pca8802 NXP Semiconductors, pca8802 Datasheet - Page 29

• Manufacturer Part Number: pca8802
• Description: Smartcard Rtc; Ultra Low Power Oscillator With Integrated Counter For Initiating One Time Password Generation
• Manufacturer: NXP Semiconductors

NXP Semiconductors
16. Soldering of WLCSP packages
PCA8802_1
Product data sheet
16.1 Introduction to soldering WLCSP packages
16.2 Board mounting
16.3 Reflow soldering
This text provides a very brief insight into a complex technology. A more in-depth account
of soldering WLCSP (Wafer Level Chip-Size Packages) can be found in application note
AN10439 “Wafer Level Chip Scale Package” and in application note AN10365 “Surface
mount reflow soldering description” .
Wave soldering is not suitable for this package.
All NXP WLCSP packages are lead-free.
Board mounting of a WLCSP requires several steps:
Key characteristics in reflow soldering are:
Table 16.
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
Package thickness (mm)
< 1.6
1.6 to 2.5
> 2.5
1. Solder paste printing on the PCB
2. Component placement with a pick and place machine
3. The reflow soldering itself
•
•
•
Lead-free versus SnPb soldering; note that a lead-free reflow process usually leads to
higher minimum peak temperatures (see
reducing the process window
Solder paste printing issues, such as 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) while being 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
Lead-free process (from J-STD-020C)
Figure
Rev. 01 — 19 February 2009
36.
Package reflow temperature ( C)
Volume (mm
< 350
260
260
250
3
)
Figure
350 to 2000
260
250
245
Table
36) than a PbSn process, thus
16.
PCA8802
> 2000
260
245
245
© NXP B.V. 2009. All rights reserved.
Smartcard RTC
29 of 34