Design recommendations when using

WLCSP34 package

AN4630

5

Design recommendations when using WLCSP34

package

Design recommendations when using WLCSP34 package

The application board for the WLCSP34 package was designed in a four layers due the

more complexity to treat the CSP package. The print of the four layers is shown in Figure

17: "WLCSP34 four layers board".

Figure 17: WLCSP34 four layers board

A good ground connection is essential for the RF performances. This point is important for

all RF devices in all packages, but it is critical in a CSP package due to the reduced

dimension of the device. A good ground connection, that means low resistance between

the ground balls of the device and the ground layer, produces a low cross talk among

critical blocks that means RF performance not impacted.

The ground connection of the BlueNRG in WLCSP package on the TOP layer is shown in

Figure 18: "WLCSP34 ground connection (TOP layer view)". Laser vias are used to

connect TOP layer ground and INNER2 layer ground. The ground laser vias have to be put

under GND balls, under the GND_SMPS ball and under the unused balls.

In the TOP layer the GND_SMPS has to be kept separated from the GND.

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