Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-02-05
2002-08-27
Paladini, Albert W. (Department: 2827)
Metal working
Method of mechanical manufacture
Electrical device making
C029S829000, C029S831000, C174S200000, C257S787000, C438S166000
Reexamination Certificate
active
06438826
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to electronic components, methods of sealing electronic components with resin and apparatus therefor, and particularly to electronic components including a semiconductor chip mounted on a printed circuit board in the form of a flip chip, methods of sealing the same with resin and apparatus therefor.
2. Description of the Background Art
Conventionally a semiconductor chip is mounted on a glass epoxy board or a similar printed circuit board (hereinafter referred to as a PCB) in the form of a flip chip and then sealed with resin to produce an electronic component in such a process as follows: initially, a PCB with a semiconductor chip mounted thereon is placed on a stage. Then, a dispenser is used to apply a thermosetting resin having liquid phase cold, such as epoxy resin, along one side of the semiconductor chip. The epoxy resin permeates through capillarity into the entirety of a gap formed between the PCB and the semiconductor chip and also forms a fillet along another side of the semiconductor chip. Then the resin is heated and cured. Thus a resin mold is formed in the gap between the PCB and the semiconductor chip and in a region extending along each side of the semiconductor chip.
Sealing a flip chip with resin, as conventional, however, is disadvantageous; first of all, utilizing capillarity to allow epoxy resin to permeate into the entirety of a gap provided between a PCB and a semiconductor chip, is time consuming and thus increases the process time. Furthermore, the resin seal may have dimensions with insufficient precision. Such disadvantages are increasingly serious as in recent years electronics are reduced in weight, thickness and size and accordingly there exists an increasing demand for electronic components reduced in size. More specifically, a PCB and a semiconductor chip have therebetween further smaller a gap and the PCB and the semiconductor chip have their respective electrodes electrically connected via bumps further increased in number, and allowing epoxy resin to permeate thus requires a long period of time. Furthermore, as an electronic component is reduced in size it is required to have a dimension with high precision.
Secondly, although gradually cold, thermosetting resin having liquid phase cold cures and thus varies in viscosity while it is used. As such, its delivery rate must be monitored constantly and the resin thus has a poor level of workability. Furthermore, there are constraints in handling thermosetting resin. For example, if thermosetting resin having liquid phase cold is stored it must be stored in an atmosphere of no more than −40° C. and when it is used it must be used cold. In addition, thermosetting resin having liquid phase cold is more expensive than that having solid phase cold which is used in normal transfer-molding.
SUMMARY OF THE INVENTION
The present invention contemplates a high-quality electronic component, a method of sealing the electronic component with resin in a reduced period of time and a resin seal apparatus, wherein in transfermolding, a liquid, thermosetting resin is introduced.
To achieve the above object the present invention provides an electronic component including a printed circuit board, a semiconductor chip mounted on the printed circuit board and a bump electrically connecting the printed circuit board and the semiconductor chip together, and between the printed circuit board and the semiconductor chip at a predetermined location there is provided a resin seal integrally. On at least one of a surface of the printed circuit board and a surface of the semiconductor chip opposite to the surface of the printed circuit board there is provided a protrusion dimensioned to protrude to have a height no more than the bump.
As such in the step of sealing the chip with resin when melted resin is heated and cured if the bump softens the pressure received via the semiconductor chip can be distributed to and applied on not only the bump but the protrusion and the printed circuit board and the semiconductor chip would never have a gap therebetween smaller in dimension than the height of the protrusion. This can prevent such defects as deformation of a softened bump, short circuit between adjacent bumps, and the like.
Furthermore the present invention provides a method of sealing an electronic component with resin, wherein a semiconductor chip mounted on a printed circuit board is sealed with resin to fabricate the electronic component, including the steps of: preparing a resin molding die divided into a main die and an intermediate die opened and closed, as desired, relative to the main die in arrangement; setting in any of the main die at a predetermined position the printed circuit board with the semiconductor chip mounted thereon; closing the main die with the semiconductor chip set therein and the intermediate die together, and also adjoining together the intermediate die and a periphery of the printed circuit board in the main die to clamp the molding die; after the step of closing and adjoining, stretching a mold release film over a back surface of the semiconductor chip and a front surface of the intermediate die; after the step of stretching, closing together another main die and the intermediate die with the mold release film posed therebetween, to further clamp the molding die; pressing the mold release film into close contact with the back surface of the semiconductor chip; at the step of closing together another main die and the intermediate die and the step of pressing, introducing melted resin into a cavity and curing the introduced resin therein to seal with the resin the semiconductor chip mounted on the printed circuit board, the cavity being defined by the printed circuit board, the intermediate die and the mold release film; after the semiconductor chip is molded with resin, opening the molding die; and removing the mold release film stretched across the back surface of the semiconductor chip and the front surface of the intermediate die.
Since melted resin introduced into a cavity is cured to form a resin seal, the resin seal can be formed in a shorter period of time than when capillarity is employed. Furthermore, the melted resin can be introduced into a cavity defined by a film of resin, the intermediate die and the printed circuit board and even if the melted resin has low viscosity it can be prevented from entering a gap provided between the group of dies and the intermediate die.
Furthermore the present invention in one embodiment provides the present method with the step of closing another main die and the intermediate die and the step of pressing performed separately.
As such the semiconductor chip can be pressed with appropriate pressure. Thus the bump of solder can be free from pressure otherwise applied more than required and thus softening and deforming the bump. Furthermore, with the film of resin interposed the die for a chip can initially press the semiconductor chip and the top die can then press the intermediate die. As such, the film of resin can be free of wrinkle in a region defining the cavity. As such the resultant electronic component can aesthetically be less defective.
Furthermore the present invention in a preferred embodiment provides the present method wherein the intermediate die and another main die are closed together by adjoining their respective surfaces inclined or similarly unleveled, as required, to allow the dies, when closed together, to remove a wrinkle of at least the mold release film stretched across the back or heat-sink surface of the semiconductor chip.
As such before the dies are completely closed the inclinations sandwich the film of resin and thus stretch it tight. This ensures that the film of resin can be free of wrinkle in a region defining the cavity. Thus the resultant electronic component can aesthetically be less defective.
Furthermore the present invention provides the present method preferably further including the step of internally vacuuming at l
Araki Kouichi
Okamoto Hirotaka
Osada Michio
Takase Shinji
Fasse W. F.
Fasse W. G.
Paladini Albert W.
Towa Corporation
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