AN4159

PCB design rules

Doc ID 023639 Rev 3

9/27

4

PCB design rules

The pressure sensor senses mechanical stress coming from the PCB board, hence it

should be kept minimal.

PCB land and solder masking general recommendations are shown below. Refer to the

LPS331AP datasheet for pad count, size and pitch.

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It is recommended to open a solder mask external to PCB land

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The area below the sensor (on the same side of the board) must be defined as keepout

area. It is strongly recommended not to place any structure in top metal layer

underneath the sensor.

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Traces connected to pads should be as much symmetric as possible. Symmetry and

balance for pad connection will help component self alignment and will lead to a better

control of solder paste reduction after reflow

●

For better performances over temperature, it is strongly recommended not to place

large insertion components like buttons or shielding boxes at distances less than 2 mm

from the sensor

●

Pin #1 indicator must be left unconnected to ensure proper device operation

Figure 6.

Recommended land and solder mask design for LGA packages

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A = Clearance from PCB land edge to solder mask opening

≥ 0.25 mm to ensure that

solder mask is opened externally to device area

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B = PCB land length = LGA solder pad length + 0.1 mm

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C = land width = LGA solder pad width + 0.1 mm

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D = Solder mask opening length = PCB land length + 0.3 mm: design 0.05 mm inside

and 0.25 mm outside

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E = Solder mask opening width = PCB land width + 0.1 mm