JP2014057017A - Die shear strength test device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the frequency of occurrence of element destraction when performing die shear strength test, in a brittle material having low breaking strength such as an LED.SOLUTION: When integrating a shear tool, rotatably around an axis, with a shear tool fitting part through a rotating axis support member, the test surface of the shear tool always comes into face to face contact with the LED chip side surface. Since shear force is applied locally to the LED chip, element destraction can be prevented.

Description

  The present invention relates to a die bond strength test apparatus for die-bonded semiconductor chips, and more particularly to a shearing tool pressing mechanism for a semiconductor chip.

  Various die attach agents are used for the die bond joint in LED chip mounting depending on the type of element, electrode structure, and application. Conventionally, silver paste in which conductive silver particles are mixed with an epoxy binder has been used as a standard polymer conductive adhesive. However, in order to realize higher output and ensure high reliability as LED applications expand. The binder resin of the polymer conductive adhesive is made of silicone that has long-term stability to heat and light, gold-gold flip-chip bonding using gold bumps to improve thermal characteristics, and flux The gold-tin eutectic bonding used has come to be adopted.

These bonding techniques aim to improve the performance of the bonded portion. However, if the process control is not sufficient, a mounting defect, that is, a bonding defect may be caused. For example, in the above example, there are a decrease in adhesive strength due to a silicone binder, failure to achieve metal diffusion bonding due to ultrasonic and load conditions in gold-gold flip-chip bonding, and generation of voids in gold-tin eutectic bonding.
Therefore, in order to perform these joining stably, it is necessary to always maintain optimum joining conditions in the process while evaluating the joining reliability.

  In general, the bonding strength of semiconductor chips by die bonding is evaluated by the shear peel strength. FIG. 6 and FIG. 7 show the state of the diesure strength test. FIG. 6 shows the thickness of the die attach agent 4 from the surface of the substrate 3 so that the tip height (share height) of the shear tool 1 made of metal and having a flat test surface from the substrate 3 is avoided. Fig. 7 (a) shows the situation of Fig. 6 as viewed from above the chip 2, showing the state of pressing against the side surface of the die-bonded chip 2 while setting the height to exceed t. The test surface of the tool 1 is kept parallel to the side surface of the chip 2 and is pressed at a constant speed (shear speed). FIG. 7B shows a state in which the test surface of the shear tool 1 is pressed against the side surface of the chip 2. The shear tool 1 applies a force Q in the shearing direction of the chip 2, and the shear tool 1 is more horizontal than the chip 2. Receives reaction force H. Since the shear tool 1 is moved in the shear direction at a constant speed, the horizontal reaction force H gradually increases and becomes the maximum immediately before the chip is peeled off from the chip bonding surface on the surface of the substrate 3. Measure as strength.

  In the case of LEDs, the dimensions of the joint surface are so small that the shear tool used to test the joint strength needs to accurately measure very little force and deflection. Usually, a semi-automatic die shear strength test apparatus is used as an apparatus for performing a test while setting the shear height and the shear speed with high accuracy according to an input value.

  By the way, the LED chip is cut out from the wafer by a method such as a braking process after scribing with a scriber and a dicing with a dicer. However, these methods are easily accompanied by minute deformation of the chip outer shape. . For example, an LED chip formed into a chip by scribing and braking with a diamond scriber may have an edge formed at the scribing position. In addition, LED chips that have been fully diced may have side warping due to chipping, chipping of the back surface, or deformation of the cutting blade. Therefore, in reality, the side surface of the LED chip includes unevenness, and it is difficult to say that the test surface of the shear tool 1 is in sufficient surface contact with the chip side surface in the above-described die scher strength test.

  In addition, even if the semi-automatic die shear strength test apparatus described above is used, the operation of arranging the side surface of the LED chip to be parallel to the test surface of the shear tool 1 is driven in the X direction, the Y direction, and the θ rotation angle. Since the sample in which the LED chip is die-bonded on the substrate is placed on the enabled sample stage, and the input operation of the arrangement adjustment is performed while looking through the binocular stereomicroscope, the visual adjustment is performed as shown in FIG. As shown in FIG. 5, during the test, the tip side of the shear tool 1 may not be kept sufficiently parallel to the test surface of the shear tool 1, and a slight tilt angle ψ of about 1 to 2 ° may occur. (If the inclination angle exceeds 2 °, the operator can easily identify the inclination, so the inclination does not further increase.)

  In that case, as shown in FIG. 1B, the test surface of the shear tool is brought into contact with one end of the side surface of the LED chip, and a shearing force Q is locally applied to the portion. In this case, since the material used for the LED is a brittle material having a low breaking strength, the breaking mode in the die shear strength test is not the bonding surface peeling but the chip breaking mode as shown in FIG. End up.

  In the die shear strength test, when the chip breaking mode occurs, the bond strength and bonding stability of the original joint, which is the original purpose, are not accurately evaluated, and the optimum bonding conditions are always maintained in the process. Becomes difficult.

  The present invention has been made in view of the above problems, and its objective is to reduce the occurrence of chip breaking mode and accurately measure the peel strength in a die shear strength test of LED chips, which are brittle materials with low strength. It is to provide a die shear strength test apparatus capable of performing.

In order to achieve the above object, according to the first aspect of the present invention,
In a fixing structure of a shear tool and a shear tool mounting portion that holds the shear tool, a rotating shaft support member that allows the shear tool to rotate about a longitudinal axis of the shear tool (hereinafter simply referred to as an axis) By using a die shear strength measurement joint testing device characterized by being integrated with the shear tool mounting portion via
Since the test surface of the share rule always comes into contact with the side surface of the LED chip, it is possible to prevent element destruction caused by locally applying a shearing force to the LED chip.

  According to the present invention, it is possible to provide a die shear strength test apparatus capable of reducing chip generation mode generation, suppressing occurrence of jump values, and performing stable and accurate evaluation.

FIG. 1 shows a state in which a chip breaking mode occurs in an LED die shear strength test. FIG. 1 (a) shows a situation in which the chip side surface is not kept parallel to the test surface of the shear tool. 1 (b) shows a state where the test surface of the shear tool is locally in contact with the side surface of the chip, and FIG. 1 (c) shows a state where a local shearing force is applied to the chip and the chip is broken. FIG. 2 is a diagram schematically showing a movable part of a die shear strength test apparatus including a shear tool holding mechanism which is a principal part mechanism of the present invention. FIG. 3 is a diagram showing the behavior of the test surface of the shear tool when the peel strength measurement is performed using the die shear strength test apparatus according to the present invention. FIG. FIG. 3B shows a state in which a rotational force N is generated at the axial center of the shear tool, and the test surface of the shear tool contacts the side surface of the LED chip. FIG. 4 is a diagram illustrating an example of a multi-chip LED. FIG. 5 is a view showing a holding mechanism for a share tool in a conventional apparatus. FIG. 6 is a view showing a general die shear strength test as viewed from the side of the LED chip. FIG. 7 is a diagram illustrating a state in which FIG. 6 is viewed from above the LED chip, and FIG. FIG. 7B is a diagram illustrating the above.

(Die shear strength test equipment)
FIG. 2 is a view showing a movable part of the die shear strength test apparatus. In particular, a shear tool 11 holding mechanism, which is a principal part mechanism of the present invention, is schematically shown with the shear tool mounting part 16 as a half sectional view. That is, the configuration of the present invention is characterized in that the shear tool 11 and the shear tool mounting portion 16 are integrated via the rotary shaft support member 15 so that the shear tool 11 can be rotated about the axis. In addition, in the example of FIG. 2, although it shows as a general deep groove ball bearing as the rotating shaft support member 15, it is not related to this, It selects and uses suitably from the classification of another rolling bearing or a sliding bearing. Also good.

  FIG. 5 shows a holding mechanism of the share tool 101 in the conventional apparatus for comparison with FIG. 2, and the other parts are omitted because they are the same as FIG. As shown in FIG. The share tool 101 is fixed to the tool mounting portion 106 with a fixing screw 109.

In the movable part of FIG. 2, the parts other than the above-described shear tool 11 holding mechanism are shown for explaining the measuring mechanism by taking the case of a current general die shear strength test apparatus as an example.
First, reference numeral 18 denotes a sensor unit. For example, the sensor unit 18 has a recess (not shown) with an opening facing downward (in the direction of the shear tool mounting portion), and the shear tool is mounted on the top surface of the recess. An end of a shear tool mounting portion supporting arm (hereinafter referred to as a supporting arm) 17 extended on the axis from the portion 16 is fixed in a cantilever state, and a strain gauge is disposed on a side surface of the supporting arm 17. When a reaction force at the time of peel strength measurement is applied to the shear tool 11, the support arm 17 bends, and strain is also propagated to the strain gauge. The resistance value change accompanying the physical strain of the strain gauge is converted into a voltage value by a Wheatstone bridge circuit and output as a peel strength measurement value.
Reference numeral 19 denotes a vertically moving block, which serves as a base for arranging the center line of the shear tool 11, the shear tool mounting portion 16 and the sensor portion 18 so as to be aligned on the axis. By moving the vertical movement block 19 in the axial direction by driving the motor, the share height can be adjusted.
Reference numeral 20 denotes a sample stage, on which a substrate 3 to which a sample LED chip 2 is bonded is installed, and the side surfaces of the LED chip are arranged in parallel to the test surface of the shear tool 11 in the X direction, Y direction, and θ rotation angle. Can be adjusted by motor drive.

FIG. 3 shows the behavior of the test surface of the shear tool 11 when peel strength measurement is performed using the die shear strength test apparatus according to the present invention. When the side surface of the LED chip 2 is inclined at an angle ψ with respect to the test surface of the shear tool 11, the LED sample stage 20 moves in the test surface direction (X direction) of the shear tool 11 with the start of measurement. When the contact point is contacted at a point P on the side surface (FIG. 3A), a rotational force N is generated at the center of the shear tool 11 (indicated by a point O), and the LED sample stage 20 is further moved. The test surface is in contact with the side surface of the LED chip 2 (FIG. 3B).
When viewed microscopically at this stage, depending on the unevenness of the side surface of the LED chip 2 as a sample, the test surface becomes completely parallel to the plane recognized by the average of so-called surface roughness. It is important that the test surface is not in contact, and the test surface is in contact with the test surface while being automatically adjusted so that the reaction force from the side surface of the LED chip 2 is uniform over the entire test surface.
As a result, the shearing force Q from the test surface is not locally concentrated on the side surface of the LED chip 2 but is automatically adjusted so that it is always applied widely. Therefore, the peeling using the die shear strength test apparatus according to the present invention is performed. In the strength measurement, the occurrence of the chip breaking mode in the aforementioned peel strength measurement can be suppressed.

  3B, the action line of the shearing force Q that the LED chip 2 receives from the test surface of the shear tool 11 is tilted, and the test surface of the shear tool 11 (the LED chip 2 of the LED chip 2) is tilted. The force Qcosψ in the direction perpendicular to the side surface) and the force Qsinψ in the sliding direction on the test surface of the shear tool 11 are decomposed. However, as described above, the inclination angle ψ is considered to be very large, about 2 degrees. It can be considered that the influence of inclination is slight (Q cos 2 ° = 0.999). In other words, it can be said that it is an error range, considering that the peel strength measurement value in the normal die shear strength test is observed with a variation of at least about 20%.

As described above, in the die shear strength test of the LED chip which is a brittle material having a low breaking strength, the chip breaking mode is likely to occur because the shear tool 101 is fixed, and thus the chip breaking mode occurs. However, using the die shear strength tester according to the present invention reduces the occurrence of chip breakage mode, suppresses the occurrence of jump values, and enables stable and accurate evaluation. Become.
(Test method for multi-chip LED)

  By using the die shear strength test apparatus according to the present invention, the labor required for the die shear strength test can be reduced in some special LED optical devices. A specific example in this case will be described below.

FIG. 4 is an example of a light emitting device (hereinafter referred to as a multi-chip LED) using a plurality of LED elements in a single package called a multi-chip LED by those skilled in the art. A multi-chip LED 200 includes a plurality of (12) light-emitting devices. It shows a state in which the LED chip 202 is die-bonded.
For example, today, for high light output type LED lighting, a configuration that obtains white by mixing with blue LEDs and yellow and red phosphors, or a configuration that emits RGB colors and obtains white by mixing these colors. and so on. As the package base material, a ceramic base provided with wiring or an aluminum plate surface subjected to insulation treatment and then provided with wiring is used.

By the way, in daily process management for creating quality in the die bonding process, bonding strength is measured as confirmation of equipment condition or product quality and daily inspection.
When performing the die shear strength test in the multi-chip LED 200 as shown in FIG. 4, the most labor intensive in the past is that each LED chip has an angle shift (α, β, γ in FIG. 4). It was forced to adjust the arrangement by driving the θ rotation angle so that the side surface of the chip was parallel to the test surface of the shear tool 1.

By using the die shear strength test apparatus according to the present invention, in the LED light emitting device such as the multi-chip LED 200, the angle adjustment according to each LED chip is omitted, and the sample stage is driven in the X and Y directions according to the pitch of the LED arrangement. A simple measurement is possible in which the arrangement adjustment is completed only by feeding by operation and the strength is measured.
When there is an LED chip that has been mounted with a large angular deviation, the following two processes can be considered. The first idea is to select and measure an LED chip with a small angle deviation. Usually, the above measures are sufficient because the number of samples carried out in the daily inspection is small (because of destructive inspection). As a second idea, measure the strength with a sample that has a margin for the angle deviation of the LED chip beforehand, and set the lower control limit applied to the daily inspection based on the sample data. Also good.
As described above, the die shear strength test apparatus according to the present invention is a test apparatus in which the occurrence of jump values due to measurement factors is low, so that the measurement values are stable, and even the above simple measurement functions effectively for statistical process management. This can greatly reduce the labor and time required for daily inspections.

  The present invention is not limited to the above-described embodiments, and various applications and modifications can be considered without departing from the gist of the present invention.

1,11,101 Share tool
2 LED chip 3 Substrate 4 Die attach agent (joint)
15 Rotating shaft support member 16,106 Shear tool mounting part 17,107 Shear tool mounting part support arm 18,108 Sensor part 19 Vertical movement block 20 Sample stage 121 Fixing screw

Claims (1)

A die shear strength measurement joint testing device,
In the fixing structure of the share tool and the share tool mounting part holding the share tool,
A die shear strength measuring joint testing apparatus, wherein the shear tool is integrated with the shear tool mounting portion via a rotating shaft support member that is rotatable about a longitudinal axis of the shear tool.

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