June 2014

DocID025707 Rev 2

1/21

TN1163

Technical note

Description of WLCSP for microcontrollers and

recommendations for use

Introduction

This document describes the WLCSP (wafer level chip size package), and provides

recommendation on how to use it. Only WLCSP for microcontrollers are described herein.

The competitive market of portable equipment, in particular the mobile phone market, is

driven by the challenging development of highly integrated devices. To allow manufacturers

of portable equipment to minimize the dimension of their devices, STMicroelectronics has

developed WLCSP with reduced size, thickness and weight. The electrical performance of

such components is improved by using shorter connections than in standard plastic

packages such as TSSOP, SSOP or BGA.

The WLCSP family has been designed to fulfill the same quality levels and same reliability

performance as standard semiconductor plastic packages. As a consequence these new

WLCSP can be considered as new surface mount devices which are assembled on a

printed circuit board (PCB) without any special or additional process steps. In particular

these packages do not require any extra underfill to increase reliability performance or to

protect the device. These packages are compatible with existing pick-and-place equipment

for board mounting. Only Lead-free RoHS compliant WLCSP are available in mass

production. The packages offered in WLCSP are listed in Table 1.

This document addresses the following topics:

• Package description

• Device marking

• Packing specifications and labeling

• Storage and shipping recommendations

• Soldering assembly recommendations

• Package changes and package quality

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