
NXP Semiconductors
PCA9550
2-bit I 2 C-bus LED driver with programmable blink rates
? Process issues, such as application of adhesive and ?ux, clinching of leads, board
transport, the solder wave parameters, and the time during which components are
exposed to the wave
? Solder bath speci?cations, including temperature and impurities
15.4 Re?ow soldering
Key characteristics in re?ow soldering are:
? Lead-free versus SnPb soldering; note that a lead-free re?ow process usually leads to
higher minimum peak temperatures (see Figure 26 ) 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
? Re?ow temperature pro?le; this pro?le includes preheat, re?ow (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 classi?ed in accordance with
Table 15 and 16
Table 15.
SnPb eutectic process (from J-STD-020C)
Package thickness (mm)
Package re?ow temperature ( ° C)
Volume (mm 3 )
< 350
≥ 350
< 2.5
≥ 2.5
Table 16.
235
220
Lead-free process (from J-STD-020C)
220
220
Package thickness (mm)
Package re?ow temperature ( ° C)
Volume (mm 3 )
< 350
350 to 2000
> 2000
< 1.6
1.6 to 2.5
> 2.5
260
260
250
260
250
245
260
245
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 re?ow
soldering, see Figure 26 .
PCA9550_5
? NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 05 — 13 October 2008
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