Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-06-14
2001-03-06
Tolin, Gerald (Department: 2835)
Metal working
Method of mechanical manufacture
Electrical device making
C361S719000, C439S485000
Reexamination Certificate
active
06195880
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to securing electronic components together. More particularly, it relates to a strap spring for attaching a heat sink to an electronic device on a printed circuit board.
BACKGROUND OF THE INVENTION
A heat sink placed in contact with an electronic device transfers heat through conduction from the semi-conductor device contained in the electronic package. U.S. Pat. No. 4,884,331—Hinshaw shows a commonly used pin fin heat sink used to dissipate the conducted heat.
Springs or clips, such as those shown in U.S. Pat. No. 4,745,456—Clemens, or U.S. Pat. No. 4,660,123—Hermann, have been used to secure heat sinks to electronic devices, and a catalog entitled “Thermalloy Semiconductor Accessories,” pp. 15-29, Thermalloy, Inc., Dallas, Tex. (USA) also shows clips for attaching heat sinks to electronic devices. Page 17 of the Thermalloy catalog shows two types of wire springs for securing a heat sink to a pin grid array (PGA). Co-pending application Ser. No. 349,672, filed Dec. 5, 1994, “Strap For Heat Sink Clip Assembly,” shows and describes several different clips for securing a heat sink to an electronic device. Another type of anchor for securing a heat sink to a printed circuit board is shown in co-pending application Ser. No. 08/477,794 filed Jun. 7, 1995. Both of these co-pending applications are incorporated herein by reference as if set forth in their entirety.
However, if a heat sink is larger than the microprocessor there is no secure way to attach the heat sink to the microprocessor. The microprocessor is typically, but not necessarily, a socket. Surface mount applications for Ball Grid Array (BGA), Column Grid Array (CGA), Land Grid Array (LGA), Plastic Quad Flat Pack (PQFP), are all examples of devices that are not in sockets.
In the above-mentioned prior art attachment means, which clip the heat sink to the circuit board, the circuit boards often warp due to the spring loading by the attachment device. Therefore, devices that provide attachment to the board normally have to be kept close to the microprocessor, so that the board is not put under large bending stresses. Also, some prior art clips require a soldering operation to affix the hook in the board. This usually would be a wave soldering operation, which is not normally done when surface mount technology is used.
It is therefore an object of the present invention to provide an anchor which can be inserted through a printed circuit board to secure a heat sink and an electronic device to the board.
SUMMARY OF THE INVENTION
The foregoing and other objects, features and advantages of the invention will be better understood from the following more detailed description and appended claims. It has now been found that the deficiencies of the prior art can be overcome by a strap spring in which the spring contacts the circuit board directly below the microprocessor. All of the spring loading is in compression through the circuit board is concentrated at the microprocessor. The ends of the clip snap through holes or slots in the heat sink to attach the entire assembly together. Therefore, the board is allowed to “float” and no bending moment is applied. The strap spring of the present invention can be constructed in embodiments that are easily removable by dislocating the inside corners of the attaching portions and popping them back through the holes. Embodiments of the present invention are also disclosed that have barbs or other means to snap through the board on two sides of the clip thereby locking the clip into the heat sink. Since the strap spring of the present invention easily snaps the assembly together, it can be easily automated for high production.
REFERENCES:
patent: 4575038 (1986-03-01), Moore
patent: 4884331 (1989-12-01), Hinshaw
patent: 5331507 (1994-07-01), Kyung
patent: 5594624 (1997-01-01), Clemens
patent: 5602719 (1997-02-01), Kinion
patent: 5617292 (1997-04-01), Steiner
patent: 5668348 (1997-09-01), Lin
patent: 5847928 (1998-12-01), Hinshaw
patent: 5850691 (1998-12-01), Bell
patent: 5870286 (1999-02-01), Butterbaugh
Hinshaw Howard G.
Smithers Matthew C.
Cohen & Pontani, Lieberman & Pavane
Thermalloy Inc.
Tolin Gerald
LandOfFree
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