Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-06-02
2004-04-06
Cuneo, Kamand (Department: 2827)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S761000
Reexamination Certificate
active
06717820
ABSTRACT:
This invention relates generally to circuit board assemblies. In particular, the invention relates to assemblies of circuit boards and optical transceiver modules.
BACKGROUND OF THE INVENTION
Infrared transceivers modules are often incorporated into electronic devices to enable bi-directional wireless communication with other electronic devices. For example, it is known for a portable digital assistant (PDA) to communicate with a laptop computer, a printer, or another PDA via a standard Infrared Data Association (IrDA) link. Similarly, IR transceivers are becoming increasingly popular for use in hand-portable telephones, enabling telephone users to swap stored numbers, play wirelessly-linked games, or wirelessly link their telephones to IR-enabled accessories.
The advantages of using an IR link over standard electrical connectors are numerous and well documented. These advantages include: 1) greater alignment tolerance; 2) the ability to hermetically seal the data interface; 3) no cables susceptible to RF interference; and 4) no electro-magnetic compatibility (EMC) issues.
An IR transceiver module typically comprises a light emitting diode (LED) and a photodiode, packaged together with appropriate supporting circuitry to form a self-contained unit. Electrical terminals are exposed on the outside of the package to enable the module to be electrically coupled to external circuitry.
By combining the various components of an IR transceiver into a single package or module, the size or form-factor of the transceiver system can be considerably reduced. Furthermore, the modules tend to be more durable and often consume less power than equivalent transceivers consisting of discrete components.
When an IR link or communication channel is created between two IR transceiver modules, the LED in the first transceiver optically couples with the photodiode in the second transceiver, and the LED in the second transceiver optically couples with the photodiode in the first transceiver. Although the transceivers typically operate in the infrared optical frequency band it is equally possible for other optical frequency bands to be used in forming the communication channel.
FIG. 1
shows a prior art hand-portable telephone
100
, such as the Model 6110 cellular telephone available from Nokia Mobile Phones Oy, Finland, which incorporates a known IR transceiver module (not shown). The telephone includes a standard keypad
110
, a display
120
, and an antenna
130
. The telephone housing
140
encloses circuitry including a IR transceiver module positioned adjacent an IR transparent window
150
. The window is transparent to IR radiation enabling the IR transceiver module to communicate optically with other devices outside the housing
140
.
FIG. 2
is a more detailed view of the internal circuitry of the hand-portable telephone of
FIG. 1
, showing the IR transceiver module
200
mounted on an end portion of a main printed circuit board (PCB)
250
. The transceiver module
200
is formed with a first molded lens shape
210
over the LED and a second molded lens shape
220
over the photodiode. Leads
230
provide mounting supports and electrical interconnections between the IR transceiver
200
and the printed circuit board
250
. A typical length “L” for the IR transceiver body is approximately 10 mm, a typical depth “D” is 5 mm, and a typical height “H” is 4 mm. A typical thickness “T” for the printed circuit board
250
is 1 mm.
Consumer pressure is driving electronic device manufacturers such as radio telephone manufacturers to produce ever slimmer products. One way to help reduce the thickness of these products is to minimising the thickness of printed circuit boards contained in the products. Components mounted on the printed circuit boards contribute to the overall circuit board thickness. Therefore, by reducing the height of components on the circuit board, the circuit board thickness may be reduced which in turn can enable slimmer products to be manufactured. Excessive height above a circuit board can thus be a problem for components.
One solution for reducing the height of components on a circuit board is to simply use smaller components. Components are now available which when mounted directly on a circuit board stand less than 1 mm from the board surface. However, for components with optical lenses such as infrared transceiver modules, the module height is limited by the diameter of the lens. The lenses must be of a minimum size to ensure adequate performance of the IR transceiver and to satisfy legislated eye safety requirements (lenses smaller than the minimum size can concentrate light emitted from the transceiver to dangerous levels). Some manufacturers have overcome the lens size limitation by cutting off small portions from each lens. This approach again leads to a degradation in the performance of the IR transceiver. The smallest IR transceiver module currently available has a height of 2.5 mm.
Another solution for reducing the height of components on a circuit board is disclosed in U.S. Pat. No. 5,506,445, assigned to Hewlett-Packard Company, USA.
FIGS. 3 and 4
illustrate this solution which involves mounting a leadframe IR transceiver adjacent an end surface of a printed circuit board by means of a series of shaped leads
230
. An alternative lead arrangement adopted by one manufacturer, Vishay Company, USA, is shown in FIG.
5
. This solution has drawbacks. Firstly, the leads on these packages need to be long enough to enable them to correctly attach to the circuit board. However, long leads cause co-planarity problems which in turn causes a high percentage of products to fail during manufacture. Secondly, the complex arrangement of the leads makes lead trimming difficult and expensive to achieve during manufacture. Thirdly, the lack of a surface on which the IR transceiver body is supported results in an inherently unstable device assembly. Altemating motion stresses are concentrated directly on the solder joints coupling the IR transceiver module to the printed circuit board. An additional problem which the applicant has found In practice is that the IR transceiver does not lend itself to automated assembly. The complex alignment and a lack of pick and place surface mean that manual assembly is necessary for this type of product.
The foregoing illustrates that there is need for a low profile optical transceiver which overcomes the drawbacks associated with the prior art.
SUMMARY OF THE INVENTION
The present invention provides a system for assembling a circuit board and an optical transceiver module, in which the optical transceiver module is mounted onto an additional substrate. The additional substrate allows the optical transceiver module to be placed within an open slot of the main circuit board, thus reducing the effective height of the module from the circuit board surface. Suitably, the additional substrate provides electrical interconnections between the optical transceiver module and the circuit board.
According to a first aspect, the present invention provides a circuit board assembly comprising; a planar circuit board having a major surface and a side surface, a planar substrate mounted on the major surface of the circuit board, an extended portion of the planar substrate extending beyond the side surface, and an optical transceiver module mounted on the extended portion of the substrate adjacent the side surface of the printed circuit board.
According to a second aspect, the present invention provides a circuit board assembly comprising; a planar circuit board having a major surface, and a side surface defining a recess, a planar substrate mounted on the major surface of the circuit board, an extended portion of the planar substrate extending over the recess, and an optical transceiver module mounted on the extended portion of the substrate so as to be disposed in the recess.
According to a third aspect, the present invention provides an optical transceiver module package for mounting on a planar circuit board having a major surface and a side surface, the major
Agilent Technologie,s Inc.
Cuneo Kamand
Dinh Tuan
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