SMT component packages
- an overview of the component packages used for surface mount technology
(SMT) components
Surface mount technology (SMT) components come in a variety
of packages. As technology has improved many packages have decreased in size.
Additionally there is a variety of different SMT packages for integrated
circuits dependent upon the interconnectivity required, the technology being
used and a variety of other factors.
To provide some degree of uniformity, sizes of most SMT
components conform to industry standards, many of which are JEDEC
specifications. Obviously different SMT packages are used for different types of
components, but the fact that there are standards enables activities such as
printed circuit board design to be simplified. Additionally the use of standard
size packages simplifies the manufacture because pick and place machines can use
standard feed for the SMT components, considerably simplifying the manufacturing
process and saving costs.
The different SMT packages can be categorised by the type of
component, and there are standard packages for each.
Passive rectangular components
These SMT components are mainly resistors and capacitors which form the bulk of
the number of components used. There are several different sizes which have been
reduced as technology has enabled smaller components to be manufactured and used
- 1812 - 4.6 mm � 3.0 mm (0.18" � 0.12")
- 1206 - 3.0 mm � 1.5 mm (0.12" � 0.06")
- 0805 - 2.0 mm � 1.3 mm (0.08" � 0.05")
- 0603 - 1.5 mm � 0.8 mm (0.06" � 0.03")
- 0402 - 1.0 mm � 0.5 mm (0.04" � 0.02")
- 0201 - 0.6 mm � 0.3 mm (0.02" � 0.01")
Of these sizes, the 1812, and 1206 sizes are now only used
for specialised components or ones requiring larger levels of power to be
dissipated The 0603 and 0402 SMT sizes are the most widely used.
Tantalum capacitors
As a result of the different construction and requirements for tantalum SMT
capacitors, there are some different packages that are used for them. These
conform to EIA specifications.
- Size A 3.2 mm � 1.6 mm � 1.6 mm (EIA 3216-18)
- Size B 3.5 mm � 2.8 mm � 1.9 mm (EIA 3528-21)
- Size C 6.0 mm � 3.2 mm � 2.2 mm (EIA 6032-28)
- Size D 7.3 mm � 4.3 mm � 2.4 mm (EIA 7343-31)
- Size E 7.3 mm � 4.3 mm � 4.1 mm (EIA 7343-43)
Semiconductors
There is a wide variety of SMT packages used for semiconductors including
diodes, transistors and integrated circuits. The reason for the wide variety of
SMT packages for integrated circuits results from the large variation in the
level of interconnectivity required. Some of the main packages are given below
Transistor packages
- SOT-23 - Small Outline Transistor. This is SMT package has three
terminals for a diode of transistor, bit it can have more pins when it may
be used for small integrated circuits such as an operational amplifier, etc.
It measures 3 mm � 1.75 mm � 1.3 mm
- SOT-223 - Small Outline Transistor. This package is used for higher
power devices. It measures 6.7 mm � 3.7 mm � 1.8 mm. There are generally
four terminals, one of which is a large heat-transfer pad
Applications
SMT packages are used for most printed circuit designs that are going to be
manufactured in any quantity. Although it may appear there is a relatively wide
number of different packages, the level of standardisation is still sufficiently
good. In any case it arises mainly out of the enormous variety in the function
of the components.
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