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AMIS-42700 Datasheet, PDF (13/14 Pages) AMI SEMICONDUCTOR – Dual High-Speed CAN Transceiver | |||
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AMISâ42700
Soldering
Introduction to Soldering Surface Mount Packages
This text gives a very brief insight to a complex
technology. A more inâdepth account of soldering ICs can
be found in the ON Semiconductor âData Handbook IC26;
Integrated Circuit Packagesâ (document order number 9398
652 90011). There is no soldering method that is ideal for all
surface mount IC packages. Wave soldering is not always
suitable for surface mount ICs, or for printedâcircuit boards
with high population densities. In these situations reflow
soldering is often used.
Reâflow Soldering
Reâflow soldering requires solder paste (a suspension of
fine solder particles, flux and binding agent) to be applied to
the printedâcircuit board by screen printing, stenciling or
pressureâsyringe dispensing before package placement.
Several methods exist for reâflowing; for example,
infrared/convection heating in a conveyor type oven.
Throughput times (preheating, soldering and cooling) vary
between 100 and 200 seconds depending on heating method.
Typical reâflow peak temperatures range from 215°C to
260°C.
Wave Soldering
Conventional single wave soldering is not recommended
for surface mount devices (SMDs) or printedâcircuit boards
with a high component density, as solder bridging and
nonâwetting can present major problems. To overcome
these problems the doubleâwave soldering method was
specifically developed.
If wave soldering is used the following conditions must be
observed for optimal results:
⢠Use a doubleâwave 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 printâcircuit board;
⢠Smaller than 1.27 mm, the footprint
longitudinal axis must be parallel to the
transport direction of the printedâcircuit board.
The footprint must incorporate solder thieves at
the downstream end.
⢠For packages with leads on four sides, the footprint must
be placed at a 45° angle to the transport direction of the
printedâcircuit board. The footprint must incorporate
solder thieves downstream and at the side corners.
During placement and before soldering, the package must
be fixed with a droplet of adhesive. The adhesive can be
applied by screen printing, pin transfer or syringe
dispensing. The package can be soldered after the adhesive
is cured. Typical dwell time is four seconds at 250°C. A
mildlyâactivated flux will eliminate the need for removal of
corrosive residues in most applications.
Manual Soldering
Fix the component by first soldering two diagonallyâ
opposite end leads. Use a low voltage (24 V or less)
soldering iron applied to the flat part of the lead. Contact
time must be limited to 10 seconds at up to 300°C.
When using a dedicated tool, all other leads can be
soldered in one operation within two to five seconds
between 270°C and 320°C.
Table 7. Soldering Process
Soldering Method
Package
Wave
Reâflow (Note 9)
BGA, SQFP
Not suitable
Suitable
HLQFP, HSQFP, HSOP, HTSSOP, SMS
Not suitable (Note 10)
Suitable
PLCC (Note 11), SO, SOJ
Suitable
Suitable
LQFP, QFP, TQFP
Not recommended (Notes 11 and 12)
Suitable
SSOP, TSSOP, VSO
Not recommended (Note 13)
Suitable
9. All SMD packages are moisture sensitive. Depending upon the moisture content, the maximum temperature (with respect to time) and body
size of the package, there is a risk that internal or external package cracks may occur due to vaporization of the moisture in them (the so
called popcorn effect). For details, refer to the dry pack information in the âData Handbook IC26; Integrated Circuit Packages; Section:
Packing Methodsâ.
10. These packages are not suitable for wave soldering as a solder joint between the printedâcircuit board and heatsink (at bottom version) can
not be achieved, and as solder may stick to the heatsink (on top version).
11. If wave soldering is considered, then the package must be placed at a 45° angle to the solder wave direction. The package footprint must
incorporate solder thieves downstream and at the side corners.
12. Wave soldering is only suitable for LQFP, TQFP and QFP packages with a pitch (e) equal to or larger than 0.8 mm; it is definitely not suitable
for packages with a pitch (e) equal or smaller than 0.65 mm.
13. Wave soldering is only suitable for SSOP and TSSOP packages with a pitch (e) equal to or larger than 0.65 mm; it is definitely not suitable
for packages with a pitch (e) equal to or smaller than 0.5 mm.
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