IPC-7351-2005_表面贴装焊盘布局设计和标准通用要求.pdf - 第24页

ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ 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 requir…

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Table 3-4 J Leads (unit: mm)
Lead Part
Minimum
(Least)
Density
Level C
Median
(Nominal)
Density
Level B
Maximum
(Most)
Density
Level A
Heel (to find Z
dim) (J
H
)
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
Toe (to find G dim)
(J
T
)
-0.30 -0.20 -0.10
Round-off factor
Round off to the nearest two place
even decimal, i.e., 1.00, 1.20, 1.40
Side (J
S
) 0.01 0.03 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
Table 3-5 Rectangular or Square-End Components
(Capacitors and Resistors) Equal to or Larger
than 1608 (0603) (unit: mm)
Lead Part
Minimum
(Least)
Density
Level C
Median
(Nominal)
Density
Level B
Maximum
(Most)
Density
Level A
Toe (J
T
) 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
H
) -0.05 -0.05 -0.05
Round-off factor
Round off to the nearest two place
even decimal, i.e., 1.00, 1.20, 1.40
Side (J
s
) -0.05 0.00 0.05
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 3-6 Rectangular or Square-End
Components (Capacitors and Resistors)
Smaller than 1608 (0603) (unit: mm)
Lead Part
Minimum
(Least)
Density
Level C
Median
(Nominal)
Density
Level B
Maximum
(Most)
Density
Level A
Toe (J
T
) 0.00 0.10 0.20
Round-off factor
Round off to the nearest two place
decimal, i.e., 1.00, 1.05, 1.10, 1.15
Heel (J
H
) -0.05 -0.05 -0.05
Round-off factor
Round off to the nearest two place
decimal, i.e., 1.00, 1.05, 1.10, 1.15
Side (J
S
) 0.00 0.00 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 0.15 0.20
Table 3-7 Cylindrical End Cap
Terminations (MELF) (unit: mm)x
Lead Part
Minimum
(Least)
Density
Level C
Median
(Nominal)
Density
Level B
Maximum
(Most)
Density
Level A
Toe (J
T
) 0.2 0.4 0.6
Round-off factor
Round off to the nearest two place
even decimal, i.e., 1.00, 1.20, 1.40
Heel (J
H
) 0.02 0.1 0.2
Round-off factor
Round off to the nearest two place
even decimal, i.e., 1.00, 1.20, 1.40
Side (J
S
) 0.01 0.05 0.1
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 3-8 Bottom Only Terminations (unit: mm)
Lead Part
Minimum
(Least)
Density
Level C
Median
(Nominal)
Density
Level B
Maximum
(Most)
Density
Level A
Toe (J
T
) 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
H
) 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
S
) 0.01 0.03 0.08
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
Table 3-9 Leadless Chip Carrier with
Castellated Terminations (unit: mm)
Lead part
Minimum
(Least)
Density
Level C
Median
(Nominal)
Density
Level B
Maximum
(Most)
Density
Level A
Heel (J
H
) (to find
Z dim)
0.45 0.55 0.65
Round-off factor
Round off to the nearest two place
even decimal, i.e., 1.00, 1.20, 1.40
Toe (J
T
) (to find G
dim)
0.05 0.15 0.25
Round-off factor
Round off to the nearest two place
even decimal, i.e., 1.00, 1.20, 1.40
Side (J
S
) -0.15 -0.05 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
February 2005 IPC-7351
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ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ
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
T
) 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
H
) 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
S
) 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)
(J
T
)
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
H
)
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
S
) -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
T
) 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
H
) 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
S
) -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
T
) 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
H
) 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
S
) -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
T
) 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
H
) 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
S
) -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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