IPC-7526-2007 模板和误印板清洗指南.pdf - 第23页

ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ 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…

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solder cleaning process step be reviewed with local POTW

officials before commencing the discharge of wastewater.

Such a review may result in the POTW waiving the need

for a permit, or in reducing the monitoring requirements of

a required permit. Superfund regulations place liability on

all drain uses if contaminated sewer sites cannot be linked

to the generator. If using the drain for ﬁltered wastewater

discharge, the user could be held liable for a neighbor’s

problem and be required to share in the clean-up costs.

Even though there is no universal US EPA rule for elec-

tronics part cleaning, any state can have its own regulations

for these processes. Throughout the USA, these vary

greatly from one regulatory agency to another, from mini-

mal to very strict. Regulatory personnel’s interpretation and

knowledge of this process will determine the difficulty that

one will have with discharging the wastewater. Some local

communities may decide to prohibit a discharge of indus-

trial wastewater. Other communities will follow the state’s

requirements and will rely on the state to monitor the

wastewater for them.

In the past, many nations and regions (states) allowed com-

bining of domestic sewage with industrial wastewater

including heavy metals as long as the ﬁnal wastewater

complied with the regulations. However, today many of

these cleaning operations are now considered as a point

source discharge. With increasing frequency, regulatory

personnel are taking samples of wastewater from the wash

tank drain and the rinse water drain of the cleaning equip-

ment.

In most European countries and many Asian ones, it is a

legal requirement that the discharge be measured directly

from the machine or the individual wastewater treatment

plant and that dilution of the wastewater stream either from

within the machine or without it, is expressively forbidden.

In other words, if the discharge from the machine does not

conform to the regulations, the water must be puriﬁed in

such a way that it does.

One of the more difficult aspects of wastewater treatment is

that of heavy metal cations. Taking the three most impor-

tant ones for electronics cleaning, the known regulations at

the time of this writing may vary from place to place as

follows:

In some nations, the permitted concentration is expressed

in peak milligrams-per-liter, in other, parts-per-million. For

the sake of simplicity, the two units were considered here

as equivalent. Very few regulations in the world permit

integrating/averaging to determine the limit.

In the calculation of this average, those nations with unlim-

ited permitted total in cation concentration were ignored:

this ﬁgure is therefore an average of those nations with a

ﬁnite limit.

It is evident that removing heavy metals from wastewater

does not destroy these metals. At the best, they are trans-

ported into another form, such as concentrate from mem-

brane treatment or regenerated two bed ion exchangers, as

residues from mixed bed ion exchangers or as a solid pre-

cipitate after hydroxide or ferrite treatment. All these waste

materials are at least as dangerous as the original cations in

the wastewater. They are only displaced. It is a bounden

duty to ensure they are disposed of in as environmentally

friendly manner as possible, no matter the chosen way.

10.3 Solid Waste The disposal of spent or waste-

cleaning chemicals is regulated in most countries as haz-

ardous waste. Spent cleaning chemistries, ﬁlter cartridges,

activated carbon or others must be analyzed and character-

ized by someone knowledgeable in hazardous waste gen-

eration, storage and shipment regulations. In the USA, the

federal TCLP (Toxic Characteristic Leachate Procedure)

test is the minimum that must be performed. Applicability

of the hazardous waste rules subject a facility to extensive

regulations on personnel training, storage and handling

requirements and record keeping. Even if hazardous waste

rules are not applicable, local or state rules on solid waste

may apply. Some states offer technical assistance to aid in

this determination. Documentation of test results and

records must be kept to assure the regulatory agency of

compliance with today’s ‘‘cradle to grave’’ requirement.

Complete records of the amount of regulated wastes gener-

ated, transported, and disposed are required.

In addition to analogue regulations, there are very severe

rules in Europe simply for the transport of hazardous waste

and, for that matter, any toxic material. Furthermore, most

regions operate licensed liquid and solid chemical disposal

sites, which are specially constructed to protect the air, sur-

face and ground waters (especially phreatic sites) and the

surrounding soil. Every load of waste must be clearly

labeled as to the nature of the contents. Generally, it is a

wise precaution to make sure that a site can accept a given

waste before despatching it. Combustible waste is usually

incinerated in special kilns. In particular, special licenses

are required to transport waste across a national frontier,

according to the Basel Convention.

IPC-7526 February 2007

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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

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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

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