JPS62257750A - Forming method for bump electrode - Google Patents

Abstract

PURPOSE:To form a solder composition and the shape of a bump electrode uniformly by ejecting molten solder to bump formation foundation electrode surfaces shaped to one or both of a flip chip or a circuit substrate from a nozzle for a dispenser. CONSTITUTION:A cylindrical box body 12 is mounted to a dispenser 10, and flaky solder 9 is inserted and stored previously into the box body 12. A sheathed wire heater 11 is installed to the peripheral side of the box body 12. The upper section of the box body 12 is connected to a pressure source for supplying the circuit substrate 15 side with molten solder 14 ejected from a nozzle 13 for the dispenser 10. That is, molten solder 14 blown out of the nozzle 13 is determined by applying pulse pressure to a head for the dispenser 10 by the operation of a gas ON-OFF valve. Accordingly, solder bumps are formed uniformly at high speed.

Description

[Detailed Description of the Invention] [Summary] For example, when forming protruding electrodes called solder bumps on a circuit board on which a leadless chip or flip chip is mounted, a certain amount of low melting point solder is sprayed from a nozzle of a dispenser. A method of humping is presented.

[Industrial application field]

The present invention relates to a method for forming bump electrodes for forming solder protrusions on a circuit board or a flip chip.

One of the challenges for IC mounting boards for high-speed computers is, for example, reducing signal propagation delay time.
For this reason, it is preferable to solder an LSI element with a flip-chip structure, which has a significantly shortened internal wiring distance, by a flip-chip connection method, also called face-down bonding, which does not require much connection distance, rather than wire bonding.

However, in order to make a soldering connection, it is necessary to form soldering protrusions of several 100 μm called solder bumps on the substrate or flip chip surface in advance.

The present invention is a hump forming method based on the need to form low-melting point solder bumps uniformly and at high speed, which is particularly the case with flip-chip bonding.

[Conventional technology]

FIG. 3 explains the connection configuration according to FIG. 1, which is a cross-sectional view of the board in which the frisobutty knob is connected face down onto the board.

In the figure, 20 is a circuit board, 21 is a circuit board t7i20
Flip chip mounted with two solders on top, 23
is a pad electrode of the flip chip 21, and 24 is a bump' electrode of the substrate 20 connected to the pad electrode 23.

The hump electrode 24 is formed with a thicker conductive layer than the other wiring conductive film 25 on the substrate, and the free-seven pad 21 is soldered to the substrate 20 side via the electrode 24 by, for example, flow soldering.

To ensure reliable soldering, the hump electrodes 24 of the substrate 20 are generally formed with a solder layer in advance by plating. However, although solder bumps formed using the plating method can relatively easily form electrodes that are 5 thick, there are concerns about surface contamination of the substrate because the substrate is immersed in an electrolytic solution.

Another method is to form a hump using a thin-deposition method, but the thin-deposition method requires masking the substrate surface except for the surface on which the wiring conductive film 25 is formed where the hump is to be formed. Accurate alignment between the substrate masks and tight adhesion to prevent solder from running around (halo) are required to avoid short circuits with the conductive film 25 or a drop in withstand voltage.

[Problem that the invention seeks to solve]

Since the plating method for forming the bumps is a wet process, there is a concern that the surface of the substrate may be contaminated.

In addition, the thin-deposition method requires a high-precision mask and mask alignment between the vapor deposition source and the hump-forming substrate (or flip chip) when vapor-depositing alloys with good solder wettability that lead to bump formation. There are problems such as difficulty in uniformly applying the coating.

[Means for solving problems]

For forming solder humps for flip-chip connection methods.

The above problems are solved by the bump electrode forming method of the present invention, which is performed by jetting molten solder from a nozzle of a dispenser onto the hump-forming base electrode surface formed on either or both of a flip chip or a circuit board. be able to.

[Effect]

This is because a dispenser quantitatively squirts molten solder from above onto a base electrode surface previously formed on either or both of a flip chip or a circuit board, and solidifies it onto the electrode surface. The solder composition and the protrusion shape of the bump electrode are formed uniformly.

In this case, if solder bumps are to be formed on the 5th circuit board side, it is convenient to mount the board on an xY table equipped with a predetermined positioning mechanism in order to speed up the relative positioning of the board using the dispenser.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a cross-sectional view showing the structure of the dispenser, and FIG. 2 is a cross-sectional view of the bump-forming base electrode.

The dispenser 10 has a cylindrical housing 1 made of aluminum.
2, and a low melting point eutectic solder (melting temperature 183° C.) used for bump formation or a flaky solder 9 having an indium/tin composition is inserted and accumulated in the housing 12 in advance.

For example, a sheathed wire heater 11 is attached to the outer periphery of the casing I2 to melt the flaky solder inside the casing. Further, a thermocouple sensor 19 for temperature control is provided near the nozzle end 13 of the housing.

A nozzle 13 for spouting molten solder is formed at the lower end of the casing 12.

Moreover, the nozzle 13 of the dispenser is located above the cylindrical housing 12.
It is connected to a gas on-off valve and a pressure source such as nitrogen gas for appropriately quantifying the melted solder 14 ejected from the solder 14 and supplying it to the circuit board 15 side (the gas pressure source, etc. is not shown). That is, each time a pulse pressure is applied to the head of the dispenser 10 by operating the gas on-off valve, the amount of molten solder 14 ejected from the nozzle 13 is quantified.

The circuit board 15 has the hump-forming base electrode 16.

The table 17 is equipped with a substrate positioning mechanism that allows the stage 18 to be moved arbitrarily according to orthogonal XY coordinate axes.
fixed on top.

However, when mounting one circuit board 15, the stage 18 has a built-in heater that heats the board to at least 100°C.

FIG. 2 is a cross-sectional view showing an example of the structure of the hump-forming base electrode 16, in which chromium (Cr), copper (Cu), and gold (A
By sequentially laminating the electrodes 16, the electrodes 16 lead to a flip-chip connection with good solder wettability and high bonding strength.
is formed.

Although the embodiments 1 and j described the formation of solder bump electrodes of the present invention provided on the circuit board side, the same applies to the formation of solder hump protrusions on pad electrodes that are contaminated from flip chips.

〔Effect of the invention〕

According to the method for forming a hump electrode using the solder dispenser of the present invention described above, the low melting point solder hump especially for flip-chip connection can be uniformly formed, and the solder hang can be formed uniformly by the positioning mechanism of the ×Y table installed in conjunction with the dispenser. It has the remarkable effect of being implemented quickly.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of the dispenser of the present invention. FIG. 2 is a cross-sectional view of the hump-forming base electrode. FIG. 3 is a sectional view of a conventional flip-chip connection board. In the figure, 5 and 25 are wiring conductive films, and 9 is a solder accumulation part. 10 is a disbenzer, 13 is a nozzle of 10. 14 is molten solder ejected from a nozzle. 17 is the table half for aligning the board. Goto]
3rd box

Claims (1)

[Claims] 1. A method for forming bump electrodes, which comprises jetting molten solder from a nozzle of a dispenser onto a bump-forming base electrode surface formed on either or both of a flip chip or a circuit board.