IPC-7351-2005_表面贴装焊盘布局设计和标准通用要求.pdf - 第25页

ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Sometimes a dimension is presented as a minimum dis- tance. This occurs when deﬁning a space(s) that exists between lands at MMC. The printed board manufacturer may not always inspect the board in accordanc…

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Dimensions that have had their tolerance spread reduced

are so indicated in the tables. Parts that are available with

shape characteristics or tolerance limits that fall outside the

recommended norms require land patterns that must be

altered slightly from those presented.

Users of these specialized parts are encouraged to develop

their own land patterns which then become unique to a

speciﬁc component vendor part. A dimensioning system

with speciﬁc equations has been provided to facilitate

unique land pattern development or enhance process usage.

3.1.5.3 Land Pattern Dimensions Land pattern dimen-

sions are provided in the sectional standards according to

the concepts of maximum material conditions (MMC).

Table 3-10 Butt Joints (unit: mm)

Lead Part

Minimum

(Least)

Density

Level C

Median

(Nominal)

Density

Level B

Maximum

(Most)

Density

Level A

Toe (J

) 0.6 0.8 1.0

Round-off factor

Round off to the nearest two place

even decimal, i.e., 1.00, 1.20, 1.40

Heel (J

) 0.6 0.8 1.0

Round-off factor

Round off to the nearest one place

decimal, i.e., 1.0, 1.1, 1.2, 1.3

Side (J

) 0.1 0.2 0.3

Round-off factor

Round off to the nearest two place

decimal, i.e., 1.00, 1.05, 1.10, 1.15

Courtyard excess 0.2 0.8 1.5

Table 3-11 Inward Flat Ribbon L and Gull-

Wing Leads (Tantalum Capacitors) (unit: mm)

Lead Part

Minimum

(Least)

Density

Level C

Median

(Nominal)

Density

Level B

Maximum

(Most)

Density

Level A

Toe (to ﬁnd G dim)

)

0.07 0.15 0.25

Round-off factor

Round off to the nearest two place

even decimal, i.e., 1.00, 1.20, 1.40

Heel (to ﬁnd Z

dim) (J

)

0.2 0.5 0.8

Round-off factor

Round off to the nearest two place

even decimal, i.e., 1.00, 1.20, 1.40

Side (J

) -0.10 -0.05 0.01

Round-off factor

Round off to the nearest one place

decimal, i.e., 1.0, 1.1, 1.2, 1.3

Courtyard excess 0.1 0.25 0.5

Table 3-12 Flat Lug Leads (unit: mm)

Lead Part

Minimum

(Least)

Density

Level C

Median

(Nominal)

Density

Level B

Maximum

(Most)

Density

Level A

Toe (J

) 0.15 0.35 0.55

Round-off factor

Round off to the nearest two place

even decimal, i.e., 1.00, 1.20, 1.40

Heel (J

) 0.25 0.35 0.45

Round-off factor

Round off to the nearest one place

decimal, i.e., 1.0, 1.1, 1.2, 1.3

Side (J

) -0.04 0.01 0.05

Round-off factor

Round off to the nearest two place

decimal, i.e., 1.00, 1.05, 1.10, 1.15

Courtyard excess* 0.1 0.25 0.5

* Depends on thermal requirements.

Table 3-13 Flat, No Lead (unit: mm)

Lead Part

Minimum

(Least)

Density

Level C

Median

(Nominal)

Density

Level B

Maximum

(Most)

Density

Level A

Toe (J

) 0.20 0.30 0.40

Round-off factor

Round off to the nearest two place

decimal, i.e., 1.00, 1.05, 1.10, 1.15

Heel (J

) 0.00 0.00 0.00

Round-off factor

Round off to the nearest two place

decimal, i.e., 1.00, 1.05, 1.10, 1.15

Side (J

) -0.04 -0.04 -0.04

Round-off factor

Round off to the nearest two place

decimal, i.e., 1.00, 1.05, 1.10, 1.15

Courtyard excess 0.1 0.25 0.5

Note: The rationale for the relatively large negative heel stems from the

tolerances for the lead lengths as also being relatively large. In order to

maintain a minimum clearance of 0.20 mm to the thermal tab it becomes

necessary to trim the heel by -0.2 mm. Without a thermal tab the heel can

usually be increased to as much as 0.50 mm.

Table 3-14 Small Outline (SO), No-Lead (unit: mm)

Lead Part

Minimum

Level C

Median

Level B

Maximum

Level A

Toe (J

) 0.20 0.30 0.40

Round-off factor

Round off to the nearest two place

decimal, i.e., 1.00, 1.05, 1.10, 1.15

Heel (J

) 0.00 0.00 0.00

Round-off factor

Round off to the nearest two place

decimal, i.e., 1.00, 1.05, 1.10, 1.15

Side (J

) -0.04 -0.04 -0.04

Round-off factor

Round off to the nearest two place

decimal, i.e., 1.00, 1.05, 1.10, 1.15

Courtyard excess 0.1 0.25 0.5

Note: With a thermal tab the heel can usually be increased to as much as

0.1 mm.

IPC-7351 February 2005

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Sometimes a dimension is presented as a minimum dis-

tance. This occurs when deﬁning a space(s) that exists

between lands at MMC. The printed board manufacturer

may not always inspect the board in accordance with the

limit concepts shown in the table. However, these limits

may be used as the criteria for go/no-go acceptance of the

printed board land pattern. The dimensions shown in each

table are those that have been used in the equations

described in 3.1 for determining the recommended land

patterns. The maximum material condition for each land

pattern analysis level describes the most robust joint or

land protrusion for that level land pattern.

3.1.5.4 Courtyard Determination The courtyard of any

land pattern is the smallest area that provides a minimum

electrical and mechanical clearance of both the component

maximum boundary extremities and/or the land pattern

maximum boundary extremities. The intent of the court-

yard is to aid the designer in determining the minimum

area occupied by the combination of component and land

pattern. The information provided in Tables 3-2 through

3-14 is intended to relate to those excesses that should be

added to the maximum dimension to derive the appropriate

courtyard condition.

As an example, if a component was the major determining

factor of the boundary condition, it would have the excess

added to the dimensions. The same holds true for a land

pattern that has the greater extremities. If either dimension

were 14.5 mm, and the excess from tables 3-2 through 3-14

indicated an excess of 0.8 mm, the resulting courtyard

would theoretically be 16.1 mm. The tables further deﬁne

a round-up feature. If the round-up were recommended as

being to the nearest 0.5 mm, the courtyard would become

16.5 mm.

It should be noted that 16.5 mm is a number that, when

divided by 2 to obtain the component centroid, provides 2

decimal places to the right of the number. It therefore may

be appropriate to keep this number in an even approxima-

tion such as 16.6 mm. This would provide 8.3 mm to either

side of the center of the component to help designers posi-

tion the component in relation to some grid or placement

algorithm.

When manufacturing allowance must be considered in the

design process the courtyard represents the starting point of

the minimum area needed for the component and the land

pattern. Manufacturing, assembly and testing representa-

tives should assist in determining the additional room

needed to accommodate placement, testing, modiﬁcation

and repair. This manufacturing allowance is usually depen-

dent on the density and complexity of the product, and is

not deﬁned in this document. The manufacturing allowance

is determined by application and manufacturing process

requirements (see Figure 3-5).

3.1.5.5 Land Pattern Naming Convention The RLP

(Registered Land Pattern) numbering scheme previously

used in IPC-SM-782A has been replaced with an intelligent

land pattern naming convention which will aid in the stan-

dardization of electronic schematic symbols for engineer-

ing.

Each land pattern in the IPC-7351 has received a name

containing a preﬁx for the device type, a pin pitch, a nomi-

nal lead span corresponding to the ‘‘L’’ dimension (or a

pair of nominal lead spans for components with termina-

tion leads on four sides), and a pin quantity. In the case of

ball grid array (BGA) packages, the column and row num-

bers are given as there are no end termination lead spans.

The purpose of the number is to aid in communication

between engineering, design, and manufacturing. Speciﬁc

syntax explanations include:

The + (plus sign) stands for ‘‘in addition to’’ (no space

between the preﬁx and the body size).

The - (dash) is used to separate the pin qty.

The X (capital letter X) is used instead of the word ‘‘by’’

to separate two numbers such as height X width like

‘‘Quad Packages.’’

The suffix letters of L, M and N are reserved by IPC. The

suffix letters ‘‘L,’’ ‘‘M,’’ and ‘‘N’’ have been reserved to

signify when the land protrusion is at their minimum

(least), maximum (most), or median (nominal) protrusion

or use environment as follows:

M – Maximum (Most) Material Condition

(Density Level A)

N – Median (Nominal) Material Condition

(Density Level B)

L – Minimum (Least) Material Condition

(Density Level C)

Note: Ball Grid Array (BGA) and Quad Flat No-Lead

(QFN) packages do not receive a suffix of ‘‘L,’’ ‘‘M’’ or

‘‘N’’ as they are only listed in the median (nominal) den-

sity level.

IPC-7351-3-05

Figure 3-5 Courtyard Boundary Area Condition

Component / Pattern

(Maximum Boundary)

Courtyard

Excess

Courtyard

(Minimum Area)

Manufacturing

Allowance

Courtyard

Manufacturing Zone

February 2005 IPC-7351

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Additional suffixes for alternate components that do not

follow JEDEC, EIA or IEC standards are as follows:

‘‘A’’ – Alternate Component (used for SOP and QFP

when component tolerance or height is different)

‘‘B’’ – Second Alternate Component

Additional suffices for JEDEC and EIA Standard parts that

have several alternate packages are as follows:

AA, AB, AC JEDEC or EIA Component Identiﬁer (Used

primarily on Chip Resistors, Inductors and Capacitors).

The naming conventions shown in Table 3-15 are subject to

change as new component families are identiﬁed. The most

current naming convention listing can be found on the IPC

website (www.ipc.org) under ‘‘PCB Tools and Calcula-

tors.’’.

Table 3-15 IPC-7351 Land Pattern Naming Convention

COMPONENT, CATEGORY LAND PATTERN NAME

Ball Grid Array’s, Inch Based (1.27 mm / 0.05 in Pitch) ........ BGA127P + Number of Pin Columns X Number of Pin Rows - Pin Qty

Ball Grid Array’s, Metric Based (1.50 mm Pitch) ................... BGA150P + Number of Pin Columns X Number of Pin Rows - Pin Qty

Ball Grid Array’s, Metric Based (1.00 mm Pitch) ................... BGA100P + Number of Pin Columns X Number of Pin Rows - Pin Qty

Ball Grid Array’s, Metric Based (0.80 mm Pitch) ..................... BGA80P + Number of Pin Columns X Number of Pin Rows - Pin Qty

Ball Grid Array’s, Metric Based (0.75 mm Pitch) ..................... BGA75P + Number of Pin Columns X Number of Pin Rows - Pin Qty

Ball Grid Array’s, Metric Based (0.65 mm Pitch) ..................... BGA65P + Number of Pin Columns X Number of Pin Rows - Pin Qty

Ball Grid Array’s, Metric Based (0.50 mm Pitch) ..................... BGA50P + Number of Pin Columns X Number of Pin Rows - Pin Qty

Ball Grid Array’s w/Staggered Pins (1.27 mm Pitch) ........... SBGA127P + Number of Pin Columns X Number of Pin Rows - Pin Qty

Capacitors, Chip, Array ................................................................ CAPCA + Pitch P + Body Width X Body Length in Metric - Pin Qty

Capacitors, Chip, Polarized .................................................................................................................... CAPCP + Body Size in Metric

Capacitors, Chip, Nonpolarized ................................................................................................................ CAPC + Body Size in Metric

Capacitors, Chip, Wire Rectangle ...................................................................................................... CAPCWR + Body Size in Metric

Capacitors, Molded, Nonpolarized ........................................................................................................... CAPM + Body Size in Metric

Capacitors, Molded, Polarized ............................................................................................................... CAPMP + Body Size in Metric

Capacitors, Aluminum Electrolytic ................................................................................... CAPAE + Base Body Width (W) + Height (H)

Ceramic Flat Packages ....................................................................................................... CFP127P + Lead Span Nominal - Pin Qty

Column Grid Array’s ........................................................................ CGA + Number of Pin Columns X Number of Pin Rows - Pin Qty

Diodes, Molded (JEDEC Standard Package) ........................................................................................... DIOM + Body Size in Metric

Diodes, MELF ..................................................................................................................................... DIOMELF + Body Size in Metric

Inductors, Chip ........................................................................................................................................... INDC + Body Size in Metric

Inductors, Chip, Array .................................................................... INDCA + Pitch P + Body Width X Body Length in Metric - Pin Qty

Inductors, Molded ...................................................................................................................................... INDM + Body Size in Metric

Inductors, Precision Wire Wound ............................................................................................................... INDP + Body Size in Metric

Plastic Leaded Chip Carriers Square (JEDEC Standard Package) ............................................................................. PLCC - Pin Qty

Plastic Leaded Chip Carriers Rectangular (JEDEC Standard Package) .................................................................. PLCCR - Pin Qty

Plastic Leaded Chip Carrier Sockets Square ............................................................................................................ PLCCS - Pin Qty

Plastic Leaded Chip Carrier Sockets Rectangular .................................................................................................. PLCCRS - Pin Qty

Plastic Quad Flat Packages, 0.635 mm Pitch, Pin 1 Side ........................................................................................ PQFPS - Pin Qty

Plastic Quad Flat Packages, 0.635 mm Pitch, Pin 1 Center ..................................................................................... PQFPC - Pin Qty

Bumper Quad Flat Packages, 0.635 mm Pitch, Pin 1 Side ...................................................................................... BQFPS - Pin Qty

Bumper Quad Flat Packages, 0.635 mm Pitch, Pin 1 Center .................................................................................. BQFPC - Pin Qty

Quad Flat Packages, 1.00 mm Pitch .................................................. QFP100P + Lead Span L1 X Lead Span L2 Nominal - Pin Qty

Quad Flat Packages, 0.80 mm Pitch .................................................... QFP80P + Lead Span L1 X Lead Span L2 Nominal - Pin Qty

Quad Flat Packages, 0.65 mm Pitch .................................................... QFP65P + Lead Span L1 X Lead Span L2 Nominal - Pin Qty

Shrink Quad Flat Packages, 0.50 mm Pitch ...................................... SQFP50P + Lead Span L1 X Lead Span L2 Nominal - Pin Qty

Shrink Quad Flat Packages, 0.40 mm Pitch ...................................... SQFP40P + Lead Span L1 X Lead Span L2 Nominal - Pin Qty

Shrink Quad Flat Packages, 0.30 mm Pitch ...................................... SQFP30P + Lead Span L1 X Lead Span L2 Nominal - Pin Qty

Thin Quad Flat Packages, 0.80 mm Pitch, Height ≤ 1.60 mm .......... TQFP80P + Lead Span L1 X Lead Span L2 Nominal - Pin Qty

Thin Quad Flat Packages, 0.65 mm Pitch, Height ≤ 1.60 mm .......... TQFP65P + Lead Span L1 X Lead Span L2 Nominal - Pin Qty

IPC-7351 February 2005

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