Electric heating – Heating devices – Combined with pressure application means
Reexamination Certificate
2001-05-22
2002-07-02
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
Combined with pressure application means
C219S443100, C219S444100
Reexamination Certificate
active
06414271
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a contact heating device for heating an object to be heated in contact therewith such as a die bonding heater or the like used when a semiconductor bare chip is mounted on a substrate.
2. Prior Art
As a packaging method for mounting a semiconductor bare chip on a circuit substrate, the ACF bonding method is known, by which pad electrodes on a chip and those on a substrate are bonded by using a resin-based adhesive such as an anisotropic conductive film or the like. As another mounting method, the flip chip bonding method, by which pad electrodes on a chip and those on a substrate are bonded by using low melting braze material such as Au—Si, Au—Sn alloys or the like, is also utilized for manufacturing multiple chip modules.
As shown in
FIG. 5A
, in the flip chip bonding method, a semiconductor chip
8
is placed on a multi-layered substrate
85
, a pressing tool
910
fixedly bonded to a bonding heater
92
is brought into contact with an upper surface of the chip
8
and then the chip is pressed while heated. The semiconductor chip
8
is brazed on the substrate
85
by melting solders
82
,
87
between pad electrodes
81
,
86
. After cooling, bonding of the pad electrodes
81
,
86
and wiring are completed and the semiconductor chip
8
is fixed on the substrate
85
. After this operation, the pressing tool
910
is separated from the semiconductor chip
8
and moved to another semiconductor chip
8
. The pressing tool
910
captures the chip to carry out the same bonding operation.
As characteristics of a bonding heater
92
, firstly, it is required to efficiently transfer necessary and sufficient heat to the bond material via a semiconductor chip
8
in order to soften or melt bond material such as solders
82
,
87
used for bonding of bump electrodes or the like.
Secondly, from the viewpoint of production efficiency, it is important that time for a temperature rise to a required temperature and time for a temperature fall after bonding until the bond material is solidified are both short.
Thirdly, since pressure as well as heat is applied when a semiconductor chip
8
is bonded, the bonding heater
92
and tool
910
are required to have mechanical strength and abrasion resistance.
To achieve these performances, the bonding heater
92
is constituted by a sintered body composed of a small amount of heat-resistant metal such as titanium, molybdenum or the like as a sintering additive and diamond particles (for example, a diamond sintered body, as disclosed in Japanese Patent Laid-Open Publication No. 11-240762) and utilized as a tool
910
. This is a pulse heater method, in which large pulse current is allowed to flow in the heat-resistant metal itself such as titanium, molybdenum or the like contained in the tool in order to heat the tool.
Japanese Patent Laid-Open Publication No. 10-134938 discloses a bonding heater shown in FIG.
5
B. The heater is composed of a ceramic head
91
(or tool) and a ceramic holder
94
for connecting the head
91
to another member. Here, a thermal conductivity of the head
91
is made higher than that of the holder
94
. The head
91
is fixedly bonded to a ceramic heater
92
by using a high melting point glass bonding layer
911
. Glass material of this bonding layer
911
has a composition consisting of a combination of any selecting from silicon nitride, aluminum nitride, alumina, silicon oxide, zirconia, alkaline-earth metal oxide and rare-earth element oxide and has a high melting point of 1500-1800° C.
To accelerate a temperature fall, in Japanese Patent Laid-Open Publication No. 11-339929, use of a water cooling jacket is proposed to improve a temperature fall speed which is slow due to cooling by standing. As shown in
FIG. 6
, the water cooling jacket
96
is embedded in a holder body
95
and forcibly cools the holder
94
, thereby indirectly cooling the bonding heater
92
and tool
91
provided to the heater holder
94
.
While, microcomputers requiring a small size, high density and high speed processing such as a portable telephone, mobile computer and the like are rapidly being further widespread, higher performances are being achieved. Under these circumstances, more highly integrated semiconductor chip packaging and miniaturization are further required. Along with this, semiconductor chips have a more variety of sizes and arc required to be mounted on multi-layered packaging substrates.
In the conventional bonding heater as shown in an example in
FIG. 5A
, as described above, a bonding heater
92
and tool
910
are integrally bonded to each other. In an example in
FIG. 5B
as well, a ceramic heater
92
and a head
91
are completely bonded by a bonding material
911
. Therefore, such conventional bonding heaters are not adaptable to chips having different chip sizes. In addition, even if only either the tool
91
and
910
or bonding heater
92
is damaged, both of these need to be replaced.
In the bonding heater
92
, the tool
91
and
910
needs to have a uniform surface temperature over tho surface area in order to uniformly bond pad electrodes on the whole surface of a semiconductor chip
8
. However, the conventional bonding heater
92
has a disadvantage that the temperature of a peripheral portion of the tool
91
and
910
lowers due to heat dissipation into air.
Since location accuracy of mounting or the like in semiconductor chip packaging significantly affects performances of electronic equipment, deformation of the contact heating device itself due to thermal expansion is also a problem. When the contact heating device employs a pulse heater method, large current pulses are applied to a resistor composed of titanium or molybdenum for a rapid temperature rise. As a result, the heater itself is vibrated and the actually mounted position is displaced from the position where the semiconductor chip
8
is originally located. This displacement significantly affects performances of the electronic equipment on which the semiconductor chip is mounted.
On the other hand, in a constant heater method, in which the heater is continuously used, when the heater is used at a temperature of 500° C., the temperature of the holder
94
rises to 100-150° C. However, since the holder
94
is composed of metallic material, a warpage occurs due to a temperature distribution generated in the holder
94
. Consequently, accuracy of semiconductor chip mounting location is deteriorated.
The bonding heater
92
is also required to speed up a temperature rise and temperature fall to shorten the work tact. In particular, in the above flip chip process, the temperature needs to be rapidly increased to a prescribed temperature to soften the bond material and position the semiconductor chip
8
. However, it takes a long time to heat up the bonding heater
6
using heat-resistant metal such as titanium, molybdenum or the like to a prescribed temperature.
Furthermore, the bonding heater
92
is required to shorten time required for cooling to shorten the work tact. For example, time for a use temperature fall from 400° C. to 100° C. needs to be 10 seconds or less. However, in the bonding heater
92
using heat-resistant metal such as titanium, molybdenum or the like, time required to cooling, for example, from 400° C. to 100° C. is 20 seconds or longer even if a water cooling jacket
96
is used as shown in FIG.
6
.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a contact heating device which can be assembled so that each element can be individually replaced if either a ceramic heater or tool is damaged.
Another object of the present invention is to provide a contact heating device capable of making a temperature of a tool contact surface uniform.
Another object of the present invention is to provide a contact heating device which does not vibrate so that a semiconductor chip is not displaced and precisely positioned during soldering operation.
Another object of the present invention is to provide a contact hea
Arima Hiroyuki
Shimozuru Hideaki
Turumaru Takafumi
Yokoyama Kiyoshi
Hogan & Hartson LLP.
Kyocera Corporation
Patel Vinod D
Walberg Teresa
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