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SA58671 Datasheet, PDF (20/24 Pages) NXP Semiconductors – 1.2 W/channel stereo class-D audio amplifier | |||
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NXP Semiconductors
SA58671
1.2 W/channel stereo class-D audio ampliï¬er
14. Soldering of WLCSP packages
14.1 Introduction to soldering WLCSP packages
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 âWafer Level Chip Scale Packageâ and in application note AN10365 âSurface
mount reï¬ow soldering descriptionâ.
Wave soldering is not suitable for this package.
All NXP WLCSP packages are lead-free.
14.2 Board mounting
Board mounting of a WLCSP requires several steps:
1. Solder paste printing on the PCB
2. Component placement with a pick and place machine
3. The reï¬ow soldering itself
14.3 Reï¬ow soldering
Key characteristics in reï¬ow soldering are:
⢠Lead-free versus SnPb soldering; note that a lead-free reï¬ow process usually leads to
higher minimum peak temperatures (see Figure 18) than a PbSn process, thus
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
⢠Reï¬ow temperature proï¬le; this proï¬le includes preheat, reï¬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) 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 classiï¬ed in accordance with Table 7
Table 7. Lead-free process (from J-STD-020C)
Package thickness (mm) Package reï¬ow 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 reï¬ow
soldering, see Figure 18.
SA58671_2
Product data sheet
Rev. 02 â 24 October 2008
© NXP B.V. 2008. All rights reserved.
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