IPC-7526-2007 模板和误印板清洗指南.pdf - 第24页
ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Paste Flux: A flux formulated in the form of a paste for joining area array components. Pitch: Center -to-Center distance between two adjacent conductors or lands. Polyglycol: Any of several condensation pol…
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APPENDIX A
Terms and Definitions
Absorbed Contaminant: A contaminant attracted to the
surface of a material that is held captive in the form of a
gas, vapor or condensate.
Adhesive: A substance such as glue or cement used to
fasten objects together. In surface mounting, an epoxy
adhesive is used to adhere SMDs to the substrate.
Adhesive Printing: Stencil printing no longer is limited to
the deposition of solder paste. Stencils may be used to
deposit adhesives on mixed-technology PCA designs in
which the bottom of the board features parts attached with
adhesives for wave soldering.
Aliphatic Solvent: ‘‘Straight chain’’ solvents, derived
from petroleum, of low solvent power.
Alkaline Cleaner: An aqueous engineered composition
that contains alkaline salts. These materials are in a pH
range of 7-14.
Ambient: The surrounding environment coming into con-
tact with the system or component in question. Typically
refers to room temperature processing.
Aperture (Stencil): Openings in the stencil through which
solder paste or adhesive is deposited onto the circuit board.
Aqueous Flux: Water-soluble organic flux.
Aspect Ratio: Aperture width to depth ratio. If the wall
area exceeds the land area, the surface tension of the sol-
der paste will be such that more of the paste will adhere to
the wall, risking a clogging condition.
Azeotropic Cleaning Mixture: A liquid mixture of two or
more solvents that behave like a single solvent. The vapor
pressure by partial evaporation of the liquid has the same
composition as the liquid cleaning chemistry.
Bare Board: An unassembled (unpopulated) printed cir-
cuit board.
Base Solderability: The ease with which a metal or metal
alloy can be wetted by molten solder under minimum real-
istic conditions.
Batch Cleaning Process: The cleaning of multiple parts
or ‘‘batches of parts’’ as a group where process cycle times
are controlled.
BOD: Biological oxygen demand.
Bridging, Electrical: The unintentional formation of a
conductive path between conductors.
B-Side: The bottom side of a printed circuit assembly.
COD: Chemical oxygen demand.
Cold Hand Cleaning: Manual cleaning using a presatu-
rated wipe or brush that contains a cleaning chemistry that
readily evaporates.
Corrosion: The attack of cleaning chemistry, fluxes, and
flux residues on base metals.
Degradation: A decrease in the performance characteris-
tics or service life of the cleaning chemistry.
Dewetting: A condition that results when molten solder
coats a surface and then recedes to leave irregularly shaped
mounds of solder that are separated by areas that are cov-
ered with a thin film of solder and with the basis metal not
exposed.
Double-Sided Printed Board: A printed board with a
conductive pattern on both of its sides.
Emulsion Cleaning: An aqueous cleaning mixture that
holds immiscible soils, such as adhesive, in suspension.
Feature: The general term that is applied to a physical
portion of a part, such as a surface, hole or slot.
Fine-Pitch Technology: A surface mount assembly tech-
nology with component terminations on less than 0.625mm
(0.025-inch) centers.
Flux: A chemically and physically active compound that,
when heated, promotes the wetting of a base metal surface
by molten solder by removing minor surface oxidation and
other surface films and by protecting the surfaces from
reoxidation during a soldering process.
Flux Activity: The degree or efficiency with which a flux
promotes wetting of a surface with molten solder.
Flux Residue: A flux-related contaminant that is present
on or near the surface of a solder connection.
Hydrophilic: Water loving or having a strong affinity for
water.
Hydrophobic: Water hating or having a strong aversion to
water.
Hydroscopic: Water loving or having a strong affinity to
water.
In-line Cleaning: Parts are processed continuously on a
conveyor with process cycle time being controlled by the
conveyor speed.
Ionic Cleanliness: The degree of surface cleanliness as
measured by the number of ions or weight of ionic matter
per unit square of surface.
Manual Cleaning: A cleaning step where parts are pro-
cessed manually with process cycle time controlled by
operator.
February 2007 IPC-7526
17
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Paste Flux: A flux formulated in the form of a paste for
joining area array components.
Pitch: Center-to-Center distance between two adjacent
conductors or lands.
Polyglycol: Any of several condensation polymers of eth-
ylene glycol.
Residue: Any visual or measurable form of process-
related contamination.
Rework: The act of reprocessing noncomplying articles,
through the use of original or alternate equivalent process-
ing, in a manner that assures compliance of the article with
applicable drawings or specifications.
Saponifier: An alkaline chemical designed to react with
organic fatty acids, such as rosin to form a water-soluble
soap.
Screen-Printing: The transferring of an image to a surface
by forcing a suitable media through an imaged-screen
mesh.
Screen and Stencil Cleaning: The process of removing
unused solder paste/flux from application tools to maintain
them in an acceptable condition for reuse.
Semiaqueous Cleaning: Organic solvent blends are used
for washing or dissolving the contaminant followed by
water rinsing.
Solderability: The ability of a metal to be wetted by mol-
ten solder, a function of the termination finish at the time
of soldering. Total soldering ability is a function of match-
ing the design, process, components and substrate to facili-
tate the formation of a robust solder joint.
Solder Ball: A small sphere of solder adhering to a lami-
nate, resist, or conductor surface.
Solder Paste: Finely divided particles of solder, with addi-
tives to promote wetting and to control viscosity, tackiness,
slumping, drying rate, etc, that are suspended in a cream
flux.
Solder Paste Considerations: Solder paste properties
such as particle size and shape, flux type, viscosity and
slump characteristics have a major impact on the printing
process. Excessive solder paste can result in solder balls or
bridging.
Solder Printing: The deposition of solder paste by repro-
ducing a pattern on the printed circuit board.
Solvent Cleaning: The removal of organic and inorganic
soils using a blend of polar and nonpolar organic solvents.
Squeegee: Both polyurethane and metal squeegees are
used to force solder paste through the apertures of a sten-
cil and onto the circuit board.
Squeegee Side/Board Side: Refers to the two sides of the
stencil when mounted in the frame. The squeegee side is
the side on which the squeegee travels to print the pattern;
the board side comes in contact with the substrate to trans-
fer the solder paste.
Stencil Border: Consists of a polyester fabric stretched on
the frame to hold the metal stencil and to permit uniform
contact with the board under squeegee pressure for a con-
trolled snap-off.
Stencil Frame: Typically made of aluminum, which is
cast or extruded. The cleaning agent must be compatible
with the alloy of construction.
Surfactant: An aqueous organic or inorganic wetting
agent designed to wet the surface of the product and dis-
place the contaminant.
Ultrasonic Cleaning: Immersion cleaning that is done by
passing high-frequency solund waves through a cleaning
medium to casue cavitation (microagitation).
IPC-7526 February 2007
18
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