Technological for soldering question

[RSaat.1]

We plan to use in one of our products WLCSP49 package.

Please see page 126(PDF attached) - According to Table 80. "WLCSP49 recommended PCB design rules (0.4 mm pitch)" , the recommended Dpad Dimension is 220 µm.

We perform some measurements on the PCB and found out that The actual Pad size is between 178-192 µm.

·        Do you have any recommendations for the stencil in this case?

·        Are we going to face with reliability problems?

·        What is the minimum Dpad Dimension that allowed?

Thanks

Roni

[KDJEM.1]

Hello @RSaat.1​ and welcome to Community :) ,

To mount a WLCSP on a PCB, ST recommends the use of a solder stencil with an aperture of 330 x 330 μm2 maximum and a stencil typical thickness of 125 μm.

I recommend you, for more information, to refer to the TN1163: Description of WLCSP for microcontrollers and recommendations for its use and precisely Package quality and reliability Section. This document describes the wafer level chip size package (WLCSP) and provides recommendation on how to use it.

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Thank you.

Kaouthar