BLUENRG-MSCSP datasheet(40/42 Pages) STMICROELECTRONICS

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PCB assembly guidelines

BlueNRG-MS

PCB assembly guidelines

For Flip Chip 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 125 µm.

Flip Chips are fully compatible with the use of near eutectic 95.8% Sn, 3.5% Ag, 0.7% Cu

solder paste with no-clean flux. ST's recommendations for Flip Chip board mounting are

illustrated on the soldering reflow profile shown in Figure 17.

Figure 18: Flip Chip CSP (2.66 x 2.56 x 0.5 pitch 0.4 mm) package reflow profile

recommendation

Table 22: Flip Chip CSP (2.66 x 2.56 x 0.5 pitch 0.4 mm) package reflow profile

recommendation

Profile

Value

Typ.

Max.

Temp. gradient in preheat (T = 70 – 180 °C)

0.9 °C/s

3 °C/s

Temp. gradient (T = 200 – 225 °C)

2 °C/s

3 °C/s

Peak temp. in reflow

240 - 245 °C

260 °C

Time above 220 °C

60 s

90 s

Temp. gradient in cooling

-2 to - 3 °C/s

-6 °C/s

Time from 50 to 220 °C

160 to 220 s

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 (N 2or N 2H 2) is recommended during the whole

reflow, especially above 150 °C.

Flip Chips are able to withstand three times the previous recommended reflow profile to be

compatible with a double reflow when SMDs are mounted on both sides of the PCB plus

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 paste is highly recommended to avoid any cleaning operation. To

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

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