Stock material or miscellaneous articles – Self-sustaining carbon mass or layer with impregnant or...
Reexamination Certificate
1998-11-18
2001-08-07
Turner, Archene (Department: 1775)
Stock material or miscellaneous articles
Self-sustaining carbon mass or layer with impregnant or...
C428S141000, C428S174000, C428S195100, C428S209000, C428S210000, C428S332000, C428S446000, C428S469000, C428S698000, C428S704000
Reexamination Certificate
active
06270898
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a tool tip and a bonding tool comprising the tool tip and a control method for the bonding tool, and more specifically, it relates to improvements of structures of a tool tip employed in a step of bonding electrodes of a semiconductor chip to lead wires or external terminals and a bonding tool comprising the tool tip and a control method for the bonding tool.
BACKGROUND TECHNIQUE
Generally in packaging of a semiconductor chip, it is necessary to carry out a step of connecting electrodes formed on the semiconductor chip and external terminals or lead wires with each other. In this step, the electrodes of the semiconductor chip and the external terminals or the like are connected with each other with interposition of a brazing filler metal of gold or tin, an anisotropic conductive film or resin such as a conductive adhesive.
At this time, a tool tip is employed for locating and pressing the semiconductor chip on and against prescribed positions of the external terminals or the like and directly heating the brazing filler metal of gold or tin or the anisotropic conductive film or indirectly heating the same through the semiconductor chip.
For the tool tip, there are two types of heating systems, namely a constant heat system of regularly heating the same to a required temperature and a pulse heat system of instantaneously heating the same only as needed in response to the bonding specification of the semiconductor chip.
In either heating system, high accuracy is required of a pressing surface on the forward end of the tool tip as a consequence of high densification of packaging of the semiconductor chip. Since temperature distribution of the pressing surface in heating is homogeneous and flatness of the pressing surface is excellent from this requirement and the homogeneity of the temperature distribution and the flatness can be maintained over a long time, a technique of sticking a diamond film to the pressing surface on the forward end of the tool tip is employed.
In case of the pulse heat system, however, there is such a problem that heat response is inferior as compared with a tool tip consisting of a pure metal such as nichrome, molybdenum, inconel or stainless steel to which no diamond film is stuck since temperature rise of the diamond film stuck to the pressing surface on the forward end results from heat transfer from a tool base material.
Namely, the tool tip employing a diamond film requires a long time as compared with the tool tip consisting of a pure metal for heating and cooling the pressing surface on the forward end of the tool tip to prescribed temperatures in response to current pulses. Therefore, it is difficult to reduce the time required for single bonding of the semiconductor chip.
In relation to this point, there has been proposed a method of making a diamond film synthesized by a vapor-phase synthetic method on a pressing surface on a forward end of a tool tip conductive so that the diamond film itself will generate heat, and the problem related to heat response is solved in Japanese Patent Laying-Open Gazette No. 5-304191 or Japanese Patent Laying-Open Gazette No. 5-226421.
Also U.S. Pat. No. 5,488,350 proposes to employ a conductive diamond film synthesized by a vapor-phase synthetic method as a heat generator.
The technique disclosed in the aforementioned Japanese Patent Laying-Open Gazette No. 5-304191, however, employs a structure in which the diamond film is brazed to a tool base material of a metal whose coefficient of thermal expansion is different. Hence, there are such problems that distortion takes place in the diamond film due to difference of thermal expansion in temperature rise and flatness of the pressing surface on the forward end of the tool tip is hard to ensure.
According to the technique disclosed in the aforementioned Japanese Patent Laying-Open Gazette No. 5-226421, there are such problems that the cost for the tool tip increases and the tool tip is easy to break in handling thereof since the material used for the tool tip itself is diamond.
According to the technique disclosed in U.S. Pat. No. 5,488,350, further, the conductive diamond film is formed in a pattern similarly to a heater wire, i.e., the conductive diamond film is selectively grown in order to homogenize temperature distribution of the heat generator. Therefore, SiO
2
or the like is formed on a substrate or insulating diamond in a reverse pattern shape relative to the pattern of the conductive diamond film through sputtering or the like, for forming the conductive diamond film by employing this as a mask. However, it is necessary to carry out this formation process by controlling the film thickness of SiO
2
with high accuracy. Further, there are such problems that a step of dissolving/removing SiO
2
is required after forming the conductive diamond film and the tool tip manufacturing cost increases.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a tool tip maintaining the flatness of a flat surface on a forward end of the tool tip with high accuracy, in which handling and attachment/detachment to/from equipment is easy and a manufacturing method of a heat generating part is simpler, and to provide a bonding tool comprising the tool tip and a control method for the bonding tool, which have been proposed in order to solve such problems.
A tool tip in one aspect based on the present invention has, in a tool tip employing a vapor-phase synthesized conductive polycrystalline diamond film for a forward end portion of a bonding tool for pressure bonding, a substrate mainly composed of at least one material selected from a group consisting of a diamond polycrystal, Si, SiC, AlN, Si
3
N
4
and single-crystalline diamond, a conductive polycrystalline diamond film, applied to a surface employed for pressure bonding, a surface opposite to this surface or at least two side surfaces intersecting with these surfaces on the aforementioned substrate, which is in the ranges of at least 1×10
−4
&OHgr;cm and less than 1×10
3
&OHgr;cm in specific resistance and at least 0.1 &mgr;m and not more than 500 &mgr;m in film thickness and a metal film applied onto the aforementioned conductive polycrystalline diamond film for introducing power into the aforementioned conductive polycrystalline diamond film.
Regarding the conductive polycrystalline diamond film, it is difficult to form the same as a continuous film whose film thickness is homogeneous if the film thickness is not more than 0.1 &mgr;m. Further, in-plane temperature distribution abruptly deteriorates if the film thickness is not more than 0.1 &mgr;m, since a local heating value depends on the film thickness of conductive polycrystalline diamond.
If the film thickness is in excess of 500 &mgr;m, on the other hand, the electric energy required for temperature rise increases since the heat capacity of the tool tip increases. Consequently, the temperature rise characteristic and the cooling characteristic of the tool tip become inferior. Further, the cost for forming the conductive polycrystalline diamond film increases while warping of the material increases due to stress of the conductive polycrystalline film. In addition, a polishing time for attaining flatness of the surface of the conductive polycrystalline diamond film abruptly lengthens and the working cost for the surface of the conductive polycrystalline diamond film increases.
For the above reasons, it is possible to obtain a conductive polycrystalline diamond film which is excellent in flatness and temperature rise/cooling characteristics with a low film forming cost by rendering the film thickness of the conductive polycrystalline diamond at least 0.1 &mgr;m and not more than 500 &mgr;m.
As to the specific resistance of the conductive polycrystalline diamond film, contact resistance with the metal film increases to readily spark in energization if the specific resistance of the conductive polycrystalline diamond is high. In order to avoid this, therefore, specific resistance of n
Fujimori Naoji
Iguchi Takahisa
Kumazawa Yoshiaki
Shiomi Hiromu
Tanaka Katsuyuki
Sumitomo Electric Industries Ltd.
Turner Archene
W.F. Fasse
W.G. Fasse
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