Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With contact or lead
Reexamination Certificate
2002-04-24
2003-06-03
Clark, Sheila V. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With contact or lead
C257S784000
Reexamination Certificate
active
06573595
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor package. More specifically, the present invention discloses a ball grid array semiconductor package having a resin coated substrate with a metal core.
2. Description of the Prior Art
As electronic devices have become more compact and with more features, integrated circuits utilized in such electronic devices have been required to be reduced in size while transistor count inside the device has increased.
As a result, semiconductor packaging has continually advanced. Currently, a popular packaging method is the ball grid array (BGA). This type of semiconductor device uses balls for conductive leads in place of traditional wire leads.
Refer to
FIG. 1
, which is a sectional view showing the construction of a conventional BGA semiconductor package.
The conventional BGA device includes a semiconductor chip
102
having an integrated circuit and a plurality of signal input/output pads
104
. The chip is bonded to the central portion of the upper surface of a printed circuit board (PCB)
110
by a bonding layer
106
. The PCB
110
comprises a resin substrate
111
having a circuit pattern on each of the upper and lower surfaces. The circuit patterns on the upper and lower surfaces of the substrate
111
are formed by a plurality of conductive traces
112
,
113
, respectively. The conductive traces
112
and
113
are coated over with a high molecular resin solder mask
130
.
A chip pad
116
is formed on the central portion of the upper surface of the resin substrate
111
to receive and mount the chip
102
. The chip
102
is bonded to the pad
116
by a bonding layer
106
. A plurality of first conductive traces
112
are formed on the upper surface of the substrate
111
at predetermined intervals, thereby forming an upper circuit pattern. The upper circuit pattern is coated with a solder mask
130
. A plurality of second conductive traces
113
are formed on the lower surface of the substrate
111
and are each electrically connected to an associated one of the first conductive traces
112
through conductive via holes
114
. A circular solder ball land
115
, having a double-layered construction comprising a nickel layer
115
b
and a gold layer
115
c
, is formed on each of the second conductive traces
113
through an electrolytic plating process. A solder ball
120
, is welded to each of the solder ball lands
115
and is used as a signal input/output terminal of the package
100
during signal communication of the package
100
with a main board (not shown). The signal input/output pads
104
of the chip
102
are electrically connected to the first conductive traces
112
using wires
140
. The semiconductor chip
102
and the wires
140
are covered using an epoxy molding compound thereby forming an envelope
150
on one side of the package.
The conventional BGA device as described above, has several disadvantages. For example, the multiple masking processes and the number of processing steps and materials make such devices relatively expensive. In addition, the PCB substrate of the conventional device does not easily dissipate heat and is therefore susceptible to problems associated with temperature.
Therefore, there is need for an improved ball grid array semiconductor package with improved thermal performance, higher reliability, and lower cost.
SUMMARY OF THE INVENTION
To achieve these and other advantages and in order to overcome the disadvantages of the conventional method in accordance with the purpose of the invention as embodied and broadly described herein, the present invention provides a ball grid array semiconductor package having a resin coated substrate with a metal core with improved thermal performance, higher reliability, and lower cost.
The BGA semiconductor package with resin coated metal core in accordance to an embodiment of the present invention comprises a metal core, resin substrate covering, solder balls, chip adhesive material, a chip, bonding wires, and encapsulant.
The metal core is, for example, a metal lead frame that is utilized in a conventional lead frame semiconductor package. The metal core is made from a conductive material, for example, copper material. Electrically conductive paths may be formed in the metal frame to create paths for electrical signals to be routed as desired. The metal core is coated with a resin to form a metal core resin covered substrate structure.
The semiconductor chip is adhesively bonded to the resin coated substrate having a metal core by means of an adhesive.
A plurality of bonding wires are bonded or attached between conductive contacts or traces on the active side of the semiconductor chip and the metal core. It should be noted that the resin coating covers both sides of the metal core except for selected areas of the metal core. For example, where it is desired to attach the bonding wires or the solder balls.
The bonding wires are utilized to create selective electrical connections between conductive contacts, pads, or traces on the semiconductor chip and the metal core.
A plurality of solder balls are formed which are electrically connected to the metal core. The solder balls are formed from, for example, Pb, Sn, or other conductive material. The solder balls act as electrodes of the semiconductor device and allow flow of input and output signals between the semiconductor chip and printed circuit boards, frames, or devices on which the semiconductor device is electrically connected.
A liquid encapsulant is formed to cover desired areas of the resin coated substrate, bonding wires, adhesive material, and semiconductor chip. The encapsulant is formed by, for example, printing or molding methods. The encapsulant adhesively fixes and protectively seals the semiconductor chip to the resin coated substrate thereby shielding the semiconductor chip and the bonding wires from the external environment. Additionally, since the substrate is of resin material, the adhesion between the substrate and the encapsulant is much stronger than if a standard metal core substrate was used.
The present invention comprises covering the metal lead frame structure with a resin. The encapsulant of the semiconductor device of the present invention adheres to the resin material. Since the encapsulant and the resin may be of similar materials, the thermal expansion properties are similar and the adhesion between the substrate and the encapsulant is much greater.
Additionally, the heat dissipation properties of the metal core are better than a substrate made solely of resin. Therefore, the thermal performance of the semiconductor device of the present invention is superior.
Furthermore, in an embodiment of the present invention, since the substrate of the present invention comprises a conventional lead frame metal core coated with resin, the production cost of the semiconductor device is lowered. This is due to the fact that the substrate of the present invention utilizing the metal core as conductive paths is less expensive to produce than a resin substrate which requires additional manufacturing processes to provide electrically conductive paths. An advantage of the present invention is that by utilizing inexpensive metal lead frames for the metal core, production costs are lowered.
A common concern with semiconductor devices is the floor life, moisture level, and moisture resistance. Industry standards and requirements are available for moisture/reflow sensitivity for devices. In these specifications, certain standards are given such as moisture resistance, moisture classification level and floor life.
An advantage of the present invention is that by utilizing the resin coated metal core substrate, the semiconductor device of the present invention is capable of consistently meeting the highest level requirements. This not only greatly reduces inventory management and cost of said management, but also allows devices to operate longer without succumbing to failure due to moisture or high temperature.
Another advantage of the prese
Chen James
Wang Rong-Huei
Clark Sheila V.
Rosenberg , Klein & Lee
Scientek Corp.
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