JPH06268029A - Manufacture of heating tool for thermocompression bonding - Google Patents

Abstract

PURPOSE:To eliminate adhesion of melted material and contamination on the surface of tool, which are to be the troubles at the time of bonding. CONSTITUTION:Head holding parts 4 are arranged on the both sides of a ceramic head 6, namely, the bonding part of a heating tool main body is formed in a recessed shape. Alloy foil to be used as soldering material is arranged in the groove of the main body bonding part and is used for the bonding with the head. Melted material adhesion on the bonding plane and the reaction of the bonding plane are eliminated by replacing the head to ceramics.

Description

Detailed Description of the Invention

[0001]

[Industrial application] The thermocompression bonding method is a connection method in which heating and pressurization are performed at the same time, and is used for connecting semiconductor chip leads and lead frames, connecting semiconductor devices to a substrate, etc. Is. The present invention relates to a method for manufacturing a heating tool for thermocompression bonding in which a head portion is made of ceramics.

[0002]

2. Description of the Related Art Thermocompression bonding is a so-called solid phase connection in which two kinds of metals are connected to each other while being heated and pressurized to a temperature below their melting points.
Alternatively, it is used for liquid phase connection such as eutectic connection and solder connection.

In the case of liquid phase connection, the wettability and the reactivity between the connection surface of the head portion of the tool and the melt become problems. That is,
When the wettability and reactivity with the melt are high, the melt reacts with the head portion, and the connecting surface of the tool is contaminated with the melt. Therefore, depending on the connecting position, the temperature of the tool head connecting surface and the applied pressure may be non-uniform. In addition, this causes variation in connection strength and connection failure. Therefore, it is necessary to periodically grind the head portion of the tool.

At present, a metal material having low wettability and reactivity with the melt is used, or a vapor deposition method (PVD, CVD) is used for the head connection surface.
A thin film formed by the above method is used as a heating tool for thermocompression bonding.

[0005]

In order to prevent the tool head connection surface from being contaminated due to the adhesion of the melt, the connection surface having poor wettability with the melt may be used. For example, molybdenum alloy is a material having low wettability / reactivity with a brazing material and is used as a tool material. A heating tool in which diamond containing a sintering aid is vapor-deposited on the connection surface is also used. However, although molybdenum alloy is a material having poor wettability, since it is a metallic material, it is necessary to consider some reaction with the melt. In the case of sintered diamond, the auxiliary material contained may react with the melt. Therefore, when the number of times of connection increases, the connection surfaces of these heating tools are contaminated by the melt deposits or the reaction products, so it is necessary to regularly remove the dirt on the head connection surface by polishing or the like. there were. Therefore, recently, a heating head in which a head connection surface is formed of a ceramic thin film having poor reactivity and wettability with a metal has been considered and actually used. Furthermore, a method of converting the entire heating tool into ceramics is also conceivable. However, these methods appear to be costly.

In order to solve the above problems, the inventor of the present invention made the main body of the heating tool a metal, and used a ceramic having poor wettability / reactivity with the brazing material in the head portion, and the head portion and the main body were connected to each other. The inventor has invented a method for manufacturing a heating tool by a joining method (see FIGS. 1 to 3).

[0007]

In the present invention, as a means for joining a tool body made of metal and a head portion made of ceramics, a vacuum heating device and a fixing jig as shown in FIG. (Ag-Cu-Ti), Copper braze (Cu-T
i) We adopted a method of joining the tool body and head using alloy foil.

[0008]

The joining method using the brazing alloy foil is a method of joining by utilizing the eutectic point in the equilibrium diagram, that is, the alloy changes from the solid phase to the liquid phase (eutectic joining method). In addition,
Since the eutectic temperature is lower than the temperature of each metal, it is possible to join at a relatively low temperature, and the joining method is simple and highly reliable. By using this method, a part of the metal heating tool (head part) can be replaced with ceramics.

[0009]

[Example] As a material of the heating tool body, Inconel,
A nickel-based heat-resistant alloy such as Monel, a metal with a low coefficient of thermal expansion up to 450 ° C such as Invar or Kovar, an aluminum with excellent thermal conductivity, or a copper-based alloy is considered. On the other hand, the head material is oxide ceramics such as alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), or aluminum nitride (Al
Non-oxide ceramics such as N), silicon nitride (Si ₃ N ₄ ) and silicon carbide (SiC) are considered.

The bonding strength between metal and ceramics is determined by the residual thermal stress generated during cooling due to the difference in thermal expansion coefficient between the two and the wettability between the brazing material and the ceramics. When oxide-based ceramics and non-oxide-based ceramics are compared, oxide-based ceramics have a higher coefficient of thermal expansion and better wettability with brazing filler metal. Therefore, oxide-based ceramics is more suitable as the head material, and alumina is more appropriate in consideration of versatility. The metal material used for the main body may be selected in consideration of the actual usage status of the tool.

The heating tool main body and the head are joined by the following procedure. First, the main body of the heating tool, the brazing material (alloy foil), and the head 4 are washed with an organic solvent. Next, the main body is fixed using a groove having the same shape as the tool main body provided on the bottom plate 9 of the jig shown in FIG. Then, an alumina protective tube 10 for passing the head supporting plate 9 is inserted into the holes provided at four positions of the bottom plate 11 of the jig. Next, put an alloy foil, which is a brazing material, in the groove portion of the concave joint, put a head on it, and further pass a head support plate through the alumina protection tube 10 for head alignment provided on the support plate. Insert the ceramics head into the groove and fix it. Finally, the jig to which the tool has been fixed is set in a vacuum heating device and bonded in a vacuum atmosphere under predetermined conditions. In the present invention, the metal-side joining shape is concave, that is, the head supporting portions 4 are provided on both sides of the ceramics head, so that the displacement between the main body and the ceramics head can be prevented. In addition, since the excessive melt generated at the time of joining rises up the slight gap between the head and the side surface of the main body,
The side surface also contributes to the joining. Furthermore, it is considered that the head receives pressure from both sides due to the contraction of the metal due to cooling after joining, and the head is also tightened to contribute to mechanical joining. Therefore, the portion 5 shown by the thick line in FIG. 1 becomes the joining region.

The alloy foil is a silver braze (eutectic alloy of silver and copper, Ag-28 wt% Cu) which is relatively well wetted with ceramics, to which a small amount of titanium is added in order to promote wetting and reactivity (for example, , Ag-26 wt% Cu-5 wt% Ti) is used. The thickness of the foil may be about 100 μm. The joining temperature at this time is set to 850 ° C. considering that the melting point of this brazing material is 780 ° C. Although it is desirable to perform bonding in a vacuum of 10 to ⁵ torr or more,
Bonding is possible even in an inert gas atmosphere.

When joined by using a silver brazing alloy foil,
A reaction layer with a high titanium concentration and a eutectic structure of silver and copper are seen at the joint interface. Bonding is mainly performed by the reaction layer formed at the interface. For example, when the ceramic used is oxide-based ceramics such as alumina, titanium oxide is mainly formed at the interface, and when it is non-oxide-based ceramics such as silicon nitride, titanium nitride is mainly formed. It

The joining according to this method can be easily performed by using the fixing jig and the vacuum heating device shown in FIG. In addition, productivity can be increased by expanding the heating space and using a fixing jig that can mount a plurality of connecting tools.

In the case of joining with a brazing material, the heat resistance of the joint is determined by the melting point of the brazing material. Generally, it can be used up to a temperature of 50 to 60% of the melting point. Therefore,
In the case of silver brazing material, it seems that it can withstand temperatures up to 450 ° C. However, since the actual temperature at the tip of the head is lower than the temperature at the joint due to heat conduction, it is necessary to give due consideration to the selection of the alloy foil used for the brazing material. If the connection temperature is 400 ° C or higher, copper brazing material (for example, C
u-28wt% Ti, melting point 880 ℃).

[0016]

EFFECTS OF THE INVENTION Ceramics are materials that have poor wettability with metallic materials. In particular, it is hardly wet with the low melting point metal and its alloy. Therefore, when the heating tool of the present invention is used for liquid phase connection such as soldering, the problem of contamination of the connection surface like the conventional heating tool is almost solved, and it is not necessary to polish the connection surface. The heating tool can be used continuously for a long period of time.

[Brief description of drawings]

FIG. 1 is a perspective view of a heating tool for thermocompression bonding according to the present invention.

FIG. 2 is a front view of a thermocompression bonding heating tool.

FIG. 3 is a side view of a thermocompression bonding heating tool.

FIG. 4 is a front view of a tool body / head joining jig.

FIG. 5 is a side view of a tool body / head joining jig.

[Explanation of symbols]

1 ... Cylinder for mounting in the hole of the push rod part of the thermocompression bonding device, 2 ... Cartridge heater insertion hole, 3 ...
Cartridge heater supporting screw holes, 4 ... Ceramics head supporting portion, 5 ... Joining portion between main body and ceramics head, 6 ... Ceramics head, 7 ... Thermocouple insertion hole for temperature controller, 8 ... Thermocouple insertion hole for temperature measurement , 9 ... Head support plate, 10 ... Alumina protective tube, 11 ... Tool body positioning bottom plate, 12 ... Hole for passing alumina protective tube.

Claims (1)

[Claims] 1. A method of manufacturing a heating tool for thermocompression bonding, comprising joining a metal corresponding to a main body of the heating tool and a ceramics corresponding to a head with a brazing material containing an active metal.