NXP Semiconductors

PCA9574

8-bit I2C-bus and SMBus, level translating, low voltage GPIO with reset and interrupt

17.4 Reflow soldering

Key characteristics in reflow soldering are:

• Lead-free versus SnPb soldering; note that a lead-free reflow process usually leads to higher minimum peak

temperatures (see Figure 23) than a SnPb process, thus reducing the process window

• Solder paste printing issues including smearing, release, and adjusting the process window for a mix of large

and small components on one board

• Reflow temperature profile; this profile includes preheat, reflow (in which the board is heated to the peak

temperature) and cooling down. It is imperative that the peak temperature is high enough for the solder to

make reliable solder joints (a solder paste characteristic). In addition, the peak temperature must be low

enough that the packages and/or boards are not damaged. The peak temperature of the package depends on

package thickness and volume and is classified in accordance with Table 16 and Table 17

Package reflow temperature (°C)

Volume (mm³)

Package thickness (mm)

< 350

≥ 350

< 2.5

235

220

≥ 2.5

220

220

Table 16. SnPb eutectic process (from J-STD-020D)

Package reflow temperature (°C)

Volume (mm³)

Package thickness (mm)

< 350

350 to 2000

> 2000

< 1.6

260

260

260

1.6 to 2.5

260

250

245

> 2.5

250

245

245

Table 17. Lead-free process (from J-STD-020D)

Moisture sensitivity precautions, as indicated on the packing, must be respected at all times.

Studies have shown that small packages reach higher temperatures during reflow soldering, see Figure 23.

PCA9574

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Product data sheet

Rev. 6.0 — 31 May 2023

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