Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-08-31
2001-04-24
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S461000
Reexamination Certificate
active
06221749
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device produced in substantially the same size as the semiconductor chip packaged therein, a process of producing the semiconductor device, a dissolvable metal sheet to be used in the process, and a process for producing the metal sheet.
2. Description of the Related Art
As shown in
FIG. 1
, U.S. Pat. No. 5,476,211 discloses a chip size package (CSP) or a semiconductor device produced in substantially the same size as the semiconductor chip packaged therein, in which a semiconductor chip
10
has an electrode terminal carrying surface on which electrode terminals formed on an extension of the electrode terminals are formed and carried and an S-shaped wire
14
is bonded to the electrode terminal. The wire
14
is bonded on one end to the electrode terminal
12
by wire bonding, worked to an S-shape, and then cut on the other hand at a selected height. The cut end or the free tip of the wire
14
is bonded to terminals of a mother board to mount the chip
10
on the mother board, during which the S-shaped wire
14
absorbs the thermal or other stresses. The wire
14
may have a plated coating thereon, for strengthening, to maintain the initial S-shape during processing.
The prior art semiconductor device provides a simple structure enabling a chip size package to be produced using no interposers to support lead assemblies while mitigating thermal stress.
However, the prior art structure has the following problems.
First, the wires
14
must be individually bonded to the electrode terminals
12
and worked to the S-shape to form each lead assembly, which process limits improvement in the productivity and raises the production cost.
It is also technologically difficult to stably form an S-shape by wire bonding process and to provide a constant height of the tip
16
.
Wire bonding of the wire
14
may damage an active surface of the semiconductor chip
10
.
Plating of the wire
14
may cause a short-circuit to occur in the conductor wiring pattern formed on the surface of the semiconductor chip
10
. This is because the electrode terminals
12
formed on an electrode terminal carrying surface of the semiconductor chip
10
are electrically connected to the semiconductor chip
10
via a conductor wiring pattern formed on a passivation film, in which the conductor wiring is not covered by the passivation film and is at a high density.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a semiconductor device having a lead assembly formed directly on a semiconductor chip packaged therein, in which the lead assembly has a structure for effectively mitigating stresses and can be produced efficiently and stably and also, to provide a process of producing the semiconductor device.
Another object of the present invention is to provide a dissolvable metal sheet to be used in the process and, also, to provide a process of producing the metal sheet.
To achieve the object according to the present invention, there is provided a semiconductor device comprising:
a semiconductor chip having an electrode terminal carrying surface and electrode terminals formed on, and carried by, the electrode terminal carrying surface;
leads extending substantially parallel to the electrode terminal carrying surface and each having at least one curved portion;
a first bump and a second bump which are formed on one and the other ends, respectively, of each of the leads and protrude from the ends in opposite directions toward and away from, respectively, the electrode terminal carrying surface; and
the electrode terminals of the semiconductor chip each being bonded to a top of the first bump of the lead to support the leads at a distance from the electrode terminal carrying surface of the semiconductor chip.
Typically, the first bump of the lead forms an electrode connection terminal for connecting the electrode terminal of the semiconductor chip to the lead and the second bump of the lead forms an external connection terminal for connecting the lead to an external circuit.
The electrode terminals of the semiconductor chip may each have an extension lying on the electrode terminal carrying surface and a terminal to which the first bump of the lead is bonded.
In a preferred embodiment, the first bump forming the electrode connection terminal, the lead, and the second bump forming the external connection terminal are composed of a plated deposit of gold.
In another preferred embodiment, the first bump forming the electrode connection terminal and the lead are composed of a plated deposit of gold and the second bump forming the external connection terminal is composed of a low melting point metal.
Preferably, each lead extends a distance smaller than a pitch at which the electrode terminals are formed on the electrode terminal carrying surface of the semiconductor chip.
According to the present invention, there is also provided a dissolvable metal sheet suitably applicable to production of semiconductor devices, comprising:
a dissolvable metal substrate having concavities on one side in positions corresponding to those of electrode terminals of a semiconductor chip or a semiconductor wafer;
leads lying on said one side of the substrate and each having at least one curved portion, a first connection terminal on one end and a second connection terminal on the other end, the first and second connection terminals protruding in opposite directions from said one side of the substrate, the first connection terminals filling the concavities of the substrate, the second connection terminals having a height greater than that of the leads; and
the dissolvable metal substrate being dissolvable by an etchant which does not dissolve the leads and the first and second terminals.
In a preferred embodiment, the leads and the first and second connection terminals are composed of a plated deposit of gold.
In another preferred embodiment, the leads and the second connection terminals are composed of a plated deposit of gold and the first connection terminals are composed of plural layers of different metals selected from the group consisting of gold, palladium, and nickel.
According to the present invention, there is also provided a dissolvable metal sheet suitably applicable to production of semiconductor devices, comprising:
a dissolvable metal substrate having throughholes extending therethrough in positions corresponding to those of electrode terminals of a semiconductor chip or a semiconductor wafer;
leads formed on one side of the substrate and each having at least one curved portion, a first connection terminal on one end and a second connection terminal on the other end, the first and second connection terminals protruding in opposite directions from said one side of the substrate, the first connection terminals filling the throughholes of the substrate, the second connection terminals having a height greater than that of the leads; and
the dissolvable metal substrate being dissolvable by an etchant which does not dissolve the leads and the first and second terminals.
According to the present invention, there is also provided a process of producing a dissolvable metal sheet suitably applicable to production of semiconductor devices, comprising the steps of:
forming, on one side of a dissolvable metal substrate, concavities in positions corresponding to those of electrode terminals of a semiconductor chip or a semiconductor wafer;
filling the concavities with a plated deposit of a metal;
forming leads on said one side of the substrate, said leads lying on said one side of the substrate and each having at least one curved portion and bonded on one end to the plated deposit; and
forming, on the other end of the leads, a plated deposit of a metal having a height greater than that of the leads.
According to the present invention, there is also provided a process of producing a dissolvable metal sheet suitably applicable to production of semiconductor devices, comprising the steps of:
forming throughholes exten
Horiuchi Michio
Kirloskar Mohan
Takeuchi Yukiharu
Lee Calvin
Pennie & Edmonds LLP
Shinko Electric Industries Co. Ltd.
Smith Matthew
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