Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-05-07
2003-11-25
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S825000, C029S832000, C029S840000, C029S846000, C029S847000, C438S612000, C438S122000, C361S767000, C361S774000, C361S777000, C216S036000
Reexamination Certificate
active
06651323
ABSTRACT:
FIELD OF THE INVENTION
The invention is generally directed to surface mount circuit board technology, and more particularly is directed to surface mount solder pads used in circuit boards for electrically interconnecting electronic components.
BACKGROUND OF THE INVENTION
Surface mount circuit board technology provides a number of advantages over older, so called “through-hole” circuit board technology. Such advantages include higher electronic component density, lower costs, and ease of manufacturing. While, surface mount circuit boards provide some advantages, some challenges still remain.
Some electronic components, such as high power transistors, high power devices, and the like benefit from some sort of heat sink to ensure proper intended operation. Even operation of lower power devices may benefit somewhat from use in conjunction with heat sinks. Through-hole circuit boards easily accommodate mounting of separate massive aluminum heat sinks on the circuit boards. However, it is much more difficult to mount such massive aluminum heat sinks on surface mount circuit boards.
Additionally, because of the higher component density employed in surface mount circuit boards, there is less space available for separate heat sinks. Such circuit boards devote a significant amount of space to a large number of surface mount solder pads. The solder pads, typically made of copper or gold, are used for soldering to leads of the electronic components, and are interconnected by conductive circuit traces.
In much of the prior art, surface mount solder pads are made as small as possible, so as to provide for the higher component density. As a general matter, in such cases the solder pads are often no larger than necessary for the soldering.
What is needed is a surface mount solder pad that is adapted to function as a heat sink for an electronic component soldered to the pad.
SUMMARY OF THE INVENTION
The invention provides a surface mount solder pad that is adapted to function as a heat sink for an electronic component soldered to the pad. Accordingly, the invention advantageously provides for reasonably high electronic component density, low cost, and ease of manufacturing, while still providing for proper intended component operation.
Many surface mount components, such as high power surface mount transistors, high power surface mount devices, and the like generate excess heat and therefore benefit from the teachings of the invention. For example, a surface mount component such as a surface mount power MOSFET (Metal Oxide Semiconductor Field Effect Transistors) or the like benefits in that the solder pad of the invention has an enhanced surface area that is sufficiently large (to sink enough excess heat generated by the component) so as to provide for the component's proper intended operation.
In much of the prior art, surface mount solder pads are often no larger than necessary for soldering. However, it should be understood that improper operation such as so called “thermal runaway,” as well as component damage could possibly result in some cases, if solder pads are made too small, and the teachings of the invention are not employed.
Briefly and in general terms the method and apparatus of the invention include providing a printed wiring board having solder pads disposed on its surface that are adapted for soldering to leads of surface mount components. The solder pads are electrically interconnected by conductive traces also disposed on the surface. At least one of the solder pads has the enhanced surface area that is selected larger than necessary for the soldering, and that is selected sufficiently large so as to sink enough heat generated by the one of the surface mount components to provide for its proper operation. Such solder pad includes a major surface having features extending into the major surface, so as to provide for the enhanced surface area.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
REFERENCES:
patent: 4766670 (1988-08-01), Gazdik et al.
patent: 4804615 (1989-02-01), Larson et al.
patent: 4924352 (1990-05-01), Septfons
patent: 5176811 (1993-01-01), Keim et al.
patent: 5511306 (1996-04-01), Denton et al.
patent: 5733466 (1998-03-01), Benebo et al.
Arbes Carl J.
Nguyen Tai
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