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BOARD LAYOUT

Copper

Trace Width

Solder Mask

Thickness

Solder

Pad Width

Solder Mask

Opening

Copper Trace

Thickness

Component Location

TPA2012D2

SLOS438C – DECEMBER 2004 – REVISED MARCH 2007

In making the pad size for the WCSP balls, it is recommended that the layout use nonsolder mask defined

(NSMD) land. With this method, the solder mask opening is made larger than the desired land area, and the

opening size is defined by the copper pad width. Figure 36 and Table 2 shows the appropriate diameters for a

WCSP layout. The TPA2012D2 evaluation module (EVM) layout is shown in the next section as a layout

example.

Figure 36. Land Pattern Dimensions

SOLDER PAD

COPPER

COPPER

STENCIL

DEFINITIONS

PAD

OPENING

THICKNESS

OPENING

THICKNESS

Nonsolder mask

275

µm

275

µm x 275 µm Sq.

375

µm (+0.0, -25 µm)

1 oz max (32

µm)

125

µm thick

defined (NSMD)

(+0.0, -25

µm)

(rounded corners)

(1)

Circuit traces from NSMD defined PWB lands should be 75

µm to 100 µm wide in the exposed area inside the solder mask opening.

Wider trace widths reduce device stand off and impact reliability.

(2)

Best reliability results are achieved when the PWB laminate glass transition temperature is above the operating the range of the

intended application.

(3)

Recommend solder paste is Type 3 or Type 4.

(4)

For a PWB using a Ni/Au surface finish, the gold thickness should be less 0.5 mm to avoid a reduction in thermal fatigue performance.

(5)

Solder mask thickness should be less than 20

µm on top of the copper circuit pattern

(6)

Best solder stencil performance is achieved using laser cut stencils with electro polishing. Use of chemically etched stencils results in

inferior solder paste volume control.

(7)

Trace routing away from WCSP device should be balanced in X and Y directions to avoid unintentional component movement due to

solder wetting forces.

the TPA2012D2 is important for the efficiency of the Class-D amplifier. Any resistance or inductance in the trace

between the device and the capacitor can cause a loss in efficiency.

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