PCA9901GD datasheet(21/27 Pages) NXP

21 / 27 page

PCA9901_1

Product data sheet

Rev. 01 — 3 December 2009

21 of 27

NXP Semiconductors

PCA9901

One wire single LED driver

15.4 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 15) 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 7 and 8

Table 7.

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 8.

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

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 15.

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