3.4

Placement

1. It is recommended to use leads recognition instead of package outline for accurate placement on footprint with

adequate resolution tool.

2. Tolerance of ±50 µm is recommended.

3. 1.0 N placement force is recommended. Too much placement force can lead to squeezed out solder paste

and cause solder joints to short. Too low placement force can lead to insufficient contact between package

and solder paste that could cause open solder joints or badly centered packages.

4. For assembly, a perfect supporting of the PCB (all the more on flexible PCB) is recommended during solder

paste printing, pick and place and reflow soldering by using optimized tools.

3.5

PCB design preference

1. Any via around or inside the footprint area must be closed to avoid solderpaste migration in the via.

2. Position and dimensions of the tracks should be well balanced. A symmetrical layout is recommended to

prevent assembly troubles.

3.6

Reflow profile

Figure 24. ST ECOPACK recommended soldering reflow profile for PCB mounting

250

0

50

100

150

200

240

210

180

150

120

90

60

30

300

270

-6 °C/s

240-245 °C

2 - 3 °C/s

Temperature (°C)

-2 °C/s

-3 °C/s

Time (s)

0.9 °C/s

60 sec

(90 max)

Note:

Minimize air convection currents in the reflow oven to avoid component movement. O2 rate inside the oven must

be below 500 ppm. Maximum soldering profile corresponds to the latest IPC/JEDEC J-STD-020.

ESDAxxWY

Recommendations on PCB assembly

DS14779 - Rev 1

page 10/13