Semiconductor device, semiconductor module and hard disk

Details Semiconductor device, semiconductor module and hard disk Semiconductor device, semiconductor module and hard disk

2002-09-09

2003-10-21

Nelms, David (Department: 2818)

Active solid-state devices (e.g., transistors, solid-state diode

Housing or package

C257S503000, C257S678000, C438S495000, C438S512000, C438S613000, C438S710000, C360S245900

Reexamination Certificate

active

06635956

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device, a semiconductor module and a hard disk, and especially to a structure capable of efficiently dissipating heat from a semiconductor chip.
Due to the recent growth of the use of semiconductor devices in portable devices and small/densely-mounted devices, the reduction in size and weight and the improvement in heat dissipation properties are demanded at the same time. In addition, semiconductor devices are mounted on various types of substrates, which, in turn, are mounted in various many systems as semiconductor modules. As for such a substrate, the use of a ceramic substrate, a printed board, a flexible sheet, a metal substrate or a glass substrate etc. may be contemplated, and the following description gives one example thereof. Here, the semiconductor module is explained as being mounted on a flexible sheet.
FIG. 14
shows an example in which a semiconductor module using a flexible sheet is mounted in a hard disk
100
. This hard disk
100
may be, for example, the one described in detail in an article of Nikkei Electronics (No. 691, Jun. 16, 1997, p.92-).
This hard disk
100
is accommodated within a casing
101
made of a metal, and comprises a plurality of recording disks
102
that are integrally attached to a spindle motor
103
. Over the surfaces of individual recording disks
102
, magnetic heads
104
are respectively disposed each with a very small clearance. These magnetic heads
104
are attached at the tips of suspensions
106
which are affixed to the ends of respective arms
105
. A magnetic head
104
, a suspension
106
and an arm
105
together form one integral body and this integral body is attached to an actuator
107
.
The magnetic heads
104
must be electrically connected with a read/write amplifying IC
108
in order to perform read and write operations. Accordingly, a semiconductor module comprising this read/write amplifying IC
108
mounted on a flexible sheet
109
is used, and the wirings provided on this flexible sheet
109
are electrically connected, ultimately, to the magnetic heads
104
. This semiconductor module
110
is called “flexible circuit assembly”, typically abbreviated as “FCA”.
From the back surface of the casing
101
, connectors
111
provided on the semiconductor module
110
are exposed, and these connector (male or female)
111
and connectors (female or male) attached on a main board
112
are engaged. On this main board
112
, wirings are provided, and driving ICs for the spindle motor
103
, a buffer memory and other ICs for a drive, such as ASIC, are mounted.
The recording disk
102
spins at, for example, 4500 rpm via the spindle motor
103
, and the actuator
107
detects the position of the magnetic head
104
. Since this spinning mechanism is enclosed by a cover provided over the casing
101
, there is no way to completely prevent the accumulation of heat, resulting in the temperature rise in the read/write amplifying IC
108
. Therefore, the read/write amplifying IC
108
is attached to the actuator
107
or the casing
101
etc. at a location having a better heat dissipation property than elsewhere. Further, since revolutions of the spindle motor
103
tend to high speed such as 5400, 7200 and 10000 rpm, this heat dissipation has more importance.
In order to provide further detail of the FCA explained above, the structure thereof is shown in FIG.
15
.
FIG. 15A
is the plan view, and
FIG. 15B
is a cross-sectional view taken along the line A—A which cuts across the read/write amplifying IC
108
provided on one end of the module. This FCA
110
is attached to an internal portion of the casing
101
in a folded-state, so that it employs a first flexible sheet
109
have a two-dimensional shape that can easily be folded.
On the left end of this FCA
110
, the connectors
111
are attached, forming a first connection section
120
. First wirings
121
electrically connected to these connectors
111
are adhered on the first flexible sheet
109
, and they extend all the way to the right end. The first wirings
121
are then electrically connected to the read/write amplifying IC
108
. Leads
122
of the read/write amplifying IC
108
to be connected to the magnetic heads
104
are connected with second wirings
123
which, in turn, are electrically connected to third wirings
126
on a second flexible sheet
124
provided over the arm
105
and suspension
106
. That is, the right end of the first flexible sheet
109
forms a second connection section
127
at which the first flexible sheet
109
is connected to the second flexible sheet
124
. Alternatively, the first flexible sheet
109
and the second flexible sheet
124
may be integrally formed. In this case, the second wirings
123
and the third wirings
126
are provided integrally.
On the back surface of the first flexible sheet
109
on which the read/write amplifying IC
108
is to be provided, a supporting member
128
is disposed. As for this supporting member
128
, a ceramic substrate or an Al substrate may be used. The read/write amplifying IC
108
is thermally coupled with a metal that is exposed to inside of the casing
101
through this supporting member
128
, so that the heat generated in the read/write amplifying IC
108
can be externally released.
With reference to
FIG. 15B
, a connecting structure between the read/write amplifying IC
108
and the first flexible sheet
109
will now be explained.
This flexible sheet
109
is constituted by laminating, from the bottom, a first polyimide sheet
130
(first PI sheet), a first adhesion layer
131
, a conductive pattern
132
, a second adhesion layer
133
and a second polyimide sheet
134
(second PI sheet), so that the conductive pattern
132
is sandwiched between the first and second PI sheets
130
and
134
.
In order to connect the read/write amplifying IC
108
, a portion of the second PI sheet
134
and the second adhesion layer
133
are eliminated at a desired location to form an opening
135
which exposes the conductive pattern
132
. The read/write amplifying IC
108
is electrically connected thereto through leads
122
as shown in the figure.
The semiconductor device packaged by an insulating resin
136
as shown in
FIG. 15B
has heat dissipating paths indicated by arrows for externally dissipating its heat, but there has been a problem in that, due to the thermal resistance given by the insulating resin
136
, the heat generated by the read/write amplifying IC
108
cannot be efficiently dissipated to the outside the device.
Further details will now be explained using this example in hard disk application. As for the read/write transfer rate of a hard disk, a frequency of 500 MHz to 1 GHz, or even a greater frequency, is required, so that the read/write speed of the read/write amplifying IC
108
must be fast. To this end, the paths of the wirings on the flexible sheet that are connected to the read/write amplifying IC
108
has to be reduced, and the temperature rise in the read/write amplifying IC
108
must be suppressed.
Especially, since the recording disks
102
are spinning at a high speed, and the casing
101
and the lid provide a sealed space, the interior temperature would rise up to around 70 to 80° C. On the other hand, a typical allowable temperature for the operation of an IC is approximately 125° C. This means that, from the interior temperature of 80° C., a further temperature rise by approximately 45° C. is permissible for the read/write amplifying IC
108
. However, where the thermal resistance of the semiconductor device itself and FCA is large, this allowable operation temperature can easily be exceeded, thereby disabling the device to provide its actual performance level. Accordingly, a semiconductor device and FCA having superior heat dissipating properties are being demanded.
Furthermore, since the operation frequency is expected to further increase in the future, further temperature rise is also expected in the read/write amplifying IC
108
itself due to the heat genera

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