IPC-SM-782A 表面安装设计和焊盘设计标准(带BGA).pdf - 第86页
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, …
5.0 LAND PATTERN DIMENSIONS
Figure 3 provides the land pattern dimensions for tantalum
capacitors. These numbers represent industry consensus on
the best dimensions based on empirical knowledge of fabri-
cated 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
(mm) Z (mm) G (mm) X (mm)
Y (mm) C (mm)
Placement Grid
(No. of Grid Elements)ref ref
180A 3216 4.80 0.80 1.20 2.00 2.80 6x12
181A 3528 5.00 1.00 2.20 2.00 3.00 8x12
182A 6032 7.60 2.40 2.20 2.60 5.00 8x18
183A 7343 9.00 3.80 2.40 2.60 6.40 10x20
Figure 3 Tantalum capacitor land pattern dimensions
▼
▼
▼
▼
▼
▼
▼
▼
▼
C
G
Z
X
Y
Grid
placement
courtyard
▼
IPC-782-8-4-3
IPC-SM-782
Subject
Tantalum Capacitors
Date
5/96
Section
8.4
Revision
A
Page3of4
电子技术应用 ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ
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
180A 0.10 0.10 0.40 0.69 1.11 0.94 –0.01 0.94 0.40 –0.20 0.23
181A 0.10 0.10 0.40 0.64 1.06 0.94 0.04 0.99 0.40 –0.21 0.22
182A 0.10 0.10 0.60 0.64 1.26 1.04 0.05 1.09 0.60 –0.30 0.31
183A 0.10 0.10 0.60 0.69 1.31 1.04 –0.00 1.04 0.60 –0.30 0.31
Figure 4 Tolerance and solder joint analysis
Zmax = Lmin + 2J
T
min + T
T
Where:
J
T
min = Minimum toe fillet
T
T
= Combined tolerances
at toe fillet
Gmin = Smax - 2J
H
min - T
H
Where:
J
H
min = Minimum heel fillet
T
H
= Combined tolerances
at heel fillet
Xmax = Wmin + 2J
S
min + T
S
Where:
J
S
min = Minimum side fillet
T
S
= Combined tolerances
at side fillet
▼
Wmin
Lmin
▼
▼
Zmax
▼
▼
1
/2 T
T
J
T
min
Smax
J
H
min
Xmax
▼
▼
Toe Fillet
1
/2 T
S
▼
▼
▼
Heel Fillet Side Fillet
▼
▼
▼
▼
▼
J
T
max
J
H
max
J
S
max
J
S
min
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
▼
Gmin
▼
▼
1
/2 T
H
▼
▼
▼
IPC-782-8-4-4
IPC-SM-782
Subject
Tantalum Capacitors
Date
5/96
Section
8.4
Revision
A
Page4of4
电子技术应用 ｗｗｗ．ＣｈｉｎａＡＥＴ．ｃｏｍ
1.0 SCOPE
This subsection provides the component and land pattern
dimensions for metal electrode face components (MELFs).
Basic construction of the MELF device is also covered. At the
end of this subsection is a listing of the tolerances and target
solder joint dimensions used to arrive at the land pattern
dimensions.
2.0 APPLICABLE DOCUMENTS
See Section 8.0 for documents applicable to the subsections.
3.0 COMPONENT DESCRIPTIONS
Resistors, ceramic capacitors, and tantalum capacitors may
all be packaged in these tubular shapes.
3.1 Basic Construction
See Figures 1a and 1b.
3.1.1 Termination Materials
End terminations should be
solder-coated with a tin/lead alloy. The solder should contain
between 58 to 68% tin. Solder may be applied to the termi-
nation by hot dipping or by plating from solution. Plated sol-
der terminations should be subjected to post-plating reflow
operation to fuse the solder. The tin/lead finish should be at
least 0.0075 mm [0.0003 in] thick. The terminations should be
symmetrical, and should not have nodules, lumps, protru-
sions, etc., that compromise the symmetry or dimensional tol-
erances of the part.
The most common termination materials include palladium-
silver alloy, silver, and gold. Solder finish applied over precious
metal electrodes should have a diffusion barrier layer between
the electrode metallization and the solder finish. The barrier
layer should be nickel or an equivalent diffusion barrier, and
should be at least 0.00125 mm [0.00005 in] thick. The end
termination shall cover the ends of the components, and shall
extend around the entire periphery.
3.1.2 Marking
Parts are available with or without marked
values.
3.1.3 Carrier Package Format
Bulk rods, 8 mm tape/4
mm pitch is preferred for best handling. Tape and reel speci-
fications provide additional requirements.
3.1.4 Resistance to Soldering
Parts should be capable of
withstanding five cycles through a standard reflow system
operating at 215°C. Each cycle shall consist of 60 seconds
exposure at 215°C. Parts must also be capable of withstand-
ing a minimum of 10 seconds immersion in molten solder at
260°C.
IPC-782-8-5-1a
Figure 1a Metal electrode face component construction
IPC-782-8-5-1b
Figure 1b Break-away diagram of MELF components
IPC-SM-782
Surface Mount Design
and Land Pattern Standard
Date
5/96
Section
8.5
Revision
A
Subject
Metal Electrode Face
(MELF) Components
Page1of4
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