KR101199184B1 - The printed circuit board and the method for manufacturing the same - Google Patents

Abstract

The present invention relates to a printed circuit board, which includes a circuit pattern and a pad formed on an insulating layer, and a nickel alloy layer formed on the circuit pattern or the pad and having a hardness of 550 HV or less. Therefore, a low-hardness nickel plating layer is formed on the base pad containing copper, and wire bonding property is improved and solder adhesiveness is ensured.

Description

[0001] The present invention relates to a printed circuit board and a method of manufacturing the same,

The present invention relates to a printed circuit board and a method of manufacturing the same.

The circuit board includes a circuit pattern on an electrically insulating substrate, and is a substrate for mounting electronic components or the like.

1 is a cross-sectional view of a conventional printed circuit board.

Referring to FIG. 1, a pad 3 is formed on the insulating layer 1 of the printed circuit board 10 by being connected to the circuit pattern 2. The pad 3 may have various shapes according to the type of the component mounted or connected thereto.

The pad 3 may be mounted with a solder ball and bonded to the device, and may be wire bonded.

The pad 3 is generally formed simultaneously with the circuit pattern 2 by patterning a copper foil layer formed on the insulating layer 1. Therefore, the pad 3 formed of copper is oxidized and corroded with time, so that soldering and wire bonding are not performed smoothly.

The embodiment provides a new printed circuit board and a manufacturing method thereof.

The embodiment provides a printed circuit board having improved wire bonding property and a method of manufacturing the same.

The embodiment includes a circuit pattern and a pad formed on the insulating layer, and a nickel alloy layer formed on the circuit pattern or the pad and having a hardness of 550 HV or less.

Meanwhile, a method of manufacturing a printed circuit board according to an embodiment may include preparing an insulating substrate on which a circuit pattern and a pad are formed, and forming a nickel alloy layer having a hardness of 550 HV or less on the circuit pattern or the pad. Include.

According to the present invention, a low hardness nickel plating layer is formed on a base pad containing copper to improve wire bonding properties and to secure solder adhesion.

In addition, by replacing the conventional gold plating with a palladium plating layer by plating the palladium plating layer with a thin film, it is possible to reduce the cost by using inexpensive palladium.

In addition, by forming the low-hardness nickel layer, the surface grains are densely formed and reliability is ensured.

1 is a cross-sectional view of a conventional printed circuit board.
2 is a cross-sectional view of a printed circuit board according to a first embodiment of the present invention.
3 to 10 are cross-sectional views illustrating a method for manufacturing the printed circuit board of FIG. 2.
11 is a cross-sectional view of a printed circuit board according to a second exemplary embodiment of the present invention.
12 to 17 are cross-sectional views illustrating a method for manufacturing the printed circuit board of FIG. 11.
18 is a photograph showing a top surface and a cross section of a conventional surface treated pad.
19 is a photograph showing a top surface and a cross section of a pad manufactured according to the present invention.
20 is a graph showing wire bonding properties according to the hardness of nickel of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise.

In order to clearly illustrate the present invention in the drawings, thicknesses are enlarged in order to clearly illustrate various layers and regions, and parts not related to the description are omitted, and like parts are denoted by similar reference numerals throughout the specification .

Whenever a portion of a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the case where it is "directly on" another portion, but also the case where there is another portion in between. Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

The present invention provides a circuit board having a wire bonding property by performing a surface treatment including a low hardness nickel alloy layer on a copper base layer with respect to a circuit pattern of an insulating substrate.

Hereinafter, a heat dissipation circuit board according to a first embodiment of the present invention will be described with reference to FIGS. 2 to 10.

2 is a cross-sectional view of a printed circuit board according to a first embodiment of the present invention.

Referring to FIG. 2, the printed circuit board 100 according to the first embodiment of the present invention may include a base pad 120 connected to an insulating plate 110 and a circuit pattern 125 formed on the insulating plate 110. ) And a solder resist 160 covering the circuit pattern.

The insulating plate 110 may be a supporting substrate of a printed circuit board on which a single circuit pattern is formed, but refers to an insulating layer region in which one circuit pattern (not shown) is formed among printed circuit boards having a plurality of stacked structures. You may.

When the insulating plate 110 means one insulating layer among a plurality of stacked structures, a plurality of circuit patterns (not shown) may be continuously formed on the upper or lower portion of the insulating plate 110.

The insulation plate 110 may be a thermosetting or thermoplastic polymer substrate, a ceramic substrate, an organic-inorganic composite material substrate, or a glass fiber impregnated substrate. When the insulation plate 110 includes a polymer resin, the insulation plate 110 may include an epoxy-based insulation resin. It may alternatively include polyimide resin.

A plurality of base pads 120 connected to the plurality of circuit patterns 125 are formed on the insulating plate 110. The base pad 120 is a bump for mounting an element mounted on the printed circuit board 100 and refers to a base pad 120 to which solder (not shown) is attached or wire bonded.

The circuit pattern 125 and the base pad 120 may be formed of a conductive material, and may be formed by simultaneously patterning a copper foil layer formed on the insulating plate 110. Therefore, the circuit pattern 125 and the base pad 120 may be formed of an alloy including copper, and roughness may be formed on a surface thereof.

The first metal layer 130 is formed on the top and side surfaces of the circuit pattern 125 and the base pad 120.

The first metal layer 130 is a nickel alloy layer containing nickel (Ni), and roughness is formed on a surface thereof.

The first metal layer 130 may be formed of only nickel, or may include nickel, and may be formed of an alloy with P (phosphorus), B (boron), W (tungsten), or Co (cobalt), and have a thickness of 1 to 10 μm. Has

In this case, the first metal layer 130 may be a nickel alloy layer having a low hardness and may be a nickel alloy layer having a hardness of about 550 HV or less, and preferably 450 to 500 HV.

The second metal layer 140 is formed to surround the top and side surfaces of the first metal layer 130.

The second metal layer 140 is an alloy layer including one metal of palladium, silver, gold, and copper, and may have roughness formed on a surface thereof.

The second metal layer 140 has a thickness of 0.01 to 1 μm, preferably 0.03 to 0.3 μm.

The second metal layer 140 may be preferably an alloy layer including palladium, and may be formed of an alloy of palladium with P (phosphorus), B (boron), W (tungsten), or Co (cobalt).

A third metal layer (not shown) may be further formed on the upper surface of the second metal layer 140, which is not limited to one layer.

The stacked structure of the circuit pattern 125, the first metal layer 130, and the second metal layer 140 on the circuit pattern 125 constitutes one metal circuit pattern, and the base pad 120 and the base pad The stacked structure of the first metal layer 130 and the second metal layer 120 on the 120 forms one pad.

A solder resist 160 is formed on the insulating plate 110 to cover the circuit pattern 125.

The solder resist 160 is to protect the surface of the insulating plate 110 and is formed on the front surface of the insulating plate 110, and the upper surface of the base pad 120 stacked structure to be exposed, that is, the second metal layer 140. It has an opening 165 that opens.

The wire 150 is bonded on the exposed second metal layer 140 of the base pad 120.

The wire 150 may be formed of an alloy including at least one metal of copper, gold, silver, or palladium, and preferably, may be formed of a gold alloy.

As such, by forming a low-hardness nickel alloy layer on the base pad 120 including copper, wire bonding property can be secured while performing low-cost surface treatment, and the surface is uniformly formed to improve reliability.

In this case, when the second metal layer 140 is used as an alloy of palladium, a pad having excellent strength, hardness, and ductility may be formed, and the alloy may be plated to have a brighter, smaller grain size than pure palladium. . In addition, when forming the alloy, by increasing the hydrogen overvoltage to reduce the hydrogen content in the plating layer has excellent corrosion resistance, and serves to prevent the diffusion of other elements, the reliability is high.

In addition, in the case of forming the palladium plating layer, by preventing the oxidation of the copper foil layer, the nickel alloy layer of the lower by the role of diffusion can be improved the bonding strength of the solder and the wire 150.

The printed circuit board 100 may further include an adhesive layer (not shown) between the base pad 120 and the first and second metal layers 130 and 140.

Hereinafter, a method of manufacturing the printed circuit board 100 of FIG. 2 will be described with reference to FIGS. 3 to 10.

3 to 10 are cross-sectional views illustrating a first method for manufacturing the printed circuit board of FIG. 2.

First, as shown in FIG. 3, the conductive layer 126 is stacked on the insulating plate 110, and when the insulating plate 110 is an insulating layer, a laminated structure of the insulating layer and the conductive layer 126 is a conventional copper clad. laminate).

The conductive layer 126 is etched in the stacked structure of the insulating plate 110 and the conductive layer 126 to form the base pad 120 and the circuit pattern 125 of FIG. 4.

Next, the first base layer 120 of FIG. 5 is formed by electroplating the patterned base pad 120 and the circuit pattern 125 with the seed layer.

The first metal layer 130 may be formed of only nickel, or may include nickel, and may be formed of an alloy with P (phosphorus), B (boron), W (tungsten), or Co (cobalt). It is formed to have a thickness of 10μm.

In this case, the alloy containing nickel uses low hardness nickel, may be a nickel alloy layer having a hardness of about 550HV or less, preferably 450 to 500HV may be satisfied.

Roughness may be imparted to the circuit pattern 125 and the base pad 120 to smoothly perform plating. The roughening may be performed by roughly plating copper with the seed layer on the circuit pattern 125 and the base pad 120. Can be done.

The first metal layer 130 is plated to the top and side surfaces of the circuit pattern 125 and the base pad 120 by electroplating the circuit pattern 125 and the base pad 120 with the seed layer.

Next, as shown in FIG. 6, the second metal layer 140 is formed by electroplating the first metal layer 130 with the seed layer.

At this time, the second metal layer 140 is preferably an alloy layer containing palladium (Pd), and specifically includes palladium, and P (phosphorus), B (boron), W (tungsten), Co (cobalt), etc. It may be formed of an alloy containing, preferably forming an alloy layer of Pd-Co.

The second metal layer 140 may have a thin thickness by adjusting a voltage, may satisfy 0.01 to 1 μm, preferably 0.03 to 0.3 μm, and may be formed to have roughness on a surface thereof.

The second metal layer 140 is formed to the top surface and side surfaces of the first metal layer 130 by forming the first metal layer 130 as a seed layer.

Next, as illustrated in FIG. 2, the printed circuit board 100 of FIG. 2 is formed by applying the solder resist 160 to have an opening 165 that opens the pad structure while filling the circuit pattern 125.

Meanwhile, the printed circuit board 100 of FIG. 2 may also be manufactured by electroless plating.

8 to 10 are cross-sectional views illustrating a second method for manufacturing the printed circuit board of FIG. 2.

First, as shown in FIG. 4, the patterned circuit pattern 125 and the base pad 120 are formed on the insulation plate 110, and then electroless plating is performed to form a first surface on the front surface of the insulation plate 110 as shown in FIG. 8. The plating layer 135 is formed.

In this case, roughness may be imparted to the surface of the insulating plate 110 by performing a desmear process for removing the smear of the insulating plate 110.

The first metal layer 130 formed by performing electroless plating may be formed of only nickel or may include nickel and may be formed of an alloy with P (phosphorus), B (boron), W (tungsten), or Co (cobalt). It can be formed to have a thickness of 1 to 10μm. At this time, low hardness nickel is used, and a nickel alloy layer having a hardness of about 550 HV or less is formed.

Next, electroless plating is performed as shown in FIG. 9 to form a second plating layer 145 on the first plating layer 135.

The second plating layer 145 is an alloy layer containing palladium (Pd). Specifically, the second plating layer 145 is an alloy containing palladium, and includes P (phosphorus), B (boron), W (tungsten), Co (cobalt), and the like. It may be formed, preferably an alloy layer of Pd-Co can be formed.

The second plating layer 145 may have a thinner thickness than the first plating layer 135 and may be formed of a thin film having a thin thickness of 0.03 to 0.3 μm.

Finally, as shown in FIG. 10, the first and second plating layers 135 and 145 are etched so that only the area covering the circuit pattern 125 and the base pad 120 remains, so that the first and the second plating layers 135 and 145 are etched on the circuit pattern 125 and the base pad 120. The first metal layer 130 etched from the plating layer 135 and the second metal layer 140 etched from the second plating layer 140 are formed.

In this case, in the case of the printed circuit board 100 formed of electroless plating, the first metal layer 130 may be formed to surround side surfaces of the base pad 120 and the circuit pattern 125, but the second metal layer 140 may be formed. ) Is formed only on the upper surface of the first metal layer 130, and thus the configuration thereof is partially different from that of the printed circuit board 100 of FIG. 2.

Hereinafter, a printed circuit board according to a second exemplary embodiment of the present invention will be described with reference to FIGS. 11 to 17.

11 is a cross-sectional view of a printed circuit board according to a second exemplary embodiment of the present invention.

Referring to FIG. 11, the printed circuit board 200 according to the second exemplary embodiment of the present invention may include a base pad 220 connected to an insulating plate 210 and a circuit pattern 225 formed on the insulating plate 210. ) And a solder resist 260 covering the circuit pattern.

The insulation plate 210 may be a thermosetting or thermoplastic polymer substrate, a ceramic substrate, an organic-inorganic composite material substrate, or a glass fiber impregnated substrate. When the insulation plate 210 includes a polymer resin, the insulation plate 210 may include an epoxy-based insulation resin. It may alternatively include polyimide resin.

A plurality of base pads 220 connected to the plurality of circuit patterns 225 are formed on the insulating plate 210. The base pad 220 is a bump for mounting an element mounted on the printed circuit board 200 and refers to a base pad 220 to which solder (not shown) is attached or wire bonded.

The circuit pattern 225 and the base pad 220 may be formed of a conductive material, and may be formed by simultaneously patterning a copper foil layer formed on the insulating plate 110, and may be formed of an alloy including copper.

The first metal layer 230 is formed on the top and side surfaces of the circuit pattern 225 and the base pad 220.

The first metal layer 230 may be formed of only nickel, or may include nickel, and may be formed of an alloy with P (phosphorus), B (boron), W (tungsten), or Co (cobalt), and have a thickness of 1 to 10 μm. Form to have. In this case, nickel is a low hardness nickel, may be a nickel alloy layer having a hardness of about 550HV or less, preferably may have a hardness of 450 to 500HV.

A solder resist 260 is formed on the insulating plate 210 to cover the circuit pattern 225.

The solder resist 260 is to protect the surface of the insulating plate 210 and is formed on the front surface of the insulating plate 210. The solder resist 260 opens the upper surface of the base pad 220 stacked structure to be exposed and opens the first metal layer 230. Has an opening 265.

The second metal layer 240 is formed on the first metal layer 230 of the exposed base pad 220.

The second metal layer 240 is an alloy layer containing at least one metal of palladium, silver, gold, or copper, and preferably, may be an alloy layer containing palladium (Pd).

Specifically, the second metal layer 240 includes palladium, and may be formed of an alloy including P (phosphorus), B (boron), W (tungsten), Co (cobalt), and the like, preferably Pd-Co Alloy layer can be formed.

The second metal layer 240 may have a thinner thickness than the first metal layer 230 and may be formed of a thin film having a thin thickness of 0.03 to 0.3 μm.

In this case, the second metal layer 240 may be formed to surround the side surface of the opening 265 of the solder resist 260.

As described above, unlike the printed circuit board 100 of FIG. 2, the printed circuit board 200 of FIG. 11 has a second metal layer 240 formed only in a pad structure and extends to the side surface of the opening 265 of the solder resist 260. It has a structure that is formed.

Alternatively, the first and second metal layers 230 and 240 may be formed only on the base pad 220 so that the first and second metal layers 230 and 240 extend to the side surface of the opening 265.

As shown in FIG. 2, wire bonding may be performed on the second metal layer 240 of the exposed base pad 220 and attached to the device.

As such, by plating a low-hardness nickel alloy layer on the base pad 220 including copper, a pad having improved electrical properties and wire bonding property can be formed, and the discoloration of the metal is improved by plating a palladium alloy on the surface. And heat resistance can be enhanced.

12 to 17 are cross-sectional views illustrating a method for manufacturing the printed circuit board of FIG. 11.

First, as illustrated in FIG. 12, when the conductive layer is stacked on the insulating plate 210, and the insulating plate 210 is an insulating layer, the laminated structure of the insulating layer and the conductive layer may be a conventional copper clad laminate (CCL).

The base layer 220 and the circuit pattern 225 of FIG. 13 are formed by etching the conductive layer in a stacked structure of the insulating plate 210 and the conductive layer.

Next, the first plating layer 235 is formed by performing electroless plating on the patterned base pad 220 and the circuit pattern 225 as shown in FIG. 13.

At this time, the first plating layer 235 is a nickel alloy layer of low hardness including nickel, and is formed to have a thickness of 1 to 10 μm.

In this case, roughness may be given to the insulating plate 210, the circuit pattern 225, and the base pad 220 to smoothly plate.

Next, as shown in FIG. 14, the first plating layer 235 is etched to form the first metal layer 230.

In this case, the first metal layer 230 may be etched with a width greater than that of the circuit pattern 225 and the base pad 220 so as to surround side surfaces of the circuit pattern 225 and the base pad 220.

Next, as shown in FIG. 15, the solder resist 260 is coated to have an opening 265 that opens the first metal layer 230 on the base pad 220 while filling the circuit pattern 225.

Next, a mask 270 is formed on the solder resist 260 as shown in FIG. 16.

The mask 270 may include a window 275 that opens the opening 265 of the solder resist 260, and may be formed of a photoresist or a dry film.

In this case, the width of the window 275 may be larger than the width of the opening 265 of the solder resist 260.

Next, as shown in FIG. 18, plating is performed on the first metal layer 230 exposed through the window 275 to form the second metal layer 240.

In this case, before forming the second metal layer 240, a desmear process may be performed to provide roughness to a portion of the side surface and the upper surface of the opening 265 of the solder resist 260.

The second metal layer 240 is an alloy layer containing palladium (Pd). Specifically, the second metal layer 240 is an alloy containing palladium, and includes P (phosphorus), B (boron), W (tungsten), Co (cobalt), and the like. It may be formed, preferably an alloy layer of Pd-Co can be formed.

The second metal layer 240 is formed of a thin film having a thin thickness of 0.01 to 1 μm, preferably 0.03 to 0.3 μm by performing non-plating or electroplating.

Finally, the printed circuit board 200 of FIG. 11 may be completed by removing the mask 270.

Thus, the printed circuit board formed according to the present invention has improved adhesion to the wire bonding formed later by the pad having a laminated structure of a copper layer-low hardness nickel alloy plating layer-palladium alloy plating layer.

Meanwhile, the effects of the present invention will be described with reference to FIGS. 18 to 20.

18 is a photograph showing a top surface and a cross section of a conventional surface-treated pad, FIG. 19 is a photograph showing a top surface and a cross section of a pad manufactured according to the present invention, and FIG. 20 is a wire bonding according to the hardness of nickel of the present invention. A graph showing the last name.

In the case of Fig. 18, a pad structure formed of a laminated structure of a copper base layer / high hardness nickel alloy layer / palladium alloy layer is photographed, and the hardness of the nickel alloy layer satisfies about 700 HV.

19, the present invention has a laminated structure of a copper base layer / low hardness nickel alloy layer / palladium alloy layer, and the hardness of the nickel alloy layer satisfies about 450 HV.

Examining the cross-sectional photograph of the present invention including the low hardness nickel alloy layer of FIG. 19C, it can be seen that voids are not formed therein and are plated evenly, as shown in FIG. 18C. Further, referring to FIGS. 19A and 19B, it can be seen that the grain size of the treated surface is smaller and denser than that of FIGS. 18A and 18B.

Solder adhesion was measured for both structures.

In general, with the instrument Dage-4000, wire bonding is required to have a wire pull force of about 3 to 4g or more, and solder adhesiveness is required to have a ball pull force of about 230g or more.

The pad structure of FIG. 18 and the pad structure of FIG. 19 measured using the measuring instrument obtained the following results.

18 pad structure
(Nickel hardness 700HV) Pad structure of FIG. 19
(Nickel hardness 450HV) Ball pull (g) 418 505

As shown in Table 1, even if the nickel hardness is adjusted, solder adhesion generally satisfies the required value of 230 g or more.

Next, the force of the wire pull according to each hardness was measured.

Referring to FIG. 20, when the strength of the wire pull is greater than or equal to 550 HV of the hardness of the nickel alloy layer, it satisfies generally required wire bonding of 3 to 4 g or more, and indicates the highest wire bonding between 450 and 500 HV. can see.

Therefore, when the nickel alloy layer of low hardness is used, the wire bonding property can be performed without securing the silver plating layer while improving the solder bonding property while maintaining the same level as the conventional one.

On the other hand, the wire bonding property and the solder adhesion were measured with respect to the plating thickness.

Plating layer thickness (μm) Experiment result Ni layer (450HV) Pd layer Wire bonding property (g) Solder Adhesive (g) 2 0.06 505 441 2 0.13 6.8 354 4 0.06 5.3 579 4 0.13 6.2 431 6 0.06 5.1 505 6 0.13 6.4 312

As shown in Table 2, when the thickness of the nickel alloy layer is between 1 and 10 μm and the thickness of the palladium alloy layer is between 0.03 and 0.3 μm, in the case of the low hardness nickel alloy layer, the wire bonding property and the solder adhesive property are desired. It can be seen that the degree is met.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Printed Circuit Board 100, 200
Insulation Plate 110, 210
Circuit pattern 125, 225
Pad 120, 220

Claims (16)

Circuit patterns and pads formed on the insulating layer, and
Nickel alloy layer formed on the circuit pattern or the pad and having a thickness of 1 to 10 μm and a hardness of 450 to 500 HV.
And a printed circuit board. The method of claim 1,
The printed circuit board includes at least one metal layer on the nickel alloy layer. delete delete The method of claim 2,
The metal layer is a printed circuit board is an alloy layer containing at least one of palladium, silver, gold or copper. The method of claim 2,
The metal layer includes palladium,
The printed circuit board of the palladium and the alloy containing at least one of phosphorus, boron, tungsten or cobalt. The method of claim 2,
The metal layer has a thickness of 0.03 to 0.3μm. Preparing an insulating substrate on which circuit patterns and pads are formed, and
Forming a nickel alloy layer having a thickness of 1 to 10 μm and a hardness of 450 to 500 HV on the circuit pattern or the pad;
And a step of forming the printed circuit board. delete delete 9. The method of claim 8,
And forming a metal layer on the nickel alloy layer by an alloy including at least one of palladium, silver, gold, and copper. The method of claim 11,
The forming of the metal layer may include:
Imparting roughness to the surface of the nickel alloy layer, and
And forming the metal layer by electroplating an alloy containing palladium using the nickel alloy layer as a seed layer. The method of claim 11,
The nickel alloy layer is 1 to 10 μm, wherein the metal layer is formed to have a thickness that satisfies 0.03 to 0.3 μm. The method of claim 11,
The metal layer includes palladium, and is formed of an alloy containing at least one of phosphorus, boron, tungsten or cobalt. 9. The method of claim 8,
The nickel alloy layer is a manufacturing method of a printed circuit board formed of a nickel alloy having a hardness of 450 to 500HV. 9. The method of claim 8,
Bonding a wire formed of an alloy containing copper, silver or gold on the nickel alloy layer on the pad.

Images