74LX1G04

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Figure 1 : RECOMMENDED SOLDERING REFLOW PROFILE FOR LEADFREE FLIP-CHIP

MOUNTING ON PCB

For Flip-Chip 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 125µm. Flip-Chips are fully compatible with

the use of near eutectic 95.5Sn 4Ag 0.5Cu solder paste with no clean flux. ST's recommendations for

Flip-Chip board mounting are illustrated on the soldering reflow profile shown in figure 1 below.

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, specially above 150°C.

Flip-Chips 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 plus one additional

repair. A maximum of three soldering reflows are allowed for these leadfree packages (with repair step

included). The use of a no clean flux is highly recommended to avoid any cleaning operation. In order 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

3˚C/s max