KR20200104674A - Method for joining using laser - Google Patents

Abstract

Provided is a bonding method using a laser, capable of preventing thermal damage to a polymer-based component when bonding the polymer-based component to a substrate using the laser. The above method comprises the following steps of: positioning a bonded component to be bonded on a substrate; placing a laser absorbing object on the bonded component; and irradiating the laser to the bonded component. The laser absorbing object is configured to be in contact with a part of the bonded component.

Description

Bonding method using laser {Method for joining using laser}

The present invention relates to a bonding method, and more particularly, to a bonding method using a laser.

Small, light, thin, high-performance multifunctional for various industries, including not only personal smartphone devices, but also high-end products such as servers, game consoles, and network servers, and optical communication modules, radar modules, displays, and solar cells. The demand for modules tends to increase. Accordingly, chips are getting thinner, and the size and pitch of the interconnections connecting the chips and the substrates are getting smaller.

The process being developed to keep pace with the technological trends of this industry is to apply a non-conductive paste (NCF) or a non-conductive film (NCF) on a substrate, place the chip or substrate to be bonded on the substrate, and then laser The bonding process is completed by applying heat required for bonding to the bonding portion by applying. In some cases, a chip or a substrate to be bonded may be placed underneath. In this case, when the chip or substrate is not flat and exhibits a warpage phenomenon, pressure is applied to the chip or substrate through an object that hardly absorbs laser, such as quartz, so that bonding can be stably performed. In this case, an appropriate temperature may be applied to the substrate on the stage. The warpage of the chip or substrate occurs due to the difference in thermal expansion coefficient of the chip or substrate when the thickness of the chip or substrate is as thin as 200 μm or less, and is made of various materials such as metal and dielectric.

However, in this process, the temperature of the junction is raised by the laser. This is because the laser is absorbed by the chip or substrate in the form of thermal energy, and the absorbed thermal energy is transferred to the junction by a conduction phenomenon.

In the case of polymer-based sensors, the thermal conductivity is very low, but heat is not properly dissipated into the junction, causing excessive temperature rise in the localized area of the polymer-based sensor, causing thermal deformation or even thermal damage to the sensor. Due to this problem, the sensor may malfunction or cause defects.

In addition, when various types of components such as sensors or chips of different sizes, or packages or substrates are integrated on the same substrate, damage to the device or the underlying substrate may occur. Or heat damage may occur.

As a related prior document, there is a "method of manufacturing a dye-sensitized solar cell using a laser and a dye-sensitized solar cell" described in Korean Patent Application Registration No. 1187112.

The problem to be solved by the present invention is to provide a bonding method capable of preventing thermal damage to a component of a polymer substrate when bonding a polymer-based component to a substrate using a laser.

A bonding method according to a feature of the present invention includes: positioning a bonding component to be bonded on a substrate; Placing a laser absorbing object on the bonded part; And irradiating a laser to the bonded component, wherein the laser absorbing object is configured to come into contact with a part of the bonded component.

According to an embodiment of the present invention, a polymer-based component can be bonded to a substrate without thermal deformation or thermal damage using a laser. In addition, when various components of various sizes or volumes are bonded to a single substrate, they can be bonded without damage or deformation of the components, the substrate, or the bonding material.

1 is a diagram showing a bonding process using a laser.
2 is a diagram showing a process of bonding a polymer-based sensor using a laser.
3 is a diagram showing a process of bonding sensors or chips of various sizes or packages or substrates using a laser.
4 is a diagram showing a bonding method using a laser according to the first embodiment of the present invention.
5 is a diagram showing a bonding method using a laser according to a second embodiment of the present invention.
6 is a diagram showing a bonding method using a laser according to a third embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. However, the present invention may be implemented in various forms and is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and similar reference numerals are assigned to similar parts throughout the specification.

Throughout the specification, when a part is said to be "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element interposed therebetween. . In addition, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

Expressions described in the singular in this specification may be interpreted as the singular or plural unless an explicit expression such as "one" or "single" is used.

Hereinafter, a bonding method using a laser according to an embodiment of the present invention will be described with reference to the drawings.

1 is a diagram showing a bonding process using a laser.

As shown in Fig. 1(a), a non-conductive paste (NCP) or a non-conductive film (NCF) is applied on the substrate. In some cases, NCP or NCF may be formed under the chip or substrate to be bonded. Thereafter, as shown in (b) of FIG. 1, a chip or a substrate to be bonded is placed on the substrate through a pick & place process. Next, as shown in (c) of FIG. 1, a laser is applied to a chip or a substrate positioned on the substrate to apply heat required for bonding to the bonding portion to complete the bonding process. In this case, when the chip or substrate is not flat and exhibits a warpage phenomenon, pressure is applied to the chip or substrate through an object that hardly absorbs laser, such as quartz, so that bonding can be stably performed.

In this case, an appropriate temperature may be applied to the substrate on the stage. However, warpage of the chip or substrate occurs. Such a warpage of a chip or substrate occurs because the thickness of the chip or substrate is as thin as 200 μm or less, and when it is made of various materials, such as metals and dielectrics, the difference in thermal expansion coefficients of these materials.

In such a bonding process, the reason why the temperature of the junction is increased by the laser is that the laser is absorbed by the chip or the substrate in the form of thermal energy, and the absorbed thermal energy is transferred to the junction by a conduction phenomenon. The absorption of the laser is expressed as an equation as follows.

Where x is the depth at which the laser is absorbed and I _o is the laser intensity of the surface. α is the absorption coefficient of the material and is a function of wavelength and temperature and the material.

2 is a diagram showing a process of bonding a polymer-based sensor using a laser.

As shown in FIG. 2, NCP or NCF is coated on a substrate, and a polymer-based sensor to be bonded is placed on the substrate. In this case, an object that hardly absorbs laser, such as quartz, can be placed on the polymer-based sensor. Then, a laser is applied to the polymer-based sensor located on the substrate to apply heat required for bonding to the bonding portion to complete the bonding process.

However, in the case of a polymer-based sensor, the thermal conductivity is very low. As a result, if the laser illuminates the entire surface of the substrate and the electrode connected to the substrate is unevenly disposed on the lower surface of the sensor, the heat does not flow properly into the junction, causing excessive temperature rise in the local area of the polymer-based sensor, causing thermal deformation. Or even the sensor can be damaged by heat. As a result, the polymer-based sensor may malfunction or cause defects.

3 is a diagram showing a process of bonding sensors or chips of various sizes or packages or substrates using a laser.

As shown in FIG. 3, various types of components such as sensors or chips of different sizes, or packages or substrates (eg, bonding of micro LEDs and driver ICs or bonding of sensors) may be integrated on the same substrate. In this case, the height of each component is different, so it is difficult to place an object that hardly absorbs laser, such as quartz, on the components. In addition, when parts of different sizes are bonded at the same time using a laser, a component having a small volume may receive an excessively high intensity laser, causing damage to the component or the substrate under the component. In addition, when small-sized parts are first bonded with a laser and then bulky parts are bonded with a laser, a laser may be additionally applied to the first-bonded part, and accordingly, a laser may be applied to the small part or the bonded part or the substrate below it. Or heat damage may occur.

In the above description, the substrate may be a substrate to which various materials and processes are applied depending on applications such as PCB, silicon, backplane, flexible and stretching substrate, organic substrate, and ceramic substrate.

In an embodiment of the present invention, when a polymer-based component is bonded to a substrate, a bonding method is provided in which local heat is transferred based on a laser to perform bonding.

4 is a diagram showing a bonding method using a laser according to the first embodiment of the present invention.

As shown in FIG. 4, a non-conductive layer 2 is placed on the substrate 1. A plurality of pads 11 are formed on the substrate 1. The substrate 1 may be a printed circuit board, a silicon substrate, or an interposer substrate. The pad 11 may include underbump metallization (UBM) such as copper or gold. Here, the non-conductive layer 2 may be formed of a non-conductive paste (NCP) or a non-conductive film (NCF). NCP/NCF may contain a base resin, a curing agent, and a reducing agent, and may contain a filler such as silica. In some cases, the NCP or NCF for the non-conductive layer 2 may be formed under the polymer-based component to be bonded.

Then, the polymer substrate component 3 to be bonded is placed on the substrate 1. The polymer substrate component to be bonded to be positioned on the substrate 1 is referred to as “bonding component” for convenience of description.

Placing the bonded component 3 on the substrate 1 may include placing a solder bump 31 disposed on the lower surface of the bonded component 3 on the pad 11 . The solder bump 31 may be attached to the lower pad 32 disposed on the lower surface of the bonding component 3. The solder bump 31 formed under the bonding component 3 may contact the pad 11. The lower pad 32 may include UBM such as copper or gold. The solder bump 31 may include, for example, Sn, In, SnBi, SnAgCu, SnAg, AuSn, InSn, BiInSn or InSn, and may include at least one material selected from other Sn or In alloys. The size of the solder bump 31 may range from 0.1 μm to 300 μm.

The non-conductive layer 2 can fill the empty space between the substrate 1 and the bonding component 3, and the non-conductive layer 2 is formed of the pad 11, the lower pad 32, and the solder bump 31. It can come into contact with the surface. The non-conductive layer 2 may have a predetermined viscosity to fill the empty space.

Next, in the embodiment of the present invention, a laser absorbing object 4 made of a material that absorbs laser is placed on the bonded component 3. The laser absorbing object 4 may also be referred to as a laser absorbing layer, and may be made of, for example, a metal, silicon, ceramic, dielectric, or the like capable of absorbing laser. The laser absorbing object 4 may be composed of a single material capable of absorbing a laser, or may be composed of several layers or parts. In addition, the laser absorbing object 4 may include a material having a thermal conductivity of 80 W/m·K or more. The laser absorbing object 4 may have a thickness within 3 mm to 10 μm.

In particular, in an embodiment of the present invention, the laser absorbing object 4 is designed such that the laser absorbing object 4 contacts only a portion close to the joint in the jointed part 3, such as a polymer-based sensor. For example, as shown in FIG. 4, when the portions close to the joint portion of the joint component 3 are referred to as the first portion P1 and the second portion P2, the laser absorbing object 4 is The laser absorbing object 4 is configured to cover the entire upper part of the bonded part 3 so as to contact only the first part P1 and the second part P2, and the first protrusion 41 and the first protrusion 41 and the second It is configured in a form including two protrusions 42. That is, the first protrusion 41 and the second protrusion 42 are formed at the corresponding positions of the laser absorbing object 4 corresponding to the first part P1 and the second part P2 of the bonding component 3, , The entire laser absorbing object 4 is not in contact with the upper side of the joined part 3, and only the first protrusion 41 and the second protrusion 42 of the laser absorbing object 4 contact the joined part 3 . Here, the bonding portion is a portion to which the substrate 1 and the bonding component 3 are bonded, and may include a solder bump 31 and a pad 11.

Then, a laser is applied. The laser may be, for example, a helium-neon laser, an Argon laser, a UV laser, an IR laser, or an Excimer laser, and may have a wavelength of 500 nm to 2 μm, for example.

The laser can be irradiated to the top and/or bottom of the bonded part 3. Part of the laser can be absorbed by the bonding component 3, the solder bump 31 and the pad 11 and turned into heat. Heat is transferred to the solder bump 31 and the pad 11, so that the solder bump 31 and the pad 11 may be attached. In addition, the non-conductive layer 2 may be cured due to heat.

As described above, with the laser absorbing object 4 positioned above the bonding part 3, only a part of the laser absorbing object 4, i.e. the first protrusion 41 and the second protrusion 42, is By having a structure in contact with the first part (P1) and the second part (P2), when the laser is irradiated, the laser is not transmitted to most of the bonding part 3, which is a polymer-based part, or even if it is transmitted, the laser The strength of can be greatly reduced, and in particular, it is transmitted only to the first portion P1 and the second portion P2, which are positions corresponding to the joint portion of the joint component 3.

Thermal energy required for bonding is supplied only through the first and second protrusions 41 and 42 of the laser absorbing object 4 in contact with only the upper portion of the position corresponding to the bonding portion of the bonding component 3. Therefore, it is possible to prevent thermal deformation or thermal damage of polymer substrate components that may occur during the laser-based bonding process.

5 is a diagram showing a bonding method using a laser according to a second embodiment of the present invention.

In the second embodiment of the present invention, a laser bonding process is described when various types of components (referred to as bonding components) such as sensors or chips of different sizes to be bonded, or packages or substrates have an arrangement form. In other words, it represents a bonding process in the case of forming an array with a plurality of bonding parts of different sizes to be bonded.

In this case, there are a plurality of bonding parts having a first size (or first volume) and a second bonding part having a second size (or second volume), and the arrangement form of the bonding parts having different sizes or volumes to be bonded. The configuration will be described as an example, where the first size (or first volume) is smaller than the second size (or second volume). This is only an example, and the present invention is not limited thereto. Here, a detailed description of a process performed similarly to the first embodiment will be omitted.

First, as shown in the accompanying FIG. 5 (a), the bonding parts 3a of the first size are placed on the substrate 1. In this case, solder bumps disposed on the lower surfaces of the bonding components 3a of the first size may be disposed on the pads of the substrate 1. The non-conductive layer may fill the empty space between the substrate 1 and the bonding components 3a of the first size.

Next, a laser absorbing object 4 made of a material that absorbs a laser is placed on the bonding parts 3a of the first size. In particular, in the embodiment of the present invention, the laser absorbing object 4 touches the entire upper portion of the first-sized jointed parts 3a or touches the upper part of the first-sized jointed parts 3a ( For example, as in the first embodiment, the laser-absorbing object may be configured to contact only a portion close to the joint portion of the joint parts 3a of the first size). At this time, the laser absorbing object 4 is formed in a form that does not touch the substrate 1 except for the bonding parts 3a of the first size. That is, the laser absorbing object 4 is formed to cover the substrate 1, but is formed in a form that does not touch the portions except for the bonding parts 3a of the first size.

Then, a laser is applied. At this time, only the temperature of the bonded part to be bonded to which the laser absorbing object physically touches is raised to perform the bonding process. Even if a bonding material such as flux, NCP, and NCF required for bonding is applied to all pads on the substrate, heat energy is supplied only to the bonding material under the bonding component to be bonded, resulting in a change in the properties of the bonding material due to heat. I never do that. Therefore, damage or deformation of the substrate can be minimized.

Next, as shown in FIG. 5B, the bonding parts 3b of the second size are placed on the substrate 1. Even at this time, the non-conductive layer may fill the empty space between the substrate 1 and the bonding parts 3b of the second size.

Next, a laser absorbing object 4 made of a material that absorbs a laser is placed on the bonding parts 3b of the second size. In particular, in the embodiment of the present invention, the laser-absorbing object 4 touches the entire upper portion of the bonded parts 3b of the second size or the upper part of the bonded parts 3b of the second size ( For example, as in the first embodiment, the laser-absorbing object may be configured to contact only a portion close to the junction of the bonded parts 3b of the second size). At this time, the laser absorbing object 4 is formed in a form that does not touch the substrate 1 except for the bonding parts 3b of the second size. That is, the laser absorbing object 4 is formed to cover the substrate 1, but is formed in a form that does not touch the portions except for the bonding parts 3b of the second size.

Then, a laser is applied. At this time, the bonding process is performed by only raising the temperature of the bonded part to be bonded to which the laser absorbing object is physically contacted.In particular, the bonded part or bonded part because the laser is not transmitted to the bonded part of the first size already bonded to the substrate Or you can protect the substrate.

6 is a diagram showing a bonding method using a laser according to a third embodiment of the present invention.

In the third embodiment of the present invention, a detailed description of a process performed similarly to the first embodiment will be omitted.

In the third embodiment of the present invention, when there are a plurality of bonding parts having different sizes to be bonded and forming an arrangement, a process of simultaneously bonding bonding parts having different sizes to a substrate is shown.

Specifically, as shown in FIG. 6, bonding parts 3a of a first size and bonding parts 3b of a second size are positioned on the substrate 1. In this case, solder bumps disposed on the lower surfaces of the bonding components 3a of the first size and the bonding components 3b of the second size may be disposed on the pad of the substrate 1. The non-conductive layer may fill the empty space between the substrate 1 and the bonding components 3a and 3b of the first and second sizes.

Next, a laser-absorbing object 4 made of a material that absorbs a laser is placed on the bonding parts 3a of the first size and the bonding parts 3b of the second size. In particular, in the embodiment of the present invention, the laser absorbing object 4 touches the entire upper portion of each of the first size bonding parts 3a and the second size bonding parts 3b, or the first size bonding. In the form of contacting the upper part of each of the parts 3a and the second sized bonding parts 3b (for example, as in the first embodiment, the laser absorbing object is the first and second sized bonding parts (Can be configured to contact only the portion close to the junction of 3a, 3b). At this time, the laser absorbing object 4 is formed in a form that does not touch the substrate 1 except for the bonding parts 3a of the first size and the bonding parts 3b of the second size. That is, the laser absorbing object 4 is formed to cover the substrate 1 but does not touch the portions except for the bonding parts 3a and 3b of the first and second sizes.

Then, a laser is applied. At this time, only the temperature of the bonded part to be bonded to which the laser absorbing object physically touches is raised to perform the bonding process. In the third embodiment of the present invention, unlike the second embodiment, bonding components having different sizes can be simultaneously integrated on the substrate, and heat energy is supplied only to the bonding material under the bonding component, No characteristic change occurs. Therefore, damage or deformation of the substrate can be minimized.

The bonding method according to an embodiment of the present invention includes an RF/analog or digital device or an optical device for communication, or a display device such as a micro LED, or a power semiconductor, or a bio device, or a solar cell or sensor/MEMS (Micro- Electro Mechanical Systems) can be applied to electronic devices or modules, and can also be applied when integrating devices of the same or different types on a substrate.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (1)

Positioning a bonded component to be bonded on a substrate;
Placing a laser absorbing object on the bonded part; And
Irradiating a laser to the bonded part
Including,
The laser-absorbing object is configured to be in contact with a part of the bonding component.

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