IPC-D-859.pdf - 第65页

Magnetic tape may also be supplied for drilling and rout- ing machines. Data tapes supplied in the D–350 series for- mat, shall be single- image, unless otherwise speciﬁed. 5.5.1 Artwork Masters A copy of the 1:1 artwork…

A. Via window sizes and spacings should be as shown in

Figure 5–41.

B. The selection of a via design will depend on the spe-

ciﬁc layout of the adjacent conductor levels; Figure

5–42 illustrates typical examples. Allow as much over-

lap between the top and bottom conductors as possible

within the design constraints.

C. The vias should be staggered as shown in Figure 5–43,

when routing a conductor from an upper level to the

bottom level. Although this uses more room than does

the routing of a conductor directly through a single

window, yield and reliability are improved. (The print-

ing of a conductor through the thickness of two dielec-

tric layers can result in low yields.)

D. If design or space restrictions prevent the staggering of

vias on adjacent levels, an alternate means of routing a

conductor through multiple levels should be used such

as that is shown in Figure 5–44. With this arrangement

a blind through-hole land is printed through the via

window on the second level to contact the bottom con-

ductor. The top (or third level) conductor is then printed

through another via window to contact the blind land

on the second level.

5.4 Coatings and Markings

5.4.1 Conformal Coatings

The use of conformal coat-

ings shall be in accordance with IPC-CC-830, and may be

any one of the following:

Type AR—Acrylic Resin

Type ER—Epoxy Resin

Type FC—Fluorocarbon Resin

Type SR—Silicon Resin

Type UR—Polyurethane Resin

Type XY—Paraxylene Resin

5.4.2 Compatibility The use of coatings, including the

substrate preparation/cleaning required prior to their appli-

cation, shall be compatible with all other parts and materi-

als used in the hybrid circuit, and the hybrid circuit assem-

bly.

Marking, shown in paragraph 5.4.3, and conformal coating,

shall all be compatible.

5.4.3 Legends When speciﬁed on the master drawing,

marking inks may be used to provide identiﬁcation mark-

ing on the hybrid circuit to provide reference designators,

part numbers, revision status, orientation/polarization sym-

bols, bar codes, etc. Marking inks shall be nonconductive

non-nutrient and shall be able to withstand assembly pro-

cesses. Legends shall be of sufficient size and clarity to

optimize their usage. Usually a minimum height of 1.5 mm

[0.060] with a minimum line width of 0.3 mm [0.012] is

used.

5.5 Artwork Artwork generation and measurement tech-

niques shall be in accordance with requirements of IPC-D-

310.

The appropriate artwork tolerances and allowances shall be

incorporated into the production of the phototool. Single-

image masters, as well as multiple masters may be pro-

vided as part of the data package.

The appropriate media for producing artwork, ﬁlm or glass,

shall be used. IPC-D-310, indicates the dimensional change

due to changes in temperature and humidity on each of

these products.

When required, the artwork shall have incorporated into it

quality conformance coupons, as stated in paragraph 3.2.

Symbolization artwork to deﬁne legend, shall also be sup-

plied as a part of the tooling package (see IPC-D-325).

When computer generated artwork is supplied, it shall be

supplied in magnetic tape format. The IPC artwork shall be

described in IPC-D-350, ‘‘Numerical Control Terms.’’

IPC-859-5-36

Figure 5–36 Nominal thick-ﬁlm resistor dimensions for

trimming and overglazing (see Table 5–5)

IPC-859-5-37

Figure 5–37 Closed resistor loops

IPC-D-859 December 1989

Magnetic tape may also be supplied for drilling and rout-

ing machines. Data tapes supplied in the D–350 series for-

mat, shall be single- image, unless otherwise speciﬁed.

5.5.1 Artwork Masters A copy of the 1:1 artwork mas-

ter for each layer shall be provided as part of the drawing

set. Each artwork master shall contain a minimum of three

(3) dimensioned targets. These targets shall be on grid, and

shall register with each other from layer to layer.

5.5.2 Base Material The artwork master shall be sup-

plied on 200 µm [0.0075 ± 0.005 inch] thick biaxially ori-

ented, dimensionally stable, polyester type ﬁlm, or on glass

photographic plates.

5.5.3 Accuracy The accuracy of the artwork master shall

be such that each artwork master shall have all centers of

land areas, conductors, and other features located with

respect to the true grid position within the positional toler-

ances established. For the composite artwork master, the

features of all layers shall coincide within the tolerance

speciﬁed.

IPC-859-5-38

Figure 5–38 Worksheet for determining resistor pastes based on number of squares needed.

December 1989 IPC-D-859

5.5.4 Pinholes There shall be no pinholes on the 1:1 art-

work master larger than 25 µm [0.001 inch], or which

reduce the artwork conductor width by more than 10 per-

cent. Areas outside of the functional board outline shall not

be subject to inspection, and may have pinholes. Pinholes

within the functional board outline that are covered with

opaque ink shall be acceptable.

5.5.5 Opaque Defects (Specks) There shall be no

opaque defects within the functional board outline larger

than 25 µm [0.001 inch] on the 1:1 artwork master, or

which reduce the conductor width by more than 10 percent.

Areas outside of the functional board outline shall not be

subject to inspection, and may have opaque defects. Areas

where opaque defects within the functional board outline,

that have been removed with a sharp pointed hand tool,

shall be acceptable.

5.5.6 Reproduction Conditions The temperature, rela-

tive humidity, date, and photographic facility identiﬁcation

shall appear on each artwork master ﬁlm in such a manner

that the artwork master can be readily separated from any

photographic reproductions. Alternately, traceability to

records from automatic monitoring and recording facilities

can be speciﬁed.

5.5.7 Packaging and Handling of Artwork Masters

Each artwork master 360 mm x 450 mm [14 x 17 inches]

or under, shall be separately packaged in a glass lined or

polyethylene envelope. Artwork master 360 mm x 450 mm

[14 x 17 inches] to 450 mm x 560 mm [14 x 17 inches]

shall be packaged ﬂat in a box, and constrained with a

sheet of low density foam. Artwork master larger than 450

mm x 560 mm [14 x 17 inches] may be rolled (minimum

diameter 76 mm [3 inches]) and enclosed in a container

made of ﬁberboard or metal. One inch rubberized hair felt

or equivalent shall be placed in each end of the container

for protection.

5.6 Documentation The documentation package for a

printed wiring board should include the master drawing

and copies of the secondary artwork masters. More than

one copy of the master drawing should be supplied to the

vendor. Other documentation, which may be included with

package, could include mag tapes for the generation of

photoplotted artwork and NC tapes for component place-

ment. Documentation shall meet the requirements of IPC-

D-325.

Numerical control tapes should be included with the ven-

dor documentation package when available. These can be

in a paper tape format, or on mag tape, depending on the

vendor’s capabilities. The code in which the tapes are writ-

ten should also be provided.

5.6.1 Master Drawing The master drawing shall meet

the requirements of paragraph 3.3 and IPC-D-325 and

include, as a minimum, the information detailed in Table

5–5.

5.6.1.2 Marking The master drawing shall include the

speciﬁcation requirement for all supplemental marking,

that is, those markings other than those etched in the pat-

tern. The drawing note shall include the kind of ink or

IPC-859-5-39

Dim

Min/

Max

Producibility mm

[inch]

Most ↔ Least

ABC

Screened resistor

size:

• Number of

squares

L/W

Min

Max

0.5 sq.

5.0 sq.

0.5 sq.

10.0 sq.

0.3 sq.

10.0 sq.

• Length L Min 1.27

[0.050]

1.02

[0.040]

1.02

[0.040]

• Width, ±1% tol-

erance

W Min 1.02

[0.040]

0.89

[0.035]

0.89

[0.035]

• Width, 5% toler-

ance

W Min 0.76

[0.030]

0.64

[0.025]

0.64

[0.025]

Conductor termi-

nal, distance

beyond width

of resistor

Min 0.38

[0.015]

0.25

[0.010]

0.20

[0.008]

Conductor termi-

nal, distance

beyond length

of resistor

Min 0.38

[0.015]

0.25

[0.010]

0.20

[0.008]

Resistor overlap,

onto conductor

terminal

Min 0.25

[0.010]

0.20

[0.008]

0.20

[0.008]

Conductors,

distance from

resistor

Min 0.51

[0.020]

0.38

[0.015]

0.38

[0.015]

Edge of sub-

strate, distance

from resistor

Min 0.76

[0.030]

0.51

[0.020]

0.51

[0.020]

Figure 5–39 Thick-ﬁlm screened resistor sizes

and locations

▼

Screened

Resistor

IPC-D-859 December 1989