IPC-SM-782A-表面贴装焊盘图形设计标准.pdf.pdf - 第82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 inductors.

These numbers represent industry consensus on the best

dimensions based on empirical knowledge of fabricated land

patterns.

In the table, the dimensions shown are at maximum material

condition (MMC). The least mate-rial 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)

C (mm) Y (mm)

Placement Grid

(No. Grid Elements)ref ref

160 2012 Chip 3.00 1.00 1.00 2.00 1.00 4x8

161 3216 Chip 4.20 1.80 1.60 3.00 1.20 6x10

162 4516 Chip 5.80 2.60 1.00 4.20 1.60 4x12

163 2825 Prec 3.80 1.00 2.40 2.40 1.40 6x10

164 3225 Prec 4.60 1.00 2.00 2.80 1.80 6x10

165 4532 Prec 5.80 2.20 3.60 4.00 1.80 8x14

166 5038 Prec 5.80 3.00 2.80 4.40 1.40 8x14

167 3225/3230 Molded 4.40 1.20 2.20 2.80 1.60 6x10

168 4035 Molded 5.40 1.00 1.40 3.20 2.20 8x12

169 4532 Molded 5.80 1.80 2.40 3.80 2.00 8x14

170 5650 Molded 6.80 3.20 4.00 5.00 1.80 12x16

171 8530 Molded 9.80 5.00 1.40 7.40 2.40 8x22

Figure 3 Inductor land pattern dimensions

▼

Grid

placement

courtyard

▼

IPC-782-8-3-3

IPC-SM-782

Subject

Inductors

Date

8/93

Section

8.3

Revision

Page3of4

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

, and C

) 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

) 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

min J

max C

min J

max C

min J

max

160 0.2 0.2 0.663 0.32 0.98 0.721 0.02 0.74 0.663 –0.13 0.53

161 0.2 0.2 0.663 0.32 0.98 0.787 0.02 0.81 0.663 –0.18 0.48

162 0.2 0.2 0.663 0.47 1.13 0.970 –0.02 0.95 0.663 –0.13 0.53

163 0.2 0.2 0.663 0.47 1.13 0.773 –0.08 0.70 0.325 0.06 0.39

164 0.2 0.2 0.663 0.52 1.18 0.970 –0.07 0.90 0.490 0.06 0.54

165 0.2 0.2 0.663 0.47 1.13 0.970 –0.02 0.95 0.490 0.05 0.54

166 0.2 0.2 0.663 0.39 1.06 0.758 –0.12 0.64 0.325 0.01 0.33

167 0.2 0.2 0.490 0.46 0.94 0.648 0.17 0.82 0.346 0.03 0.37

168 0.2 0.2 0.583 0.50 1.09 0.837 –0.12 0.72 0.412 –0.11 0.31

169 0.2 0.2 0.663 0.47 1.13 0.894 0.23 1.12 0.346 0.03 0.37

170 0.2 0.2 0.346 0.58 0.92 1.058 0.03 1.09 0.490 –0.14 0.34

171 0.2 0.2 0.583 0.48 1.07 0.837 0.10 0.94 0.412 –0.11 0.31

Figure 4 Tolerance and solder joint analysis

▼

Wmin

Lmin

▼

Zmax

▼

/2 T

min

Smax

min

Xmax

▼

Toe Fillet

/2 T

▼

Heel Fillet Side Fillet

▼

max

min

▼

Gmin

▼

/2 T

▼

IPC-872-8-3-4

IPC-SM-782

Subject

Inductors

Date

8/93

Section

8.3

Revision

Page4of4

1.0 SCOPE

Microminiature leadless devices are available to the circuit

designer in rectangular form for discrete components such as

tantalum capacitors.

This subsection provides the component and land pattern

dimensions for tantalum capacitors along with an analysis of

tolerance and solder joint assumptions used to arrive at the

land pattern dimensions. Basic construction of the inductor is

also covered.

2.0 APPLICABLE DOCUMENTS

See Section 8.0 for documents applicable to the subsections.

3.0 COMPONENT DESCRIPTIONS

A variety of values exist for tantalum capacitors. The following

sections describe the most common types.

3.1 Basic Construction See Figure 1.

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 a post-plating reflow

operation to fuse the solder. The tin/lead finish should be at

least 0.0075 mm [0.0003 in] thick.

The termination shall be symmetrical, and shall not have nod-

ules lumps, protrusions, etc., that compromise the symmetry

or dimensional tolerances of the part. The end termination

shall cover the ends of the components, and shall extend out

to the top and bottom of the component.

Most common termination materials include palladium-silver

alloy, silver, and gold. Solder finish applied over precious

metal electrodes shall 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.

3.1.2 Marking Parts are available with or without marked

capacitance 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-782-8-4-1

Figure 1 Tantalum capacitor construction

IPC-SM-782

Surface Mount Design

and Land Pattern Standard

Date

5/96

Section

8.4

Revision

Subject

Tantalum Capacitors

Page1of4