Справочник Пользователя для Philips PNX2000
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Product data
Rev. 03 – 23 August 2004
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Philips Semiconductors
PNX2000
Audio video input processor
13. Soldering
13.1 Introduction to soldering surface mount packages
This text gives a very brief insight to a complex technology. A more in-depth account of
soldering ICs can be found in our Data Handbook IC26; Integrated Circuit Packages
(document order number 9398 652 90011).
soldering ICs can be found in our Data Handbook IC26; Integrated Circuit Packages
(document order number 9398 652 90011).
There is no soldering method that is ideal for all 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. In these situations reflow soldering is
recommended.
used for certain surface mount ICs, but it is not suitable for fine pitch SMDs. In these
situations reflow soldering is recommended. 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.
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 and 200 seconds depending on heating method.
heating in a conveyor type oven. Throughput times (preheating, soldering and cooling)
vary between 100 and 200 seconds depending on heating method.
Typical reflow peak temperatures range from 215 to 270
°
C depending on solder paste
material. The top-surface temperature of the packages should preferably be kept:
•
below 220
°
C (SnPb process) or below 245
°
C (Pb-free process)
— for all BGA and SSOP-T packages
— for packages with a thickness
≥
2.5 mm
— for packages with a thickness < 2.5 mm and a volume
≥
350 mm
3
so called
thick/large packages.
•
below 235
°
C (SnPb process) or below 260
°
C (Pb-free process) for packages with a
thickness < 2.5 mm and a volume < 350 mm
3
so called small/thin packages.
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.
(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.
developed.
If wave soldering is used the following conditions must be observed for optimal results:
•
Use a double-wave soldering method comprising a turbulent wave with high upward
pressure followed by a smooth laminar wave.
pressure followed by a smooth laminar wave.
•
For packages with leads on two sides and a pitch (e):