KR20060059547A - Method of treating the printed circuit boards surface using atmospheric pressure plasma and apparatus for forming atmospheric pressure plasma - Google Patents

Abstract

The present invention relates to a method for treating a surface of a printed circuit board using atmospheric pressure plasma and a plasma forming apparatus for performing the same. The method includes forming a discharge gas including atmospheric gas into a plasma state under atmospheric pressure. Exposing the printed circuit board to the discharge gas formed in the plasma state, thereby increasing the surface energy of the printed circuit board. In the above-described method, no harmful gas is generated in the plasma treatment process of the substrate as compared to the conventional method, and the cost reduction and productivity of the surface treatment process for improving the surface energy can be improved.

Description

TECHNICAL FIELD OF TREATING THE PRINTED CIRCUIT BOARDS SURFACE USING ATMOSPHERIC PRESSURE PLASMA AND APPARATUS FOR FORMING ATMOSPHERIC PRESSURE PLASMA}

1 is a configuration diagram schematically showing a plasma forming apparatus of the present invention.

2 is a process flowchart showing a method of forming a printed circuit board on which a chip is mounted.

3 is a cross-sectional view of a printed circuit board formed by the method of FIG. 2.

4 is a graph showing the IR spectrum of the discharge gas formed in the plasma state in the plasma forming apparatus.

5 is a graph showing an IR spectrum of discharge gas discharged after plasma treatment of a printed circuit board in a plasma forming apparatus.

FIG. 6 is a graph showing a time-dependent change in surface composition of an XPS analysis result of a printed circuit board according to surface treatment time in a plasma according to Example 1. FIG.

-Explanation of symbols for the main parts of the drawing-

100 chamber 110 plasma discharge electrode

112: first electrode 114: second electrode

116: dielectric 120: gas providing unit

130: power supply unit 140: printed circuit board stage                 

150: gas outlet 160: guide ring

P: printed circuit board

The present invention relates to a surface treatment method and a plasma forming apparatus for a printed circuit board using plasma, and more particularly, to a surface treatment method and a plasma forming apparatus for a printed circuit board using plasma formed under atmospheric pressure.

A printed circuit board (PCB) refers to a printed circuit board in which various types of chips are mounted on a substrate made of phenol resin or epoxy resin, and a circuit connecting the respective chips is densely shortened and fixed on the surface of the resin plate. The printed circuit boards are classified into single-sided boards, double-sided boards, and multilayer boards according to the number of wiring circuit surfaces.

In general, the single-sided printed circuit board is mainly used as a phenol substrate and is employed in products having a relatively complicated circuit configuration such as radios, telephones, and simple measuring instruments. Double-sided printed circuit boards mainly use epoxy resin substrates and are used in relatively complex products such as color TVs, VTRs, and facsimile machines. In addition, multilayer printed circuit boards are employed in high-precision devices such as 32-bit or more computers, electronic switchboards, and high-performance communication equipment. In addition, a flexible printed circuit board (flexible PCB) is used to flexibly cope with cases in which circuit boards such as automation devices and camcorders need to be moved, and when circuit boards need to be bent to insert components.                         

When the chip is mounted on the printed circuit board described above, the chip is coated with an epoxy resin compound (EMC) to protect the chip in a subsequent process, and the EMC does not have excellent interfacial adhesion with the printed circuit board. It does not have the characteristics. Therefore, in order to increase the interfacial adhesion between the printed circuit board and the EMC, the printed circuit board must be plasma treated.

Referring to the plasma processing process of a general printed circuit board, first, the printed circuit board is loaded into a plasma reaction chamber, and then fluorine-compound gas such as CF ₄ or C ₂ F ₆ and argon gas are discharged at a low pressure / vacuum state (about 300 mTorr or less). A 5 to 50 ratio mixed discharge gas is provided into the chamber. Subsequently, a plasma is formed by discharging the discharge gas provided into the chamber by using power having a frequency of a radio frequency (RF) band. Subsequently, the surface layer of the printed circuit board is micro-etched using the formed plasma to activate the surface thereof. Subsequently, after completion of the plasma reaction, all of the reaction gas present in the chamber is discharged. Thereafter, the plasma-treated printed circuit board is unloaded in the chamber.

The biggest problem of the above-described method for processing a printed circuit board plasma using a low pressure / vacuum plasma is to use a fluorocarbon compound as a discharge gas. Representative fluorocarbon compounds used as the discharge gas include CF _4, C ₂ F ₆ , CHF ₃ and the like, and the gases are highly used for etching wafers in a semiconductor process due to their excellent reactivity with silicon.

The fluorocarbon compound introduced into the chamber is formed of fluorine radicals due to plasma discharge, and various kinds of free radicals generated in this process react with the surface of the printed circuit board to cause fine etching on the surface of the substrate. This etching generates a large amount of fluorine compounds. Various kinds of fluorine compounds including fluorocarbon compounds are the main substances causing global warming, and emission regulations are currently strictly applied in Korea.

In addition, the low pressure / vacuum plasma treatment has the advantage of obtaining the uniformity of the plasma, but the equipment is very large and expensive because at least a vacuum pressure of about 300 mTorr is required. In addition, there is a drawback that the time required for discharging the discharge gas to form a plasma than the time used for the surface treatment has a problem that there is a limit to the mass production application.

Accordingly, an object of the present invention is to provide a surface treatment method of a printed circuit board which plasma-processes the printed circuit board in a short time without generating harmful gas.

Another object of the present invention is to provide a plasma forming apparatus for surface treatment of a substrate by forming a plasma within a short time without generating harmful gas.

In the method for treating a surface of a printed circuit board according to an embodiment of the present invention for achieving the above object, the method comprises the steps of forming a discharge gas containing atmospheric gas in the plasma state under atmospheric pressure and the discharge formed in the plasma state Exposing the printed circuit board to gas to increase the surface energy of the printed circuit board.

In addition, in the plasma forming apparatus according to the embodiment of the present invention for achieving the above-mentioned other object, the apparatus includes a chamber having a space in which a process for increasing the surface energy of the substrate using an atmospheric pressure plasma is performed. . It includes a plasma discharge electrode provided in the chamber, the at least one anode and the cathode coated with a dielectric spaced apart in parallel. And a gas providing unit that provides a discharge gas including atmospheric gas to the plasma discharge electrode to form an atmospheric pressure plasma for increasing surface treatment energy of the substrate. It includes a power supply for supplying power to the positive electrode and the negative electrode of the plasma discharge electrode to form the discharge gas in the plasma state.

Therefore, the surface treatment method of the printed circuit board using the plasma forming apparatus having the above-described configuration does not generate harmful gas because the discharge gas containing the atmospheric gas is formed in the plasma state. In addition, the method can increase the surface energy of the printed circuit board to improve the adhesion between the substrate and the epoxy compound, as well as reduce the cost and productivity of the plasma processing process.

Hereinafter, with reference to the accompanying drawings of the present invention will be described in detail.                     

1 is a configuration diagram schematically showing a plasma forming apparatus of the present invention.

Referring to FIG. 1, the plasma forming apparatus includes a chamber 100, a plasma discharge electrode 110 provided in the chamber, a gas providing unit 120 providing a discharge gas including atmospheric gas to the plasma discharge electrode, and the And a power supply unit 130 for supplying power to the plasma discharge electrode, a substrate stage 140 supporting the substrate, and a gas exhaust unit 150.

The chamber 100 provides a space for forming a discharge gas including atmospheric gas into an atmospheric plasma and a space for increasing surface energy of a printed circuit board (P) using the discharge gas formed in the plasma. Preferably, the chamber has a cylindrical shape and a flat top surface thereof.

The plasma discharge electrode 110 is disposed above the chamber and includes a first electrode 112 as an anode and a second electrode 114 as a cathode. Specifically, the plasma discharge electrode 110 has a structure in which at least one first electrode 112 and the second electrode 114 coated with the dielectric 116 are sequentially arranged in parallel in a first direction. . In this case, the first electrode 112 and the second electrode 114 are spaced apart from each other by about 1 to 10 mm to form a discharge space.

Preferably, the plasma discharge electrode 110 is formed by separating the first electrode 112, the second electrode 114, the first electrode 112, and the second electrode 114 coated with the dielectric 116 from each other. The second electrode 114, the first electrode 112, the second electrode 114, and the first electrode 112 coated with the dielectric 116 or the dielectric 116 may be spaced apart from each other. It has a structure arranged in parallel in a first direction.

Here, the first electrode 112 and the second electrode 114 is a mesh-shaped metal electrode or a coil-shaped metal electrode having a rod shape, preferably a rod-shaped aluminum metal electrode. Examples of the dielectric material are alkali metal oxides such as aluminum oxide (Al ₂ O ₃ ), aluminum nitride (AlN), silicon barium oxide (BaSiO ₃ ), and the like.

The gas providing unit 120 is a gas providing line inserted into the chamber 100 to provide atmospheric gas to the plasma discharge electrode. Specifically, the gas providing unit 120 is a gas providing line extending from the outside to the inside of the chamber, and a plurality of gases in the gas line for uniformly providing the discharge gas into the discharge space of the plasma discharge electrode. Blowing holes are formed.

Atmospheric gas contained in the discharge gas may be used as a general atmospheric gas alone or mixed with specific gases. Preferably, a discharge gas in which a small amount of argon gas is mixed with oxygen and nitrogen gas is used. This is because when only the pure atmospheric gas is used to form the plasma, the plasma discharge may be unstable at an initial stage, and thus, plasma discharge should be performed while injecting a small amount of argon.

The power supply unit 130 is provided outside the chamber to apply power to the plasma discharge electrode to excite the discharge gas into a plasma state. In more detail, a dielectric barrier discharge is generated between the first electrode and the second electrode by applying current to the first electrode and the second electrode of the plasma discharge electrode. The dielectric barrier discharge generated in this way forms a discharge gas provided between the first electrode and the second electrode in a plasma state.

The dielectric barrier discharge may form a discharge gas including an atmospheric gas in a plasma state at room temperature and normal pressure, thereby minimizing deformation and damage of a substrate supported in the chamber.

The substrate stage 140 is provided to face the plasma discharge electrode 110 and supports a substrate for plasma processing. Here, the substrate may be, for example, a glass substrate, a semiconductor wafer, a printed circuit board and a plastic substrate. The gas discharge unit 150 is formed at one lower side of the chamber 100 to discharge the plasma gas reacted with the substrate and the particles formed during the plasma treatment of the substrate, out of the chamber.

In addition, a guide ring 160 is provided between the plasma discharge electrode 110 and the substrate stage 140 to concentrate the plasma on the upper surface of the substrate.

The plasma forming apparatus having the above-described configuration can form a discharge gas which does not cause harmful gas containing fluorine compound at a normal temperature and atmospheric pressure in a plasma state, so that surface energy of the printed circuit board can be reduced at low cost without environmental pollution. It is possible to perform a plasma surface treatment process to increase the.

2 is a process flowchart illustrating a method of forming a printed circuit board on which a chip is mounted, and FIG. 3 is a cross-sectional view of the printed circuit board formed by the method of FIG. 2.                     

Referring to FIGS. 2 and 3, after the printed circuit board P having the via holes 10, the internal circuit wiring 12, the external circuit wiring 14, and the like are formed in the resin substrate, a photoresist film ( (Not shown) (steps S10 and S20). The photoresist film is an organic film for protecting circuit wiring of a printed circuit board.

Subsequently, after selectively exposing the photoresist film, the exposed photoresist film is developed / baked to form a printed circuit board on which the photoresist pattern 22 is formed (step S30).

Subsequently, the chip 24 is mounted to be electrically connected to the metal wiring of the printed circuit board exposed to the photoresist pattern (step S40). The chip is an IC chip and is electrically connected to the metal wiring by a bonding process of the wire wiring 26.

Subsequently, in order to improve the interfacial adhesion between the printed circuit board (P) on which the IC chip is mounted and the epoxy compound (EMC) formed to protect the IC chip 24, an atmospheric pressure plasma is formed and then the atmospheric pressure plasma is used. The printed circuit board P is processed (steps S50, S60).

The plasma treatment is performed to increase the surface energy of the printed circuit board to increase adhesion with the epoxy compound. In this case, since the plasma is formed under atmospheric pressure using a discharge gas including atmospheric gas, the plasma does not react with a material formed on the surface of the printed circuit board to form a harmful substance.

Subsequently, in order to protect the IC chip mounted on the printed circuit board P, an epoxy compound is coated to seal the IC chip (step S70).                     

Hereinafter, an atmospheric pressure plasma forming method and a substrate processing method using the same using the plasma forming apparatus shown in FIG. 1 will be described in detail.

First, the substrate P to be surface treated is mounted on the substrate stage 140 of the chamber 100. Subsequently, the power supply unit 130 supplies a current having a frequency in the range of about 6 to 60 kHz to the plasma discharge electrode 110 to include the atmospheric gas to the plasma discharge electrode 110 through the gas providing unit 120. To provide a discharge gas. The discharge gas is a mixed gas in which a general atmospheric gas composed of nitrogen gas and oxygen gas and a small amount of argon gas are mixed, and is provided into the chamber 100 at a flow rate of about 10 to 30 (l / min). When only the pure atmospheric gas is used to form the plasma, the plasma discharge is initially unstable, and thus plasma discharge is performed while a small amount of argon is injected together to prevent this.

The discharge gas provided to the plasma discharge electrode 110 is formed in a plasma state by plasma discharge between the first electrode 112 and the second electrode 114.

Subsequently, the discharge gas formed in the plasma state is reacted with the surface of the substrate P to surface-treat the printed circuit board P. Specifically, the plasma formed on the plasma discharge electrode 110 reacts with the substrate P positioned under the plasma discharge electrode 110 to surface-treat the substrate P. Thereafter, the plasma reacted with the substrate P is discharged to the outside of the chamber through the gas discharge unit 150 formed below the chamber 100. The substrate may be, for example, a glass substrate, a semiconductor wafer, a printed circuit board, a plastic substrate, or the like. It is preferably a printed circuit board.

Since the surface energy of the printed circuit board has a low surface energy, an IC chip is subsequently mounted on the printed circuit board and then the IC chip is formed using an epoxy molding compound (EMC). When the process of packaging the IC chip has a problem of low interfacial adhesion with the epoxy compound.

Therefore, in order to solve the above problem, the surface of the printed circuit board is surface treated using atmospheric pressure plasma. The plasma surface treatment is performed to increase the surface energy of the printed circuit board to increase adhesion with the epoxy compound. Here, since the plasma is formed under atmospheric pressure using the discharge gas including the atmospheric gas, the plasma does not react with the material formed on the surface of the printed circuit board to form harmful substances.

Hereinafter, the present invention will be described in detail by applying embodiments of the present invention. The above embodiments do not limit the invention.

Example 1

A printed circuit board is mounted on the substrate stage of the plasma forming apparatus shown in FIG. Subsequently, the power supply unit supplies a current having a frequency in the range of about 50 kHz to the plasma discharge electrode, thereby discharging the discharge gas including nitrogen, oxygen, and argon supplied to the plasma discharge electrode at a flow rate of about 25 (L / min). Discharged. Subsequently, the plasma formed by the discharge was reacted with the surface of the first printed circuit board for about 4 minutes to surface-treat the surface of the printed circuit board. Thereafter, the reactant and the plasma generated during the surface treatment were discharged out of the chamber through a gas outlet formed under the chamber. As a result, the printed circuit board has increased surface energy and improved adhesion with the epoxy resin compound.

Example 2

A surface treatment process was performed in the same manner as in Example 1, but instead of the printed circuit board, a printed circuit board was contaminated by organic materials. As a result, organic matter present on the surface of the printed circuit board was removed.

Example 3

The surface treatment process was performed in the same manner as in Example 1, except that a contaminated glass substrate or a semiconductor wafer was applied instead of the printed circuit board. As a result, contaminants present on the surface of the glass substrate or semiconductor wafer have been removed.

Example 4

A surface treatment process was performed in the same manner as in Example 1, but only nitrogen gas was used as the discharge gas. As a result, it was found that the surface tension of the printed circuit board of Example 1 was reduced. In other words, it can be seen that only nitrogen has a poor surface treatment capability.

Example 5

The surface treatment process was performed in the same manner as in Example 1, but only oxygen gas was used as the discharge gas. As a result, it was found that the surface tension of the printed circuit board of Example 1 was reduced. In other words, it can be seen that the surface treatment capability of the printed circuit board is poor using only oxygen gas.

Evaluation experiment 1

The untreated plasma printed circuit board and the printed circuit board surface-treated in Examples 1, 4 and 5 were measured by contact angles using three liquids such as distilled water, methylene iodide (CH ₂ I ₂ ) and ethylene glycol. Surface free energy of the substrate was measured. In addition, the surface free energy of the substrate was measured by measuring a change in contact angle using an epoxy resin in order to determine how the surface-treated printed circuit board can affect the improvement of adhesion ability with the actual epoxy resin. The results are shown in Table 1 below.

As shown in Table 1, it can be seen that the surface treatment ability for the printed circuit board is the best when the plasma of the discharge gas of Example 1 is formed. In addition, when the plasma is formed in the state in which argon gas is removed, it can be seen that the surface treatment capability of the printed circuit board is weak as can be seen in Examples 4 and 5.

γS (mJ / m2) γSL (mJ / m2) γSSP (mJ / m2) γS + (mJ / m2) γS- (mJ / m2) Epoxy resin contact angle Example 1 Untreated Substrate Example 4 Example 5 44.65 42.88 41.18 38.81 41.89 38.90 34.16 35.38 2.76 3.98 7.02 3.43 0.15 0.23 0.69 0.12 12.86 17.17 17.84 23.75 35.3 40.7 41.1 42.8

γS: surface tension coefficient

γSL: nonpolar element

γSSP: Polar Element

γS +: acidic factor

γS-: basic factor

Evaluation experiment 2

In order to determine whether harmful substances were generated during the plasma formation of the discharge gas including the atmospheric gas, the IR spectrum of the discharge gas was measured after the plasma was formed in the same manner as in Example 1 without a printed circuit board. The result is shown in FIG. In FIG. 4, (b) is ozone gas, (c) and (g) are nitrous oxide, and (e) is a gas containing a carbonyl group (C = O).

As shown in FIG. 4, when the discharge gas of Example 1 is plasma discharged, it is understood that no harmful substances are generated because ozone (O ₃ ) gas and nitrous oxide (N ₂ O) gas are mainly generated. have.

Evaluation experiment 3

After the plasma formation of the discharge gas containing the atmospheric gas to the surface treatment of the printed circuit board to determine whether the generation of harmful substances according to the time of the printed circuit board in the same manner as in Example 1 2 minutes, 4 minutes respectively After 6 minutes plasma treatment, the IR spectrum of the discharged gas was measured. The result is shown in FIG. In Figure 5 (b) and (f) is ozone gas, (c) and (g) is nitrous oxide, (d) is nitrogen oxide (N ₂ O ₂ ), (e) is a gas containing a carbonyl group to be.

As shown in FIG. 5, in the case of surface treatment of the printed circuit board by plasma discharge of the discharge gas of Example 1, ozone (O ₃ ), nitrogen oxide (N ₂ O ₂ ), and nitrous oxide (N ₂ O) Since carbon monoxide (CO) and carbon dioxide (CO ₂ ) are mainly generated, it can be seen that no harmful substances containing fluorine compounds are generated. That is, ozone (O ₃ ) and nitrous oxide (N ₂ O) generated during plasma formation react with the organic film present on the surface of the printed circuit board to form products as shown in FIG. 5. These products can be seen as a result of the surface modification reaction of the printed circuit board.

Evaluation experiment 5

XPS analysis of the plasma-treated printed circuit board surface in Example 1 in order to find out the degree of surface modification of the printed circuit board of Example 1 in more detail. FIG. 6 is a graph showing a time-dependent change in surface composition of an XPS analysis result of a printed circuit board according to surface treatment time of a plasma in Example 1. FIG.                     

Referring to the graph of FIG. 6, it can be seen that as the treatment time of the plasma increases, the content of ozone gas decreases, and the contents of carbon monoxide gas and carbon dioxide gas increase. That is, it is a result indicating that no harmful substances are generated in the product generated during the substrate treatment process.

The surface treatment method of the substrate using the atmospheric plasma according to the present invention can increase the surface energy of the printed circuit board to improve the adhesion of the epoxy compound to the printed circuit board.

In addition, since the method uses a plasma formed of a discharge gas including a general atmospheric gas under atmospheric pressure, it is possible to solve the problem of a low pressure / vacuum plasma treatment process using a corrosive gas. In addition, the plasma processing method may implement an inline system in a package process that cannot be performed in a low pressure / vacuum plasma.

As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified without departing from the spirit and scope of the invention described in the claims below. And can be changed.

Claims (6)

Forming a discharge gas including atmospheric gas into a plasma state under atmospheric pressure; And Exposing the printed circuit board to the discharge gas formed in the plasma state, thereby increasing the surface energy of the printed circuit board. The method of claim 1, wherein the plasma is formed, Applying electric power to a plasma discharge electrode which is provided inside a chamber providing a space for performing a process for increasing surface energy of a printed circuit board by applying the plasma, and a cathode coated with a dielectric and an anode disposed sequentially; ; And And providing a reaction gas to the plasma discharge electrode to which the power is applied to form a plasma for increasing the surface energy of the printed circuit board. The method of claim 1, wherein the atmospheric gas comprises at least one selected from the group consisting of oxygen gas, hydrogen gas, nitrogen gas, and carbon dioxide gas. The method of claim 1, wherein the discharge gas further comprises argon gas. The surface treatment of a printed circuit board according to claim 1, wherein the step of increasing the surface energy is a process of etching the surface of the printed circuit board or a process of removing impurities present on the surface of the printed circuit board. Way. A chamber having a space for performing a process for increasing surface energy of a printed circuit board using an atmospheric plasma; A plasma discharge electrode disposed in the chamber and sequentially disposed at least one anode and a cathode coated with a dielectric and spaced apart in parallel; A gas providing unit providing a discharge gas including an atmospheric gas to the plasma discharge electrode to form an atmospheric plasma for increasing surface treatment energy of the printed circuit board; And And a power supply for supplying power to the anode and the cathode of the plasma discharge electrode in order to form the discharge gas into a plasma state.

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