JP2013157390A - Wiring board and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board which has reduced residual strain remaining in a protection layer of a terminal formed by thin films and high connection reliability such that the terminal is not likely to separate from an insulation substrate.SOLUTION: In a wiring board, each of a terminal 2 and wiring 3 includes a base metal layer 4, a main conductor layer 5 and a protection layer 6 from bottom on an insulation substrate 1. At a connection part of the wiring 3 with the terminal 2, a cut line 9 across the wiring 3 in a width direction is formed in the protection layer 6. Because residual strain remaining in the protection layer 6 can be reduced by the cut line 9, the wiring board having high connection reliability such that the terminal 2 is not likely to separate from the insulation substrate 1 can be obtained.

Description

  The present invention relates to a wiring board and an electronic device for mounting an electronic component such as a light emitting element or a constant voltage diode having thin film wiring.

  Conventionally, when forming a wiring pattern on an insulating substrate such as a ceramic, a thick film method in which a high melting point metal conductive paste is printed on the surface of a green sheet by a thick film printing method or the like and then fired is employed. In recent years, since wiring boards such as ceramics have been required to have high density wiring patterns and improved dimensional accuracy, conductors such as wiring formed on the upper surface of an insulating substrate are formed by ion plating, sputtering, A thin film wiring substrate that is formed by a thin film method such as a vapor deposition method has been adopted. The layer configuration of the thin film wiring is such that a base metal layer and a main conductor layer are sequentially laminated on the upper surface of an insulating substrate (see, for example, Patent Document 1).

  When a light emitting element such as an LED is mounted on such a thin film wiring board and used as a headlight or a street light for an automobile, the wiring is required to have high rust prevention reliability. At that time, when using low resistance copper for lowering the electrical resistance for the main conductor layer, a protection layer (for example, nickel layer) for preventing corrosion of the copper is applied to the main conductor layer (for example, nickel layer). The thickness of the protective layer is increased to improve rust prevention.

Japanese Unexamined Patent Publication No. 64-11394

  However, as the thickness of the protective layer is increased as in the case of the conventional wiring board, the rust prevention is improved, but the residual strength remaining in the protective layer is liable to cause a decrease in the connection strength of the base metal layer to the insulating substrate. There was a problem. Furthermore, when a heat generating element such as a light emitting element is mounted on the terminal, a thermal stress is generated in the terminal, and there is a problem that the thermal stress and the residual stress of the protective layer described above are combined and the terminal is easily peeled off.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a wiring board and an electronic device in which stress is reduced and peeling of terminals is suppressed.

  According to a first aspect of the present invention, there is provided a wiring board comprising: an insulating substrate; a terminal formed on the main surface of the insulating substrate; and a wiring connected to the terminal and extending on the main surface of the insulating substrate. The terminal and the wiring are provided with a base metal layer, a main conductor layer, and a protective layer in order from the bottom on the insulating substrate, and extend in the width direction of the wiring at the connection portion of the wiring with the terminal. The protective layer is formed with a cut.

  According to a second aspect of the present invention, there is provided a wiring board comprising: an insulating substrate; a terminal formed on the main surface of the insulating substrate; and a wiring connected to the terminal and extending on the main surface of the insulating substrate. The terminal and the wiring include a base metal layer, a main conductor layer, and a protective layer in order from the bottom on the insulating substrate, and the protective layer is divided into a plurality of regions in plan view. It is characterized in that a cut is formed.

  An electronic device of the present invention comprises the wiring board of the present invention having the above-described configuration and an electronic component connected to the terminal.

  According to the first form of the wiring board of the present invention, the terminal and the wiring are provided with the base metal layer, the main conductor layer, and the protective layer in order from the bottom on the insulating substrate, and the wiring of the wiring is connected to the terminal of the wiring. Since the cut is formed in the protective layer across the width direction, the residual stress remaining in the protective layer of the terminal portion due to the cut can be reduced, so the stress applied to the base metal layer is reduced and the terminal is insulated. It can be set as the wiring board which has the high connection reliability which is hard to peel from a board | substrate.

  According to the second form of the wiring board of the present invention, the terminal and the wiring are provided with the base metal layer, the main conductor layer, and the protective layer in order from the bottom on the insulating substrate, and the terminal is divided into a plurality in plan view. Since the cut is formed in the protective layer, the residual stress of the protective layer can be reduced by dividing the protective layer of the terminal by the cut, and as a result, the stress applied to the base metal layer is reduced, It can be set as the wiring board which has the high connection reliability which a terminal does not peel easily from an insulating substrate.

  According to the electronic device of the present invention, since the wiring board of the present invention having the above-described configuration and the electronic component connected to the terminal are provided, the stress applied to the base metal layer is reduced, and the terminal and the wiring are separated from the insulating substrate. An electronic device having high connection reliability that is difficult to peel off can be obtained.

(A) is a top view which shows 1st Embodiment of the wiring board of this invention, (b) is a principal part enlarged top view which expands and shows the A section of (a). (A)-(c) is a principal part enlarged top view which shows the other example of 1st Embodiment of the wiring board of this invention. (A)-(c) is sectional drawing in the cut | interruption vicinity of the wiring board of this invention. (A)-(c) is a principal part enlarged top view which shows 2nd Embodiment of the wiring board of this invention.

  The wiring board and electronic device of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1A is a top view showing an example of a first embodiment of a wiring board according to the present invention, and FIG. 1B is an enlarged view of a main part showing an A portion of FIG. It is a top view. In the example shown in FIG. 1, a terminal 2 is formed on the main surface of the insulating substrate 1, and an example of a wiring substrate in which the wiring 3 connected to the terminal 2 extends on the main surface of the insulating substrate 1 is shown. .

  As shown in FIGS. 1A and 1B, the first embodiment of the wiring board of the present invention includes an insulating substrate 1, terminals 2 formed on the main surface of the insulating substrate 1, Wiring 3 connected to the terminal 2 and extending on the main surface of the insulating substrate 1. The terminal 2 and the wiring 3 are provided with a base metal layer 4, a main conductor layer 5, and a protective layer 6 in order from the bottom on the insulating substrate 1, and across the width direction of the wiring 3 at the connection portion of the wiring 3 with the terminal 2. A cut 9 is formed in the protective layer 6. With such a configuration, the protective layer 6 is thickened to prevent corrosion of the wiring board, and even in the wiring board where the stress applied to the base metal layer 4 is likely to increase, it remains in the protective layer 6 in the terminal 2 portion due to the break 9. Since the residual stress can be reduced, the stress applied to the base metal layer 4 is reduced, and the wiring board having high connection reliability in which the terminal 2 is difficult to peel off from the insulating substrate 1 can be obtained. That is, since the cut 9 is formed in the protective layer 6, the length of the protective layer 6 continuous from the terminal 2 is shortened, and the residual stress inherent in the protective layer 6 in the terminal 2 portion is reduced. The connection portion of the wiring 3 with the terminal 2 includes not only the boundary portion between the wiring 3 and the terminal 2 but also the wiring 3 in the vicinity of the boundary. For example, in a region from the boundary of the wiring 3 to 1.5 mm. is there.

In the example shown in FIG. 1B, the cut 9 is formed in a continuous groove shape across the width direction of the wiring 3. On the other hand, in the example shown in FIGS. 2A and 2B, a plurality of cuts are formed in the width direction of the wiring 3 at intervals, forming a perforated cut 9. It is. The case where the cut 9 is a continuous groove as in the example shown in FIG. 1 (b) is preferable because the residual stress of the protective layer 6 can be reduced most, but the cut 9 is shown in FIGS. As in the example shown in b), the residual stress can be similarly reduced even in the case of perforations. In this case, the ratio of the total length of the plurality of cuts 9 to the width of the wiring 3 is preferably 50% or more. Also, in this case, the protective layer 6 is thinned by the cuts 9, and the portion is divided, so that even if the main conductor layer 5 corrodes from a pinhole or the like of the thinned portion of the protective layer 6, the corrosion spreads. It can be difficult.

  If the shape of the cut 9 in plan view is a groove shape, it may be linear as in the example shown in FIG. 1B, or may be elliptical as in the example shown in FIG. A shape in which a plurality of circular cuts are connected may be used. As in the example shown in FIG. 2 (c), when a plurality of cuts 9 are connected continuously, the portion of the protective layer 6 between the cuts 9 remains thick, and once melted, The residual stress of the protective layer 6 is effectively reduced, and it is more preferable for corrosion because it hardly spreads even if it occurs.

  In addition, the shape of each cut 9 in the case of a perforation is not particularly limited, and may be a rectangular shape as in the example shown in FIG. 2A, or as in the example shown in FIG. Alternatively, it may be circular, or may be other rhombuses, trapezoids, triangles or hexagons.

  The example shown to Fig.3 (a)-(c) is an example which shows the formation position in the depth of the cut | interruption 9, and a depth direction. In the example shown in FIG. 3A, the cut 9 is formed to the same depth as the thickness of the protective layer 6, and the main conductor layer 5 formed under the protective layer 6 is exposed. .

  As in the example shown in FIGS. 3B to 3C, it is preferable to form the cut 9 so that the main conductor layer 5 is not exposed, because the main conductor layer 5 can be prevented from corroding. In this case, if the thickness of the protective layer 6 is about 5 μm, corrosion of the main conductor layer 5 can be suppressed. Further, the position of the cut 9 in this case may be on the opposite side to the main conductor layer 5 as in the example shown in FIG. 3B, or the main conductor layer as in the example shown in FIG. However, it is easier to form and to control the thickness of the remaining protective layer 6 on the side opposite to the main conductor layer 5 as in the example shown in FIG.

The insulating substrate 1 includes a plurality of insulating layers, and the insulating layer includes, for example, an aluminum oxide (alumina: Al ₂ O ₃ ) sintered body, an aluminum nitride (AlN) sintered body, and a silicon carbide (SiC) sintered body. Body, mullite sintered body, and ceramics such as glass ceramics. For example, when the insulating layer is formed of an aluminum oxide sintered body, first, an appropriate organic binder and solvent are added to and mixed with raw material powders of aluminum oxide, silicon oxide, magnesium oxide and calcium oxide to form a slurry. At the same time, this is formed into a sheet shape by a doctor blade method or the like to produce a plurality of ceramic green sheets to be an insulating layer. Then, these ceramic green sheets are superposed and thermocompression bonded to produce a laminated body, and this laminated body is fired at a high temperature of about 1500 ° C. to 1600 ° C. to produce the insulating substrate 1.

The terminal 2 and the wiring 3 are formed by forming a base metal layer 4, a main conductor layer 5, and a protective layer 6 in order from the bottom on the upper surface of the insulating substrate 1. 3A to 3C, the diffusion prevention layer 7 is formed on the surface of the protective layer 6, and the surface layer 8 is further formed on the surface of the diffusion prevention layer 7. Yes. The surface layer 8 is formed to adhere an electronic component with an adhesive such as solder, and is made of, for example, Au (gold) having good wettability with solder. The diffusion prevention layer 7 is for preventing the protective layer 6 from diffusing to the surface of the thin Au surface layer 8. For example, when the thickness of the Au surface layer 8 is increased to such an extent that the protective layer 6 can absorb the diffusion to the surface of the Au surface layer 8, the diffusion prevention layer 7 is not required, but the high cost Au In order to form the surface layer 8 as thin as possible, it is preferable to form the diffusion prevention layer 7 between the protective layer 6 and the Au surface layer 8.

The base metal layer 4 is made of, for example, a Ti alloy such as Ti (titanium) or TiW (titanium tungsten), and has a thickness of, for example, 0.01 to 0.5 μm. The main conductor layer 5 is made of, for example, Cu (copper) and has a thickness of, for example, 1.0 to 100.0 μm. The protective layer 6 is made of, for example, Ni (nickel) and has a thickness of, for example, 0.5 to 10.0 μm. Further, the diffusion preventing layer 7 is made of, for example, Pd (palladium) and has a thickness of, for example, 0.1 to 1.0 μm. For example, when low resistance Cu is used for the main conductor layer 5, the resistance of the wiring can be lowered, and the stress due to Ni of the protective layer can be relieved by Cu.

The terminal 2 and the wiring 3 are formed by using a conventionally well-known thin film forming method such as an ion plating method, a sputtering method, or a vapor deposition method. For example, Cu serving as a part of the base metal layer 4 and the main conductor layer 5 is formed on the surface of the insulating substrate 1 by ion plating, sputtering, vapor deposition, or the like. Thereafter, a reversal pattern of the terminal 2 and the wiring 3 is formed by a photolithography method using DFR (dry film resist). Thereafter, the main conductor layer 5 is formed by electrolytic Cu plating, and the DFR is removed. Thereafter, a part of the Cu and the underlying metal layer 4 other than the terminal 2 and the wiring 3 are removed using a wet etching method, and the protective layer 6 and the diffusion preventing layer 7 and the electroless plating method are used. The surface layer 8 is formed.

  The cut 9 is formed by laser irradiation such as a YAG laser (yag laser). When the cut 9 is formed by laser irradiation, the protective layer 6 near the cut 9 is once melted and solidified again to become a dense metal. Therefore, even if the protective layer 6 is thinned, the effect of preventing corrosion is unlikely to be reduced. It becomes. Moreover, since the residual stress is released even when the protective layer 6 near the cut 9 is once melted by laser irradiation, it is preferable as a stress relaxation method. Further, when the cut 9 is formed by laser irradiation, the surface of the protective layer 6 near the cut 9 is oxidized and the solder wettability is deteriorated, so that it also functions as a solder flow stop. Therefore, it is necessary to form a solder dam or the like. Is preferred.

  For example, when the cut 9 is formed using a YAG laser even during laser irradiation, the laser absorption rate of the metal varies depending on the wavelength of the YAG laser, and the YAG laser is used in the protective layer 6 made of Ni and the main conductor layer 5 made of Cu. The laser absorption rate is different. For example, in a YAG laser with a fundamental wavelength of 1064 μm, by adjusting the output of the YAG laser, Ni with a laser absorption rate of 30% is melted and evaporated, but the Cu of the main conductor layer 5 under the protective layer 6 is Laser absorptivity is 10% or less so that it is not melted and scattered. As a result, the main conductor layer 5 is not melted and scattered by the YAG laser, and the cut 9 is not formed in the main conductor layer 5, so that the resistance value does not change.

  When the cut 9 is formed in a groove shape as in the example shown in FIG. 1B, for example, a YAG laser having a fundamental wavelength of 1064 μm is used, and a frequency of 15 to 30 kHz and an output of 10 to 20 A is 0.1 to 5.0. It can be formed by continuous laser irradiation while scanning at a scanning speed of about mm / second. Moreover, when forming the cut | interruption 9 as several cut | interruption 9 like the example shown to Fig.2 (a)-(c), it can form by irradiating a laser intermittently, scanning on the same conditions. .

Further, in order to make the shape of the cut 9 to be the shape of each of the examples shown in FIGS. 3A, 3B, and 3C, the types and thicknesses of the metal of the protective layer 6 and the main conductor layer 5 are used. It can be produced by adjusting the laser frequency, output, laser irradiation time, and the like. The break 9 in the example shown in FIGS. 3A and 3B is formed by adjusting the above-described frequency, output, and laser irradiation time by the YAG laser having the above-described wavelength. In the example shown in FIG. 3A, it is preferable that all the thickness of the protective layer 6 is evaporated and scattered, and in the example shown in FIG. 3B, the middle part of the thickness of the protective layer 6 is evaporated and scattered. In the example shown in FIG. 3C, when the protective layer 6 is evaporated and scattered by laser irradiation, the protective layer 6 once melted by the laser irradiation is formed in a lid shape on the upper part of the cut 9, and this lid The main conductive layer 5 is not exposed by the protective layer 6 having a shape.

  The cut line 9 may be formed by another method. For example, if the resist is peeled after forming the resist film after forming the main conductor layer 4 and forming the protective layer 6 at the position where the cut 9 is formed, the protective layer 6 is not formed at the position where the resist film is formed. In addition, as in the example shown in FIG. 3A, a cut 9 having the same depth as the thickness of the protective layer 6 is formed from which the main conductor layer 5 is exposed. However, since the main conductor layer 4 is exposed at the bottom of the cut 9, it is preferable to coat the main conductor layer 4 so as not to corrode. In this coating, for example, when the Au surface layer 8 is formed by electrolytic plating or electroless plating as described above, Au is also formed on the surface of the main conductor layer 4 exposed at the bottom of the cut 9. This is the coating of the main conductor layer 4. The cut 9 as in the example shown in FIG. 3B is formed after the main conductor layer 4 is formed and the protective layer 6 having a lower thickness between the cut 9 and the main conductor layer 5 is formed thereon. What is necessary is just to form the resist film of the depth (height) of the cut | interruption 9 in the position which forms 9 and form the upper protective layer 6 of the same thickness.

  Furthermore, it is preferable that the peripheral part of the cut 9 is oxidized. In this case, when an electronic component is mounted and connected to the terminal 2 by brazing of solder or the like, the flow of solder stops at the cut line 9, so that the solder of the electronic component connected to the connection of the electronic component does not need to be formed again. Since the thickness can be prevented from being reduced and the amount of solder can be secured, it is possible to provide a wiring board with high connection reliability in which electronic components are prevented from being peeled off. That is, when the metal in the periphery of the cut 9 is oxidized, the solder is less likely to get wet in the oxidized portion, and the flow of solder stops at the cut 9. When a laser having a relatively long wavelength, such as a YAG laser, is used for the oxidation, the effect as a solder dam is enhanced because it easily spreads to the vicinity of the groove.

  In the second embodiment of the wiring board according to the present invention, as in the example shown in FIGS. 4A to 4C, the cuts 9 formed in the protective layer 6 are formed in a plurality of regions in a plan view of the terminal 2. Unlike the first embodiment in that it is formed so as to be divided, the other points have the same configuration. With such a configuration, even when the dimensions of the terminal 2 are increased, the length of the terminal 2 is shortened by dividing the terminal 2 into a plurality by the cut line 9, so that the residual stress of the protective layer 6 can be reduced. As a result, the stress applied to the base metal layer 4 is reduced, and a wiring board having high connection reliability in which the terminal 2 is difficult to peel from the insulating substrate 1 can be obtained.

In the example shown in FIG. 4A, the cut 9 is formed in a groove shape along the outer periphery of the terminal 2 at the peripheral portion of the terminal 2, and the example shown in FIG. The cut 9 is formed vertically and horizontally along each of the outer sides of the terminal 2 to the end of the terminal 2, and the example shown in FIG. 4C is the cut 9 of the example shown in FIG. Are formed in perforations. As in the example shown in FIG. 4A, when the groove-like cut 9 is formed in the peripheral portion of the terminal 2, the residual stress inside the terminal 2 can be effectively relieved over the entire circumference. . Further, as in the example shown in FIG. 4B, when the groove-like cut 9 is formed vertically and horizontally to the end of the terminal 2, the residual stress in the inner region of the terminal 2 and the entire circumference are effectively relieved. In addition, by dividing the outer region of the terminal 2, the residual stress in the outer region having a large residual stress can be reduced more effectively, so that the residual stress of the entire terminal 2 can be further reduced. . When the shape of the terminal 2 in plan view is a quadrilateral shape as in the example shown in FIG. 4B, the residual stress increases at the corners of the quadrilateral, so that the corners as in the example shown in FIG. It is effective to form the cut 9 so as to reduce the partial area. Further, as in the example shown in FIG. 4C, when the cut 9 is perforated, it is led from a pinhole or the like of the thinned portion of the protective layer 6 as in the case of the first embodiment. Even if the body layer 5 corrodes, the corrosion can hardly be spread.

  The cut 9 may be formed in any way as long as the terminal 2 is formed so as to be divided into a plurality of short regions. When the number of cuts 9 is larger, the length of the divided region is shortened and the residual stress can be reduced. However, when the number of cuts 9 is increased, an electronic component is bonded to the terminal 2 with a bonding material such as solder. In some cases, the number of parts that are difficult to be joined increases and the connection reliability decreases. Therefore, in order to efficiently reduce the residual stress with a small number of cuts 9, as shown in FIGS. 4A to 4C, the terminals are divided into an inner region and an outer region in a plan view. It is preferable to form in the peripheral part of 2.

  When it is desired to connect an electronic element or an electronic component only to the inside of the terminal 2 with a brazing material, the protective layer 6 in the vicinity of the cut 9 is formed when the cut 9 is formed to divide the terminal 2 into an outer side and an inner side by laser irradiation. The surface is oxidized and the solder wettability is deteriorated, and it also functions as a solder flow stop. Therefore, it is not necessary to separately form a solder dam, which is preferable.

  The second embodiment is more effective by combining the configurations of the first embodiment. This is particularly effective when the cut 9 is not formed up to the end of the terminal as shown in FIGS. 4 (a) and 4 (c).

  The electronic device of the present invention includes the wiring board of the present invention having the above-described configuration and an electronic component (not shown) connected to the terminal 2. With such a configuration, the stress applied to the base metal layer 4 is reduced, and an electronic device having high connection reliability in which the terminal 2 and the wiring 3 are not easily separated from the insulating substrate 1 can be obtained.

  The electronic component is an electronic component such as a light emitting device (LED) or a constant voltage diode (zener diode), and these electronic components are connected via an adhesive such as a brazing material.

1: Insulating substrate 2: Terminal 3: Wiring 4: Base metal layer 5: Main conductor layer 6: Protection layer 7: Diffusion prevention layer 8: Surface layer 9: Break

Claims (4)

An insulating substrate;
Terminals formed on the main surface of the insulating substrate;
A wiring board connected to the terminal and extending on the main surface of the insulating board,
The terminal and the wiring each include a base metal layer, a main conductor layer, and a protective layer in order from the bottom on the insulating substrate, and the protective layer extends in the width direction of the wiring at a connection portion of the wiring with the terminal. A wiring board characterized in that a cut is formed in the wiring board. An insulating substrate;
Terminals formed on the main surface of the insulating substrate;
A wiring board connected to the terminal and extending on the main surface of the insulating board,
The terminal and the wiring include a base metal layer, a main conductor layer, and a protective layer in order from the bottom on the insulating substrate, and a cut is formed in the protective layer so as to divide the terminal into a plurality of regions in plan view. A wiring board characterized by being made. The wiring board according to claim 1, wherein the cut is formed so that the main conductor layer is not exposed. An electronic device comprising: the wiring board according to claim 1; and an electronic component connected to the terminal.

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