PCF85263AT datasheet(84/100 Pages) NXP

84 / 100 page

PCF85263A

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Product data sheet

Rev. 4.1 — 27 November 2015

84 of 100

NXP Semiconductors

PCF85263A

Tiny RTC with alarm, battery switch-over, and I2C-bus

• Board specifications, including the board finish, solder masks and vias

• Package footprints, including solder thieves and orientation

• The moisture sensitivity level of the packages

• Package placement

• Inspection and repair

• Lead-free soldering versus SnPb soldering

21.3 Wave soldering

Key characteristics in wave soldering are:

• 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

21.4 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 48) 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 70 and 71

Table 70.

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

Package thickness (mm)

Package reflow temperature (

C)

Volume (mm3)

< 350

 350

< 2.5

235

220

 2.5

220

Table 71.

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

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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