IPC-A-610C(电子组装件的验收条件) - 第361页

IPC-2221 – 6.3.2 B2-External Conductors, Uncoated, Sea Level to 3050 m Electrical clearance requirements for uncoated external conductors are significantly greater than for conductors that will be protected from external…

NOTE: Appendix A is quoted from IPC-2221 Generic Stan-

dard on Printed Board Design (February 1998) and is pro-

vided for information only. It is current as of publication

date of this document. The user has the responsibility to

determine the most current revision level of IPC-2221 and

specify the speciﬁc application to their product. Paragraph

and table numbers are from IPC-2221.

The following statement from IPC-2221 applies to this Appen-

dix ONLY: 1.4 Interpretation – ‘‘Shall,’’ the imperative form

of the verb, is used throughout this standard [IPC-A-610C

Appendix A] whenever a requirement is intended to express a

provision that is mandatory.

IPC-2221 –

6.3 Electrical Clearance Spacing between

conductors on individual layers should be maximized when-

ever possible. The minimum spacing between conductors,

between conductive patterns, layer to layer conductive

spaces (z-axis), and between conductive materials (such as

conductive markings or mounting hardware) and conductors

shall be in accordance with Table 6-1, and defined on the

master drawing. For additional information on process allow-

ances effecting electrical clearance, see Section 10.

When mixed voltages appear on the same board and they

require separate electrical testing, the specific areas shall be

identified on the master drawing or appropriate test specifica-

tion. When employing high voltages and especially AC and

pulsed voltages greater than 200 volts potential, the dielectric

constant and capacitive division effect of the material must be

considered in conjunction with the recommended spacing.

For voltages greater than 500V, the (per volt) table values

must be added to the 500V values. For example, the electri-

cal spacing for a Type B1 board with 600V is calculated as:

600V - 500V = 100V

0.25 mm + (100V x 0.0025 mm)

= 0.50 mm clearance

When, due to the criticality of the design, the use of other

conductor spacings is being considered, the conductor spac-

ing on individual layers (same plane) shall be made larger

than the minimum spacing required by Table 6-1 whenever

possible. Board layout should be planned to allow for the

maximum spacing between external layer conductive areas

associated with high impedance or high voltage circuits. This

will minimize electrical leakage problems resulting from con-

densed moisture or high humidity. Complete reliance on coat-

ings to maintain high surface resistance between conductors

shall be avoided.

IPC-2221 –

6.3.1 B1-Internal Conductors Internal

conductor-to-conductor, and conductor-to-plated-through

hole electrical clearance requirements at any elevation. See

Table 6-1.

IPC-2221 –

Table 6-1 Electrical Conductor Spacing

Voltage

Between

Conductors

(DC or AC

Peaks)

Minimum Spacing

Bare Board Assembly

B1 B2 B3 B4 A5 A6 A7

0-15 0.05 mm 0.1 mm 0.1 mm 0.05 mm 0.13 mm 0.13 mm 0.13 mm

16-30 0.05 mm 0.1 mm 0.1 mm 0.05 mm 0.13 mm 0.25 mm 0.13 mm

31-50 0.1 mm 0.6 mm 0.6 mm 0.13 mm 0.13 mm 0.4 mm 0.13 mm

51-100 0.1 mm 0.6 mm 1.5 mm 0.13 mm 0.13 mm 0.5 mm 0.13 mm

101-150 0.2 mm 0.6 mm 3.2 mm 0.4 mm 0.4 mm 0.8 mm 0.4 mm

151-170 0.2 mm 1.25 mm 3.2 mm 0.4 mm 0.4 mm 0.8 mm 0.4 mm

171-250 0.2 mm 1.25 mm 6.4 mm 0.4 mm 0.4 mm 0.8 mm 0.4 mm

251-300 0.2 mm 1.25 mm 12.5 mm 0.4 mm 0.4 mm 0.8 mm 0.8 mm

301-500 0.25 mm 2.5 mm 12.5 mm 0.8 mm 0.8 mm 1.5 mm 0.8 mm

> 500

See para. 6.3

for calc.

0.0025 mm

/volt

0.005 mm

/volt

0.025 mm

/volt

0.00305 mm

/volt

0.00305 mm

/volt

0.00305 mm

/volt

0.00305 mm

/volt

B1 - Internal Conductors

B2 - External Conductors, uncoated, sea level to 3050 m

B3 - External Conductors, uncoated, over 3050 m

B4 - External Conductors, with permanent polymer coating (any elevation)

A5 - External Conductors, with conformal coating over assembly (any elevation)

A6 - External Component lead/termination, uncoated

A7 - External Component lead termination, with conformal coating (any elevation)

Appendix A

Electrical Conductor Spacing

A-1IPC-A-610C January 2000

IPC-2221 –

6.3.2 B2-External Conductors, Uncoated,

Sea Level to 3050 m

Electrical clearance requirements for

uncoated external conductors are significantly greater than for

conductors that will be protected from external contaminants

with conformal coating. If the assembled end product is not

intended to be conformally coated, the bare board conductor

spacing shall require the spacing specified in this category for

applications from sea level to an elevation of 3050 m. See

Table 6-1.

IPC-2221 –

6.3.3 B3-External Conductors, Uncoated,

Over 3050 m

External conductors on uncoated bare board

applications over 3050 m require even greater electrical spac-

ings than those identified in category B2. See Table 6-1.

IPC-2221 –

6.3.4 B4-External Conductors, with Perma-

nent Polymer Coating (Any Elevation)

When the final

assembled board will not be conformally coated, a permanent

polymer coating over the conductors on the bare board will

allow for conductor spacings less than that of the uncoated

boards defined by category B2 and B3. The assembly electri-

cal clearances of lands and leads that are not conformally

coated require the electrical clearance requirements stated in

category A6 (see Table 6-1). This configuration is not appli-

cable for any application requiring protection from harsh,

humid, contaminated environments.

Typical applications are computers, office equipment, and

communication equipment, bare boards operating in con-

trolled environments in which the bare boards have a perma-

nent polymer coating on both sides. After they are assembled

and soldered the boards are not conformal coated, leaving

the solder joint and soldered land uncoated.

Note: All conductors, except for soldering lands, must be

completely coated in order to ensure the electrical clearance

requirements in this category for coated conductors.

IPC-2221 –

6.3.5 A5-External Conductors, with Confor-

mal Coating Over Assembly (Any Elevation)

Externalcon-

ductors that are intended to be conformal coated in the final

assembled configuration, for applications at any elevation, will

require the electrical clearances specified in this category.

Typical applications are military products where the entire final

assembly will be conformal coated. Permanent polymer coat-

ings are not normally used, except for possible use as a sol-

der resist. However, the compatibility of polymer coating and

conformal coating must be considered, if used in combina-

tion.

IPC-2221 –

6.3.6 A6-External Component Lead/

Termination, Uncoated

External component leads and ter-

minations, that are not conformal coated, require electrical

clearances stated in this category.

Typical applications are as previously stated in category B4.

The B4/A6 combination is most commonly used in commer-

cial, non-harsh environment applications in order to obtain the

benefit of high conductor density protected with permanent

polymer coating (also solder resist), or where the accessibility

to components for rework and repair is not required.

IPC-2221 –

6.3.7 A7-External Component Lead/

Termination, with Conformal Coating (Any Elevation)

in exposed conductors versus coated conductors on bare

board, the electrical clearances used on coated component

leads and terminations are less than for uncoated leads and

terminations.

Appendix A

Electrical Conductor Spacing (cont.)

A-2 IPC-A-610CJanuary 2000

Standard Improvement Form IPC-A-610C

The purpose of this form is to provide the

Technical Committee of IPC with input

from the industry regarding usage of

the subject standard.

Individuals or companies are invited to

submit comments to IPC. All comments

will be collected and dispersed to the

appropriate committee(s).

If you can provide input, please complete

this form and return to:

IPC

2215 Sanders Road

Northbrook, IL 60062-6135

Fax 847 509.9798

1. I recommend changes to the following:

Requirement, paragraph number

Test Method number , paragraph number

The referenced paragraph number has proven to be:

Unclear Too Rigid In Error

Other

2. Recommendations for correction:

3. Other suggestions for document improvement:

Submitted by:

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Company E-mail

Address

City/State/Zip Date

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