Electric resistance heating devices – Heating devices – Radiant heater
Reexamination Certificate
2000-10-12
2001-10-09
Jeffery, John A. (Department: 3742)
Electric resistance heating devices
Heating devices
Radiant heater
C219S085120, C228S264000
Reexamination Certificate
active
06301436
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a desoldering unit for removing an electronic element from a circuit board by melting solder surrounded the electronic element, and more particularly to a photothermic desoldering unit that employs the effect of light and heat to provide even desoldering temperature to melt solder for removal of an electronic element from a circuit board without damaging the circuit board and other adjourning electronic elements.
A desoldering unit is particularly designed for melting solder surrounded electronic elements soldered onto a circuit board, so that the electronic elements may be removed from the circuit board for replacement or repair. Currently, there are three types of desoldering apparatus frequently employed in the electronic industrial field, namely, hot-air blower, BGA (Ball Grid Array) Rework Station, and compact desoldering heater.
The hot-air blower produces hot air and blows the same directly toward a target electronic element that is to be removed from a circuit board (see the attached reference document), so that solder surrounded the target electronic element is molten to release the electronic element from the circuit board. Thereafter, a vacuum suction tube is used to suck the released electronic element to move it from the circuit board. Since hot air from the hot-air blower not only blows toward the target electronic element to be removed but also areas on the circuit board in vicinity of the target electronic element, the hot-air blower is only suitable for desoldering electronic elements fixed on the circuit board of a surface mount device (SMD). Since it is uneasy to control a distance between the blower and the target electronic element to be removed and the temperature of hot air used to melt the solder surrounded the target electronic element, areas on the circuit board adjacent to the target electronic element tend to be heated, softened and deformed and could no longer be utilized normally.
The BGA Rework Station is a unit designed for professional use and is very expensive (see the attached reference document). It also employs the physical principle of hot air and therefore has the same disadvantages as the hot-air blower, such as uneven distribution of hot air over the circuit board and the target electronic element, undesired damage of adjourning electronic elements on the same circuit board, etc. Moreover, the BGA Rework Station is only suitable for electronic elements on electronic devices using BGA type package that represents connection of electronic elements only to the surface of a circuit board.
An example of the compact desoldering heater is shown in
FIGS. 1 and 2
. As shown, the compact desoldering heater mainly includes a console
1
on which a switch
11
and a temperature control knob
12
are provided, and a heating element
13
horizontally mounted on a top of the console
1
. A surface temperature of the heating element
13
is controlled through the switch
11
and the temperature control knob
12
. To use the compact desoldering heater to melt solder and remove an electronic element
21
from a circuit board
2
, the circuit board
2
is positioned directly on the heating element
13
with pins
22
projected from a bottom surface of the electronic element
21
immediately on a top surface of the heating element
13
. Heat from the heating element
13
melts solder surrounded the pins
22
to achieve the purpose of removing the target electronic element
21
from the circuit board
2
. Such compact desoldering heater melts the solder by directly contacting with and heating the solder and is only suitable for contacting with a rear side of the circuit board
2
. More specifically, the compact desoldering heater is only applicable for electronic elements on electronic devices using Dual In-line Package (DIP) in which pins are downward extended through the circuit board.
In view that the above-mentioned conventional desoldering apparatus have their respective disadvantages and each of them could be applied to desolder and remove electronic element limited to only one single type of package, it is desirable to develop a universal desoldering unit that eliminates problems existing in the conventional desoldering apparatus, such as uneasily controlled eating temperature, softened and deformed adjourning areas on the circuit board, damaged adjacent electronic elements on the same circuit board, and could be used to desolder and remove electronic elements from circuit boards of electronic device of all kinds of packaging types, including SMD, BGA, and DIP types of packaging.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a photothermic desoldering unit that uses heat produced by a light source to indirectly reach a temperature value needed to complete the desoldering.
Another object of the present invention is to provide a photothermic desoldering unit that is applicable to electronic elements on electronic devices using different packaging types, including SMD, BGA, DIP, etc.
A further object of the present invention is to provide a photothermic desoldering unit that enables good control of heating temperature to melt the solder surrounded the target electronic element without softening and deforming the circuit board or damaging adjacent electronic elements.
To achieve the above and other objects, the photothermic desoldering unit of the present invention mainly includes a console provided with a switch and a temperature control knob, and a working frame mounted on a top of the console. A light source is provided in the working frame and a reflective aluminum plate is fixed near an open top of the working frame to close the same and reflect light emitted from the light source. Temperature sensors are provided at an inner side of the aluminum plate to sense a surface temperature of the aluminum plate. Power supply to the light source and luminance of the light source are controlled through the switch and the temperature control knob, respectively. When a surface temperature of the aluminum plate sensed by the sensors is the same as a temperature value set through the temperature control knob, power supply to the light source is disconnected. Light from the light source generates heat that is reflected by the aluminum plate to a circuit board disposed on top edges of the working frame to melt solder surrounded a target electronic element on the circuit board, allowing the electronic element to be removed from the circuit board without causing deformation of the circuit board or damage of adjacent electronic elements.
REFERENCES:
patent: 2166728 (1939-07-01), Page
patent: 2710331 (1955-06-01), Stegeman
patent: 3205572 (1965-09-01), Jochems
patent: 3710069 (1973-01-01), Papadopoulos et al.
patent: 3764772 (1973-10-01), Matuschek
patent: 3765475 (1973-10-01), Hooper
patent: 3789853 (1974-02-01), Reinhard
patent: 4270260 (1981-06-01), Krueger
patent: 4575608 (1986-03-01), Wictorin et al.
patent: 5278938 (1994-01-01), Spigarelli et al.
patent: 5552579 (1996-09-01), Krueger
patent: 735064 (1955-08-01), None
patent: 61-46822 (1986-03-01), None
patent: 6-260147 (1994-09-01), None
patent: 10-41360 (1998-02-01), None
Lissner, R.W., “Module Removing Tool”, IBM Tech. Discl. Bull., vol. 11, No. 10, Mar. 1969.*
Vavoso, G., “Removal of Soldered Components”, IBM Tech. Discl. Bull., vol. 12, No. 12, May 1970.
Bednarek Michael D.
Jeffery John A.
Shaw Pittman LLP
LandOfFree
Photothermic desoldering unit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Photothermic desoldering unit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photothermic desoldering unit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2596592