PCB recommendations

BAT30F3

8/10

Doc ID 16915 Rev 2

4.2

Assembly

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

solder stencil aperture of 330 x 330 µm 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 11.

Figure 11.

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 damage. 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