Method for electrically connecting fine pitch electrodes

Abstract

The present invention provides a method for electrically connecting fine pitch electrodes, the method comprising: a first step of providing a first connector having a plurality of first electrodes; a second step of forming a flux printing layer on the first electrode of the first connector; a third step of arranging a meltable conductive ball having an average diameter (R) of 2 to 20 μm on the flux printing layer; a fourth step of partially melting the meltable conductive ball on the flux printing layer to form a preliminary bonding portion for connection to the first electrode; a fifth step of reapplying flux onto the preliminary bonding portion; a sixth step of arranging a second connector having a plurality of second electrodes on the preliminary bonding portion; and a seventh step of applying a laser or heat to the preliminary bonding portion to form a bonding portion achieved through metal-to-metal bonding via intermetallic bonding between the first electrode and the second electrode.

Description

Electrical connection method between fine-pitch electrodes

[0001] One aspect of the present invention relates to a molten conductive ball array film that electrically connects between microelectrodes and a method for manufacturing the same.

[0002] In addition, one aspect of the present invention relates to a micro-electrical connection structure and a micro-electrical connection method using a molten conductive ball array film.

[0003] In addition, one aspect of the present invention relates to a micro-electrical connection method using a molten conductive ball array film.

[0004] In addition, one aspect of the present invention relates to a pick-and-place device, and more specifically, to a device for pick-and-place fine particles using electrostatic adsorption.

[0005] Currently, methods for electrically connecting structures with microelectrodes are known. In particular, various bonding materials, such as anisotropic conductive films (ACFs), anisotropic conductive pastes (ACPs), solder pastes, and solutions containing conductive particles, are used to bond semiconductor devices to substrates.

[0006] Among these, the method using ACF is the most common. However, for micro LED chips with extremely small electrode gaps (less than 10 μm), electrical shorts can occur, despite the use of insulating particles to prevent them. Similarly, the method using ACF and solder paste also presents printing difficulties and electrical shorts for micro-sized gaps (less than 10 μm).

[0007] In particular, during the manufacturing process of micro LED displays, it is difficult to bond micro LEDs to a substrate using conventional ACF films, etc., because the gap between the electrodes of micro LEDs is very narrow. Due to the above-mentioned problems, the method using solder paste is used to bond mini LEDs with a size of 100 μm × 100 μm (gap of 50 μm or more) or more. In addition, the connection using the conductive balls of ACF has the problem of an unstable connection because it is not a metal-to-metal connection, but a method in which the non-melted conductive balls destroy the electrodes to connect.

[0008] Meanwhile, pick-and-place (P&P) devices for electronic components play a crucial role in the electronics assembly process, quickly and accurately picking up electronic components and placing them in designated locations on a circuit board (PCB). Current P&P devices can handle electronic components of various sizes and shapes, from small SMD (Surface-Mount Device) components to large components.

[0009] However, most of the existing pick-and-place devices use negative pressure, so if the adherend is a fine particle, the part may be damaged upon contact, or if the size of the part is very small, the accuracy is low, and especially in the case of spherical particles, there is a problem that the vacuum is not well formed.

[0010] One aspect of the present invention relates to a melted conductive ball array film and a method for manufacturing the same for a completely different type of connection that can prevent electrical shorts even at minute electrode spacings of semiconductor devices while simultaneously forming metal-to-metal bonds by melting conductive balls to achieve high reliability.

[0011] In addition, another aspect of the present invention is to provide a micro-electrical connection structure and a micro-electrical connection method using a molten conductive ball array film.

[0012] Another aspect of the present invention is to provide a pick-and-place device using electrostatic adsorption.

[0013] The electrical connection method between fine pitch electrodes according to the present invention is:

[0014] A first step of providing a first connector having a plurality of first electrodes;

[0015] A second step of forming a flux printing layer on the first electrode of the first connecting body;

[0016] A third step of placing a molten conductive ball having an average diameter (R) of 2 to 20 μm on the flux printing layer;

[0017] A fourth step of forming a preliminary bonding portion to be connected to the first electrode by partially melting the molten conductive ball on the flux printing layer;

[0018] Step 5 of re-applying flux on the above pre-bonding portion;

[0019] A sixth step of placing a second connector having a plurality of second electrodes on the pre-bonding portion; and

[0020] It is characterized by including a seventh step of forming a bonding portion formed by a metal-to-metal bonding between the first electrode and the second electrode by applying a laser or heat to the above pre-bonding portion.

[0021] At this time, it is preferable to apply pressure to the first connector and the second connector in the seventh step.

[0022] In addition, it is preferable to further include an eighth step of filling an underfill to fill the space around the bonding portion and reinforce the contact points.

[0023] In addition, it is preferable that the plurality of first electrodes or the plurality of second electrodes have a gap of 20 μm or less between each other, and the diameter of the molten conductive ball is preferably smaller than the width of the first electrode or the width of the second electrode.

[0024] At this time, it is also preferable that the bonding portions are spaced apart from each other, and that the distance between the bonding portions is shorter than the distance between the first electrodes.

[0025] In addition, it is preferable that the above-mentioned melting conductive ball be made of a eutectic alloy and have a melting point of 130 to 350°C.

[0026] According to another aspect of the present invention, a method for electrical connection between fine pitch electrodes is provided.

[0027] A first step of providing a first connector having at least one first electrode;

[0028] A second step of arranging a molten conductive ball array film comprising a substrate having adhesiveness on a surface on the first electrode, at least one molten conductive ball adhered to the substrate, and a glass transition temperature of the substrate lower than the melting point of the molten conductive ball;

[0029] A third step of arranging a second connector having at least one second electrode on the molten conductive ball array film so that the second electrode is in contact with the molten conductive ball; and

[0030] It is characterized by including a fourth step of forming a bonding portion formed by a metal-to-metal bonding between the first electrode and the second electrode by applying a laser or heat to the above-mentioned melting conductive ball array film.

[0031] In addition, it is preferable that the above-mentioned substrate includes a film layer and an adhesive layer on the film layer.

[0032] At this time, when the glass transition temperature of the adhesive layer is T1, the glass transition temperature of the film layer is T2, and the melting point of the molten conductive ball is T3, T1 <T2<T3의 관계를 가지는 것이 좋다.

[0033] Additionally, the above melting conductive ball may have an average diameter (R) of 2 to 20 μm.

[0034] Additionally, the above-mentioned melting conductive ball may be a eutectic alloy having a melting point of 130 to 350°C.

[0035] Additionally, the above-mentioned molten conductive ball may contain a flux component.

[0036] Additionally, the above-mentioned molten conductive ball may further have a flux layer on its outer surface.

[0037] Additionally, it is preferable that the above-mentioned material contains epoxy resin.

[0038] The molten conductive ball array film according to one aspect of the present invention can be used as a material that forms an intermetallic compound between structures having a micro-electrode spacing of 10 μm or less, thereby forming a strong electrical and physical connection through a metal-metal bond.

[0039] According to another aspect of the present invention, a micro-electrical bonding structure is formed by forming a metal-metal bond between the materials to be connected by forming a metal-metal compound by forming a bonding portion with a low melting point conductive ball, thereby forming a strong electric bonding structure.

[0040] A micro-electrical bonding method according to another aspect of the present invention can realize a bond with high reliability by enabling bonding at low temperatures using a low melting point material while preventing electrical shorts even in a structure having an electrode spacing of 10 μm or less among a plurality of electrodes.

[0041] This connection method can be used for micro-electrical bonding structures, such as PCB bonding, TC (thermal-comperssure) bonding, BGA bonding, etc. in devices such as flexible displays, LCDs, OLED panels, touchscreens, and micro LED displays.

[0042] A pick-and-place device using electrostatic adsorption according to one aspect of the present invention can prevent damage to electrodes and target components by adsorbing target components in a non-contact manner using electrostatic adsorption, and has the effect of having high adsorption power by using an insulator with a certain range of dielectric constant around the electrode. In addition, it has an adsorption groove to expand the contact area, so that even spherical particles can be adsorbed stably.

[0043] FIG. 1 is a schematic diagram of a molten conductive ball array film according to one embodiment of the present invention.

[0044] Figure 2 is a process diagram of a molten conductive ball array film.

[0045] Figure 3 is a conceptual diagram of a pick-and-place device that can be used in a molten conductive ball array film.

[0046] Figure 4 is a conceptual diagram of a pick-and-place device according to an embodiment of the present invention.

[0047] Figure 5 is a conceptual diagram illustrating a pick-and-place device according to a first embodiment of the present invention.

[0048] FIG. 6 illustrates an example of a micro electrical connection structure according to one embodiment of the present invention.

[0049] Figure 7 is a process diagram illustrating one embodiment of a micro electrical connection method according to the present invention.

[0050] Figure 8 is a process diagram illustrating one embodiment of a micro electrical connection method according to the present invention.

[0051] Figure 9 is a process diagram illustrating one embodiment of a micro electrical connection method according to the present invention.

[0052] Figures 10 to 14 illustrate optical microscope photographs of the molten conductive ball array films according to the manufactured examples.

[0053] Figures 15 to 19 show electron microscope photographs according to experimental examples.

[0054] An electrode was formed on a glass substrate, and the molten conductive ball array film of Comparative Example 1 was placed on the electrode without applying flux, and then heated with a laser to form a pre-bonding portion, a bump, to form a metal-to-metal bond, and then the electrode of the micro LED was bonded to the bump, and then irradiated with an 8,000 mW green laser for 30 sec to manufacture a micro electrical connection structure. After that, to confirm whether an electrical connection was made, electricity was applied and it was confirmed that the micro LED did not light up.

[0055] (Comparative Experiment Example 3) If the solder ball melts first and oxidizes, it does not light up.

[0056] After forming electrodes on a glass substrate, applying flux, and arranging the molten conductive ball array film of Comparative Example 2, the electrodes were heated with a laser to form a pre-bonding portion, a bump, and a metal-to-metal bond was formed. After that, the electrodes of the micro LED were bonded to the bump, and then irradiated with a 4,000 mW IR laser for 30 sec to manufacture a micro electrical connection structure. After that, electricity was applied to confirm whether an electrical connection was made. At this time, it was confirmed that some solder micro LEDs did not light up. At this time, the diameter of the molten conductive balls used was 10 μm.

[0057] In this case, it can be confirmed that a uniform solder bump is not formed, and the molten conductive ball is melted, so that a bond between the electrode and the metal is only partially formed.

[0058] The features, structures, effects, etc. exemplified in each of the aforementioned embodiments can be combined or modified to implement other embodiments by those skilled in the art. Therefore, the contents related to such combinations and modifications should be construed as being included within the scope of the present invention.

[0059] The present invention can be utilized in a micro-electrical connection method using a molten conductive ball array film.

Claims

1. A first step of providing a first connector having a plurality of first electrodes; A second step of forming a flux printing layer on the first electrode of the first connecting body; A third step of placing a molten conductive ball having an average diameter (R) of 2 to 20 μm on the flux printing layer; A fourth step of forming a preliminary bonding portion to be connected to the first electrode by partially melting the molten conductive ball on the flux printing layer; Step 5 of re-applying flux on the above pre-bonding portion; A sixth step of placing a second connector having a plurality of second electrodes on the pre-bonding portion; and A method for electrical connection between fine pitch electrodes, comprising a seventh step of forming a bonding portion formed by a metal-to-metal bonding between the first electrode and the second electrode by applying a laser or heat to the preliminary bonding portion.

2. In paragraph 1, An electrical connection method between fine pitch electrodes that applies pressure to the first connector and the second connector in the seventh step.

3. In paragraph 1, A method for electrical connection between fine pitch electrodes, further comprising an eighth step of filling an underfill to fill a space around the bonding portion and reinforce the contact points.

4. In paragraph 1, A method for electrically connecting the plurality of first electrodes or the plurality of second electrodes with a micro-pitch electrode gap of 20 μm or less.

5. In paragraph 4, A method for electrical connection between micro-pitch electrodes in which the diameter of the above-mentioned molten conductive ball is smaller than the width of the first electrode or the width of the second electrode.

6. In paragraph 5, A method for electrical connection between micro-pitch electrodes, wherein the bonding portions are spaced apart from each other and the distance between the bonding portions is shorter than the distance between the first electrodes.

7. In paragraph 1, The above melting conductive ball is a method for electrical connection between fine pitch electrodes having a melting point of 130 to 350°C with a eutectic alloy.

8. A first step of providing a first connector having at least one first electrode; A second step of arranging a molten conductive ball array film comprising a substrate having adhesiveness on a surface on the first electrode, at least one molten conductive ball adhered to the substrate, and a glass transition temperature of the substrate lower than the melting point of the molten conductive ball; A third step of arranging a second connector having at least one second electrode on the molten conductive ball array film so that the second electrode is in contact with the molten conductive ball; and A method for electrical connection between fine pitch electrodes, comprising a fourth step of forming a bonding portion formed by a metal-to-metal bonding between the first electrode and the second electrode by applying a laser or heat to the above-mentioned molten conductive ball array film.

9. In paragraph 8, The above description is a method for electrical connection between a film layer and a fine pitch electrode including an adhesive layer on the film layer.

10. In paragraph 9, When the glass transition temperature of the adhesive layer is T1, the glass transition temperature of the film layer is T2, and the melting point of the molten conductive ball is T3, T1 <T2<T3의 관계를 가지는 미세피치 전극간 전기적 접속 방법.

11. In paragraph 8, The above melting conductive ball is an electrical connection method between fine pitch electrodes having an average diameter (R) of 2 to 20 μm.

12. In paragraph 8, The above melting conductive ball is a method for electrical connection between fine pitch electrodes having a melting point of 130 to 350°C with a eutectic alloy.

13. In paragraph 8, The above melting conductive ball is an electrical connection method between fine pitch electrodes containing a flux component.

14. In paragraph 8, The above melting conductive ball is an electrical connection method between fine pitch electrodes having a flux layer on the outer surface.

15. In paragraph 8, The above description relates to a method for electrical connection between fine pitch electrodes comprising epoxy resin.

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