SSTUB32866 Datasheet, PDF (24/29 Pages) NXP Semiconductors – 1.8 V 25-bit 1 : 1 or 14-bit 1 : 2 configurable registered buffer with parity for DDR2-800 RDIMM applications

NXP Semiconductors
SSTUB32866
1.8 V DDR2-800 configurable registered buffer with parity
13. Soldering
13.1 Introduction to soldering surface mount packages
There is no soldering method that is ideal for all surface mount IC packages. Wave
soldering can still be used for certain surface mount ICs, but it is not suitable for fine pitch
SMDs. In these situations reflow soldering is recommended.
13.2 Reflow soldering
Reflow soldering requires solder paste (a suspension of fine solder particles, flux and
binding agent) to be applied to the printed-circuit board by screen printing, stencilling or
pressure-syringe dispensing before package placement. Driven by legislation and
environmental forces the worldwide use of lead-free solder pastes is increasing.
Several methods exist for reflowing; for example, convection or convection/infrared
heating in a conveyor type oven. Throughput times (preheating, soldering and cooling)
vary between 100 seconds and 200 seconds depending on heating method.
Typical reflow temperatures range from 215 °C to 260 °C depending on solder paste
material. The peak top-surface temperature of the packages should be kept below:
Table 12. SnPb eutectic process - package peak reflow temperatures (from J-STD-020C)
Package thickness
Volume mm³ < 350
Volume mm³ ≥ 350
< 2.5 mm
240 °C + 0/−5 °C
225 °C + 0/−5 °C
≥ 2.5 mm
225 °C + 0/−5 °C
225 °C + 0/−5 °C
Table 13. Pb-free process - package peak reflow temperatures (from J-STD-020C)
Package thickness
Volume mm³ < 350
Volume mm³ 350 to Volume mm³ > 2000
2 000
< 1.6 mm
260 °C + 0 °C
260 °C + 0 °C
260 °C + 0 °C
1.6 mm to 2.5 mm
260 °C + 0 °C
250 °C + 0 °C
245 °C + 0 °C
≥ 2.5 mm
250 °C + 0 °C
245 °C + 0 °C
245 °C + 0 °C
Moisture sensitivity precautions, as indicated on packing, must be respected at all times.
13.3 Wave soldering
Conventional single wave soldering is not recommended for surface mount devices
(SMDs) or printed-circuit boards with a high component density, as solder bridging and
non-wetting can present major problems.
To overcome these problems the double-wave soldering method was specifically
developed.
If wave soldering is used the following conditions must be observed for optimal results:
SSTUB32866_2
Product data sheet
• Use a double-wave soldering method comprising a turbulent wave with high upward
pressure followed by a smooth laminar wave.
• For packages with leads on two sides and a pitch (e):
– larger than or equal to 1.27 mm, the footprint longitudinal axis is preferred to be
parallel to the transport direction of the printed-circuit board;
Rev. 02 — 9 October 2006
© NXP B.V. 2006. All rights reserved.
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