IPC-SM-782A 表面安装设计和焊盘设计标准(带BGA).pdf - 第93页

5.0 LAND PATTERN DIMENSIONS Figure 3 provides the land pattern dimensions for SOT 23 components. These numbers represent industry consensus on the best dimensions based on empirical knowledge of fab- ricated land pattern…

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4.0 COMPONENT DIMENSIONS
Figure 2 provides the component dimensions for SOT 23 components.
Component
Identifier
L (mm) S (mm) W (mm) T (mm) H (mm) P (mm)
min max min max min max min max max nom
SOT 23 2.30 2.60 1.10 1.47 0.36 0.46 0.45 0.60 1.10 0.95
Figure 2 SOT 23 component dimensions
2.80–3.00
W
L
P
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
H
S
T
▼
▼
See profile
table
Profile Dimension TO 236 Des
Low 0.01–0.10 AB
Medium 0.08–0.13 ——
High 0.1–0.25 AA
1.20–1.40
Dimensions are in millimeters
IPC-782-8-6-2
IPC-SM-782
Subject
SOT 23
Date
8/93
Section
8.6
Revision
Page2of4
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5.0 LAND PATTERN DIMENSIONS
Figure 3 provides the land pattern dimensions for SOT 23
components. These numbers represent industry consensus
on the best dimensions based on empirical knowledge of fab-
ricated land patterns.
In the table, the dimensions shown are at maximum material
condition (MMC). The least material condition (LMC) should
not exceed the fabrication (F) allowance shown on page 4.
The LMC and the MMC provide the limits for each dimension.
The dotted line in Figure 3 shows the grid placement court-
yard which is the area required to place land patterns and
their respective components in adjacent proximity without
interference or shorting. Numbers in the table represent the
number of grid elements (each element is 0.5 by 0.5 mm) in
accordance with the international grid detailed in IEC publica-
tion 97.
RLP No.
Component
Identifier Z (mm) G (mm) X (mm)
Y (mm) C (mm) E (mm)
Placement Grid
(No. of Grid
Elements)ref ref ref
210 SOT 23
(reflow solder)
3.60 0.80 1.00 1.40 2.20 0.95 8x8
*Note: If a more robust pattern is desired for wave soldering, add 0.2 mm to ‘‘Z’’ and identify as RLP 210W.
Figure 3 SOT 23 land pattern dimensions
ZG
Y
Y
C
▼▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
E
X
▼
▼
Grid placement courtyard
▼
IPC-782-8-6-3
IPC-SM-782
Subject
SOT 23
Date
8/93
Section
8.6
Revision
Page3of4
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6.0 TOLERANCE AND SOLDER JOINT ANALYSIS
Figure 4 provides an analysis of tolerance assumptions and
resultant solder joints based on the land pattern dimensions
shown in Figure 3. Tolerances for the component dimensions,
the land pattern dimensions (fabrication tolerances on the
interconnecting substrate), and the component placement
equipment accuracy are all taken into consideration.
Figure 4 provides the solder joint minimums for toe, heel, and
side fillets, as discussed in Section 3.3. The tolerances are
addressed in a statistical mode, and assume even distribution
of the tolerances for component, fabrication, and placement
accuracy.
Individual tolerances for fabrication (‘‘F’’) and component
placement equipment accuracy (‘‘P’’) are assumed to be as
given in the table. These numbers may be modified based on
user equipment capability or fabrication criteria. Component
tolerance ranges (C
L
,C
S
, and C
W
) are derived by subtracting
minimum from maximum dimensions given in Figure 2. The
user may also modify these numbers, based on experience
with their suppliers. Modification of tolerances may result in
alternate land patterns (patterns with dimensions other than
the IPC registered land pattern dimensions).
The dimensions for minimum solder fillets at the toe, heel, or
side (J
T
,J
H
,J
S
) have been determined based on industry
empirical knowledge and reliability testing. Solder joint
strength is greatly determined by solder volume. An observ-
able solder fillet is necessary for evidence of proper wetting.
Thus, the values in the table usually provide for a positive sol-
der fillet. Nevertheless, the user may increase or decrease the
minimum value based on process capability.
RLP No.
Tolerance
Assumptions (mm)
Solder Joint
Toe (mm) Heel (mm) Side (mm)
FPC
L
J
T
min J
T
max C
S
J
H
min J
H
max C
W
J
S
min J
S
max
210 0.2 0.2 0.30 0.44 0.65 0.37 0.10 0.33 0.10 0.17 0.32
Figure 4 Tolerance and solder joint analysis
Zmax
Lmin
▼
▼
▼
▼
1
/2 T
T
J
T
min
Zmax = Lmin + 2J
T
min + T
T
Where:
J
T
min = Minimum toe fillet
T
T
= Combined tolerances
at toe fillet
Smax
J
H
min
Gmin = Smax - 2J
H
min - T
H
Where:
J
H
min = Minimum heel fillet
T
H
= Combined tolerances
at heel fillet
1
/2 T
H
Xmax
Xmax = Wmin + 2J
S
min + T
S
Where:
J
S
min = Minimum side fillet
T
S
= Combined tolerances
at side fillet
▼
▼
Toe Fillet
▼
▼
▼
Heel Fillet Side Fillet
▼
▼
▼
▼
▼
J
T
max
J
H
max
J
S
min
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
Gmin
▼
1
/2 T
S
J
S
max
▼
▼
▼
Wmin
▼
IPC-782-8-6-4
IPC-SM-782
Subject
SOT 23
Date
8/93
Section
8.6
Revision
Page4of4
电子技术应用　　　　　ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ