Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Bump leads
Reexamination Certificate
1998-05-04
2001-11-27
Wilczewski, Mary (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Bump leads
C257S668000, C257S778000, C257S787000
Reexamination Certificate
active
06323551
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin sealed-type semiconductor device, in which a semiconductor element and a lead for external connection are molded by a resin, and a method of manufacturing the same.
2. Description of the Related Art
With the advancement of an IC (integrated circuit) card and a memory card, it is requested that a semiconductor device which is incorporated into the card be thin and small. An example of the thin and small semiconductor device is a structure called CPS (chip size package) and the well-known example is described in Japanese Patent Application Laid-Open (JP-A) No. 9-17910. JP-A No. 9-17910 discloses a structure in which a lead frame is fixed to a semiconductor element, an electrode of the semiconductor element and the lead frame are connected electrically, a portion of the lead frame is sealed by a resin, and an outer terminal is provided on the surface of the lead frame which is not sealed by the resin.
However, the conventional resin sealed-type semiconductor device has following drawbacks.
When the pitch between the leads is narrow, the size of a solder bump which can be formed on the lead becomes small and the amount of solder is reduced. As a result, when the semiconductor device is disposed on a printed board and connected thereto, relaxation of stress by the solder is not sufficient and cracking may be formed on the solder bump which connects the printed board and the semiconductor device. In a case in which the solder bump is used in a severe temperature environment, the stress is directly and repeatedly applied to the solder bump due to the difference between the coefficient of thermal expansion of the portion sealed by the mold resin and the coefficient of thermal expansion of the printed board. The cracking is thereby generated due to the occurrence of brittle fracture on the solder bump.
Further, the solder bumps are formed in column of files on the plurality of leads and the distance between the solder bumps is short. As a result, if the pitch between the leads is narrow, the melted solder bumps contact at the time of mounting to the printed board or the like. Accordingly, a short circuit may occur between the adjacent leads.
Moreover, in a stage in which a product using the semiconductor device is manufactured, soldering is effected by heating the product in a reflow device at about 300° C., and thereafter, when the product is cooled to an ordinary temperature, the stress is generated due to the difference between the coefficient of contraction of the sealed portion and the coefficient of contraction of the printed board. Consequently, cracking may be generated on the solder bump which has become especially fragile in the cooling process. It is difficult to find such cracking on the product during the inspection immediately after the product is manufactured, and the defective product may be shipped as a good item.
SUMMARY OF THE INVENTION
The present invention has solved the drawbacks of the above-described conventional art, and the object thereof is to provide a resin sealed-type semiconductor device, which can be reliably connected to a printed board or the like, and a method of manufacturing the same.
In order to achieve the above-described object, a first aspect comprises: a semiconductor element in which a circuit pattern and a plurality of electrodes for electrically connecting the circuit to the exterior are formed on a circuit forming surface of a semiconductor board; a plurality of leads which are formed of a strip-shaped metal piece and each of which includes a rectangular exposed portion for connecting to the exterior electrically and mechanically, the leads being disposed on a plane surface at predetermined intervals so that the long edges of the exposed portions are in parallel, and each of the leads being electrically connected to each of the electrodes of the semiconductor element; a sealing portion which is molded by a resin such that the sealing portion covers at least portions of the plurality of leads other than the exposed portions and the circuit forming surface of the semiconductor element, and a plurality of solder bumps which have a predetermined height and are provided so as to cover the entire surface of the exposed portion of each of the plurality of leads.
In accordance with the first aspect, the exposed portions of the plurality of leads are rectangular and the solder bumps having predetermined height are provided so as to cover the entire surfaces of the exposed portions. Accordingly, for example, when a resin sealed-type semiconductor device is disposed on a printed board or the like, the device can be reliably connected thereto electrically and mechanically.
A second aspect comprises: a semiconductor element in which a plurality of electrodes is formed on the surface; a plurality of inner leads which are disposed on the surface of the semiconductor element and which are connected to the electrodes, respectively; a sealing resin which exposes an area of each of the inner leads which is long in the extending direction and seals the plurality of inner leads and the surface of the semiconductor element; and a plurality of convex outer terminals which are formed on the exposed area of each of the inner leads.
The outer terminals of the second aspect can cover substantially the entire surfaces of the exposed areas of the inner leads. Further, the outer terminals of the second aspect can form substantially elliptical convex configurations. The entire surfaces of the exposed portions can be covered by the outer terminals having substantially elliptical configurations.
A third aspect comprises: a semiconductor element in which a plurality of electrodes are formed on the surface; a plurality of inner leads which are disposed on the surface of the semiconductor element and which are connected to the electrodes, respectively; a sealing resin which exposes an area of each of the inner leads which is long in the extending direction and seals the plurality of inner leads and the surface of the semiconductor element; and a plurality of outer electrodes which are formed on the exposed area of each of the inner leads, the outer electrodes which are adjacent to each other being disposed at positions which are different distances away from the distal ends of the inner leads.
As described above, the exposed areas of the third aspect are rectangular and can be disposed on the plane surface at predetermined intervals so that the long edges of the rectangular areas are in parallel.
In this way, because the outer electrodes which are adjacent to each other are disposed in the exposed areas of the inner leads at the positions which are different distances away from the distal ends of the inner leads, even if the pitch between the adjacent leads is narrow, the outer electrodes can be formed without generating a short circuit and the resin sealed-type semiconductor device can be made more compact.
In the above-described aspects, the sealing portion covers the portions of the plurality of leads other than the exposed portions, and the circuit forming surface and the side surfaces of the semiconductor element. Also, molding can be effected by the resin so as to expose the reverse surface of the semiconductor device. Due to the exposure of the reverse surface of the semiconductor element, good heat dissipation can be obtained.
As described in a fourth aspect, a method of manufacturing the above-described resin sealed-type semiconductor device, comprising the steps of: manufacturing a resin sealed-type semiconductor device, which comprises (a) a semiconductor element in which a circuit pattern and a plurality of electrodes for electrically connecting the circuit to the exterior are formed on a circuit forming surface of a semiconductor board, (b) a plurality of leads which are formed of a strip-shaped metal piece and each of which includes a rectangular exposed portion for connecting to the exterior electrically and mechanically, the leads being disposed on a plane surface a
OKI Electric Industry Co., Ltd.
Volentine & Francos, PLLC
Wilczewski Mary
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