Electric heating – Heating devices – Combined with diverse-type art device
Reexamination Certificate
2000-01-06
2001-02-06
Hoang, Tu Ba (Department: 3742)
Electric heating
Heating devices
Combined with diverse-type art device
C338S048000
Reexamination Certificate
active
06184494
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a heating method employing a heating element for generating heat required to heat printed circuit board components.
BACKGROUND OF THE INVENTION
Electrical devices are often used at a wide range of operating environment temperatures. It is essential to the operation of an electrical device that it is used in such an operating environment where temperature is not above or below the rated operating environment temperatures given to the components of the device. If the operating environment temperature of the device is lower than stated in the operating instructions of a component, the component may become damaged. If the component remains undamaged despite of the low operating environment temperature, the operation of the device may, nevertheless, become disturbed. When the device is kept switched on long enough, the temperature around the device rises because of heat produced by components of good cold resistance. This makes poorly cold resistive components of the device operate in the desired manner. The temperature of the environment may refer to the air temperature inside the case in which the device is placed.
If a component of poor cold resistance is used in an environment possibly having a very low temperature, it is necessary to heat the device so as to make it function in the desired manner. U.S. Pat. No. 3,440,407, for example, discloses a multi-layer printed circuit board having in its inner layers a heating element which heats the circuit board and the components thereon. Since the heating element is placed in the inner layers, it is extremely difficult to direct the thermal power to an individual component. If the thermal power cannot be properly directed to the desired component, the operation of the components which are not wished to be heated becomes more difficult because of the excess heat. Since the heating of the printed circuit board requires wiring to be provided in the inner layers of the circuit board, the manufacturing costs of the board become relatively high. Furthermore, it is a disadvantage of the prior art temperature-controlled printed circuit board that for the heating element, the circuit board has to be provided with through holes. Furthermore, the prior art printed circuit board is prone to electromagnetic interference.
BRIEF DESCRIPTION OF THE INVENTION
An object of the invention is thus to provide a method and equipment implementing the method so as to solve the above problems. This is achieved by a method of the type presented in the introduction, which is characterized by transferring heat generated by the heating element by way of conduction from the heating element to a heat conductor on the surface of the printed circuit board, the heat being transferred further by way of conduction along the heat conductor beneath the lower surface of the component, and when the heat conductor functions as a ground plane or a signal path, restricting heat conduction away from the heat conductor to a component other than the one to be heated by connecting the heat conductor to the ground plane or the signal path with a conductor part which is more narrow than the heat conductor, or which has a smaller cross-sectional area than does the heat conductor.
The invention also relates to a printed circuit board comprising a heating element for generating heat required to heat printed circuit board components.
The printed circuit board of the invention is characterized in that the circuit board comprises a heat conductor between the heating element and the component to be heated, the heat conductor receiving heat generated by the heating element and conducting the heat along the surface of the printed circuit board beneath the lower surface of the component to be heated, and conductor parts which are more narrow than the heat conductor, or which have a smaller cross-sectional area than does the heat conductor, and when the heat conductor functions as a ground plane or a signal path, the conductor parts restrict heat conduction from the heat conductor to a component other than the one to be heated.
The invention is based on the idea that heat generated by a heating element is conducted along a heat conductor formed on a printed circuit board to the component to be heated.
The method and printed circuit board of the invention provide many advantages. In the method, heat is conducted to the component to be heated, whereby it is possible to reduce the generation of electromagnetic interference, for example. Since the component is heated by conducting heat to the component rather than supplying extra current thereto, the risk of short cuts is reduced. Furthermore, the thermal power generated by the heating element can be kept to the minimum, because the heating effect produced by the heating element can be directed very accurately to the desired object.
The heating method of the invention is technically easy to implement on a printed circuit board. Heating does not require extra layers to be made on the circuit board, and the manufacturing costs of the board do not therefore rise significantly because of heating. The heating method enables extremely reliable standard resistors to be used as a heating element. A heat conductor can be coupled to the ground plane of the circuit board, for example, to prevent electromagnetic interference from being generated. Furthermore, to prevent heat from transferring away from the heat conductor the circuit board is provided with regions free of conductive material and with tapered conductor parts.
REFERENCES:
patent: 3440407 (1969-04-01), Goltsos et al.
patent: 4374316 (1983-02-01), Inamori et al.
patent: 4582975 (1986-04-01), Daughton
patent: 5635893 (1997-06-01), Spraggins et al.
patent: 2038102 (1980-07-01), None
patent: 2300340 (1996-10-01), None
patent: 98/30075 (1998-07-01), None
Copy of International Search Report.
Patent Abstracts of Japan, 4-206480 A (Hitachi Chem Co Ltd), Jul. 28, 1992.
Patent Abstracts of Japan, 1-143164 A (Ibiden Co Ltd), Jun. 5 1989.
Isokoski Arto
Marjakangas Jari
Altera Law Group LLC
Hoang Tu Ba
Nokia Networks Oy
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