
SC16C850
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NXP B.V. 2010. All rights reserved.
Product data sheet
Rev. 2 — 11 November 2010
50 of 55
NXP Semiconductors
SC16C850
2.5 to 3.3 V UART with 128-byte FIFOs and IrDA encoder/decoder
12.4 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 25) 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 39 and 40
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 25.
Table 39.
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 40.
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