JP2011119436A - Bonding method of substrate mounting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make an AuSn sheet type preform immobile even when a nonoxidative gas is blown, and to reduce voids left under the AuSn sheet type preform. <P>SOLUTION: A bonding method includes the steps of: placing the AuSn sheet type preform 4 on the surface of a sub-mount substrate 2 in which a suction hole 3 is formed while blowing the nonoxidative gas 16 to the surface side of the sub-mount substrate 2, vacuum-sucking the AuSn sheet type preform 4 through the suction hole 3 so that the AuSn sheet type preform is sucked to the surface of the sub-mount substrate 2, and placing an LED chip 1 on the AuSn sheet type preform 4; and bonding the sub-mount substrate 2 and LED chip 1 together by heating and fusing the AuSn sheet type preform 4 from the sub-mount substrate 2 and LED chip 1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for bonding a substrate to be bonded, which is a component of a substrate mounting apparatus (for example, an LED package), and a bonded body.

  AuSn (gold-tin alloy) may be used when the substrate to be bonded and the bonded body of the substrate mounting apparatus are bonded.

  In Patent Document 1, an AuSn solder paste is applied with the element bonding surface facing upward, and the solder paste is melted by reflow treatment in a non-oxidizing atmosphere, and then cooled to form a solidified AuSn solder layer. A method is described in which an element is inverted and placed on a substrate and reflowed in a non-oxidizing atmosphere to bond the element to the substrate via an AuSn solder joint.

  In Patent Document 2, a through hole is provided in the substrate from the bottom of the solder placement hole, the inside of the through hole is vacuum-sucked to place the AuSn ball bump in the solder placement hole, and then the laser diode element is lowered to drop the AuSn ball bump. A method is described in which the laser diode element and the substrate are heated to melt the AuSn ball bump and cooled, and then cooled.

  In addition, a bonding method is also known in which an AuSn sheet-like preform is placed on a substrate, an LED chip is placed on the AuSn sheet-like preform, and then the AuSn sheet-like preform is heated and melted. The present inventor has studied a bonding method using this AuSn sheet-like preform, but has the following problems.

  AuSn is easy to oxidize, and if oxidized, it will not diffuse with Sn oxide and lead to poor bonding. Therefore, bonding work is performed in a non-oxidizing atmosphere while blowing non-oxidizing gas such as nitrogen gas around the AuSn sheet-like preform and its surroundings. . However, the LED chips to be joined are very small, about 0.3 to 1 mm square, and therefore the AuSn sheet-like preform is also very small, thin and light, so when non-oxidizing gas is sprayed, the AuSn sheet-like preform is The reform was peeled off and moved like a fly, and there was a problem that the positional accuracy was likely to be low. In addition, ambient gas entrained during bonding and gas generated by vaporization of impurities remain as voids under the AuSn sheet-like preform (between the bonded substrates), reducing the bonding area, resulting in insufficient bonding strength and heat dissipation. There was also a problem that happened. FIG. 5C is an example in which the LED chip 51 is bonded to the submount substrate 52 by the AuSn sheet-shaped preform 54. The AuSn sheet-shaped preform 54 is displaced and partially protrudes from the LED chip 51. A state in which the void 55 remains under the sheet-like preform 54 is shown.

JP 2008-10545 A JP 2002-156561 A

  Therefore, the present invention prevents the position accuracy from being lowered by preventing the AuSn sheet-shaped preform from moving even when non-oxidizing gas is blown, and also reduces the void remaining under the AuSn sheet-shaped preform to reduce the bonding. The purpose is to prevent insufficient strength and heat dissipation.

In order to solve the above problems, the present invention joins a substrate to be joined and a joined body, which are components of a substrate mounting apparatus in which the joined body is mounted on the substrate to be joined, by an AuSn sheet-like preform sandwiched between them. In the way to
An AuSn sheet-shaped preform is placed on the surface of the substrate to be bonded, which is formed with suction holes, while the non-oxidizing gas is sprayed on the surface side of the substrate to be bonded, and the AuSn sheet-shaped preform is sucked to cover the opening of the suction holes. Vacuum sucking from the holes and adsorbing to the surface of the substrate to be joined, and placing the joined body on the AuSn sheet-like preform;
A step of heating and melting the AuSn sheet-shaped preform from the substrate to be bonded and the bonded body, and bonding the substrate to be bonded and the bonded body.

In the first step, it is preferable that after the bonded body is placed on the AuSn sheet-shaped preform, the adsorption of the AuSn sheet-shaped preform from the suction hole is stopped. This is because if the joined body is placed on the AuSn sheet-shaped preform, there is no fear of the AuSn sheet-shaped preform moving, and if the adsorption continues until the next AuSn sheet-shaped preform is melted, the molten AuSn is removed. This is because it may be adsorbed.
Below, the illustration or the preferable aspect of each element is demonstrated.

1. Substrate mounting device The substrate mounting device is not limited to a device having a specific function, but examples thereof include an LED package, a laser diode, and a module.
In the case of an LED package, (a) an embodiment in which the joined body is an LED chip and the joined substrate is a submount substrate, (b) an embodiment in which the joined body is a submount substrate, and the joined substrate is a base substrate. c) A mode in which the submount substrate bonded in (a) is bonded to the base substrate in (b), (d) a mode in which the bonded body is an LED chip, and a substrate to be bonded is a base substrate, etc.

  When the joined body is a submount substrate to which the LED chip is joined as in the above-described aspect (b), an operation of placing the submount substrate as the joined body on the AuSn sheet-like preform in the first step; The second step is preferably performed by gripping the submount substrate with a chuck having a concave portion that the LED chip does not touch. Although it does not specifically limit as this chuck, A vacuum suction chuck can be illustrated.

2. AuSn sheet-like preform The planar size and shape of the AuSn sheet-like preform is not particularly limited, but is preferably matched to the size and shape of the joined surface of the joined body, and is 0.1 to 0 than the edge of the joined surface of the joined body. Those having sides of 6 mm are more preferable.
The thickness of the AuSn sheet-like preform is not particularly limited, but is preferably 15 to 35 μm and more preferably 20 to 30 μm in consideration of bonding strength, heat conduction, and cost.

3. Non-oxidizing gas Although it does not specifically limit as a non-oxidizing gas, Noble gases, such as argon, xenon, and helium, hydrogen gas, nitrogen gas, etc. can be illustrated. Although noble gas is expensive, it is highly effective. Nitrogen is preferred because of its low price and sufficient effect.
The amount of the non-oxidizing gas sprayed is not particularly limited, but is preferably 3 to 7 liters / minute when the bonded body is an LED chip and the bonded substrate is a submount substrate.

4). Suction hole Although the opening diameter of a suction hole is not specifically limited, 0.15-0.4 mm is preferable. This is because if it is smaller than 0.15 μm, the suction force tends to be low, and if it is larger than 0.4 mm, the AuSn sheet-like preform tends to be deformed so as to enter the suction hole.
The number of suction holes is not particularly limited. For example, one suction hole may be used for sucking the central portion of the AuSn sheet-like preform, or a plurality of suction holes may be used for sucking a plurality of dispersed locations of the AuSn sheet-like preform. .

  According to the present invention, even if non-oxidizing gas is blown, the AuSn sheet-like preform does not move, the positional accuracy is improved, and voids remaining between the AuSn sheet-like preform and the bonded substrate are reduced, It is possible to prevent insufficient bonding strength and insufficient heat dissipation.

It is sectional drawing which shows the process of joining a LED chip to a submount board | substrate with an AuSn sheet-like preform in an Example. It is sectional drawing which shows the first half of the process of joining a submount board | substrate with an AuSn sheet-like preform in a Example. It is sectional drawing which shows the second half of the process of joining a submount board | substrate with an AuSn sheet-like preform in the Example. The LED package of an Example is shown, (a) is a disassembled perspective view which shows the joining order notionally, (b) is the perspective view after joining. (A) is a plan view showing an embodiment with no displacement and no voids, (b) is a plan view showing a modification of the embodiment, and (c) is a plan view showing a conventional example with displacement and voids.

While the non-oxidizing gas (16, 26) is sprayed on the surface of the substrate to be bonded (2, 5), the suction hole (3, 6) is formed on the surface of the substrate to be bonded (2, 5). The AuSn sheet-like preform (4, 7) is placed so as to cover the opening of (3, 6), and the AuSn sheet-like preform (4, 7) is vacuum-sucked from the suction hole to form the bonded substrate (2, 5). Adsorbing to the surface and placing the joined body (1, 2) on the AuSn sheet-like preform (4, 7);
The AuSn sheet-like preform (4, 7) is heated and melted from the bonded substrate (2, 5) and the bonded body (1, 2), and the bonded substrate (2, 5) and bonded body (1, 2). And a step of bonding the substrate mounting apparatus.

  FIG. 1 shows a process of bonding an LED chip 1 as a bonded body to a submount substrate 2 made of aluminum nitride as a bonded substrate by an AuSn sheet-like preform 4 sandwiched between them. The planar dimension of the submount substrate 2 is larger than the planar dimension of the LED chip 1, and the LED chip 1 is bonded to a substrate position around which the upper surface of the submount substrate 2 appears. The circled numeral 1 in FIG. 4A conceptually shows this process. For example, a suction hole 3 having an opening diameter of 0.25 mm is formed in the submount substrate 2 in advance. The AuSn sheet-like preform 4 includes, for example, an AuSn eutectic sheet-like preform having a thickness of 20 μm and having four sides with a distance of 0.2 mm from the four edges of the bonding surface (rectangular lower surface) of the LED chip 1. Is used.

  As shown in FIG. 1A, the submount substrate 2 is placed on the suction table 13 having the through hole 14 in the chamber 11 having the upper opening 12. The through hole 14 and the suction hole 3 communicate with each other, and gas suction above the submount substrate 2 is started from the through hole 14 and the suction hole 3 by a vacuum suction device (not shown) connected to the back side of the suction table 13. Blowing of nitrogen gas 16 as a non-oxidizing gas is started from the gas supply pipe 15 to the surface side of the submount substrate 2.

  While continuing this gas suction and nitrogen gas 16 blowing, the AuSn sheet-like preform 4 is sucked and held by a known vacuum suction chuck 17 and inserted into the chamber 11 from the upper opening 12, and FIG. As shown in FIG. 3, the AuSn sheet-like preform 4 is positioned and placed on the surface of the submount substrate 2 so as to cover the opening of the suction hole 3. Since the AuSn sheet-like preform 4 is attracted to the surface of the submount substrate 2 by suction from the suction hole 3, the suction by the vacuum suction chuck 17 is stopped and the vacuum suction chuck 17 is retracted as shown in FIG. Let Even if the vacuum chucking chuck 17 is retracted, the AuSn sheet-like preform 4 is adsorbed on the surface of the submount substrate 2, so that it is not peeled off or shifted laterally by the nitrogen gas 16 blown, as shown in FIG. Position accuracy is maintained as shown in a).

  As shown in FIG. 1D, the LED chip 1 is sucked by a known vacuum suction chuck 18 and inserted into the chamber 11 through the upper opening 12, and as shown in FIG. The LED chip 1 is placed on the upper surface of the preform 4 and then the adsorption of the LED chip 1 is stopped. Since the LED chip 1 is kept pressed by the vacuum suction chuck 18, there is no fear that the AuSn sheet-shaped preform 4 moves, so that the suction of the AuSn sheet-shaped preform 4 from the suction hole 3 is also stopped.

  While the nitrogen gas 16 is continuously blown, the temperature of the suction table 13 and the vacuum suction chuck 18 is increased by a heater (not shown) provided thereon, so that an AuSn sheet-like preform is formed from both the submount substrate 2 and the LED chip 1. 4 is heated and melted to start bonding of the submount substrate 2 and the LED chip 1. A thick arrow in FIG. 1 (e) represents heat conduction. At the time of this bonding, even if gas due to vaporization of ambient gas or impurities is caught under the AuSn sheet-like preform 4 (between the submount substrate 2), they are sucked from the suction hole 3 and removed. Therefore, joining without voids is possible as shown in FIG. For this reason, the bonding area does not decrease, and therefore, insufficient bonding strength and insufficient heat dissipation do not occur.

  After the heating is stopped and the molten AuSn sheet-like preform 4 is solidified, the submount substrate 2 and the LED chip 1 are joined, and then, as shown in FIG. At the same time, the vacuum suction chuck 18 is retracted.

  Subsequently, as shown in FIG. 1G, the vacuum suction chuck 19 is inserted into the chamber 11 through the upper opening 12, and as shown in FIG. The bonded submount substrate 2 is sucked, and the process proceeds to the next FIG. The vacuum suction chuck 19 is formed with a recess 20 larger than the LED chip 1 so that when the vacuum suction chuck 19 sucks the submount substrate 2, the LED chip 1 is accommodated without touching (the LED chip 1 is released). . However, there may be a form in which the recess 20 is not provided.

  2 and 3 show a process of bonding the submount substrate 2 (with the LED chip 1 bonded) to the base substrate 5 made of aluminum nitride with an AuSn sheet-like preform 7 sandwiched between them. . The planar dimension of the base substrate 5 is larger than the planar dimension of the submount substrate 2, and the submount substrate 2 is bonded to the substrate position such that the upper surface of the base substrate 5 appears around it. The circled number 2 in FIG. 4A conceptually shows this process. For example, a suction hole 6 having an opening diameter of 0.25 mm is formed in the base substrate 5 in advance. In addition, the AuSn sheet-like preform 7 includes, for example, an AuSn eutectic sheet-like preform having a thickness of 20 μm and having four sides each 0.2 mm away from the four edges of the bonding surface (rectangular lower surface) of the submount substrate 2. Use renovation.

  As shown in FIG. 2 (i), the base substrate 5 is placed on the suction table 23 having the through hole 24 inside the chamber 21 having the upper opening 22. The through hole 24 and the suction hole 6 communicate with each other, and gas suction above the base substrate 5 is started from the through hole 24 and the suction hole 6 by a vacuum suction device (not shown) connected to the back side of the suction table 23. Blowing of nitrogen gas 26 as a non-oxidizing gas is started from the gas supply pipe 25 to the surface side of the submount substrate 2.

  While continuing the gas suction and the blowing of the nitrogen gas 26, the AuSn sheet-like preform 7 is sucked and held by the known vacuum suction chuck 27 and inserted into the chamber 21 through the upper opening 22, and FIG. The AuSn sheet-like preform 7 is positioned and placed on the surface of the base substrate 5 so as to cover the opening of the suction hole 6 as shown in FIG. Since the AuSn sheet-like preform 7 is attracted to the surface of the base substrate 5 by suction from the suction hole 6, as shown in FIG. 2 (k), the suction by the vacuum suction chuck 27 is stopped and the vacuum suction chuck 27 is retracted. . Even if the vacuum chucking chuck 27 is retracted, the AuSn sheet-like preform 7 is adsorbed on the surface of the base substrate 5, so that it is not peeled off or displaced laterally by the blown nitrogen gas 26, and the positional accuracy is maintained. Be drunk.

  As shown in FIG. 2 (l), the submount substrate 2 sucked by the vacuum suction chuck 19 (LED chip 1 joined) in FIG. 1 (h) is inserted into the chamber 21 through the upper opening 22. Then, as shown in FIG. 3 (m), the submount substrate 2 is placed on the upper surface of the AuSn sheet-like preform 7, and the adsorption of the submount substrate 2 is stopped. Since the sub-mount substrate 2 is kept pressed by the vacuum suction chuck 19, there is no fear that the AuSn sheet-shaped preform 7 moves, so the suction of the AuSn sheet-shaped preform 7 from the suction hole 6 is also stopped.

  While the nitrogen gas 26 is continuously blown, the temperature of the suction table 23 and the vacuum suction chuck 19 is raised by a heater (not shown) provided on them, whereby an AuSn sheet-like preform is formed from both the base substrate 5 and the submount substrate 2. 7 is heated and melted to start bonding of the base substrate 5 and the submount substrate 2. Thick line arrows in FIG. 3 (m) represent heat conduction. At the time of this bonding, even if gas due to vaporization of ambient gas or impurities is caught under the AuSn sheet-like preform 7 (between the base substrate 5), they are sucked and removed from the suction holes 6. As in FIG. 5A, joining without voids is possible. For this reason, the bonding area does not decrease, and therefore, insufficient bonding strength and insufficient heat dissipation do not occur.

  After the heating is stopped and the melted AuSn sheet-like preform 7 is solidified, the base substrate 5 and the submount substrate 2 are joined, and then, as shown in FIG. At the same time, the vacuum suction chuck 19 is retracted. As described above, as shown in FIGS. 3O and 4B, an LED module 30 in which the LED chip 1 is bonded to the submount substrate 2 and the submount substrate 2 is bonded to the base substrate 5 is produced. The

In addition, this invention is not limited to the said Example, In the range which does not deviate from the meaning of invention, it can change suitably and can be actualized.
(1) As shown in FIG. 5 (b), the embodiment described above is applied to a mode in which a plurality of LED chips 1 are bonded to a single submount substrate 2 by an AuSn sheet-like preform 4, respectively. Of course, in this case, a plurality of suction holes are formed in the submount substrate 2 to adsorb each AuSn sheet-like preform 4.

DESCRIPTION OF SYMBOLS 1 LED chip 2 Submount substrate 3 Suction hole 4 AuSn sheet-like preform 5 Base substrate 6 Suction hole 7 AuSn sheet-like preform 15 Gas supply pipe 16 Nitrogen gas 19 Vacuum adsorption chuck 20 Recessed part 25 Gas supply pipe 26 Nitrogen gas 30 LED module

Claims (4)

In a method of bonding a bonded substrate and a bonded body, which are components of a substrate mounting apparatus in which the bonded body is mounted on the bonded substrate, with an AuSn sheet-like preform sandwiched between them,
An AuSn sheet-shaped preform is placed on the surface of the substrate to be bonded, which is formed with suction holes, while the non-oxidizing gas is sprayed on the surface side of the substrate to be bonded, and the AuSn sheet-shaped preform is sucked to cover the opening of the suction holes. A first step of vacuum suction from the hole and adsorption to the surface of the substrate to be joined, and placing the joined body on the AuSn sheet-like preform;
A bonding method for a substrate mounting apparatus, comprising: a second step of heating and melting an AuSn sheet-shaped preform from a bonded substrate and a bonded body, and bonding the bonded substrate and the bonded body.   2. The method for bonding a substrate mounting apparatus according to claim 1, wherein, in the first step, after the bonded body is placed on the AuSn sheet-shaped preform, adsorption of the AuSn sheet-shaped preform from the suction hole is stopped.   The method for bonding a substrate mounting apparatus according to claim 1 or 2, wherein the substrate mounting apparatus is an LED package. The joined body is a submount substrate to which the LED chip is joined,
The operation of placing the submount substrate as a bonded body on the AuSn sheet-like preform in the first step and the second step are performed by holding the submount substrate with a chuck having a recess that is not touched by the LED chip. The method for bonding a substrate mounting apparatus according to claim 3.

Images