JPH043950A - Method and device for soldering semiconductor device - Google Patents

Abstract

PURPOSE:To conduct high-reliability soldering by positioning a semiconductor chip on a chip fitting pad put on a circuit board, by installing a vapor soldering device in an inert gas atmosphere, and by doing soldering. CONSTITUTION:A vapor soldering device is composed of a VPS container 2 where soldering is connected and a heater 3 which heats this. A first removable lid 4 is provided on the top of the VPS container 2, and under this lid 4 a wire 6 to hang a holder 5 is provided. A chip 7 having been positioned on a bump of a circuit board 18 is placed in the holder 5. Then, they are put in a sealed container 1 having the second lid 15, an inert gas is supplied from an inlet 16, and oxygen is interrupted by conducting soldering work exhausting the gas from an outlet 17. Incidentally, the VPS container 2 is made of Pyrex glass, and carbon fluoride 10 having boiling points of 230-260 deg.C is used. Besides, nitrogen is used as an inert gas to be supplied to the sealed container 1, and it is supplied at a flow rate of 5l/min. from the inlet 16. As the result, the oxidization of solder is prevented in the soldering process, and the generation of defectives can be prevented.

Description

[Detailed Description of the Invention] [Summary] The purpose of the present invention is to provide a highly reliable soldering method and device for soldering semiconductor devices, and to provide a semiconductor chip having a flip-chip type terminal structure on a circuit board. When aligning with the chip mounting pad provided on the board and joining using vapor phase soldering equipment,
The method for soldering semiconductor devices is characterized in that the vapor phase soldering device is installed in an inert gas atmosphere to perform the welding process, and the device for soldering semiconductor devices is a conventional vapor phase soldering device. Attachment container (2) and heater part (3
), as well as a sealed container (
1) and a second lid α9 to which this lid fits, constitutes a soldering apparatus for semiconductor devices.

[Industrial application field]

The present invention relates to a method and apparatus for soldering semiconductor devices.

Due to the need to process large amounts of information at high speed, information processing equipment is becoming larger in capacity, and the semiconductor devices that make up the main component of this equipment are being made smaller and larger in capacity, such as LSI and VLSI.
Integrated circuits have been put into practical use.

In conventional integrated circuits, unit elements, mainly transistors, are formed in a matrix on a semiconductor chip (hereinafter referred to as a chip) made of several squares, and bonding is performed around the chip. A circuit is connected to the pad.

After the chip is attached to a ceramic circuit board using an adhesive or a eutectic alloy, circuit connections are made by wire bonding to pads that are patterned in advance on the circuit board.

However, for large capacitance elements such as LSf, this method is difficult, and instead a flip-chip structure in which solder bumps are arranged in a matrix on the chip surface is used, and this is applied to a multilayer ceramic circuit board. A flip-chip structure has been adopted in which the conductor lines are aligned and directly welded to the numerous pads provided on the top layer.

[Conventional technology]

Most of the chips on which LSIs and νLSIs are formed have a size of 10 m square or less, and a large number of solder humps are formed in a matrix on the chips.

However, this size is 200μ in diameter and 100μ in height.
It is extremely small, about m.

Here, the solder hump is indium (In), tin 3
It is formed using a 7% lead alloy (Sn-31%Pb), Pb-5%Sn, etc., using a vacuum evaporation method, a solder ball method, a plating method, etc.

On the other hand, as a circuit board on which a semiconductor chip is mounted, a multilayer ceramic circuit board using glass ceramics or the like as a dielectric material and copper (Cu) as a conductive material is often used.

That is, pier holes (Vias) are formed at circuit connection positions in the vertical direction of multiple green sheets made of glass ceramics.
-holes) are formed, a conductor pattern such as a conductor line is printed using a screen printing method, and the pier holes are filled. After that, they are laminated and integrated, and then fired to produce a circuit board.

Then, fine pads made of Cu are made at the chip mounting positions on the circuit board formed in this way, and on top of these, platinum (Pt)/gold (Au) etc. are deposited using a vacuum evaporation method or the like. A thin film is patterned, and solder is deposited on it to form solder bumps, similar to the previous semiconductor chip.

Here, the reason why a layered structure of Pt/Au/solder is formed on the Cu pad is that solder tends to form a solid solution with Cu, and this is to prevent so-called solder eating from occurring.

Now, in order to securely attach a semiconductor chip to the bumps provided on the circuit board, it is necessary to use flux. Conventionally, flux was applied to the solder bumps, and the semiconductor chip was then precisely positioned on the solder bumps on the circuit board. This was done by heating the combined state to the melting point of the solder.

However, since flux contains active agents such as chlorine compounds and bromine compounds, if flux remains after soldering, the active components contained in this flux may cause the solder joint to deteriorate. parts may corrode.

Therefore, it is necessary to solder without using flux, and vapor phase soldering equipment (Vapor Phas
Soldering was performed using an e-Soldering Equipment (VPS) device.

FIG. 1 is a sectional view showing the configuration of the νPS device according to the present invention, which is the same as the conventional device except for the sealed container 1.

That is, the vPS device is a vPS container 2 that performs soldering.
and a heater section 3 that heats it.

That is, the νPS container 2 has a removable first lid 4 at the top, and a wire 6 below which suspends the holder 5.
A chip 7 is placed in the holder 5 in alignment with the bumps on the circuit board 18.

Further, there is a cooling mechanism 8 in the upper part of the VPS container 2 that wraps around the side surface of the container, and water 9 is circulated therein.

Further, at the bottom of the vPS container 2, there is placed fluorocarbon 10 whose boiling point is adjusted to the soldering temperature.

As for the soldering method, when the heater section 3 is energized to heat the carbon fluoride 10 and water is circulated through the cooling mechanism 8, the carbon fluoride 10 reaches a predetermined boiling point and begins to boil. While vaporizing, the carbon fluoride vapor reaches the cooling mechanism 8 at the top of the container, where it generates heat of condensation and liquefies, and then drips down along the container and returns to the liquid reservoir.

In this state, when the circuit board 18 with the semiconductor chip 7 mounted thereon is placed on the holder 5 and the first lid 4 with which it is hung is hung down, the semiconductor chip 7 and the circuit board 1 are heated by the condensation heat of the carbon fluoride vapor.
8 is heated and soldered.

The soldering work is then completed by lifting the first lid 4 and taking out the circuit board 18.

However, even when soldering work is performed using such a PS device, good soldering is not always achieved.

FIGS. 2 and 3 show the soldered state as observed with a stereoscopic microscope, with FIG. 2 showing a good state and FIG. 3 showing a bad state.

That is, when the first solder bump 1) on the semiconductor chip 7 side and the second solder bump 12 on the circuit board 18 are inserted into the vPS device and heated, as shown in FIG. Thermal fusion occurs and the solder balls 13 have a drum-shaped cross section as shown in FIG. 3(B), but some of them are not integrated as shown in FIG. 3(B). There is a line 1 between the first solder bump 1) and the second solder bump 12.
In some cases, the bonding is accompanied by 4, and since it is not fluorinated, there is contact resistance, and since there is no complete contact, a solution was needed from the aspect of reliability.

[Problem to be solved by the invention]

When soldering a semiconductor chip with a flip-chip type terminal structure to a circuit board using a VPS device,
The solder bumps on both sides are not necessarily spherical, and may bond with streaks at the joint.

Therefore, the challenge is to eliminate such adhesion.

[Means to solve the problem]

The above problem arises when aligning a semiconductor chip with a flip-chip type terminal structure to a chip mounting pad provided on a circuit board and joining it using a vapor phase soldering machine. The method for soldering semiconductor devices is characterized in that the device is installed in an inert gas atmosphere to perform the welding process, and the device for soldering semiconductor devices is a conventional vapor phase soldering container and a heater section. A soldering device for semiconductor devices, characterized in that it has a built-in conventional device, a sealed container equipped with an air inlet and an exhaust port for supplying an inert gas, and a second lid to which the container is fitted. This can be solved by configuring a mounting device.

[Effect]

The present invention was developed as a result of investigating the cause of solder balls exhibiting a streaked and hollow shape as shown in FIG. 3(B) when soldering is performed using a conventional VPS device.

In other words, the streaks 14 are caused by oxides produced by oxidation of the solder, and the chip on which the first solder hump 1) is provided is aligned with the second solder bump provided on the circuit board. , put it in the vapor phase soldering equipment and vP
It was found that this occurred during the S process.

That is, in FIG. 1, when the heater section 3 is energized, vp
When the fluorocarbon 1o at the bottom of container 2 is heated, the inside of the container is filled with fluorocarbon vapor, and the air inside is supposed to be expelled and disappear, but in reality, some air remains. It was found that this caused oxidation of the surface of the solder bump, resulting in incomplete bonding as shown in FIG.

Therefore, in the present invention, as shown in FIG. 1, the entire VPS device is placed in a sealed container 1 with a second lid 15, and an inert gas is supplied from an air supply port 16 and soldered while being exhausted from an exhaust port 17. Oxygen (0□) is cut off by performing the soldering work, and by using such a method, it is possible to eliminate soldering defects.

Supplied quickly.

As a result of soldering in the same manner as before, except that the entire vPS container 2 was placed in an N2 atmosphere,
The yield in the soldering process was about 80%, but since all the solder humps were integrated to form a solder ball, the yield could be improved to 100%.

Example C] In the νPS device having the structure shown in FIG.
was made of Pyrex glass, and the fluorocarbon IO had a boiling point of 230 to 260°C.

This fluorinated carbon is a mixture of multiple types having different boiling points.

Further, the wire 6 hanging from the first lid 4 and the holder 5 are made of stainless steel, and the diameter of the wire 6 is 1 m.

In addition, the inert gas supplied to the sealed container 1 is nitrogen (
N2) and a flow of 5 n/min from the air supply port 16 (effects of the invention) By implementing the present invention in which soldering is carried out in an inert atmosphere,
Oxidation of the solder in the soldering process can be eliminated, thereby eliminating the occurrence of defects.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the configuration of a VPS device according to the present invention, FIG. 2 is a cross-sectional view showing a good soldering state, and FIG. 3 is a cross-sectional view showing a poor soldering state. In the figure, 1 is a sealed container, 3 is a heater section, 5 is a holder, 7 is a semiconductor chip, 10 is carbon fluoride, 16 is an air supply port, and 18 is a circuit board. 2 is a VPS container, 4 is a first lid, 6 is a wire, 8 is a cooling mechanism, 15 is a second lid, 17 is an exhaust port,

Claims (2)

[Claims] (1) When a semiconductor chip with a flip-chip type terminal structure is aligned with a chip mounting pad provided on a circuit board and bonded using a vapor phase soldering device, the vapor phase soldering A method for soldering semiconductor devices, characterized in that the device is placed in an inert gas atmosphere and welding processing is performed. (2) The device for soldering semiconductor devices has a built-in conventional device consisting of a conventional vapor phase soldering container (2) and a heater section (3), and an air supply port (16) for supplying inert gas. ) and an airtight container (1) having an exhaust port (17);
A soldering device for semiconductor devices, comprising a second lid (15) fitted with the second lid.