JP2012028390A - Method of manufacturing semiconductor light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide method of manufacturing a semiconductor light-emitting device manufacturing for solving the problems that when a nondestructive inspection based on heat conduction that is known as the nondestructive inspection for a joint state of a flip-chip bonded semiconductor element is applied to an LED device having a resin encapsulation layer, it becomes difficult to determine the joint state so that manufacturing efficiency is not increased.SOLUTION: The method of manufacturing an LED device 10 with a circuit substrate 12 on which a semiconductor light-emitting element 13 is flip-chip bonded comprises: a substrate preparation step of preparing a collective substrate 51 on which the LED elements 13 are mounted; a joint determination step of heating the collective substrate 51 and measuring a temperature of a rear face of the LED element 13 by using a thermography 52 to determine quality of a joint state at an inspection part 53,; an encapsulation step of encapsulating the collective substrate 51 with a resin layer 11 containing a fluorescent material; and a dividing step of cutting the collective substrate 51 in pieces to obtain individual semiconductor light-emitting devices 10. Accordingly, the temperature of the LED element 13 is measured in such a state that the rear face is exposed, so that quality determination of the joint state can be precisely performed. And further, the collective substrate in which LED elements 13 are closely gathered is inspected, thereby increasing manufacturing efficiency.

Description

  The present invention relates to a method of manufacturing a semiconductor light emitting device in which a semiconductor light emitting element is flip-chip mounted on a circuit board.

  2. Description of the Related Art A semiconductor light emitting device (hereinafter referred to as an LED device unless otherwise specified) in which a semiconductor light emitting element (hereinafter referred to as an LED element unless otherwise specified) is mounted on a circuit board and packaged is known. This LED device often employs flip-chip mounting with excellent heat dissipation characteristics, mounting area efficiency, and productivity. However, in flip-chip mounting, if the circuit board is opaque, the joint between the electrode of the circuit board and the electrode of the LED element cannot be seen. Therefore, in nondestructive inspection using light such as fillet shape or reflection of bonding metal (solder etc.) The quality of the joined state cannot be judged.

  A method using heat conduction is known as a non-destructive method for knowing the bonding state during flip chip mounting. For example, in FIG. 1 of Patent Document 1, first, a stage 5 for fixing a semiconductor device 4 to a semiconductor element 1 flip-chip mounted on a substrate 2 (circuit substrate) on which a circuit pattern is formed via a plurality of bumps 3; A current is applied using an external power source (heating means 6), and then a back surface temperature distribution due to self-heating of the semiconductor element 1 is measured (measuring means 7), and then the bonding state of the bump 3 is determined based on the temperature distribution. An inspection apparatus for judging whether the quality is good (determination means 8) is shown.

  The inspection apparatus shown in FIG. 1 of Patent Document 1 heats the semiconductor element 1 by self-heating of the semiconductor element 1, and utilizes the temperature distribution generated by transferring the heat to the substrate 2 through the bumps 3. The joining state was judged. However, in the case of LED elements, bumps that overlap the light-emitting layer (usually p-side bumps) are the main heat dissipation path, so the heat distribution due to heat dissipation is clearly seen around the bumps that do not overlap the light-emitting layer (usually n-side bumps). It does not appear and it is difficult to judge the joining state. Also, a current application circuit must be provided outside, and a probe for electrical connection must be prepared.

  As described above, when it is attempted to apply the technique of knowing the bonding state from self-heating due to current application to the LED element, as described above, the determination accuracy varies depending on the type of electrode, and the number of peripheral devices increases. Therefore, it is desirable that the LED element be passively heated to determine whether it is good or bad. In FIG. 1 of Patent Document 2, a laser beam having a predetermined power is irradiated for a predetermined time on the central portion of the back surface 22B (surface opposite to the electrode surface) of the semiconductor chip 22, and heat is radially emitted from the center to the peripheral portion. An inspection system for inspecting the bonding state between the pad 26 and the land 27 using the transmission is shown. Here, the temperature distribution of the back surface 22B of the semiconductor chip 22 is measured by the thermography 24, and the bonding state is determined by the inspection unit 25 based on the obtained measurement result.

JP 2007-24542 A (FIG. 1) JP-A-11-201926 (FIG. 1)

The inspection system of FIG. 1 of Patent Document 2 heats an electronic component on a circuit board, and determines a bonding state from the temperature distribution measurement. However, in the case of an LED device, an LED element (die or element cut out from a wafer) is mounted on a circuit board, and the LED element is covered with a sealing member such as a resin. When the back surface side of the LED device having such a structure is heated and the temperature distribution on the back surface is observed, the temperature distribution is blurred due to the influence of the sealing member, and it is difficult to determine the bonding state of the LED elements. In other words, quality assurance related to connection becomes impossible. Even when the back surface of the LED element is exposed as a special case, the production efficiency is not improved if the LED devices are inspected one by one. Accordingly, the present invention has been made in view of these problems, and provides a manufacturing method with a high production efficiency that can guarantee the quality of the connecting portion for a semiconductor light emitting device in which a semiconductor light emitting element is flip-chip mounted on a circuit board. The purpose is that.

In order to solve the above problems, the present invention provides a method for manufacturing a semiconductor light emitting device in which a semiconductor light emitting element is flip-chip mounted on a circuit board.
A substrate preparation step of preparing a collective substrate on which a plurality of the semiconductor elements are flip-chip mounted;
A bonding determination step of heating the collective substrate, measuring the temperature of the back surface of the semiconductor light emitting element, and determining whether the bonding state is good or bad;
A sealing step of sealing the semiconductor light emitting element mounted on the collective substrate;
And an individualization step for obtaining a semiconductor light emitting device by cutting the aggregate substrate into individual pieces.

  It is preferable to measure the temperature of the plurality of semiconductor light emitting elements simultaneously in the bonding determination step.

  In the bonding determination step, it is preferable to measure the temperature between the start of heating of the collective substrate and the arrival of thermal equilibrium.

  In the method for manufacturing a semiconductor light emitting device of the present invention, the semiconductor light emitting element flip-chip mounted on the aggregate substrate prepared in the substrate preparation step is not sealed with a protective resin or the like. In this state, that is, before the sealing step, the temperature of the surface opposite to the LED element mounting surface (hereinafter referred to as the back surface) is measured, so that the quality of the bonded state can be accurately determined. Since the subsequent step of sealing the collective substrate with a resin or the like and the step of dividing into pieces do not greatly affect the bonding, the bonding quality of the LED device can be guaranteed by the bonding inspection in the bonding determination step. In addition, since the bonding state of the LED elements mounted on each circuit board is determined by a collective board in which a plurality of circuit boards are integrated, the number of setting steps for the inspection apparatus is greatly reduced, and the manufacturing efficiency is improved.

The perspective view of the LED device in the embodiment of the present invention. The perspective view of the LED apparatus of FIG. The top view which looked at the LED element of FIG. 2 from the bump surface. Sectional drawing of the LED apparatus of FIG. Explanatory drawing for manufacturing the LED device of FIG. Explanatory drawing for determining the joining state of the LED element of FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. In the description of the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted. For the sake of explanation, the scale of the members is changed as appropriate.

  FIG. 1 is a perspective view of an LED device 10 drawn for explaining the appearance of the LED device (semiconductor light emitting device) of the present embodiment. In the LED device 10, a resin layer 11 containing a phosphor is laminated on a circuit board 12. The resin layer 11 is made of a silicone resin containing a phosphor.

  A mounting state of the LED element 13 mounted on the LED device 10 of FIG. 1 will be described with reference to FIG. FIG. 2 is a perspective view of the LED device 10 in a state where the resin layer 11 is peeled off from the LED device 10 of FIG. As shown in FIG. 2, the circuit board 12 includes a plate material 16, and a − electrode 14 and a + electrode 15 formed on the plate material 16. The LED element 13 flip-chip mounted on the circuit board 12 has an n-side bump (cathode, not shown) and a p-side bump (anode, not shown) connected to the negative electrode 14 and the positive electrode 15, respectively. .

  The bump surface of the LED element 13 will be described with reference to FIG. FIG. 3 is a plan view of the LED element 13 viewed from the bump surface side. A part of the n-type semiconductor layer 21 is exposed from the p-type semiconductor layer 22 in the upper layer. There is an n-side bump 23 on the exposed portion of the n-type semiconductor layer 21, and a p-side bump 24 on the p-type semiconductor layer 22. The n-side bump 23 has a smaller plane area than the p-side bump 24, and the n-side bump 23 and the p-side bump 24 are gold bumps formed by electrolytic plating. The protective film is not shown.

  The cross section of the LED device 10 will be described with reference to FIG. 4 is a cross-sectional view of the LED device 10 taken along line AA in FIG. In order to show the n-side and p-side bumps 23 and 24 at the same time, the line AA in FIG. 2 is bent.

First, the LED element 13 will be described. As shown in FIG. 4, an n-type semiconductor layer 21 is provided under the sapphire substrate 25, and a p-type semiconductor layer 22 is formed on the lower surface of the n-type semiconductor layer 21. The n-type semiconductor layer 21 and the p-type semiconductor layer 22 are connected to an n-side bump 23 and a p-side bump 24, respectively. The sapphire substrate 25 has a thickness of 100 to 300 μm, and the n-type semiconductor layer 21 has a thickness of about 5 μm. The p-type semiconductor layer 22 has a total thickness of about 1 μm and includes a p-type GaN layer having a thickness of 100 to 200 nm. The n-side bumps and the p-side bumps 23 and 24 have a thickness of 10 to 30 μm. The light emitting layer (not shown) is at the boundary between the n-type semiconductor layer 21 and the p-type semiconductor layer 22, and the planar shape is substantially equal to the p-type semiconductor layer 22.

  Next, the circuit board side will be described. The circuit board 12 is composed of a plate 16 and-and + electrodes 14 and 15, through holes 14a and 15a, and output electrodes 14b and 15b. The negative electrode 14 and the positive electrode 15 formed on the upper surface of the plate 16 are connected to the electrodes of the mother substrate (not shown) by the output electrodes 14b and 15b formed on the lower surface of the plate 16 and through holes 14a and 15a, respectively. Connected. The − and + electrodes 14 and 15 are connected to the n-side bump 23 and the p-side bump 24, respectively. A resin layer 11 containing a phosphor covers the upper surface of the circuit board 12 and the LED element 13. The plate 16 of the circuit board 12 has a thickness of 300 μm and is made of alumina. The − and + electrodes 14 and 15 and the output electrodes 14b and 15b are copper foils having a thickness of 10 to 30 μm and laminated with nickel and gold. The through holes 14a and 15a have a diameter of 200 μm and are filled with a copper paste. The resin layer 11 has a thickness of about 400 μm and is made of silicone.

  The manufacturing process of the LED device 10 will be described with reference to FIG. FIG. 5 is an explanatory diagram for manufacturing the LED device 10.

(A) is a substrate preparation step. A collective substrate 51 on which a plurality of LED elements 13 are flip-chip mounted is prepared. When the collective substrate 51 is divided into pieces, the circuit substrate 12 (or the LED device 10 without the resin layer 11) shown in FIG. 2 is obtained. At this time, it is preferable to mount the LED elements 13 having the same electrical characteristics on one collective substrate 51. This makes it easy to suppress variations in chromaticity.

(B) is a joining process. The collective substrate 51 is heated, the temperature of the back surface of the LED element 13 is measured, and the quality of the bonded state is determined. First, the heating table 54 is set to a predetermined temperature. Temperature measurement is started from the moment when the collective substrate 51 is brought close to (or in contact with) the heating table 54. The time resolution of the thermography 52 is 25 μs, and the measurement is completed in several milliseconds. The thermography 52 sends measurement data to the inspection unit 53, and the inspection unit 53 determines whether or not the bonding is good based on the temperature rise on the back surface of the LED element 13. The thermography 52 measures a plurality of chips simultaneously at the same time, although the visual field and the accuracy are in a trade-off (in the figure, it is drawn by imagining two simultaneous measurements). This cycle is repeated until all the LED elements 13 on the collective substrate 51 are judged acceptable.

(C) is a sealing process. The LED elements 13 mounted on the collective substrate 51 are sealed with the resin layer 11. For example, the collective substrate 51 may be housed in a mold, and the resin layer 11 may be formed of a silicone resin containing a phosphor.

(D) is an individualization step. The collective substrate 51 provided with the resin layer 11 is cut with a dicing device or the like to obtain the LED device 10 which is divided into pieces. In this step, the LED device determined to be defective in bonding based on the data sent from the inspection unit 53 is removed. In addition, if marking which electrically destroys the LED element 13 determined to be defective in the bonding determination step is performed, the LED device 10 having poor bonding can be removed in the step of checking electrical characteristics (not shown). .

  The method for determining the joining state will be described in more detail with reference to FIG. 6A and 6B are explanatory diagrams for determining the bonding state of the LED elements 13. FIG. 6A is a plan view showing the LED elements 13 mounted on the collective substrate 51 and their peripheral portions, and FIG. It is a graph which shows the temperature rise of a back surface.

  In FIG. 6A, the bumps on the lower surface of the LED element 13 are indicated by dotted lines. The measuring point 61 for measuring the temperature of the back surface of the LED element 13 is substantially at the center of the chip. At the same time, the temperature of the collective substrate 51 is measured at the measurement point 62.

  In FIG. 6B, the horizontal axis represents time and the vertical axis represents temperature. When the connection is good, the temperature rise curve 63 at the measurement point 61 is obtained, and when the connection is poor, the temperature rise curve 64 is obtained. When the bonding is good, the temperature of the measurement point 61 of the LED element 13 rises rapidly. On the other hand, when the bonding is poor, the temperature of the measurement point 61 of the LED element 13 rises slowly. From this difference, it is possible to determine whether the joining state is good or bad. When the collective substrate 51 is brought into contact with the heating table 54, the temperature unevenness of the collective substrate 51 is likely to occur. The temperature rise curves 63 and 64 are corrected so as to remove the influence of the temperature rise of the collective substrate 51 using the measurement point 62. The time interval of temperature measurement is about 25 μs, and each temperature rise curve 63, 64 is saturated within 1 msec.

  Since the temperature rise at the measurement point 61 is almost caused by the heat conduction of the p-side bump 24, it can be said that FIG. 6 determines the bonding state of the p-side bump 24. When it is necessary to know the bonding state of the n-side bump 23, a measurement point may be arranged on the n-side bump 23.

  In the present embodiment, the temperature of the plurality of LED elements 13 is measured at the same time in the bonding determination step to increase manufacturing efficiency. However, in the manufacturing method of the present invention, even if the LED elements 13 are processed one by one in one temperature measurement, the determination is performed on the collective substrate 51 in which the LED devices 10 before separation are densely packed. The production efficiency is higher than the method of inspecting after mounting the LED devices one by one on the device and the method of determining the bonding of the semiconductor elements discretely arranged on the mother substrate.

In this embodiment, the temperature measurement is completed in a short time from the start of heating of the aggregate substrate in the bonding determination step. This observes the transient state of heat conduction. The temperature distribution may be measured after the LED element 13 reaches thermal equilibrium. However, when the bonding of one terminal is good and the bonding of the other terminal is poor, the one terminal is transmitted when reaching the heat parallel. Since heat diffuses toward the other terminal, the temperature distribution is blurred. For this reason, it is more preferable to measure the temperature in a transient state. In the present embodiment, the upper layer of the temperature at the measurement point 61 is measured. However, the temperature distribution on the back surface of the LED element 13 may be recognized.

10 ... LED device (semiconductor light-emitting device),
11 ... resin layer,
12 ... circuit board,
13 ... LED element (semiconductor light emitting element),
14 ...- electrodes,
14a, 15a ... through hole,
14b, 15b ... output electrodes,
15 ... + electrode,
16 ... plate material,
21 ... n-type semiconductor layer,
22 ... p-type semiconductor layer,
23 ... n-side bump,
24 ... p-side bump,
25 ... sapphire substrate,
51. Collective substrate,
52 ... Thermography,
53. Inspection section,
54 ... heating table,
61, 62 ... measurement points 63, 64 ... temperature rise curves.

Claims (3)

In a method of manufacturing a semiconductor light emitting device in which a semiconductor light emitting element is flip-chip mounted on a circuit board,
A substrate preparation step of preparing a collective substrate on which a plurality of the semiconductor elements are flip-chip mounted;
A bonding determination step of heating the collective substrate, measuring the temperature of the back surface of the semiconductor light emitting element, and determining whether the bonding state is good or bad;
A sealing step of sealing the semiconductor light emitting element mounted on the collective substrate;
A method of manufacturing a semiconductor light emitting device, comprising: a step of obtaining a semiconductor light emitting device obtained by cutting the aggregate substrate into pieces.   The method for manufacturing a semiconductor light emitting device according to claim 1, wherein the temperature of the plurality of semiconductor light emitting elements is measured simultaneously in the bonding determination step. 3. The method of manufacturing a semiconductor light emitting device according to claim 1, wherein the temperature is measured from when heating of the collective substrate is started until thermal equilibrium is reached in the bonding determination step.

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