Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – Housing or package filled with solid or liquid electrically...
Reexamination Certificate
2001-10-04
2003-02-25
Paladini, Albert W. (Department: 2827)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
Housing or package filled with solid or liquid electrically...
C257S678000, C257S704000, C257S710000, C257S730000, C257S731000, C257S787000
Reexamination Certificate
active
06525416
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to electronic devices and a sheet strip for packaging bonding wire connections of the electronic devices and method for producing them.
Electronic devices having a chip and a housing disposed directly on an active surface of the chip have a bonding channel or bonding pads in which bonding wire connections from contact areas on the active surface of the chip to contact connection areas on a lead frame are disposed. The lead frame itself furthermore has conductor tracks that lead from the contact connection areas via conductor tracks to soldering contact areas. Soldering bumps or soldering balls can be disposed as external contacts of the electronic device on the soldering contact areas.
In order to protect the bonding wires, the bonding channel or the bonding pads must be potted with a plastic compound, the potting compound completely encapsulates the bonding wires.
During the production of such electronic devices, there is the risk, during the potting of the bonding wires with the plastic compound, that their potting height will exceed the height of the soldering balls or soldering bumps and thus jeopardize external contact connection of the electronic device. Moreover, there is the risk that the soldering compound will partly wet the soldering contact areas of the lead frame and impede reliable soldering of the soldering balls or soldering bumps. Consequently, additional problems arise during the production of such electronic devices, which problems reduce the productivity.
Published, Non-Prosecution German Patent Application DE 34 42 131 A1 describes a method for encapsulating microelectronic semiconductor and layered circuits, in which a soft, sealable plastic layer is potted over components situated on a substrate. The components are covered with a plastic/metal composite sheet and then encapsulated with a hard, thermal-shock-resistant synthetic resin potting compound. The outer plastic layers of the plastic/metal composite sheet bond with the filling or the potting compound and form a temperature-and moisture-resistant encapsulation in this way. Furthermore, Published, Non-Prosecuted German Patent Application DE 195 07 124 discloses an electronic device that has, on a substrate, a surface region that is to be protected against contact and pressure. For this purpose, the substrate surface region requiring protection is completely enclosed by a resin sheet, an empty space being provided within the resin sheet. In this case, one of the surfaces of the resin sheet can be covered with a layer made of a conductive material. In order to produce the electronic device, the resin sheet is folded above the substrate in such a way that an interspace remains between the resin sheet and the surface region requiring protection. Open side edges of the folded resin sheet are thermally sealed, thereby forming a cavity that encloses the surface region requiring protection.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide electronic devices and a sheet strip for packaging bonding wire connections of the electronic devices and a method for producing them that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, in which the potting height is adjustable and soldering contact areas adjacent to the bonding channel are not wetted.
With the foregoing and other objects in view there is provided, in accordance with the invention, an electronic device. The electronic device contains a chip having an active surface and contact areas and a laminate disposed on the active area of the chip and having a bonding channel with edge regions formed therein. The laminate further has contact connection areas, conductor tracks and soldering contact areas and surrounds the bonding channel. The contact areas of the chip are disposed along the bonding channel. Bonding wires connect the contact areas of the chip to the contact connection areas of the laminate. A flowable sheet formed of a potting compound surrounds the bonding wires in the bonding channel. The flowable sheet overlaps the edge regions of the bonding channel, and the flowable sheet is a flowable sheet strip or flowable sheet patches.
The invention provides the electronic device to have the chip with the contact areas disposed along the bonding channel or within the bonding pads and the laminate which bears contact connection areas, conductor tracks and soldering contact areas on a lead frame, the laminate surrounds the bonding channel or the bonding area and is disposed on the active surface of the chip. In the case of the electronic device, the contact areas are connected to the contact connection areas via bonding wires and, by a flowable sheet strip which overlaps the edge regions of the bonding channel and serves as a potting compound for the bonding channel, the bonding wires are surrounded by the plastic compound of the flowable sheet strip.
For this purpose, the sheet strip itself contains at least two preformed, mutually opposite edge regions, which cover the edge regions of the bonding channel or of the bonding pads in an overlapping manner, and a preformed central region situated in between, which central region has a bulge and thickened portion and exhibits two convexly curved contour lines in its cross section. The central region of the sheet strip has the advantage that it can be put into a flowable state and then completely fills the bonding channel, an impermissible potting elevation being precluded by the preshaping of the central region and the potting height being adjustable by selection of a thickened portion of the central region.
Furthermore, the edge region of the sheet strip which overlaps the bonding channel ensures that soldering contact areas adjacent to the bonding channel can no longer be wetted since the edge dimensions of the sheet strip are now precisely defined and the situation where sheet material reaches the soldering contact areas adjacent to the bonding channel is thus precluded from the outset. Consequently, for electronic devices which have been equipped with such a flowable sheet strip, the result is that the main causes of rejects during the production of such electronic devices have been eliminated.
In one embodiment of the invention, the sheet strip is a composite strip containing a sheet strip having a varying thickness over the cross section, in other words the central region has a bulge and a thickened portion and a covering strip of uniform thickness. The covering strip of uniform thickness is less flowable than the sheet strip and provides for the maintenance of the dimensions in particular in the edge regions, with the result that wetting of adjacent soldering connection areas is precluded.
In a further embodiment of the invention, the covering strip is produced from a shrink material and the edge regions of the covering strip are adhesively fixed on the edge regions of the bonding channel. What is thereby achieved is that, during the heating of the sheet material in its flowable state, the covering strip shrinks on the flowable sheet material and thus presses the flowable sheet strip compound into the bonding channel and between and around the bonding wires.
In a further embodiment of the invention, the thickened portion in the central region of the sheet strip is matched exactly to the bonding channel volume, thereby advantageously ensuring that the potting compound height never exceeds the height of the soldering balls or soldering bumps and nevertheless completely surrounds the bonding wires.
A further embodiment of the invention provides for parallel edge regions of the sheet strip that overlaps the edge regions of the bonding channel to be connected gas-tightly to the edge regions of the bonding channel. The gas-tight connection can be achieved by an adhesive layer or by laminating the sheet edge regions onto the edge regions of the bonding channel. The gas-tight connection process has the advantage that the bonding channel is completely shielded
Hauser Christian
Reiss Martin
Winderl Johann
Greenberg Laurence A.
Mayback Gregory L.
Paladini Albert W.
Stemer Werner H.
Zarneke David A.
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