JPH05329681A - Multilayered brazing filler metal and its production and connecting method - Google Patents

Abstract

PURPOSE:To realize a good yield and a good joining property even after long-term preservation by laminating the metals constituting the brazing filler metal of a multiple element system alloy at the ratio of the thickness of the alloy brazing filler metal and heating the metals to the m.p. of the brazing filler metal or above. CONSTITUTION:The three-layered brazing filler metal 4 formed by cladding Au of 15mum each on both sides of Sn having 20mum thickness has the higher strength than the strength of the constituting metals. The workability by a die 19 and a punch 20 is degraded in the case of an ordinary Au-Sn alloy. The Au and the Sn diffuse and melt and form bumps 11 of the alloy brazing filler metal when the three-layered brazing filler metal 4 is press touched to semiconductor electrodes 8 and is heated to 300 deg.C. The micropieces of the brazing filler metal existing on the electrodes are coated on both sides with the Sn and Au which are oxidative metals and these micropieces not therefore exposed to the oxidative atmosphere at the time of working and melting. The micropieces are melted and made into the hemispherical bumps 11 even if fluxes are not used. The height accuracy of the bumps 11 is good and, therefore, the connection is made at the high yield when the bumps are mounted on a substrate 12 and are subjected to reflow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer brazing material, a method of manufacturing the same and a method of connecting them.

2. Description of the Related Art Conventionally, alloy brazing filler metals have been processed into sheets or rods by rolling an alloy having a desired composition in advance.
It is molded. Then, the formed brazing material is processed into a required shape in accordance with the shape of the joint and used.

FIG. 4 is a cross-sectional view for explaining a method of manufacturing a sheet-shaped brazing material of a binary alloy. Two kinds of metals 2a and 2b constituting the brazing material are weighed, put into the crucible 14 and melted,
An alloy ingot 17 is obtained by casting in a mold 16 so as to have a thickness suitable for rolling (FIG. 4 (a)). The alloy ingot 17 is hot-rolled or cold-rolled in several times so as to have a desired thickness (FIG. 4B). Rolled brazing alloy 18
Since it is wound on the spool 5, when it is used, processing such as cutting is performed according to the shape of the portion to be brazed. In addition, a rod-shaped brazing material may be obtained by wire drawing.

Further, there is a powder brazing method in which metal powders are mixed so as to have a predetermined composition and the mixture is applied to a joint with a solvent. Weigh a certain amount of metal powder that constitutes the brazing filler metal, mix with a mixer so that the whole is uniformly dispersed, add an appropriate amount of binder to this mixed metal powder, and mix it to make a paste. Get the brazing material. Apply the required amount of paste brazing material to the joint,
Brazing is completed by heating above the melting point of the brazing material.
In addition, cream solder used for soldering electronic components can be said to be a powder brazing material. For cream solder, a target solder alloy is melted, alloy powder is prepared by a gas atomizing method, and mixed with a flux suitable for the solder alloy.

[0004]

The conventional processing of brazing alloy material by rolling or drawing has the following drawbacks. If the alloy itself is extremely hard, there is a limit to the shape that can be processed, and cracks, cracks, etc. occur and yield decreases. Further, the material is oxidized depending on the hot working during rolling, the storage state of the material, and the usage state, which leads to deterioration of performance such as deterioration of bondability. Further, the workability such as cutting and winding the ribbon for the purpose of use is poor, and the yield is reduced. The powder brazing method has no problem in the processed shape, but it is difficult to obtain uniform dispersibility of the powder, and when stored for a long time, the dispersibility decreases due to the relationship of specific gravity. Further, since a binder and a flux are used, a wet process is included, and a cleaning process is required, which is costly.

[0005]

The multi-layer brazing material of the present invention is formed by multi-layering the metals constituting the multi-component alloy brazing material at a ratio of the thicknesses that make up the composition of the brazing alloy material, processing it into a predetermined shape, and connecting it to the connecting portion. After being supplied, the alloy is used by being heated to a temperature higher than the melting point of the brazing alloy to form an alloy.

In the method for producing a multi-layer brazing material according to the present invention, the metals constituting the brazing alloy material are individually rolled, the rolled metals are superposed and clad, or one of the surfaces of the constituent metals is This is for plating metal.

[0007]

Embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a sectional view for explaining a first embodiment of the method for producing a multilayer brazing material according to the present invention. When the binary alloy is made into three layers, two kinds of metal, that is, the metal 2a and the metal 2b, which constitute the brazing alloy material, are individually rolled to a predetermined thickness by three rolling rolls 1a and 1b. At this time, the thickness of each material is determined in consideration of rolling at the time of clad which is the next step. Rolled metal 2a. 2b is put into a rolling roll 1c for superposing clad to form a three-layer brazing material 4.

FIG. 2 is a cross-sectional view of another embodiment of the method for producing a multi-layer brazing material according to the present invention, which is a method for forming a binary three-layer brazing material by using a plating method. A metal 2b, which is one of the metals forming the alloy brazing material, is rolled to a predetermined thickness by a rolling roll 1 and sequentially passed through a plating tank 7 to deposit the metal 2a on the surface of the metal 2b, thereby forming a three-layer brazing material 4. Form.

FIG. 3 is a sectional view showing a process of flip-chip mounting a semiconductor element on a substrate using a three-layer brazing material which is an embodiment of the connecting method of the present invention. The three-layer brazing material 4 is punched out and supplied to the electrode 8 on the semiconductor element 9 by the die 19 and the punch 20 (FIG. 3A). The semiconductor element 9 is heated on the heater block 10a to form hemispherical bumps 11 (FIG. 3B). The semiconductor element 9 having the bumps 11 formed thereon is positioned (FIG. 3C) on the electrode 8 on the substrate 12, mounted, and reflowed to complete the connection step (FIG. 3D).

In the example, Sn was used as the central layer and Au was clad on both sides of the Sn ribbon so as to be a eutectic brazing material of Au / 20 wt% Sn. This three-layer brazing material has an Sn thickness of 20 μm centered on the finished dimension, and one Sn on one side.
5 μm each, clad with Au of 30 μm in total on both sides 5
It was set to 0 μm. The three-layer brazing material was punched using a die and a punch whose size was adjusted to the electrode on the semiconductor element, and the brazing material was pressure-bonded to the semiconductor element electrode by the punched punch. Normally, when a metal is alloyed, the strength is higher than that of each metal constituting the alloy. This tendency is particularly pronounced in Au-Sn alloys, making it difficult to work with dies and punches. The three-layer brazing material prepared according to this example has good workability and stable punching was possible. Then, the semiconductor element to which the three-layer brazing material was supplied
When heated to 00 ° C., Au and Sn were diffused and melted to form bumps of the brazing alloy material. Tiny pieces of the brazing filler metal on the electrodes are coated with Au, which is an oxidizing metal, on both sides, so that they are not exposed to the oxidizing atmosphere during processing and melting, and are melted without using a flux. It became a bump. Then mount it on the board,
When reflowed, the bump height accuracy was good, so connection was possible with a good yield. Here, the melting temperature is Au / 20.
The wt% Sn alloy is a eutectic alloy with a melting point of 280 ° C.
When the material is clad, the composition of the alloy is adjusted by controlling the thickness of Au and Sn, so the melting point will be slightly higher due to the accuracy of the thickness, so the melting temperature must be set slightly higher. In this embodiment, the multilayer brazing material is supplied to the semiconductor element to form the bump, but the bump may be formed on the electrode of the substrate. Further, although the multilayer brazing material is melted in advance to form the bumps of the alloy brazing material before connecting the substrates, the alloy brazing material may be formed simultaneously with the connection between the substrates.

The connecting method of the present invention can also be used for connecting a semiconductor encapsulating package. That is, the multilayer brazing material of the present invention is processed into a shape matching the sealing portion of the package and supplied to the connecting portion, and after the sealing components are combined, the connecting portion is pressurized and heated. In particular, when the eutectic brazing filler metal is used, the multilayer brazing filler metal of the present invention is easy to process, the life of the press jig for processing can be improved, and the reliability of the connection can be improved by making the surface layer hard to oxidize. You can improve your sex.

EFFECT OF THE INVENTION The multilayer brazing material of the present invention is free from cracks and cracks due to rolling and drawing, and yield is improved. In addition, the hot working during rolling, the material storage condition, and the oxidation of the material due to usage conditions can be reduced by placing a non-oxidizing material or a metal with low oxidizability on the surface of the brazing material, and without using flux. However, high quality bumps can be formed and a highly reliable joint can be obtained, which is advantageous in terms of cost, yield, and reliability. Further, the workability such as cutting and winding the ribbon for the purpose of use is facilitated and the yield is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a method for manufacturing a multilayer brazing material that is an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a method for manufacturing a multilayer brazing material that is another embodiment of the present invention.

FIG. 3 is a process sectional view illustrating an embodiment of the connection method of the present invention.

FIG. 4 is a process cross-sectional view showing a method for manufacturing a conventional brazing alloy material.

[Explanation of symbols]

 1a, 1b, 1c Rolling roll 2a, 2b Metal 4 Three-layer brazing material 5 Spool 6 Material guide 7 Plating bath 8 Electrode 9 Semiconductor element 10a, 10b Heater block 11 Bump 12 Substrate 13 Heating heater 14 Crucible 15 Molten alloy 16 Mold 17 Alloy Ingot 18 Alloy brazing material 19 Die 20 Punch

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[Procedure amendment]

[Submission date] January 6, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

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Claims (12)

[Claims] 1. The alloy brazing filler metal after the metal constituting the multi-component alloy brazing filler metal is multi-layered at a ratio of the thicknesses of the alloy brazing filler metal, processed into a predetermined shape, and supplied to the connecting portion. A multi-layer brazing material characterized by being used by being alloyed by heating above the melting point of. 2. The multi-component alloy brazing material has a eutectic reaction, and the metal forming the brazing alloy material is multi-layered at a ratio of thicknesses such that the eutectic point composition causes the eutectic reaction. The multilayer brazing material according to claim 1. 3. The metal constituting the multi-component brazing alloy is Au.
3. The multi-layer brazing material according to claim 1, wherein the multi-layer brazing material is Sn, and the Au and the Sn are two layers. 4. The metal constituting the multi-component brazing alloy is Au.
3. The multi-layer brazing material according to claim 1 or 2, wherein the multi-layer brazing material is Sn, and the Sn is sandwiched between the Au layers to form three layers. 5. A method for producing a multi-layer brazing material, characterized in that the metals constituting the brazing alloy material are individually rolled, and the rolled metals are superposed and clad. 6. A method for producing a multi-layer brazing material, comprising rolling one metal constituting the brazing alloy material and plating the rolled metal with another metal constituting the brazing alloy material. 7. The first substrate is a multilayer brazing material piece formed by pressing a metal constituting the multi-component alloy brazing material into a multilayer brazing material having a thickness ratio of the composition of the alloy brazing material. After supplying to the electrode of, the second substrate is mounted by aligning the multilayer brazing material piece and the electrode of the second substrate,
A connection method, characterized in that the multilayer brazing material is alloyed by heating and the electrodes of the first and second substrates are connected to each other. 8. A first substrate is a multi-layer brazing material piece formed by pressing from a multi-layer brazing material in which the metal forming the multi-component alloy brazing material is multi-layered at a ratio of the thickness of the alloy brazing material. After heating the first substrate, the multilayer brazing material pieces are melted to form protrusions of the brazing alloy material, and then the second substrate is applied to the protrusions and the second A connection method characterized in that the electrodes of the first and second substrates are connected by aligning with the electrodes of the substrate and heating. 9. A semiconductor element encapsulating package for connecting at least two parts to seal a semiconductor element, wherein at least one connecting part of the parts comprises a plurality of layers of metal constituting a multi-component alloy brazing material. After supplying a multi-layer brazing material piece formed by pressing the multi-layer brazing material according to the shape of the connecting portion, the parts are combined and heated while pressurizing the package to alloy the multi-layer brazing material. A connection method characterized in that the package is sealed together with the package. 10. The connection method according to claim 7, wherein at least one of the first and second substrates is a semiconductor element. 11. The metal constituting the multilayer brazing material is Au and Sn, according to claim 7, 8, 9 or 1.
0 connection method. 12. A multilayer brazing material piece is pressed and supplied to a substrate by punching to form a punched piece and directly pressing the punched piece against the substrate using a punch used for the punching. Claims 7, 8,
The connection method according to 9, 10, or 11.