JPS627137A - Solder supplying method and apparatus therefor - Google Patents

Abstract

PURPOSE:To mold in the desired shape with quantification without oxidation by extrusion molding a solder maintained at liquid-phase temperature or lower in specific atmosphere, thereby obtaining a new beautiful solder surface. CONSTITUTION:A heating vessel 2 having a hollow chamber 1 is mounted, and, to maintain the chamber 1 in specific atmosphere, a connecting passage 6 is provided, and gas such as nitrogen gas is supplied. A solder layer laminated on the heating vessel 2 and extrusion molded enable to flow in a vertical direction. A heater 11 and a thermocouple 12 are buried in an enclosure 10 for surrounding a linear 9, and a fine hole 14 which communicates from the die of the bottom of the vessel passes a die holder 13. A solder 18 is disposed in a space adjacent to the die, controlled to be heated by the heater 11 and the thermocouple 12 to the liquid-phase temperature or lower, and extrusion molded by a pressing plate 15 and a plunger 17.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a solder method which is applied when semiconductor pellets obtained by dividing and finely dividing a conductor wafer are solder mounted to a conductor fixed to a support such as an insulator. This invention relates to a supply method and a supply device.

[Technical Background of the Invention] Conventionally, a method using solder has been used to mount a semiconductor wafer on a conductor layer formed on an insulating material such as ceramic. Of course, the conductor layer on which the solder is placed is not limited to the case where it is formed of an insulating material, and methods in which a lead frame or the like is directly utilized are also frequently used.

The solder supply equipment used in these methods generally uses a vacuum chuck to hold ribbon-shaped solder cut to a specified size, transfer it to the conductor layer to be mounted, and perform thermocompression bonding, that is, die bonding. Met.

On the other hand, in the case of individual semiconductor devices for high output power, such as giant transistors, whose sales volume has been increasing recently, the thermal resistance value required due to their characteristics has become stricter, and from this point of view, soldering was Void formed
) is also naturally considered to minimize the amount of generation.

A method to meet this requirement is to form molten solder into particles and apply them to solder mounts.

[Problems with background technology]

First, since ribbon-shaped solder is obtained using a rolling roll, an oxide film or an organic film due to residual lubricating oil is formed on the surface of the solder, resulting in poor wetting of the solder and the incorporation of gas into the molten solder. The disadvantage is that the frequency is high and voids are easily formed. Furthermore, the heat dissipation properties of transistors, diodes, and ICs that require high output are inhibited, and the rated output cannot be obtained, which is the cause of a decrease in yield.

On the other hand, in the solder dispensing method using molten solder, there is no surface oxidation, so wetting of the solder layer is good. However, quantitative control is difficult and it is difficult to apply only pellets larger than a certain size.

This is because this solder dispensing method uses a method in which molten solder falls through the pores between the balls to form granular solder, so the molten solder oozes out from the sides of the balls, causing the granular solder to ooze out. Quantitative control is difficult, and production of small-sized products is extremely difficult.

[Purpose of the invention]

The present invention provides a novel method and apparatus for supplying solder that overcomes the above-mentioned difficulties, and is particularly resistant to oxidation, has quantitative properties, and can be molded into a desired shape.

[Summary of the invention]

By the way, the present inventor has confirmed the fact that a new and beautiful solder surface can be obtained by extrusion molding solder maintained at a temperature below the liquidus temperature, and the present invention was completed based on this fact.

In the method of the present invention, in order to maintain the solder below its liquidus temperature, it is carried out in a specific atmosphere from the viewpoint of preventing its oxidation and the generation of residue due to extrusion molding, and the extruded solder is heated to a heating conductor. We also adopted this method of mounting and melting under this specific atmosphere. Inert gases, reducing gases, and mixtures thereof can be used as gases that form this specific atmosphere. Specifically, nitrogen, argon, and krypton are used as inert gases, hydrogen is used as reducing gas, and hydrogen + gas is used as mixtures. It is hydrogen mixed with nitrogen and some oxygen. Thus, the specific atmosphere in the present invention means the above-mentioned gas atmosphere.

In the supply device that realizes this solder supply method, the temperature for extrusion molding and the temperature for melting the solder mounted on the conductor are different, and the solder is supplied to the conductor transported at a constant speed, which contributes to mass production. The extrusion molding process and the solder supply process are performed at different locations.

For this purpose, for extrusion molding, a cylindrical heating container with a bottom is prepared, a pore is provided at the bottom of the heating container through which the solder passes, and another heating container having a hollow chamber is provided. A method was adopted in which a conductor was conveyed into this hollow chamber, a through hole was formed in the hollow chamber opposite to the pore, and extrusion molding was performed, and the solder was guided to the conductor and melted.

As a means for quantitatively controlling the extruded solder, it is preferable to install a die at the bottom of the bottomed cylindrical heating container.

[Embodiments of the invention]

The present invention will be described in detail with reference to FIGS. 1 and 2.

FIG. 1 is a schematic sectional view of a solder supply device applied to carry out the method of the present invention, and FIG. 2 is a sectional view showing a part thereof.

Heating container with hollow chamber ω shown in Figures 1 and 2■
Set up. This heating container has a heater ■ and a thermocouple)
It is possible to heat and control the conductor 0, which is buried and transported to the hollow chamber (2), to a temperature higher than the solder melting point, which will be described later. The conductor 1 to be transported in this example is a circuit pattern formed by plating Ni on a copper or tungsten layer on an insulating support 0 made of ceramic or the like.

This is just an example; an integrated circuit device, etc. may carry a lead frame made of conductive metal.

Furthermore, in order to maintain a specific atmosphere in this hollow chamber ω, a passage 0 communicating with the outside of the heating container 1 is installed, and the above-mentioned gas such as nitrogen gas or 1.0% by volume of nitrogen gas is flowed into the hollow chamber of the heating container 2. At ω, a through hole (2) is provided which fits into a hole through which a solder layer (to be described later) passes.

On the other hand, a cylindrical heating container (2) with a bottom is prepared, and as shown in FIG. 1, a solder layer laminated and extruded into the heating container (2) having a hollow chamber (2) can flow in the vertical direction. This bottomed cylindrical heating container (■) has a space, the inner wall of which is made up of liner 0, and the outer wall (10) surrounding this liner.
) is embedded with a heater (11) and a thermocouple (12) so that heating can be controlled to below the liquidus temperature of the solder. A dice holder (13) is installed at the bottom of the bottomed cylindrical heating container.
A die (14) is placed in the space adjacent to this, and a pore (14) communicating with the die passes through the die holder (13). On the other hand, the die holder (13) is integrally provided with a protrusion (15) that fits into the through hole (2) provided in the hollow chamber (ω).

The pores (14) are continuously penetrated through the central portion thereof.

The space portion is provided with a press plate (16) for extruding solder and a plunger (17) to constitute a solder supply device. The solder (18) is placed in the space adjacent to the die (14), and the heater (11) is heated to below its liquidus temperature.
and a pressing plate (16) after heating control by a thermocouple (12).
Also, extrusion is carried out using a plunger (17), but no lubricating oil is used.

Before carrying out extrusion molding of the solder, etc., this bottomed cylindrical heating container ■ is placed in the above-mentioned specific atmosphere.
Furthermore, the same atmosphere is maintained in the hollow chamber via passage 0,
Moreover, since the protrusion (15) is fitted into the hollow chamber (2) through the through hole (2), the fear of solder melting can be eliminated.

Furthermore, the conductor (2) placed in the hollow chamber is heated in advance to a temperature higher than the liquidus temperature of the solder.

A certain amount of the solder pressurized by the plunger (17) and the press plate (16) is extruded into a desired shape by the die (14), but after this is completed, the bottomed cylindrical heating container is lowered to form the conductor. ■It melts as it is pressed onto the top. Meanwhile, the heating container rises and returns to its original position, completing the solder application.

As the solder, lead alloy, tin alloy, indium alloy, etc. can be used, and lead-tin silver (tin 5% by weight, silver 5% by weight,
In the case of lead BaQ (melting point 292℃), extrusion temperature 250~2
The conductor (2) of the heating container (2), which is provided with a hollow part, is preheated to about 350C at 80C and an extrusion pressure of 3 to 50 kg/Im.

As shown in Fig. 2, after the solder (19) has built up, the collet (20) sucking and holding the semiconductor pellet (21) is transferred to the through hole (■) provided in the hollow chamber, and the collet (20) is transferred to the solder (19). Press down and, if necessary, give a so-called scrubbing motion to fix it.

〔Effect of the invention〕

According to traditional solder supply methods, internal voids (
Void) was 2% to 15% of the pellet area, but
According to the method of the present invention, it is possible to control the amount to 1% or less.
Yield loss due to thermal resistance has been significantly improved.

In other words, in the case of giant transistor modules, etc., the conventional method cannot be applied to the pellet size up to the low angle position, and the thermal resistance of smaller models is 0.45°C/W, whereas the method of the present invention has a thermal resistance of 7-7°C/W. Even the square pellets showed good results with a thermal resistance of 0.4° C./W.

Due to the small number of internal voids, thermal fatigue tests were performed using the conventional method.
The cycle time was significantly improved to over 100K cycles.

Incidentally, the solder billet to be put into the heating container (2) can be purchased in a large diameter state and therefore can be obtained at low cost.

Moreover, since the die shape can be selected according to the pellet shape, it can be mounted with a minimum amount of solder.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a solder supply device according to the present invention, and FIG. 2 is a sectional view showing its sectional structure during one step.

Claims (2)

[Claims] (1) A solder supply method characterized by extruding solder held in a specific atmosphere at a temperature below its liquidus temperature and then supplying the solder to a heating conductor placed in the specific atmosphere to melt it. (2) A heating container having a hollow chamber, a conductor layer disposed in the hollow chamber, means for maintaining the hollow chamber in a specific atmosphere, another heating container having a cylindrical shape with a bottom, and a cylindrical heating container with a bottom; a pore formed in the bottom of the other heating container, a through hole provided in the hollow chamber arranged opposite to the pore, and a solder arranged in the bottomed cylindrical heating container that maintains the specific atmosphere. and means for extruding the solder at a temperature below its liquidus temperature.