15.1 Introduction to soldering
15.2 Wave and reﬂow soldering
15.3 Wave soldering
Product data sheet
This text provides a very brief insight into a complex technology. A more in-depth account
of soldering ICs can be found in Application Note AN10365 "Surface mount reﬂow
soldering description" .
Soldering is one of the most common methods through which packages are attached to
Printed Circuit Boards (PCBs), to form electrical circuits. The soldered joint provides both
the mechanical and the electrical connection. There is no single soldering method that is
ideal for all IC packages. Wave soldering is often preferred when through-hole and
Surface Mount Devices (SMDs) are mixed on one printed wiring board; however, it is not
suitable for ﬁne pitch SMDs. Reﬂow soldering is ideal for the small pitches and high
densities that come with increased miniaturization.
Wave soldering is a joining technology in which the joints are made by solder coming from
a standing wave of liquid solder. The wave soldering process is suitable for the following:
Leaded or leadless SMDs, which are glued to the surface of the printed circuit board
Not all SMDs can be wave soldered. Packages with solder balls, and some leadless
packages which have solder lands underneath the body, cannot be wave soldered. Also,
leaded SMDs with leads having a pitch smaller than ~0.6 mm cannot be wave soldered,
due to an increased probability of bridging.
The reﬂow soldering process involves applying solder paste to a board, followed by
component placement and exposure to a temperature proﬁle. Leaded packages,
packages with solder balls, and leadless packages are all reﬂow solderable.
Key characteristics in both wave and reﬂow soldering are:
Board speciﬁcations, including the board ﬁnish, solder masks and vias
Package footprints, including solder thieves and orientation
The moisture sensitivity level of the packages
Inspection and repair
Lead-free soldering versus PbSn soldering
Key characteristics in wave soldering are:
Process issues, such as application of adhesive and ﬂux, clinching of leads, board
transport, the solder wave parameters, and the time during which components are
exposed to the wave
Solder bath speciﬁcations, including temperature and impurities
Rev. 06 — 15 October 2007
stereo BTL car radio power ampliﬁer
© NXP B.V. 2007. All rights reserved.
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