WO2016032013A1

WO2016032013A1 - Method for sintering copper ink using laser

Info

Publication number: WO2016032013A1
Application number: PCT/KR2014/007888
Authority: WO
Inventors: 강경태; 유준호; 강희석; 황준영
Original assignee: 한국생산기술연구원
Priority date: 2014-08-25
Filing date: 2014-08-25
Publication date: 2016-03-03

Abstract

The present invention relates to a method for sintering a copper ink using a laser and, more specifically, to a method for sintering a copper ink using a laser that sinters a copper ink, which is applied to a substrate to form a printed pattern, by applying a laser beam to the copper ink. The method for sintering a copper ink using a laser, according to the present invention, comprises: an ink applying step for applying a copper ink, which contains copper, to a substrate to form a printed pattern; and a sintering step for sintering the copper ink by applying a laser beam to the copper ink through a laser device, wherein the laser beam has an intensity of 100W/cm2 or more and a temperature lower than the melting point of the copper contained in the copper ink, and the laser device moves a distance corresponding to the magnitude of the laser beam, which is applied to the substrate per unit time, at a scan speed of 0.6mm/s to 5mm/s.

Description

Sintering Method of Copper Ink Using Laser

The present invention relates to a sintering method of a copper ink using a laser, and more particularly, to a sintering method of a copper ink using a laser to sinter by irradiating a laser beam to a copper ink applied to a substrate to form a printed pattern.

In general, a method of forming a pattern in a PCB process is a method in which only necessary pattern parts are left on a substrate coated with copper, and unnecessary copper is removed through an etching process.

On the other hand, the inkjet spraying method is necessary for spraying a liquid containing a conductive material (currently using a large number of silver particles) along a part to form a pattern, and then leaving only the conductive material in the sprayed liquid. The liquid containing the conductive material was removed or scattered (heated).

As the development of industrial technology requires the implementation of various functions and miniaturization, light, thin, strong, and small size PCB boards are required.In order to secure these requirements, micro pattern implementation must be basically followed. The reliability of the finely implemented pattern should be secured.

Therefore, a common requirement in the current PCB process is 'light and thin short'.

Recently, the technique mainly used to secure the reliability of the fine pattern uses a technique of forming the fine pattern of the circuit board by inkjet patterning.

Since the inkjet method can directly form a fine pattern on a substrate, like the conventional printing technique using lithography, the costly process of vacuum film formation, photolithography, etching, and resist stripping process can be omitted, and the circuit can be manufactured at low cost. There is an effect that can produce a substrate.

In the inkjet patterning method, when ink is ejected from a 50 μm nozzle without processing a substrate, the diameter of a drop increases about 1.5 times when ink is ejected from the nozzle, and spreads several times when the droplet falls on an untreated substrate. There is a problem that the width of the fine pattern (wiring) is a multiple of the injection nozzle.

In addition, since the inkjet patterning technology adjusts the line width only by the jetting conditions of the ink jet nozzle, the implementation of the fine line width depends on the viscosity of the ink, the discharge amount, and the diameter of the ink jet nozzle, and the method for controlling the line width by adjusting the characteristics of the existing substrate In most cases, the substrate heating method was used.

However, the method of heating the substrate during spraying not only causes clogging of the nozzle during ink ejection, but also causes a coffee stain effect in a pattern shape.

In addition, a technique of forming a fine pattern by increasing the contact angle of ink simply by hydrophobic treatment of the substrate has been proposed, but the shape of the pattern becomes irregular due to the aggregation of printed droplets on the substrate immediately after spraying according to the characteristics of the ink. This happens.

In addition, the multi-angle substrate processing method has a main effect of reducing the contact angle, but in the step of forming a line by overlapping droplets and droplets with a small contact angle, it is difficult to avoid collision between one droplet and the next. Due to the difficulty in forming the line and the problem of uneven line shape.

In addition, the existing hydrophobic substrates for increasing the contact angle to reduce the line width had a problem in that when the droplets overlap with the droplets, the droplets and the droplets are not anchored to the substrate, and larger droplets are formed by the attraction force between the droplets, thereby not forming a line. .

In particular, although the sprayed liquid is made by an oven, there is a problem that the temperature required for scattering the liquid deforms the substrate.

In order to solve this problem, Republic of Korea Patent Publication No. 10-1058844 is coated on the surface of the substrate in the amorphous (Amorphouse) state of the phase (Amorphouse) phase change by a certain heat, and the light is collected on the nano phase change coating layer Forming a circuit pattern to be formed by phase change into conductive crystalline (Crystalline) by applying heat of a predetermined temperature range using a laser beam, and further forming a conductive pad on the circuit pattern formed by the laser beam to form the circuit pattern To improve electrical connection with the other conductive material, and the conductive pad is formed by printing a metal nanoparticle ink on the nanophase change coating layer and irradiating a laser beam to the metal nanoparticle ink, wherein the laser beam To be formed as it is irradiated using a pad lens that focuses more than a circuit pattern The manufacturing method using the circuit shown jeobim.

When the nano-phase change coating layer is sintered using the laser beam as described above, the sintered copper may be oxidized or specific resistance may be greatly generated according to the conditions such as the intensity and scan speed of the laser beam, which may cause product defects. .

However, in the conventional circuit fabrication method using a laser beam, how to specifically measure the intensity and scan speed of the laser beam irradiated to the nanophase change coating layer applied to the substrate to suppress the occurrence of copper oxide and reduce the specific resistance No specific method was shown.

The present invention is to solve the above-described problems, by specifically limiting the intensity and scan speed of the laser beam irradiated on the nano-phase change coating layer (copper ink) applied to the substrate, that the oxidation occurs in the sintered copper It is an object of the present invention to provide a method of sintering a copper ink using a laser that can prevent and reduce a specific resistance.

In order to achieve the above object, a method of sintering a copper ink using a laser of the present invention includes: an ink coating step of forming a printing pattern by applying a copper ink containing copper to a substrate; And a sintering step of sintering the copper ink by irradiating a laser beam to the copper ink using a laser device, wherein the intensity of the laser beam is 100 W / cm 2 or more and is higher than the melting point of copper contained in the copper ink. The laser device is characterized in that for moving the distance of the size of the laser beam irradiated to the substrate per unit time at a scan speed of 0.6mm / s ~ 5mm / s.

The laser device increases the scan speed of the laser device as the size of the laser beam increases while the intensity of the laser beam is the same, and increases the intensity and scan speed of the laser beam when the size of the laser beam is the same. The specific resistance of the copper ink to be sintered is made small.

The copper ink is a powder (power) type of ink in which copper having a diameter of several tens of nm or less is dispersed in a solvent, and the intensity of the laser beam is 100 to 200 W / cm 2, and the scanning speed of the laser device is Is 0.6 to 2 mm / s.

Alternatively, the copper ink is made of a hybrid type in which a powder type and a precursor type are mixed, and the powder type is made of an ink in which copper having a diameter of several tens of nm or less is dispersed in a solvent. The type is composed of an ink containing a copper precursor that changes to copper when a chemical reaction occurs when heat is applied, but when the copper ink is a hybrid type, the intensity of the laser beam is 190 ~ 300W / cm2, the scan of the laser device The speed is 1-4 mm / s.

The size of the laser beam irradiated to the substrate per unit time by the laser device is to have a size of 0.2 mm in the scanning direction.

According to the sintering method of the copper ink using the laser of the present invention as described above has the following effects.

By specifically limiting the intensity and scan speed of the laser beam irradiated to the copper ink applied to the substrate, it is possible to prevent the occurrence of oxidation in the sintered copper and to reduce the specific resistance value.

1 is a wavelength (absorbance) of the precursor (precursor) type copper ink, powder type copper ink, hybrid type copper ink according to an embodiment of the present invention,

Figure 2a is a graph showing the specific resistance according to the laser beam sintering conditions of the powder type copper ink according to an embodiment of the present invention,

Figure 2b is a graph showing the specific resistance according to the heat sintering time of the powder type copper ink according to an embodiment of the present invention,

Figure 3a is a graph showing the specific resistance according to the laser beam sintering conditions of the hybrid type copper ink according to an embodiment of the present invention,

Figure 3b is a graph showing the specific resistance according to the heat sintering time of the hybrid type copper ink according to an embodiment of the present invention,

4 is a photograph showing the sintered microstructure and the specific resistance of the copper ink according to the laser beam sintering and heat sintering of the hybrid type copper ink according to an embodiment of the present invention,

Figure 5 is a graph showing the surface analysis results according to the sintering process conditions of the hybrid type copper ink according to an embodiment of the present invention.

The copper ink sintering method using the laser of the present invention comprises an ink coating step and a sintering step.

The ink application step is a step of forming a printed pattern by applying a copper ink containing copper to a substrate such as a printed circuit board.

At this time, since the copper ink is in a liquid state, it is possible to form various printing patterns on the substrate according to the intention of the operator.

The copper ink is classified into a precursor type, a powder type, and a hybrid type, as shown in FIG. 1.

The precursor type copper ink is an ink containing a copper precursor that is converted into copper by a chemical reaction upon application of heat.

The powder-type copper ink is an ink in which copper having a diameter of several tens of nm or less is dispersed in a solvent.

The hybrid type copper ink is a solution ink in which the precursor type and the powder type are mixed.

The sintering step is a step of sintering the copper ink by irradiating a laser beam to the copper ink in a solution state using a laser device.

In this case, the intensity of the laser beam is 100W / cm 2 or more and lower than the melting point of the copper contained in the copper ink, the laser device 0.6mm / s the distance of the size of the laser beam irradiated to the substrate per unit time Move to a scan speed of ~ 5mm / s.

At this time, the size of the laser beam irradiated to the substrate per unit time by the laser device is to have a size of 0.2mm in the scan direction.

The laser device increases the scan speed of the laser device as the size of the laser beam increases, that is, in the scan direction, in the state where the laser beam intensity is the same.

For example, if the laser beams have the same intensity, assuming that the size of the laser beam is 1 mm and the scan speed is 1 mm / s, the scan speed is 2 mm / s when the size of the laser beam is 2 mm.

Hereinafter, it will be described with a specific experimental example for the present invention as described above.

Example 1

Copper ink used in Example 1 is a powder-type copper ink manufactured by Dongjin Semicom Co., Ltd., the substrate is a glass wafer (sodalime), sintered in the air atmosphere, the laser beam equipment is a CW 532nm wavelength laser beam ( Coherent, verdi_V5) was used.

At this time, the size of the laser beam irradiated to the substrate is assumed to have the same size.

In this embodiment, the size of the laser beam in the scanning direction is set to 0.2 mm.

2A is a graph showing specific resistance when sintering copper ink using a laser beam, and FIG. 2B is a graph showing specific resistance when sintering copper ink by applying heat.

As shown in Figure 2a, the specific resistance increased at strength of 106W / cm 2 or more during sintering of copper ink with a laser device of a scan speed of 0.4mm / s.

In the case of sintering copper ink with the scan speed of the laser device of 0.6 mm / s or more, the value of the specific resistance decreased as the intensity of the laser beam increased.

In particular, when the scanning speed of the laser device was 1mm / s and the intensity of the laser device was 183W / cm2, the minimum specific resistance 17μΩcm according to the sintering of the copper ink was measured, which is 10 of the bulk copper resistivity of 1.68μΩcm. That's about twice the value.

On the other hand, as shown in Figure 2b, in the case of the method of sintering by heating the copper ink by a method other than a laser beam, the specific resistance tended to increase with time over 250 ℃.

In addition, when comparing the specific resistance of the sintering using the laser beam shown in FIG. 2A and the specific resistance of the sintering using heat shown in FIG. 2B, the intensity of the laser beam is increased when the size of the laser beam irradiated to the substrate is the same. It can be seen that the higher the scan rate, the smaller the resistivity of the sintered copper.

In this experimental example, the laser beam has an intensity of 100-200 W / cm 2 and a scan speed of 0.6-2 mm / s.

Example 2

Copper ink used in Example 2 is a hybrid type copper ink manufactured by Dongjin Semiconductor Co., Ltd., the substrate is a glass wafer (sodalime), sintered in the air atmosphere, the laser beam equipment is a CW 532nm wavelength laser beam ( Coherent, verdi_V5) was used.

3A is a graph showing specific resistance when sintering copper ink using a laser beam, and FIG. 3B is a graph showing specific resistance when sintering copper ink by applying heat.

As shown in Figure 3a, the specific resistance increased at strength of 190W / cm2 or more during sintering of copper ink with a laser device of a scanning speed of 0.6mm / s.

In the case of sintering the copper ink with the scanning speed of the laser device of 1.0 mm / s or more, the value of the specific resistance gradually decreased as the intensity of the laser beam increased.

In particular, when the scanning speed of the laser device is 3mm / s and the intensity of the laser beam is 252W / cm2, the minimum resistivity of 5.3 μΩcm according to the sintering of the copper ink was measured, which is 1.68 μΩcm, which is the bulk copper resistivity. About three times the value.

On the other hand, as shown in Figure 3b, in the case of the method of sintering by heating the copper ink by a method other than a laser beam, the specific resistance tended to increase over time at 250 ℃.

In addition, when comparing the specific resistance of the sintering using the laser beam shown in FIG. 2A and the specific resistance of the sintering using heat shown in FIG. 2B, when the laser beam irradiated onto the substrate has the same size, It can be seen that the higher the scan rate, the smaller the resistivity of the sintered copper.

In this experimental example, the intensity of the laser beam is 190 to 300 W / cm 2, and the scanning speed is preferably 1 to 4 mm / s.

And, as shown in Figure 4, in the case of laser beam sintering, it can be seen that the sintering of the copper particles is made well as the specific resistance value gradually decreases as the intensity and scan speed increase.

On the other hand, in the case of heat sintering, as the temperature of the applied heat increases and as time passes, the sintering of the copper particles proceeds further, but it can be seen that the specific resistance becomes larger.

In addition, Figure 5 is a graph showing the surface analysis results according to the sintering process conditions of the hybrid type copper ink according to the present invention, the horizontal axis represents the diffraction angle, the vertical axis represents the intensity.

In the case of sintering by irradiating a laser beam to a hybrid type copper ink at an intensity of 252 W / cm 2 and a scanning speed of 4 mm / s of the laser beam indicated by (a) in FIG. 5, only a copper (Cu) peak was observed and the specific resistance was 7.07. appeared in μΩcm.

In addition, even when the laser beam was sintered by irradiating a laser beam to a hybrid type copper ink at an intensity of 190 W / cm 2 and a scanning speed of 1.0 mm / s as shown in FIG. 5B, only copper (Cu) peaks were confirmed. The resistivity was found to be 7.1 μΩcm.

On the contrary, when the laser beam is sintered by irradiating a laser beam to the hybrid type copper ink at an intensity of 190 W / cm 2 and a scanning speed of 0.6 mm / s, the laser beam indicated by (c) in FIG. 5 and the heat sintering method indicated by (d) In the case of sintering a hybrid type copper ink, it can be seen that copper oxide (Cu ₂ O) appears.

5, when sintering a hybrid type copper ink using a laser beam in an air atmosphere, copper is not oxidized when the intensity of the laser beam is 190 to 300 W / cm 2 and the scan speed is 1 to 4 mm / s. It can be seen that without sintering.

In contrast, it can be seen that copper oxide is generated when the intensity or scan speed of the laser beam is lowered or when the heat is sintered.

Through the above experiments, in the case where the size of the laser beam irradiated to the substrate is the same, it can be seen that if the intensity and scan speed of the laser beam applied to the copper ink is increased, the specific resistance of the sintered copper ink is reduced.

The sintering method of the copper ink using the laser of the present invention is not limited to the above-described embodiment, and can be carried out in various modifications within the allowable technical spirit of the present invention.

By sintering by irradiating a copper ink with a laser beam, a circuit board with a fine pattern can be easily manufactured.

Claims

An ink coating step of applying a copper ink containing copper to a substrate to form a printing pattern;

It comprises a sintering step of sintering the copper ink by irradiating a laser beam to the copper ink using a laser device,

The intensity of the laser beam is 100W / cm 2 or more and lower than the melting point of the copper contained in the copper ink,

The laser device is a method of sintering copper ink using a laser, characterized in that for moving the distance of the size of the laser beam irradiated to the substrate per unit time at a scanning speed of 0.6mm / s ~ 5mm / s.
The method according to claim 1,

The laser device increases the scan speed of the laser device as the size of the laser beam increases while the intensity of the laser beam is the same.

When the size of the laser beam is the same, the laser ink sintering method using a laser, characterized in that to reduce the specific resistance of the sintered copper ink by increasing the intensity and scan speed of the laser beam.
The method according to claim 1 or 2,

The copper ink is made of powder (power), which is an ink in which copper having a diameter of several tens of nm or less is dispersed in a solvent,

The intensity of the laser beam is 100 ~ 200W / cm2, the scanning speed of the laser device is 0.6 ~ 2mm / s method of sintering copper ink using a laser.
The method according to claim 1 or 2,

The copper ink is made of a hybrid type of powder and precursor (precursor) type,

The powder type is made of an ink in which copper having a diameter of several tens of nm or less is dispersed in a solvent,

The precursor type is made of an ink containing a copper precursor that is converted to copper when a chemical reaction occurs by applying heat,

When the copper ink is a hybrid type, the intensity of the laser beam is 190 ~ 300W / cm2, the scanning speed of the laser device is 1 ~ 4mm / s sintering method of the copper ink using a laser.
The method according to claim 1,

The size of the laser beam irradiated to the substrate per unit time by the laser device has a size of 0.2mm in the scanning direction.