PCAL9554CBS datasheet(35/42 Pages) NXP

35 / 42 page

PCAL9554B_PCAL9554C

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Product data sheet

Rev. 2 — 10 December 2012

35 of 42

NXP Semiconductors

PCAL9554B; PCAL9554C

Low-voltage 8-bit I2C-bus/SMBus low power I/O port

• Process issues, such as application of adhesive and flux, clinching of leads, board

transport, the solder wave parameters, and the time during which components are

exposed to the wave

• Solder bath specifications, including temperature and impurities

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 34) 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 25 and 26

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 34.

Table 25.

SnPb eutectic process (from J-STD-020C)

Package thickness (mm)

Package reflow temperature (

C)

Volume (mm3)

< 350

 350

< 2.5

235

220

 2.5

220

Table 26.

Lead-free process (from J-STD-020C)

Package thickness (mm)

Package reflow temperature (

C)

Volume (mm3)

< 350

350 to 2000

> 2000

< 1.6

260

1.6 to 2.5

260

250

245

> 2.5

250

245

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