IPC-SM-782A-表面贴装焊盘图形设计标准.pdf.pdf - 第115页

1.0 INTRODUCTION This section covers land patterns for components with gullwings on two sides. Each subsection contains information in accordance with the following format: 1.0 Scope 2.0 Applicable Documents 3.0 General …

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 1 (mm) Heel 2 (mm) Side 1 (mm) Side 2 (mm)

FPC

min J

max C

min J

max C

min J

max C

min J

max C

min J

max

235A 0.10 0.10 1.09 0.39 0.94 0.29 0.37 0.51 1.50 0.29 1.04 0.27 0.03 0.16 1.00 0.02 0.52

236 0.10 0.10 1.28 0.36 1.00 0.50 0.19 0.44 1.00 0.19 0.69 0.40 0.03 0.23 0.64 –0.04 0.28

237 0.10 0.10 0.40 0.34 0.54 0.30 0.27 0.42 0.30 0.27 0.42 0.30 –0.04 0.11 0.30 –0.02 0.13

Figure 4 Tolerance and solder joint analysis

Zmax

▼

/2 T

min

Zmax = Lmin + 2J

min + T

Where:

min = Minimum toe fillet

= Combined tolerances

at toe fillet

min

/2 T

Xmax = Wmin + 2J

min + T

Where:

min = Minimum side fillet

= Combined tolerances

at side fillet

Side Fillet Toe Fillet

▼

Heel Fillets

Side Fillet

▼

max

min

▼

/2 T

max

W1min

▼

X1maxX2max

▼

min

▼

/2 T

max

▼

W2min

Lmin

▼

/2 T

min

▼

max

▼

IPC-782-8-11-4

IPC-SM-782

Subject

TO 252/TO 268

Date

5/96

Section

8.11

Revision

Page4of4

1.0 INTRODUCTION This section covers land patterns for

components with gullwings on two sides. Each subsection

contains information in accordance with the following format:

1.0 Scope

2.0 Applicable Documents

3.0 General Component Description (Figure 1)

4.0 Component Dimensions (Figure 2)

5.0 Land Pattern Dimensions (Figure 3)

6.0 Tolerance and Solder Joint Analysis (Figure 4)

The following is the table of contents for this section:

Table of Contents

Components with Gullwing Leads on Two Sides

Section Component Standard Source Lead Pitch

9.1 SOIC JEDEC 1.27 mm

9.2 SSOIC JEDEC 0.63 and

0.80 mm

9.3 SOPIC EIAJ 1.27 mm

9.4 TSOP EIAJ 0.3, 0.4,

0.5 mm

9.5 CFP 1.27 mm

2.0 APPLICABLE DOCUMENTS

The following documents, of the issue in effect on the revision

date of this section, form a part of this specification to the

extent specified herein.

2.1 Electronic Industries Association (EIA)

EIA-481-A Taping of Surface Mount Components for Auto-

matic Placement

2.2 International Electrotechnical Commission (IEC)

IEC 97 Grid Elements

2.3 Electronic Industries Association of Japan

IC-74-1 General Rules for Preparation of Outline Drawings of

Integrated Circuits

IC-74-2 General Rules for Preparation of Outline Drawings of

Integrated Circuits, Thin Small Outline Packages

3.0 General Information

3.1 General Component Description

The two-sided gull

wing family has a number of generic package sizes in the

family. The body sizes are varied, but the basic family is char-

acterized by 1.27 mm or 0.63 mm lead centers with leads on

the long side of a rectangular body. The family has been

expanded to include a limited number of 0.80, 0.65, 0.50,

0.40, and 0.3 mm pitch devices.

Within the component families, body width and lead span are

constant, while body length changes as the lead count

changes.

A major advantage of this package style is that it can be pre-

tested prior to substrate assembly while still offering relatively

high density. Its small area, low height, and minimal weight are

its major advantages over DIPs. The package has orientation

features on the edge of the package to aid in handling and

identification.

Coplanarity is an issue for all components with gullwings on

two sides. In general, the leads must be coplanar within 0.1

mm. That is, when the component is placed on a flat surface,

(e.g., a granite block), no lead may be more than 0.1 mm off

the flat surface.

3.2 Process Considerations Some members of the SOIC

family are processed on the secondary side and wave sol-

dered. When parts are processed by wave solder, correct part

orientation must be observed. Consult your manufacturer

before placing SOIC’s on the wave solder side of the board.

High lead count packages and fine pitch parts, 0.63 mm or

less, should be processed by infrared reflow, conduction

reflow, or hot bar soldering, and should not be wave soldered.

1. Application for copies of EIA and EIAJ documents should

be addressed to EIA, 2001 Pennsylvania Ave N.W., Wash-

ington, DC, 20006-1813 or Global Engineering Docu-

ments, 1990 M St. N.W., Washington, DC 20036.

2. Application for copies should be addressed to IEC, 3 rue

de Varembe, PO Box 131 - 1211 Geneva 20, Switzerland

IPC-SM-782

Surface Mount Design

and Land Pattern Standard

Date

8/93

Section

9.0

Revision Subject

Components with

Gullwings on Two Sides

Page1of2

This Page Intentionally Left Blank

IPC-SM-782

Subject

Components with Gullwings on Two Sides

Date

8/93

Section

9.0

Revision

Page2of2