A solid or semi solid organic compound lacking a crystalline
structure. Resins are characterised by not having definite
and sharp melting points, are not usually conductors of electricity.
ROSIN
A naturally occurring resin usually associated as a components
of pine sap. Rosin alone is a mild flux for soldering operations.
SHELF
LIFE
Length of time under specified conditions that a stored material
in original, unopened containers retains usability.
SOLDER
A metal or metal alloy usually having a low melting point,
used to join other metals having higher melting points than
the solder together.
SOLDER
PASTE
Homogenous combinations of solder and flux, solvent and gelling
or suspension agent for automated production of solder joints.
SOLDER
PREFORMS
Manufactured solder configurations containing a predetermined
quantity of alloy, with or without a flux core or coating.
SOLDER
RESISTS
Coatings which mask off a surface which insulate those areas
of a circuit where soldering is not desired.
SOLIDUS
The temperature at which a metal alloy begins to melt.
SPECIFIC
GRAVITY
The ratio of the density of a material to the density of water.
SURFACE
MOUNT DEVICES
Electronic components, either active or passive which do not
have separate leads. The terminal leads are part of the component
body, allowing direct mounting on the surface of the printed
wiring boards.
TENSILE
STRENGTH
The characteristic of a material which describes its resistance
to fracture when the material is being stretched. I.e. Under
a tensile load.
THIXOTROPIC
The characteristic of a liquid or gel that is viscous when
static, yet fluid when physically worked.
TINNING
Coating of a terminal, lead or conductive pattern with tin
or solder alloy to improve maintain solderability or to aid
in the soldering operation.
VISCOSITY
The measure of resistance of a fluid to flow- though a specific
orifice or in a rotational viscometer.
VOLATILE
Used to describe materials which have a relatively high evaporation
rate or a tendency to evaporate.
WATER
BASED
A description of a liquidus system where the primary solvent
is water.
WAVE
SOLDERING
The technique of soldering components to a board by passing
the board over a wave of solder in a soldering pot. The wave
is maintained above the level of the pot by solder being pumped
through a manifold in the bottom of the pot.
WETTING
A physical phenomenon of liquids usually in contact with solids,
whereas the surface tension of the liquid has been reduced
so that the liquid flows and makes intimate contact in a very
thin layer over the entire substrate surface.
