Substrate bonding method for columnar connectors

Abstract

To provide a substrate bonding method for a columnar connector, for further details, a substrate bonding method for a columnar connector, which is formed in a columnar shape and connects a substrate to an electrode of a semiconductor chip to bond the semiconductor chip to the substrate.SOLUTION: A substrate bonding method for a columnar connector has the advantage that even columnar connectors with a large aspect ratio can be bonded at precise positions while maintaining their orientation perpendicularly on the substrate.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a substrate bonding method for a columnar connector, and more particularly to a substrate bonding method for a columnar connector, which bonds a columnar connector to a substrate, the columnar connector being formed in a columnar shape and connecting the substrate to an electrode of a semiconductor chip to connect the semiconductor chip to the substrate. [Background technology]

[0002] When multiple semiconductor chips are stacked and bonded to a substrate or another semiconductor chip in a package-on-package (PoP) or chip-on-chip (CoC) configuration, columnar connectors known as copper pillars or copper pins are used. Solder balls are not suitable for electrically connecting upper and lower semiconductor chips or substrates with a relatively large height difference. Solder balls are not suitable for miniaturizing semiconductor devices because it is difficult to arrange electrodes at a fine pitch.

[0003] Therefore, columnar connectors with a large aspect ratio, such as copper pillars, are used to electrically connect electrodes of upper and lower semiconductor chips or substrates.

[0004] The smaller the size of these columnar connectors, with widths of 100 μm or less, the more difficult it is to apply the process of forming solder bumps using conventional solder balls. The smaller the size and lighter the weight, the greater the possibility of defects occurring as the position and angle of the columnar connector changes due to the viscous liquid properties of the cream solder or solder paste during the melting process. In particular, the higher the aspect ratio of the columnar connector, the more likely it is that the columnar connector will tilt during the heating process due to the viscosity of the solder paste or flux.

[0005] To solve this problem, a conventional method has been tried in which the columnar connectors are pressed against the substrate using a pressure plate, and then the temperature is raised while the connectors are fixed. However, since there are often variations in the length of the thin columnar connectors and the surface height of the substrate is not uniform, there is a problem in that the numerous columnar connectors are not all pressed uniformly.

[0006] There is a need for a technology that can solve these problems and bond columnar connectors with large aspect ratios vertically to precise positions on a substrate. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been devised to meet the above-mentioned requirements, and its purpose is to provide a substrate bonding method for a columnar connector that bonds a columnar connector to a substrate in an accurate position and direction for electrically connecting the substrate and a semiconductor element. [Means for solving the problem]

[0008] The present invention is a substrate bonding method for bonding a columnar connector to a substrate, comprising the steps of: (a) providing a substrate having a metal connection film formed on each of a plurality of electrode pads; (b) applying flux to the metal connection films of the plurality of electrode pads of the substrate; (c) mounting a columnar connector on the upper surface of each metal connection film of the substrate to which the flux has been applied; (d) rotating the substrate on which the columnar connectors are mounted to turn it upside down; (e) heating the assembly of the substrate and the columnar connector so that the metal connection film of the substrate melts; and (f) after completing step (e), cooling the assembly of the substrate and the columnar connector so that the melted metal connection film of the substrate hardens. [Effects of the Invention]

[0009] The method for bonding a columnar connector to a substrate according to the present invention has the advantage that even columnar connectors with a large aspect ratio can be bonded at accurate positions on the substrate while maintaining a perpendicular orientation. [Brief explanation of the drawings]

[0010] [Figure 1] 3A to 3C are views illustrating a process of performing a substrate bonding method of a post-shaped connector according to an embodiment of the present invention. [Figure 2] 3A to 3C are views illustrating a process of performing a substrate bonding method of a post-shaped connector according to an embodiment of the present invention. [Figure 3] 3A to 3C are views illustrating a process of performing a substrate bonding method of a post-shaped connector according to an embodiment of the present invention. [Figure 4] 3A to 3C are views illustrating a process of performing a substrate bonding method of a post-shaped connector according to an embodiment of the present invention. [Figure 5] 3A to 3C are views illustrating a process of performing a substrate bonding method of a post-shaped connector according to an embodiment of the present invention. [Figure 6] 10A to 10C are views illustrating a process of performing a substrate bonding method of a columnar connector according to another embodiment of the present invention; [Figure 7] 10A to 10C are views illustrating a process of performing a substrate bonding method of a columnar connector according to another embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a method for bonding a post-shaped connector to a substrate according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0012] 1 to 5 are diagrams illustrating the process of performing a substrate bonding method for a columnar connector according to one embodiment of the present invention.

[0013] The present invention is directed to connecting a columnar connector 200 with a large aspect ratio, such as a copper pillar (Cu pillar or Cu column) or copper pin (Cu pin), to a substrate 100. Such columnar connectors 200 generally have a width of 100 μm or less, and often have a height 1.5 times or more the width. Using such small columnar connectors 200 with a large aspect ratio makes it possible to connect semiconductor chips to the substrate 100 at fine pitch intervals.

[0014] In order to bond a semiconductor chip to a substrate 100 using such a high aspect ratio columnar connector 200, the present invention is intended to bond the columnar connector 200 to the electrode of the substrate 100 in an accurate position and direction.

[0015] First, as shown in FIG. 1, a substrate 100 having a plurality of electrode pads 110 and a metal connection film 120 formed thereon is provided (step (a)). This process is generally referred to as providing a precoated substrate 100. Precoating refers to coating exposed copper portions of the substrate 100 to prevent oxidation of the copper wire circuit of the printed circuit board (PCB) and to facilitate connection with mounted components. In this embodiment, the metal connection film 120 is formed by applying such precoating to the electrode pads 110 at positions where the columnar connectors 200 are to be bonded. This PCB surface treatment method serves to prevent oxidation of exposed copper portions of the copper foil layer, which are left open on the surface of the PCB for the placement of ICs and electronic components, and to strengthen the bonding strength of the electronic component surface mount. Typically, the substrate 100 is precoated using gold, silver, tin, palladium, or an alloy of these metals. In some cases, the metal connection film 120 can be formed by applying solder paste and then precoating via reflow.

[0016] 2, flux 101 is applied to the metal connection film 120 of the electrode pad 110 of the substrate 100 (step (b)). The flux 101 is applied to the upper surface of the metal connection film 120 of the substrate 100 using a mask printing method or a dispenser.

[0017] Next, as shown in FIG. 3 , the columnar connectors 200 are mounted on the upper surface of each metal connector film 120 of the substrate 100 to which the flux 101 has been applied (step (c)). The process of mounting the columnar connectors 200 on the substrate 100 can be performed by various known methods. The columnar connectors 200 can be mounted on the substrate 100 by a pick-and-place method, in which an individual columnar connector 200 or a plurality of columnar connectors 200 are clamped using a tool such as a gripper, and then the substrate 100 is placed in a predetermined position. In some cases, the columnar connectors 200 can be mounted by placing a mask having mounting holes formed at positions corresponding to the plurality of electrode pads 110 of the substrate 100 on the upper surface of the substrate 100, and inserting the columnar connectors 200 into the mounting holes of the mask. In this case, the columnar connectors 200 can be mounted on the substrate 100 at high speed using a device such as a cyclone head. When the columnar connectors 200 are mounted on the substrate 100 in this manner, the columnar connectors 200 may not stand vertically on the top surface of the substrate 100, as shown in Fig. 3. Because the columnar connectors 200 are very small and light, the columnar connectors 200 may sometimes be mounted in an inclined position as shown in Fig. 3 due to the viscosity and surface tension of the flux 101. The present invention is characterized in that even in the case of such inclined columnar connectors 200, they are bonded to the substrate 100 in such a manner that they are vertically aligned.

[0018] In this state, the substrate bonding method for columnar connectors of this embodiment rotates the substrate 100 on which the columnar connectors 200 are mounted so that it is turned upside down as shown in Fig. 4 (step (d)). Since the columnar connectors 200 are very light compared to the viscosity of the flux 101, the columnar connectors 200 are temporarily adhered to the substrate 100 by the adhesive force of the flux 101, and the columnar connectors 200 will not fall off the substrate 100 even if it is turned upside down as shown in Fig. 4.

[0019] In this state, the assembly of the substrate 100 and the columnar connectors 200 is heated so that the metal connector films 120 of the substrate 100 melt (step (e)). When the substrate 100 and the columnar connectors 200 are heated in this manner, the metal connector films 120 melt with the aid of the flux 101, and the columnar connectors 200 are bonded to the substrate 100. At this time, the viscosity of the flux 101 or the metal connector film 120 that temporarily adheres the columnar connectors 200 to the substrate 100 decreases as the viscosity of the material that adheres the columnar connectors 200 decreases and the surface tension also weakens, so that the columnar connectors 200 are vertically aligned in accordance with the direction of gravity. In particular, the larger the aspect ratio of the columnar connectors 200, the greater the effect of gravity that vertically aligns the columnar connectors 200.

[0020] The process of heating the substrate 100 and the columnar connectors 200 to perform step (e) can be performed by various known methods. Step (e) can also be performed by a method in which the assembly of the substrate 100 and the columnar connectors 200 undergoes reflow. Alternatively, the metal connector film 120 can be heated by a method in which a laser is irradiated onto the top or bottom surface of the substrate 100 in the upside-down state in step (d).

[0021] As described above, the temperature and time change for heating the substrate 100 in step (e) can be adjusted in a variety of optimal ways depending on the size and shape of the columnar connectors 200 and the material characteristics of the flux 101 and the metal connecting film 120. By adjusting the process conditions in this manner, the columnar connectors 200 do not fall off the substrate 100, and the tilt of the columnar connectors 200 can be eliminated, allowing them to be effectively aligned vertically. Furthermore, even if the position of the columnar connectors 200 is partially deviated from the position of the electrode pads 110 during steps (b) to (d), the columnar connectors 200 will naturally move to the center of the electrode pads 110 due to the viscosity of the molten metal as the metal connecting film 120 and flux 101 melt.

[0022] On the other hand, when performing step (d), heating in a vacuum atmosphere has the advantage of preventing voids from occurring in the molten state of the metal connection film 120 and the flux 101, thereby improving the quality of the process.

[0023] Next, the assembly of the substrate 100 and the columnar connectors 200 is cooled so that the molten metal connector film 120 hardens, thereby completing the bonding of the columnar connectors 200 to the substrate 100 (step (f)).

[0024] As described above, the present invention has the advantage that it can bond the columnar connectors 200, which are difficult to handle due to their very small size and large aspect ratio and therefore difficult to mount by precisely and precisely adjusting their position and direction, to the substrate 100 in an accurate and correct posture. In particular, by switching the phase to turn the substrate 100 upside down and heating and bonding the columnar connectors 200 while they are suspended upside down on the substrate 100 by the flux 101, the present invention has the advantage that it can align the fine columnar connectors 200 in an accurate position and direction and bond them to the substrate 100 by utilizing the characteristics of gravity without using a separate complex configuration or device.

[0025] Although the present invention has been described above with reference to preferred examples, the scope of the present invention is not limited to the above-described embodiments.

[0026] For example, steps (e) and (f) may be performed by various methods other than reflow or laser heating and cooling.

[0027] It is also possible to carry out the substrate bonding method of the columnar connector according to the present invention, as described below.

[0028] The substrate bonding method of the columnar connector according to this embodiment is almost the same as the embodiment previously described with reference to Figures 1 to 5, except that a pressure plate 300 is used when performing step (d).

[0029] As shown in Figures 1 to 3, the substrate bonding method for a columnar connector according to this embodiment also involves the same steps of providing a substrate 100 on which a metal connection film 120 is formed (step (a)), applying flux 101 (step (b)), and mounting a columnar connector 200 on the substrate 100 (step (c)).

[0030] 6, the columnar connectors 200 are pressed against the upper surface of the substrate 100 using a flat pressure plate 300 (step (d-1)). Pressing the columnar connectors 200 using the pressure plate 300 in this manner can help align the columnar connectors 200 in the correct position and direction on the substrate 100, while potentially overcoming the viscosity of the flux 101.

[0031] In this state, the pressure plate 300 can be removed, or as shown in Figure 7, the pressure plate 300 and the substrate 100 can be rotated simultaneously and turned upside down while the pressure plate 300 is still pressing the columnar connector 200 (step (d-2)).

[0032] In this state, the pressure plate 300 is removed (step (d-3)).

[0033] As shown in Figure 5, bonding of the columnar connector 200 to the substrate 100 is completed by performing a step (step (e)) of heating the substrate 100 and the columnar connector 200 and a step (step (f)) of cooling the assembly of the substrate 100 and the columnar connector 200.

[0034] In some cases, rather than performing steps (e) and (f) after removing the pressure plate 300, a step (d-3) of removing the pressure plate 300 can be performed during step (e) or step (f).

[0035] This embodiment may have the same or similar effects as the embodiment previously described with reference to Figures 1 to 5. Furthermore, as described above, by additionally using the pressure plate 300, it is possible to obtain the additional effects of aligning the columnar connectors 200 with respect to the substrate 100 or reducing the degree of tilt.

[0036] The shape of the pressure plate 300 is not limited to a flat plate. As long as the pressure plate has a structure that can apply uniform pressure to the multiple columnar connectors 200 on the substrate 100, various shapes of pressure plates can be configured. [Explanation of symbols]

[0037] 100 boards 110 Electrode Pads 120 Metallic interconnect film 200 Columnar Connector 101 Flux 300 Pressure Plate

Claims

1. A substrate bonding method for bonding a columnar connector to a substrate, comprising: (a) providing a substrate on which metal connection films are formed on a plurality of electrode pads; (b) applying flux to the metal connection films of the plurality of electrode pads of the substrate; (c) mounting a columnar connector on the upper surface of each metal connection film of the substrate to which the flux has been applied; (d) rotating the substrate on which the columnar connectors have been mounted in step (c) to turn the substrate upside down so that the columnar connectors are suspended upside down; (e) heating the assembly of the substrate and the columnar connector so that the metal connection film of the substrate melts; (f) after completing the step (e), cooling the assembly of the substrate and the columnar connector so that the molten metal connection film on the substrate hardens; A method for bonding a columnar connector to a substrate, comprising:

2. 2. The substrate bonding method for a columnar connector according to claim 1, wherein said step (a) comprises coating a metal material on a plurality of electrode pads of said substrate to form said metal connection film.

3. 2. The substrate bonding method for a columnar connector according to claim 1, wherein the step (c) comprises placing a mask on the upper surface of the substrate, the mask having mounting holes formed at positions corresponding to a plurality of electrode pads on the substrate, and mounting the columnar connector on the substrate.

4. 2. The substrate bonding method for a columnar connector according to claim 1, wherein in step (c), the columnar connectors are mounted on the plurality of electrode pads of the substrate by a pick-and-place method.

5. The step (e) comprises:

2. The method for bonding a columnar connector to a substrate according to claim 1, wherein the substrate or the columnar connector is heated by irradiating it with a laser.

6. The step (e) comprises:

2. The method for bonding a columnar connector to a substrate according to claim 1, wherein the assembly of the substrate and the columnar connector is heated via reflow.

7. 2. The method for bonding a columnar connector to a substrate according to claim 1, wherein said step (e) is performed in a vacuum state.

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