Mounting device

Abstract

The present invention provides a mounting device capable of suppressing warping of chips mounted on a substrate. [Solution] The mounting device 1 includes a chip holding unit 10 for holding the chip C and mounting the chip C onto a substrate W, an irradiation unit 20 for irradiating with a laser L, and a control unit 30 for controlling the irradiation unit 20. The irradiation unit 20 irradiates the chip C with the laser L toward the surface C1 of the chip C opposite to the substrate W. The irradiation unit 20 is adjustable in wavelength λ of the laser L. The control unit 30 adjusts the wavelength λ of the laser L based on the warp state E of the chip C when it is mounted on the substrate W.

Description

[[Technical Field]]

[0001] The present disclosure relates to a mounting apparatus. [[Background Art]]

[0002] A mounting apparatus for mounting a chip onto a substrate is known. The mounting apparatus according to Patent Document 1 mounts a chip onto a substrate by pressing the chip against the substrate while holding the chip heated by a heater. [[Prior Art Literature]] [[Patent Literature]]

[0003] [[Patent Document 1]] Japanese Unexamined Patent Publication No. 2023-101866 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] By the way, there is a problem that warpage occurs in chips mounted on a substrate. Warpage of a chip causes poor connection between the chip and the substrate, and is therefore problematic.

[0005] An object of the present disclosure is to provide a mounting apparatus capable of suppressing warpage of a chip mounted on a substrate. [[Means for Solving the Problem]]

[0006] A mounting apparatus according to the present disclosure includes: a chip holding portion that holds a chip and mounts the chip onto a substrate; an irradiation portion that irradiates a laser; and a control portion that controls the irradiation portion, wherein the irradiation portion irradiates the laser toward a surface of the chip opposite to the substrate, the irradiation portion is capable of adjusting the wavelength of the laser, and the control portion adjusts the wavelength of the laser based on a warpage state of the chip when the chip is mounted onto the substrate.

[0007] The laser wavelength is adjusted based on the chip's curvature when it is mounted on the substrate. By changing the laser wavelength based on the chip's curvature, the laser's transmittance to the chip changes according to the chip's curvature. This allows the manner of thermal expansion of the chip to be changed according to the chip's curvature, and thus chip curvature can be suppressed by an appropriate method according to the chip's curvature.

[0008] This invention provides a mounting device that can suppress warping of chips mounted on a substrate.

[0009] In one embodiment, the warping state includes a first state in which the chip is warped so that it is convex toward the substrate, and a second state in which the chip is warped so that it is convex toward the opposite side from the substrate. When the control unit determines that the warping state is the first state, it sets the wavelength of the laser to the first wavelength, and when the warping state is determined to be the second state, it sets the wavelength of the laser to a second wavelength which is longer than the first wavelength.

[0010] When a short-wavelength laser (wavelength 1) is shone on the side of the chip opposite the substrate, the laser does not easily penetrate the chip due to its low transmittance, and is easily absorbed by the side of the chip opposite the substrate. As a result, the side of the chip opposite the substrate is easily heated. When the side of the chip opposite the substrate is heated, thermal expansion occurs on that side of the chip. This suppresses the warping of the chip C in the first state (which tends to bend convexly towards the substrate).

[0011] When a second wavelength laser, which has a longer wavelength, is shone on the side of the chip opposite the substrate, the laser easily penetrates the chip due to its high transmittance, and the laser easily reaches the substrate side of the chip and even the substrate itself. As a result, the substrate side of the chip is easily heated. When the substrate side of the chip is heated, thermal expansion occurs on that side of the chip. This suppresses the warping of the chip in the second state (where it tends to warp so that it becomes convex toward the opposite side of the substrate W).

[0012] In one embodiment, the control unit includes a memory that stores whether the expected warping state when the chip is mounted on the substrate is a first state or a second state for each type of chip, and the control unit reads the warping state from the memory before irradiating with the laser by the irradiation unit.

[0013] This makes it easy to determine the curvature of the chip.

[0014] In one embodiment, the laser is infrared light.

[0015] By changing the laser wavelength within the infrared range, it becomes easier to alter the laser's transmittance to the chip. [Effects of the Invention]

[0016] According to this disclosure, it is possible to provide a mounting apparatus that can suppress warping of chips mounted on a substrate. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 shows the mounting device. [Figure 2] Figure 2 shows a graph illustrating the relationship between the laser wavelength and the laser's transmittance to the chip. [Figure 3] Figure 3 shows a chip in the first state of warping. [Figure 4] Figure 4 shows a chip in the second state of warping. MODE FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described in detail based on the drawings. The following description of preferred embodiments is essentially merely illustrative, and is not intended in any way to limit the present disclosure, its applications or uses.

[0019] (Mounting Apparatus) Figure 1 shows a mounting apparatus 1. The mounting apparatus 1 is also called a bonding apparatus. The mounting apparatus 1 mounts a chip C onto a substrate W. The mounting apparatus 1 includes a chip holding portion 10, an irradiation portion 20, and a control portion 30.

[0020] (Substrate) The substrate W is a printed circuit board. The substrate W is mainly formed of resin. The substrate W is plate-shaped. The substrate W is placed on a stage 2. The stage 2 extends horizontally. A front surface W1 of the substrate W faces a side opposite to the stage 2. A back surface W2 of the substrate W faces the stage 2 and contacts the stage 2. The substrate W extends horizontally along the stage 2. On the front surface W1 of the substrate W, a plurality of electrodes W3 are formed arranged in a grid pattern.

[0021] (Chip) The chip C is based on a semiconductor material such as silicon, and integrates a complex electronic circuit by forming fine circuit patterns. Note that the chip C may also be based on a material other than silicon.

[0022] In this example, chip C is plate-shaped. Chip C is placed on surface W1 of substrate W. Surface C1 of chip C faces away from substrate W. That is, surface C1 of chip C is the side of chip C opposite to substrate W. Back surface C2 of chip C faces surface W1 of substrate W. Back surface C2 of chip C is the side of chip C facing substrate W. Multiple solder balls C3 are formed on back surface C2 of chip C in a grid pattern. Solder balls C3 correspond to electrodes W3. Chip C has a certain length (for example, a length greater than the thickness of chip C) in the horizontal direction along stage 2 and substrate W.

[0023] (Chip holding part) The chip holder 10 is also called a bonding head. The chip holder 10 has an attachment 11. The attachment 11 is provided at the substrate W-side end of the chip holder 10. The attachment 11 is plate-shaped. The attachment 11 extends horizontally along the substrate W. The attachment 11 is made of glass.

[0024] In the chip holding section 10, the attachment 11 has a holding surface 12. The holding surface 12 faces the substrate W via the chip C. The holding surface 12 has suction holes (not shown). The suction holes are in communication with a negative pressure pump (not shown).

[0025] The chip holder 10 holds the chip C. More specifically, the holding surface 12 of the attachment 11 in the chip holder 10 holds the chip C. The attachment 11 of the chip holder 10 is transparent to the laser L, which will be described later.

[0026] When the irradiation unit 20 (described later) irradiates with the laser L, the chip holding unit 10 mounts (bonds) the chip C to the substrate W.

[0027] (Irradiation area) The irradiation unit 20 irradiates with a laser L. The irradiation unit 20 is located on the opposite side of the substrate W, with the chip holding unit 10 in between. Although not shown, the irradiation unit 20 includes a laser oscillator (not shown) that emits the laser L, a bend mirror (not shown) that bends and changes the direction of the laser L emitted from the laser oscillator, and a focusing lens 21 that focuses and irradiates the direction-changed laser L.

[0028] There are multiple laser oscillators. Each of the multiple laser oscillators has a different laser wavelength λ. It is possible to switch which laser oscillator actually emits the laser L, or to change the combination of multiple lasers L emitted from multiple laser oscillators. The irradiation unit 20 is adjustable in terms of the wavelength λ of the laser L.

[0029] The irradiation unit 20 irradiates the chip C with a laser L directed toward the surface C1, which is the side of the chip C opposite to the substrate W. The laser L from the irradiation unit 20 passes through the attachment 11 of the chip holding unit 10 and irradiates the surface C1 of the chip C. The laser L irradiated onto the surface C1 of the chip C is either absorbed by the surface C1 of the chip C or passes through the chip C (through the back surface C2 of the chip C) and irradiates the surface W1 of the substrate W.

[0030] When the chip C and substrate W are heated by the laser L, the solder balls C3 on the chip C and the electrodes W3 on the substrate W melt, and the chip C and substrate W are pressed together. As a result, the chip C held by the chip holding unit 10 is mounted on the substrate W. In this way, when the irradiation unit 20 irradiates with the laser L, the chip holding unit 10 mounts the chip C onto the substrate W.

[0031] Laser L emits infrared light. The wavelength λ of laser L is, for example, between 0.76 μm and 1000 μm.

[0032] (Control Unit) The control unit 30 includes a processor 31 and a memory 32. The memory 32 stores a program for executing a predetermined algorithm to operate the processor 31. As will be described in detail later, the memory 32 stores the warping state E of the chip C.

[0033] The control unit 30 controls the irradiation unit 20. The control unit 30 controls the wavelength λ of the laser L irradiated by the irradiation unit 20. Specifically, the control unit 30 switches the laser oscillator that actually emits the laser L, or changes the combination of multiple lasers L emitted from multiple laser oscillators. The control unit 30 may also control the holding of the chip C by the chip holding unit 10.

[0034] (Relationship between wavelength and transmittance) Figure 2 shows a graph illustrating the relationship between the wavelength λ [μm] of laser L and the transmittance F [%] of laser L through chip C. The conditions for this graph are that chip C is made of silicon and has a thickness of 0.7 mm.

[0035] When the wavelength λ changes within a range H between approximately 1 μm and 1.2 μm, the transmittance F also changes. Within range H, the transmittance F decreases as the wavelength λ decreases, and increases as the wavelength λ increases. When the wavelength λ is approximately 1 μm or less, the transmittance F is 0%. When the wavelength λ is approximately 1.2 μm or more, the transmittance F is 100%.

[0036] When the transmittance F is small, the laser L has difficulty penetrating the chip C, and the laser L is more easily absorbed by the surface C1 of the chip C. When the transmittance F is large, the laser L has easier to penetrate the chip C, and the laser L can more easily reach the back surface C2 of the chip C and even the substrate W.

[0037] Note that if the material or thickness of chip C changes, the range of change H may shift or the slope of the graph may change, but basically, the general trend of the graph remains the same (of course, there are exceptions).

[0038] (Bent state) Figure 3 shows a chip with a warp state E in the first state E1. Figure 4 shows a chip with a warp state E2. Chip C may warp when it is mounted on the substrate W. In this example, chip C is not warped and is straight before being mounted on the substrate W. The degree of warping of chip C when it is mounted on the substrate W is called the warp state E.

[0039] The warp state E includes a first state E1 and a second state E2. In the first state E1, the chip C warps so that it is convex toward the substrate W. In the first state E1, the chip C warps so that it is concave toward the opposite side of the substrate W. The first state E1 is also called a smile. In the second state E2, the chip C warps so that it is convex toward the opposite side of the substrate W. In the second state E2, the chip C warps so that it is concave toward the substrate W. The second state E2 is also called a cry.

[0040] The memory 32 of the control unit 30 stores, for each type of chip C, whether the expected warp state E when the chip C is mounted on the substrate W is a first state E1 or a second state E2. The warp state E stored in the memory 32 is the expected state when the chip C is mounted on the substrate W under the condition that the entire chip C is heated evenly.

[0041] In addition to the first state E1 and the second state E2, a third state in which the chip C is not bent may also be stored as the warped state E.

[0042] The warp state E is predicted for each type of chip C (material, shape, size, etc.) through experiments or numerical simulations. If the type of chip C is known, the predicted warp state E can be determined. The type of chip C is usually known in advance. The type of chip C is input to the control unit 30 by the user, for example. Typically, the mounting device 1 continuously performs the task of mounting chips C of the same type onto the substrate W.

[0043] (Wavelength adjustment based on curvature) As shown in Figures 3 and 4, the control unit 30 adjusts the wavelength λ of the laser L irradiated by the irradiation unit 20. The control unit 30 switches the wavelength λ of the laser L between a first wavelength λ1 and a second wavelength λ2. The first wavelength λ1 is shorter than the second wavelength. The second wavelength λ2 is longer than the first wavelength λ1.

[0044] The transmittance F of a laser L with a first wavelength λ1 to tip C is different from the transmittance F of a laser L with a second wavelength λ2 to tip C. The transmittance F of a laser L with a first wavelength λ1 to tip C is smaller than the transmittance F of a laser L with a second wavelength λ2 to tip C. The transmittance F of a laser L with a second wavelength λ2 to tip C is larger than the transmittance F of a laser L with a first wavelength λ1 to tip C.

[0045] Both the first wavelength λ1 and the second wavelength λ2 may be included in the range H. Alternatively, the first wavelength λ1 may be smaller than the lower limit of the range H, while the second wavelength λ2 may be included in the range H. Conversely, the first wavelength λ1 may be included in the range H, while the second wavelength λ2 may be larger than the upper limit of the range H. Furthermore, the first wavelength λ1 may be smaller than the lower limit of the range H, while the second wavelength λ2 may be larger than the upper limit of the range H. Figure 2 illustrates the case where both the first wavelength λ1 and the second wavelength λ2 are included in the range H.

[0046] The control unit 30 adjusts the wavelength λ of the laser L based on the warp state E of the chip C when the chip C is mounted on the substrate W. More specifically, the control unit 30 adjusts the wavelength λ of the laser L based on the expected warp state E of the chip C when the chip C is mounted on the substrate W (assuming that the entire chip C is heated uniformly).

[0047] Specifically, the processor 31 of the control unit 30 reads the warp state E from the memory 32 before the irradiation unit 20 irradiates with the laser L.

[0048] The processor 31 of the control unit 30 determines whether the warping state E read from the memory 32 is in the first state E1 or the second state E2. Alternatively, the processor 31 of the control unit 30 may determine that the warping state E read from the memory 32 is in the third state where the chip C is not warped.

[0049] When the control unit 30 determines that the warping state E is a first state E1, it sets the wavelength λ of the laser L to a first wavelength λ1, and when it determines that the warping state E is a second state E2, it sets the wavelength λ of the laser L to a second wavelength λ2.

[0050] (Effects and Benefits) The wavelength λ of the laser L is adjusted based on the warpage state E of the chip C when it is mounted on the substrate W. By changing the wavelength λ of the laser L based on the warpage state E of the chip C, the transmittance F of the laser L to the chip C changes according to the warpage state E of the chip C. This allows the manner of thermal expansion of the chip C to be changed according to the warpage state E of the chip C, and thus the warpage of the chip C can be suppressed by an appropriate method according to the warpage state E of the chip C.

[0051] This provides a mounting device 1 capable of suppressing warping of chips C mounted on a substrate W.

[0052] By suppressing chip warping, connection problems between the chip and the substrate can be reduced.

[0053] When a short-wavelength laser L with a first wavelength λ1 is irradiated onto the surface C1 of chip C, the transmittance F is small, making it difficult for the laser L to penetrate chip C, and therefore it is easily absorbed by the surface C1 of chip C. As a result, the surface C1 of chip C is easily heated. When the surface C1 of chip C is heated, thermal expansion occurs on the surface C1 of chip C. This suppresses the warping of chip C (which would otherwise bend convexly towards the substrate W). Chip C is straighter than in the first state E1.

[0054] When a laser L with a long wavelength, the second wavelength λ2, is irradiated onto the surface C1 of chip C, the high transmittance F allows the laser L to easily penetrate chip C and reach the back surface C2 and even the substrate W. In particular, the laser L is absorbed by structures other than the chip, such as thin metal films and bumps, located between the back surface C2 of chip C and the surface W1 of substrate W. As a result, the back surface C2 of chip C (more specifically, the area between the back surface C2 of chip C and the surface W1 of substrate W) is easily heated. When the back surface C2 of chip C is heated, thermal expansion occurs on the back surface C2 of chip C. This suppresses the warping of chip C in the second state E2 (where it tends to warp convex toward the opposite side of substrate W). Chip C is straighter than in the second state E2.

[0055] The processor 31 of the control unit 30 stores the warp state E for each type of chip C in the memory 32, and reads the warp state E from the memory 32 before the irradiation unit 20 irradiates with the laser L. This makes it easy to determine the warp state E of the chip C.

[0056] By changing the wavelength λ of laser L within the infrared range, it becomes easier to change the transmittance F of laser L to tip C.

[0057] (Other embodiments) Although this disclosure has been described above with reference to preferred embodiments, this description is not limiting, and various modifications, substitutions, or combinations are, of course, possible.

[0058] Laser L does not necessarily have to be infrared light.

[0059] When a visible light-transmitting material such as glass is used as the chip C, the transmittance to the chip C may increase when the laser L is in the short wavelength range (visible light to near-infrared light) and decrease as the laser L approaches the long wavelength range (far-infrared light). In this case, contrary to the above embodiment, the control unit 30 may set the wavelength λ of the laser L to the second wavelength λ2 (long wavelength) when the warping state E is determined to be the first state E1 (warping so that it is convex toward the substrate W), and set the wavelength λ of the laser L to the first wavelength λ1 (short wavelength) when the warping state E is determined to be the second state E2 (warping so that it is convex toward the opposite side of the substrate W).

[0060] The control unit 30 may adjust the wavelength λ of the laser L based on the (actual or expected) warping state E of the chip C when it is mounted on the substrate W, in order to correct the warping of the chip C that was warped before it was mounted on the substrate W.

[0061] The actual warp state E of the chip C when it is mounted on the substrate W may be detected each time using a sensor, camera, or the like. The control unit 30 may adjust the wavelength λ of the laser L based on the warp state E of the chip C detected each time.

[0062] The substrate W, chip C, stage 2, and attachment 11 of the chip holding part 10 may extend diagonally with respect to the horizontal direction. [Industrial applicability]

[0063] This disclosure is extremely useful and has high industrial applicability because it can be applied to mounting devices. [Explanation of Symbols]

[0064] W board W1 surface W2 Reverse side W3 electrode C Chip C1 surface C2 back side C3 solder ball L Laser λ wavelength λ1 1st wavelength λ2 second wavelength F transmittance E. Curved state E1 First State E2 Second State H range of change 1. Mounting device 2 stages 10 Chip holding section 11 Attachments 12 Holding surface 20 Irradiation area 21 Focusing lens 30 Control Unit 31 processors 32 memory

Claims

1. A chip holding unit that holds the chip and mounts the chip onto a substrate, The irradiation unit that emits the laser, The system includes a control unit for controlling the irradiation unit, The irradiation unit irradiates the laser toward the side of the chip opposite to the substrate, The irradiation unit is capable of adjusting the wavelength of the laser, The control unit adjusts the wavelength of the laser based on the warping state of the chip when the chip is mounted on the substrate.

2. The aforementioned warping state includes a first state in which the chip is warped so that it is convex toward the substrate, and a second state in which the chip is warped so that it is convex toward the opposite side from the substrate. The mounting apparatus according to claim 1, wherein the control unit sets the wavelength of the laser to a first wavelength when the warping state is determined to be a first state, and sets the wavelength of the laser to a second wavelength which is longer than the first wavelength when the warping state is determined to be a second state.

3. The control unit includes a memory that stores whether the expected warping state when the chip is mounted on the substrate is a first state or a second state, for each type of chip. The mounting apparatus according to claim 2, wherein the control unit reads the warping state from the memory before the irradiation unit irradiates the laser.

4. The mounting apparatus according to any one of claims 1 to 3, wherein the laser is infrared light.

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