ESDA14V2-1BF3

PCB recommendations

Doc ID 15894 Rev 1

7/9

4.2

Assembly

For chip scale package mounting on the PCB, STMicroelectronics recommends the use of a

solder stencil aperture of 330 x 330 µm² maximum and a typical stencil thickness of 75 or

80 µm. Chip scale packages are fully compatible with the use of near eutectic 95.5 Sn, 4 Ag,

0.5 Cu solder paste with no-clean flux. ST's recommendations for chip scale package board

mounting are illustrated on the soldering reflow profile shown in Figure 15.

Figure 15.

ST ECOPACK® recommended soldering reflow profile for PCB mounting

Dwell time in the soldering zone (with temperature higher than 220 °C) has to be kept as

short as possible to prevent component and substrate damages. Peak temperature must not

exceed 260 °C. Controlled atmosphere (N2 or N2H2) is recommended during the whole

reflow, especially above 150 °C.

Chip scale packages are able to withstand three times the previous recommended reflow

profile in order to be compatible with a double reflow when SMDs are mounted on both sides

of the PCB and one additional repair.

A maximum of three soldering reflows are allowed for these lead-free packages (with repair

step included).

The use of a no-clean flux is highly recommended to avoid any cleaning operation. To

prevent any bump cracks, ultrasonic cleaning methods are not recommended.

0

01

2345

67

Time (min)

Temperature (°C)

2°C/s recommended

6°C/s max

220°C

125 °C

260°C max

255°C

180°C

90 sec max

10-30 sec

90 to 150 sec

3°C/s max

0

01

2345

67

Time (min)

Temperature (°C)

2°C/s recommended

6°C/s max

220°C

125 °C

260°C max

255°C

180°C

90 sec max

10-30 sec

90 to 150 sec

3°C/s max