NXP Semiconductors
PCF2120
Quartz oscillator
• 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 8 and 9
Table 8. 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
220
Table 9. Lead-free process (from J-STD-020C)
Package thickness (mm) Package reflow temperature (°C)
Volume (mm3)
< 350
350 to 2000
< 1.6
260
260
1.6 to 2.5
260
250
> 2.5
250
245
> 2000
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 reflow
soldering, see Figure 11.
temperature
maximum peak temperature
= MSL limit, damage level
minimum peak temperature
= minimum soldering temperature
peak
temperature
PCF2120_1
Product data sheet
MSL: Moisture Sensitivity Level
Fig 11. Temperature profiles for large and small components
Rev. 01 — 5 February 2008
time
001aac844
© NXP B.V. 2008. All rights reserved.
11 of 14