3.2

Solder paste

1.

Halide-free flux qualification ROL0 according to ANSI/J-STD-004.

2.

“No clean” solder paste is recommended.

3.

Offers a high tack force to resist component displacement during PCB movement.

4.

Use solder paste with fine particles: Type 4 (powder particle size 20-48 μm per IPC J STD-005).

3.3

Placement

1.

Manual positioning is not recommended.

2.

It is recommended to use the lead recognition capabilities of the placement system, not the outline centering

3.

Standard tolerance of ±0.05 mm is recommended.

4.

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.

5.

To improve the package placement accuracy, a bottom side optical control should be performed with a high

resolution tool.

6.

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.

3.4

PCB design preference

1.

To control the solder paste amount, the closed via is recommended instead of open vias.

2.

The position of tracks and open vias in the solder area should be well balanced. A symmetrical layout is

recommended, to avoid any tilt phenomena caused by asymmetrical solder paste due to solder flow away.

3.5

Reflow profile

Figure 12. 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.

BAT30F4

Solder paste

DS10126 - Rev 8

page 8/11