How to determine bump bonding conditions

Abstract

To easily find out an appropriate bump bonding condition.SOLUTION: A method for determining a bump bonding condition includes the steps of: preparing a light emission element having an element substrate, a semiconductor layer arranged on the element substrate, and an electrode arranged on the semiconductor layer; preparing a wiring board; forming a bump on the wiring board; bringing the bump into contact with the element substrate, and mounting the light emission element on the bump; performing a step of selecting one out of a plurality of bonding conditions, applying the one bonding condition to the light emission element, and deforming the bump, for each of the bonding conditions; removing the light emission element from above the bump, observing the shape of the bump, and determining an appropriate condition from the plurality of bonding conditions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for determining bump bonding conditions. [Background technology]

[0002] A semiconductor device is known in which a semiconductor element is bonded to a substrate via bumps. As a method for inspecting whether the bumps are properly formed, for example, a method is known in which a plurality of bumps are pressed with a flat plate and then the volume of the bumps is inspected based on the area occupied by the bumps (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-14842 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desired to easily find the appropriate bonding conditions for the bumps. [Means for solving the problem]

[0005] This embodiment includes the following configuration. preparing a light emitting element including an element substrate, a semiconductor layer disposed on the element substrate, and an electrode disposed on the semiconductor layer; preparing a wiring substrate; forming bumps on the wiring substrate; a step of bringing the bumps into contact with the element substrate and placing the light emitting element on the bumps; a step of selecting one of a plurality of bonding conditions and applying the selected bonding condition to the light emitting element to deform the bump, the step being performed for each bonding condition; a step of removing the light emitting element from above the bump, observing the shape of the bump, and determining an appropriate condition from among the plurality of bonding conditions; A method for determining bonding conditions for bumps, comprising: [Effects of the Invention]

[0006] From the above, it is possible to easily find the appropriate bonding conditions for the bumps. [Brief explanation of the drawings]

[0007] [Figure 1] 10A to 10C are diagrams illustrating a process of mounting a light emitting element on a bump. [Figure 2] 10A to 10C are diagrams illustrating a process of mounting a light emitting element on a bump. [Figure 3] 10A to 10C are diagrams illustrating a process of mounting a light emitting element on a bump. DETAILED DESCRIPTION OF THE INVENTION

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes embodiments of the present invention with reference to the accompanying drawings. However, the embodiments described below are merely examples of methods for manufacturing a light-emitting device that embody the technical concept of the present invention, and the present invention is not limited to the methods for manufacturing a light-emitting device.

[0009] Furthermore, this specification does not in any way specify the components set forth in the claims as components of the embodiments. In particular, the dimensions, materials, shapes, relative locations, etc. of the components described in the embodiments are not intended to limit the present invention to the embodiments unless specifically stated otherwise. The sizes and positional relationships of components shown in the drawings may be exaggerated for clarity. Furthermore, in the following description, the same names and symbols indicate the same or similar components, and detailed descriptions will be omitted as appropriate.

[0010] The process for determining the bump bonding conditions will be described with reference to FIGS.

[0011] (Process of preparing light-emitting element) First, a light-emitting element 10 is prepared. As shown in FIG. 1, the light-emitting element 10 includes a stacked structure 11 including an element substrate 13 and a semiconductor layer 12 disposed on the element substrate 13, and an electrode 14 disposed on the semiconductor layer 12. Examples of materials for the semiconductor layer include nitride semiconductors. Examples of materials for the element substrate include sapphire. There are no particular limitations on the material for the electrodes, and known materials can be used.

[0012] (Process for preparing a wiring board) A wiring board 20 having wiring 22 on the upper surface of a base material 21 is prepared. Examples of materials for the base material include glass epoxy resin, thermoplastic resin, and ceramics such as alumina and aluminum nitride. Examples of materials for the wiring include metals such as copper, aluminum, gold, silver, tungsten, iron, and nickel, and alloys such as iron-nickel alloys and phosphor bronze.

[0013] (Bump forming process) Bumps 30 are formed on the wiring 22 of the wiring substrate 20. The bumps 30 can be formed by crimping and connecting a ball (initial ball) formed by melting the tip of a wire passed through an insertion hole of a capillary by electrical discharge or the like onto the wiring 22, and then cutting the wire connected to the ball. The bumps 30 are positioned in the same positions as when the electrodes 14 of the light-emitting element 10 and the wiring 22 are actually joined. One or more bumps 30 can be arranged per electrode 14. In the example shown in FIG. 1, one bump 30 is arranged corresponding to each of the two electrodes 14. Examples of materials for the bumps include Au, Ag, and Al, with Au being preferred.

[0014] (Step of mounting light emitting element on bumps) Next, the light emitting element 10 is placed on the bumps 30. At this time, the element substrate 13 and the bumps 30 are oriented to face each other, and the element substrate 13 and the bumps 30 are brought into contact with each other.

[0015] (Bump deformation process) With the bumps 30 and the element substrate 13 of the light emitting element 10 in contact with each other, ultrasonic waves and pressure are applied to deform the bumps 30. Several bonding conditions for deforming the bumps 30 are prepared, and one of the bonding conditions is selected to deform the bumps 30. The ultrasonic frequency is, for example, between 40 kHz and 60 kHz, and several conditions are varied. The ultrasonic application time is, for example, between 20 ms and 200 ms, and several conditions are varied. The pressure is, for example, between 1 N and 3 N per bump, and several conditions are varied.

[0016] The above-mentioned multiple conditions can be set, for example, by referring to the bonding conditions of a light-emitting element whose bonding conditions have already been determined and which is similar in size to the light-emitting element for which the bonding conditions are to be determined.

[0017] (Step of determining bonding conditions) The light emitting element 10 is removed from above the deformed bump 31. The element substrate 13 and bump 31 are not bonded even when ultrasonic waves and pressure are applied, so they can be easily removed. The shape of the deformed bump 31 after removing the light emitting element 10 is observed for each of a plurality of bonding conditions in which at least one of the ultrasonic waves and pressure conditions is changed. The conditions under which the width of the deformed bump 31 is in the range of 1.2 to 1.4 times the width of the bump 30 before deformation are preferred. The conditions under which the height of the deformed bump 31 is in the range of 0.55 to 0.65 times the height of the bump 30 before deformation are preferred. The conditions under which the bump can be deformed into such a preferred shape are defined as the bump bonding conditions. [Example]

[0018] Sixty light-emitting elements measuring 1000 μm x 1000 μm were prepared (10 test elements per condition x 6 conditions). The light-emitting elements had a nitride semiconductor as the semiconductor layer and sapphire as the element substrate. The light-emitting elements also had two electrodes, a pair of positive and negative electrodes, on the nitride semiconductor layer. The top surface of the electrodes was made of Au. A wiring substrate was prepared with an aluminum nitride base and Au as the wiring. Thirty bumps, primarily composed of Au, were formed on the wiring for each light-emitting element. For example, nine bumps were formed at positions corresponding to the positive electrode of the light-emitting element, and 21 bumps were formed at positions corresponding to the negative electrode. The bumps were sized so that the outer diameter at their widest point was 84 μm and the height at their highest point was 30 μm.

[0019] A single light-emitting element is placed on two bumps, with the sapphire facing downward so that it contacts the bumps. The light-emitting element is adsorbed by a die bonder collet equipped with suction and ultrasonic oscillation functions, placed on the bumps, and then ultrasonic waves and pressure are applied. For example, if 10 light-emitting elements are used for one condition, test application for determining such conditions can be performed 10 times, with one light-emitting element and 30 bumps prepared. Alternatively, 10 light-emitting elements and 300 bumps can be prepared, and test application can be performed on all 10 light-emitting elements at once. Furthermore, the light-emitting elements may be prepared from the same lot or from different lots. In particular, by preparing light-emitting elements from different lots, test results can be obtained that take into account variations between light-emitting element lots when multiple light-emitting elements are test-applied together as described above. This allows for the selection of more suitable conditions.

[0020] Thereafter, the light emitting element is removed, and the bumps are made observable from above. The width and height of the bumps are measured. Table 1 shows conditions 1 to 6 and the measured values ​​of the bumps after deformation.

[0021] [Table 1]

[0022] It can be seen that condition 3 is the most suitable condition among conditions 1 to 6. As a result, it was decided that condition 3 would be used when actually contacting and bonding the electrodes of the light-emitting element to the bumps. It took about five hours to determine the bonding conditions. [Industrial Applicability]

[0023] The method for determining bump bonding conditions according to the embodiment of the present invention can be used in a method for manufacturing a light emitting device that includes a step of bonding a light emitting element onto a wiring substrate via a bump. [Explanation of symbols]

[0024] 10...Light emitting element 11...Laminated structure 12...Semiconductor layer 13...Element substrate 14...Electrode 20...Wiring board 21...Base material 22...Wiring 30, 31... Bump

Claims

1. preparing a light emitting element including an element substrate, a semiconductor layer disposed on the element substrate, and an electrode disposed on the semiconductor layer; preparing a wiring substrate; forming bumps on the wiring substrate; a step of bringing the bumps into contact with the element substrate and placing the light emitting element on the bumps; a step of selecting one of a plurality of bonding conditions and applying the selected bonding condition to the light emitting element to deform the bump, the step being performed for each bonding condition; a step of removing the light emitting element from above the bump, observing the shape of the bump, and determining an appropriate condition from among the plurality of bonding conditions; A method for determining bonding conditions for bumps, comprising:

2. 2. The method for determining bump bonding conditions according to claim 1, wherein the element substrate is made of sapphire.

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