SOLDER PAD FOR SURFACE MOUNT

关于Dpak元件焊盘开窗方式

Application Report

SBFA015A - January 1998 - Revised May 2003

SOLDER PAD RECOMMENDATIONS FOR

SURFACE-MOUNT DEVICES

By Wm. P. Klein, P.E.

Cost and performance requirements continue to push thepackaging of electronic systems into smaller and smallerspaces. At one time, the standard center-to-center pin spac-ing was 100 mils (0.1") on through-hole parts (DIPs).The advent of surface-mount devices (SMD) has brought pinspacings that differ from one package series to the next.The solder joint of pin-foot to printed circuit board (PCB) mustprovide the strength to hold the device in place. The closelead spacings make lead-to-lead solder bridges more preva-lent. These factors increase the importance of an optimizedPCB design.

The criteria for a well-designed solder joint is based on bothempirical data and reliability testing. Solder-joint strength isdirectly related to the total solder volume. An observablesolder fillet is evidence of proper wetting. Therefore, apositive solder fillet is usually specified. A joint can bedescribed by the solder fillets formed between the devicepins and the PCB pads. Figure 1 shows the three fillets: toe,heel, and side.

A properly designed solder pad minimizes solder bridgingwhile affording a strong and easily inspected joint.These goals have conflicting dimensional requirements.

Factors to consider when determining the dimensions of thesolder pads include part dimension tolerances, PCB produc-tion tolerances, and accuracy-of-placement tolerances.Figure 2 shows how placement accuracy can affect solderbridge formation. The designer should also consider thelimitations of the soldering process. Boards designed forwave soldering usually have slightly wider pads than thosedesigned for reflow techniques.

Two trade organizations provide industry standards. The Elec-tronic Industries Association (EIA)1 represents manufacturers inall areas of the electronics industry. The EIA’s Joint ElectronDevice Engineering Council (JEDEC)2 establishes standardpackage dimensions. The Institute for Interconnecting andPackaging Electronic Circuits (IPC)3 has established standardsfor PCB design. The Surface Mount Land Pattern Subcommit-tee of the Printed Board Design Committee of IPC has devel-oped standard pad dimensions for the packages defined by theJEDEC committee. The IPC document Surface-Mount Designand Land Pattern Standard is designated IPC-SM-782.To further assist the designer, the mathematical relationshipsin the standard have been programmed in a spreadsheetcalculator. Access to this program is available at the IPC

FIGURE 1. Solder Joint Fillets.

AB-132CCopyright © 1998-2003, Texas Instruments Incorporated

关于Dpak元件焊盘开窗方式

FIGURE 2. Device Placements.

internet web site3. Surface-mount land patterns are given formany JEDEC standard packages. Capability to customizethe patterns for special designs is also provided. The resultsof this program are tabulated in the appendices of this paperfor some of the more popular packages currently supplied byTexas Instruments.

The values listed in the following tables are based on theassumptions shown in Table I. Performance will also dependon process variables. While an effort has been made toselect nominal values for these variables, the design engi-neer should determine the optimum value through experi-mentation.

Fabrication TolerancePlacement ToleranceToe Joint MinimumHeel Joint MinimumSide Joint Minimum

0.1mm0.1mm0.4mm0.5mm0.0mm

NOTES: (1)Electronic Industries Association (EIA)

2500 Wilson BoulevardArlington, VA 22201/

(2)Joint Electron Device Engineering Council (JEDEC)

(3) The Institute for Interconnecting and Packaging

Electronic Circuits (IPC)2215 Sanders Road

Northbrook, IL 60062-6135

Phone: 847-509-9700 Fax: 847-509-9798

/index.html

TABLE I. Assumed Basic Dimensions.

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FIGURE 3. Package Dimensions.

PKG#182235265211219221239217331332348337334338324322333346

LMIN0.2280.2280.2280.3940.3940.3940.3940.3980.1020.1020.1020.1890.2910.2910.2910.2280.3950.395

LMAX0.2440.2440.2440.4190.4190.4190.4190.4190.1180.1180.1180.1970.3230.3230.3230.2440.4200.420

WMIN0.0130.0130.0130.0130.0130.0130.0130.0130.0100.0100.0110.0110.0090.0090.0090.0080.0080.008

WMAX0.0200.0200.0200.0200.0200.0200.0200.0200.0200.0200.0180.0150.0150.0150.0150.0120.0130.013

TMIN0.0160.0160.0160.0160.0160.0160.0160.0200.0140.0140.0040.0180.0220.0220.0220.0160.0200.020

TMAX0.0500.0500.0500.0500.0500.0500.0500.0400.0220.0220.0240.0260.0370.0370.0370.0500.0400.040

AMIN0.1500.1500.1500.2910.2910.2910.2910.2910.0590.0590.0590.1140.1970.1970.1970.1490.2910.291

AMAX0.1570.1570.1570.2990.2990.2990.2990.2990.0690.0690.0690.1220.2200.2200.2200.1570.2990.299

BMIN0.1890.3370.3860.3980.4470.4960.5980.6970.1100.1100.1100.1140.2720.3110.3900.1880.6130.720

BMAX0.1960.3440.3940.4130.4630.5120.6140.7130.1180.1180.1180.1220.2950.3350.4130.1970.6300.730

HMIN0.0530.0530.0530.0930.0930.0930.0930.0930.0350.0350.0350.0320.0770.0770.0770.0530.0530.095

HMAX0.0690.0690.0690.1040.1040.1040.1040.1040.0570.0570.0570.0480.0790.0790.0790.0690.0690.110

PNOM0.05000.05000.05000.05000.05000.05000.05000.05000.03740.03740.02560.02560.02560.02560.02560.02500.02500.0250

LEADCOUNT8141616182024285688202428164856

PACKAGESO-8SO-14

SO-16SO-16WSO-18SO-20SO-24SO-28SOT-23-5SOT-23-6SOT-23-8MSOP-8SSOP-20SSOP-24SSOP-28SSOP-16SSOP-48SSOP-56

TABLE II . Package Dimensions—Inches.

PKG#182235265211219221239217331332348337334338324322333346

LMIN5.795.795.7910.0110.0110.0110.0110.112.592.592.604.807.397.397.395.7910.0310.03

LMAX6.206.206.2010.6410.6410.6410.6410.643.003.003.005.008.208.208.206.2010.6710.67

WMIN0.330.330.330.330.330.330.330.330.250.250.280.280.230.230.230.200.200.20

WMAX0.510.510.510.510.510.510.510.510.510.510.460.380.380.380.380.300.330.33

TMIN0.410.410.410.410.410.410.410.510.360.360.100.460.560.560.560.410.510.51

TMAX1.271.271.271.271.271.271.271.020.560.560.610.660.940.940.941.271.021.02

AMIN3.813.813.817.397.397.397.397.391.501.501.502.905.005.005.003.787.397.39

AMAX3.993.993.997.597.597.597.597.591.751.751.753.105.595.595.593.997.597.59

BMIN4.808.569.8010.1111.3512.6015.1917.702.792.792.802.906.917.909.914.7815.5718.29

BMAX4.988.7410.0110.4911.7613.0015.6018.113.003.003.003.107.498.5110.495.0016.0018.54

HMIN1.351.351.352.362.362.362.362.360.890.890.900.811.961.961.961.351.352.41

HMAX1.751.751.752.642.642.642.642.641.451.451.451.222.012.012.011.751.752.79

PNOM1.2701.2701.2701.2701.2701.2701.2701.2700.9500.9500.6500.6500.6500.6500.6500.6350.6350.635

LEADCOUNT8141616182024285688202428164856

PACKAGESO-8SO-14SO-16SO-16WSO-18SO-20SO-24SO-28SOT-23-5SOT-23-6SOT-23-8MSOP-8SSOP-20SSOP-24SSOP-28SSOP-16SSOP-48SSOP-56

TABLE III. Package Dimensions—Millimeters.

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FIGURE 4. Pad Dimensions.

PKG#182235265211219221239217331332348337334338324322333346

ZMIN0.2730.2730.2730.4470.4470.4470.4470.4480.1470.1470.1470.2260.3510.3510.3510.2730.4480.448

ZMAX0.2770.2770.2770.4510.4510.4510.4510.4510.1510.1510.1510.2300.3550.3550.3550.2770.4520.452

GMIN0.0890.0890.0890.2540.2540.2540.2540.2780.0340.0340.0150.0970.1770.1770.1770.0890.2750.275

GMAX0.0930.0930.0930.2580.2580.2580.2580.2820.0380.0380.0190.1010.1810.1810.1810.0930.2790.279

XMIN0.0180.0180.0180.0180.0180.0180.0180.0180.0170.0170.0160.0140.0130.0130.0130.0110.0120.012

XMAX0.0220.0220.0220.0220.0220.0220.0220.0220.0210.0210.0200.0180.0170.0170.0170.0150.0160.016

YREF0.0940.0940.0940.0990.0990.0990.0990.0990.0580.0580.0680.0660.0890.0890.0890.0940.0890.089

C/CREF0.1830.1830.1830.3530.3530.3530.3530.3650.0930.0930.0830.1640.2660.2660.2660.1830.3640.364

DREF0.1500.3000.3500.3500.4000.4500.5500.6500.0750.0750.0770.0770.2300.2810.3330.1750.5750.675

ENOM0.05000.05000.05000.05000.05000.05000.05000.05000.03740.03740.02560.02560.02560.02560.02560.02500.02500.0250

PACKAGESO-8SO-14SO-16SO-16WSO-18WSO-20WSO-24WSO-28WSOT-23-5SOT-23-6SOT-23-8MSOP-8SSOP-20SSOP-24SSOP-28SSOP-16SSOP-48SSOP-56

TABLE IV. Pad Dimensions—Inches.

PKG#182235265211219221239217331332348337334338324322333346

ZMIN6.9346.9346.93411.35411.35411.35411.35411.3793.7343.7343.7345.7408.9158.9158.9156.93411.37911.379

ZMAX7.0367.0367.03611.45511.45511.45511.45511.4683.8353.8353.8355.8429.0179.0179.0177.03611.48111.481

GMIN2.2612.2612.2616.4526.4526.4526.4527.0610.8640.8640.3812.4644.4964.4964.4962.2616.9856.985

GMAX2.3622.3622.3626.5536.5536.5536.5537.1630.9650.9650.4832.5654.5974.5974.5972.3627.0877.087

XMIN0.4570.4570.4570.4570.4570.4570.4570.4570.4320.4320.4060.3560.3300.3300.3300.2790.3050.305

XMAX0.5590.5590.5590.5590.5590.5590.5590.5590.5330.5330.5080.4570.4320.4320.4320.3730.4060.406

YREF2.3882.3882.3882.5152.5152.5152.5152.5151.4731.4731.7271.6762.2612.2612.2612.3882.2612.261

C/CREF4.6484.6484.6488.9668.9668.9668.9669.2712.3622.3622.1084.1666.7566.7566.7564.6489.2469.246

DREF3.8107.6208.8908.89010.16011.43013.97016.5101.9051.9051.9501.9505.8427.1378.4584.44514.60517.145

ENOM1.2701.2701.2701.2701.2701.2701.2701.2700.9500.9500.6500.6500.6500.6500.6500.6350.6350.635

PACKAGESO-8SO-14SO-16SO-16WSO-18WSO-20WSO-24WSO-28WSOT-23-5SOT-23-6SOT-23-8MSOP-8SSOP-20SSOP-24SSOP-28SSOP-16SSOP-48SSOP-56

TABLE V . Pad Dimensions—Millimeters.

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SOT223

FIGURE 6. PCB Pad Dimensions for SOT223—Inches (mm).

# OFPKGA AND ELEADSDESIGNATORFIGURES 5 AND 635

DCYDCQ

0.0905 (2.30)0.05 (1.27)

BFIGURE 50.03 (0.76)0.017 (0.43)

XFIGURE 60.032 (0.81)0.020 (0.51)

NOTE: Pad sizes are the minimum recommended and maybe increased for improved heat dissipation.

TABLE VI. Dimensions for SOT-223—Inches (mm).

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关于Dpak元件焊盘开窗方式

DDPAK DEVICES

The three DDPAK surface-mount power package types allhave the same body dimensions. They differ only in the

number of leads and their associated lead dimensions.These values are given in Table VIII.

FIGURE 8. PCB Pad Dimensions for DDPAK—inches (mm).

# OFPKGA AND ELEADSDESIGNATORFIGURES 5 AND 6357

KTTKTTKTT

0.10 (2.54)0.067 (1.70)0.05 (1.27)

BFIGURE 50.05 (1.27)0.032 (0.81)0.028 (0.71)

XFIGURE 60.055 (1.35)0.038 (0.97)0.035 (0.89)

NOTE: Pad sizes are the minimum recommended and maybe increased for improved heat dissipation.

TABLE VII. Dimensions for DDPAK—Inches (mm).

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关于Dpak元件焊盘开窗方式

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