JP4189312B2 - Wiring board - Google Patents

Description

  The present invention relates to a wiring board for mounting an electronic component such as a semiconductor element or a piezoelectric vibrator, and in particular, a groove is formed in a vertical direction on a side surface of an insulating substrate having an electronic component mounting portion on an upper surface. The present invention relates to a wiring board.

  Conventionally, wiring boards on which electronic components such as semiconductor elements and piezoelectric vibrators are mounted are generally made of an electrically insulating material such as an aluminum oxide sintered body, a mullite sintered body, a glass ceramic sintered body, and the like on the upper surface. An insulating substrate having an electronic component mounting portion; a rectangular frame-like insulating frame attached to surround the mounting portion on the outer peripheral portion of the upper surface of the insulating substrate; and at least a side surface and a lower surface of the insulating substrate from the mounting portion The wiring conductor is led to one side.

  Also, a groove having a trapezoidal cross-sectional shape is usually formed so as to extend vertically from the side surface of the insulating substrate to the outer peripheral surface of the insulating frame and to be continuous between the insulating substrate and the insulating frame. A side conductor is formed on the inner surface of the groove on the side surface of the insulating substrate.

  The side conductor is electrically connected to the wiring conductor by contacting the part of the wiring conductor that is led out to the side or lower surface of the insulating substrate, and the electrode of the electronic component mounted on the mounting portion is electrically connected to the wiring conductor. Thus, the electrodes of the electronic component are led out to the outside through the wiring conductor and the side conductor.

  In other words, the electronic component is mounted on the mounting portion of the wiring board, and the electrode of the electronic component is electrically connected to the portion of the wiring conductor exposed to the mounting portion via a bonding wire, solder, etc., on the upper surface of the insulating frame. By joining a lid made of iron-nickel-cobalt alloy or the like and closing the mounting portion, the electronic component is hermetically sealed in the mounting portion to complete the electronic device, and the lower end of the side conductor is electrically connected to the external electric circuit board. By electrically connecting to the circuit via solder or the like, the electrode of the electronic component is electrically connected to an external electric circuit via the wiring conductor and the side conductor.

  The groove is also formed on the outer peripheral surface of the insulating frame body by extending the side conductor to the inner surface of the groove and electrically connecting the side conductor to the lid, etc. This is because, when protective plating such as nickel or gold is applied to the exposed surface, the plating solution is likely to enter the inside of the groove to prevent defects such as lack of plating.

  Also, when connecting the wiring board to the external electric circuit board, a bonding material such as solder is formed across the side conductor and the external electric circuit board, and the connection of the wiring board to the external electric circuit board is made stronger. can do.

  Recently, in such wiring boards for mounting electronic components, there is a strong demand for downsizing, and it has become necessary to make the external dimensions of the wiring board as close as possible to the external dimensions of the electronic components to be mounted. Yes. Therefore, the width of the insulating frame has become very narrow, for example, 0.5 mm or less. If a large groove is provided on the outer peripheral surface of such a narrow insulating frame, the width of the insulating frame becomes very narrow at the portion where the groove is formed. A sufficient width cannot be secured, it becomes difficult to firmly join the lid, and there arises a problem that the reliability of hermetic sealing is lowered.

To solve this problem, the cross section formed on the insulating frame has a trapezoidal groove whose width radius is smaller than the radius of the trapezoidal groove formed on the insulating substrate. A means is conceivable in which the groove of the insulating frame is positioned outside the groove of the insulating substrate. In this case, since the width of the insulating frame can be prevented from being reduced at the site where the groove is formed, the bonding width of the lid to the insulating frame can be ensured.
JP 1998-335822 A

  However, the radius of the groove formed in the insulating frame is made smaller than the radius of the groove formed in the insulating substrate so that the groove of the insulating frame is positioned outside the groove of the insulating substrate in plan view. In this case, although a bonding area between the lid and the insulating frame can be secured, a large step is generated between the groove on the side surface of the insulating substrate and the groove on the outer peripheral surface of the insulating frame, and the upper portion of the step. Is formed of only a relatively thin insulating frame, thermal stress when the lid is joined to the insulating frame along the portion where the lower surface of the insulating frame is in contact with the upper end of the groove of the insulating substrate, etc. The stress on the insulation frame body is likely to concentrate, and cracks, etc. are generated in the insulating frame body from the vicinity of the contact area between the upper ends of the groove of the insulating substrate, where the stress is particularly large, and the reliability of hermetic sealing is greatly reduced. Problem occurs.

  The present invention has been completed to solve the above-described problems, and its purpose is to secure a bonding area between the insulating frame and the lid and to cause mechanical damage such as cracks in the insulating frame. It is an object of the present invention to provide a small-sized wiring board that effectively prevents this problem and has excellent hermetic sealing reliability.

  The wiring board of the present invention includes a rectangular insulating substrate having an electronic component mounting portion on the upper surface, and a rectangular frame-shaped insulating frame attached to the outer peripheral portion of the upper surface of the insulating substrate so as to surround the mounting portion. And a wiring conductor led out from the mounting portion to at least one of a side surface and a lower surface of the insulating substrate, and a cross-sectional shape formed on the outer peripheral surface of the insulating frame so as to extend in the vertical direction has a trapezoidal shape. And a second groove having a trapezoidal cross-sectional shape extending in the vertical direction on the side surface of the insulating substrate and continuing to the first groove, and an inner surface of the second groove. A side conductor that is deposited and electrically connected to the wiring conductor, and the first and second grooves have the same width, and the first groove has a side face that is parallel to the insulating substrate. Is shallower than the second groove.

  According to the wiring board of the present invention, the second groove formed in the insulating substrate and the first groove formed in the insulating frame have the same width, and the first groove extends from the side surface of the insulating substrate. Since the depth is shallower than that of the second groove, there is a slight step between the second groove on the side surface of the insulating substrate and the first groove on the outer peripheral surface of the insulating frame. Since the widths of the first and second grooves are gradually reduced as they approach the both ends of the upper end of the groove where the stress is large and the stress is large, the machine of the insulating frame in the upper part of the step The strength of the insulating frame can be prevented from decreasing, and stress can be prevented from concentrating along the portion where the lower surface of the insulating frame is in contact with the upper end of the second groove of the insulating substrate. It is possible to prevent cracks and the like from occurring.

  Further, since the depth of the first groove from the side surface of the insulating substrate is shallower than the second groove, the width of the insulating frame is prevented from being narrowed at the portion where the first groove is formed, A sufficient bonding width between the insulating frame and the lid can be ensured.

  The wiring board of the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 are a top view and a side view showing an example of an embodiment of a wiring board according to the present invention. 1 and 2, 1 is an insulating substrate, 2 is an insulating frame, 3 is a wiring conductor, 4 is a first groove, 5 is a second groove, and 3a is a side conductor. A wiring substrate 9 is mainly constituted by the insulating substrate 1, the insulating frame 2, the wiring conductor 3, the side conductor 3a, the first groove 4, and the second groove 5.

  The insulating substrate 1 functions as a support for mounting and supporting electronic components such as semiconductor elements and capacitive elements, and has an electronic component mounting portion 1a on the upper surface. The insulating substrate 1 is made of, for example, a ceramic insulating material such as an aluminum oxide sintered body, a mullite sintered body, an aluminum nitride sintered body, a silicon carbide sintered body, a glass ceramic sintered body, an insulating resin, or It consists of a mixture of an insulating resin and an inorganic insulator powder such as ceramics. When the insulating substrate 1 is made of an aluminum oxide sintered body, a suitable organic binder, plasticizer, solvent, etc. are added to and mixed with raw material powders such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, etc. to make a slurry. The slurry is formed into a ceramic green sheet (raw sheet, hereinafter also referred to as a green sheet) by a doctor blade method or a calender roll method, and then the green sheet to be the insulating substrate 1 is appropriately punched and processed. Are laminated and fired at a temperature of about 1600 ° C.

  An insulating frame 2 is attached to the upper surface of the insulating substrate 1 so as to surround the mounting portion 1a. The insulating frame 2 is formed of the same electrically insulating material as that of the insulating substrate 1 and is preferably formed of the same material as the insulating substrate 1 in consideration of productivity, the strength of attachment to the insulating substrate 1, and the like. When the insulating frame 2 is made of, for example, an aluminum oxide sintered body, after forming a green sheet similar to that for manufacturing the insulating substrate 1, the frame-shaped green sheet is punched into a frame shape. The frame-like green sheet is formed and laminated on the upper surface of the green sheet to be the insulating substrate 1.

  A wiring conductor 3 is led out from the mounting portion 1 a of the insulating substrate 1 to at least one of the side surface and the lower surface of the insulating substrate 1. The wiring conductor 3 is made of a metallized layer when the insulating substrate 1 is made of ceramics such as an aluminum oxide sintered body, and is made of a metal paste when the insulating substrate 1 is made of resin, resin and inorganic insulating material powder. A plurality of wiring conductors 4 are formed from the periphery of the mounting portion 1a on which the electronic component is mounted to the side surface of the insulating substrate 1, or are formed as through conductors such as via conductors and are led out. .

  As the material of the wiring conductor 3, gold, copper, molybdenum, tungsten, manganese, platinum, palladium, rhodium, alloys thereof, and the like can be used. The metal paste obtained by addition and mixing is printed and applied in a predetermined pattern on the surface or side surface of the green sheet to be the insulating substrate 1 by a screen printing method or the like, so that it is predetermined at a predetermined position on the insulating substrate 1 after firing. A patterned wiring conductor 3 is formed.

  In the wiring board of the present invention, a first groove 4 having a trapezoidal cross section is formed on the outer peripheral surface of the insulating frame 2 so as to extend in the vertical direction, and extends in the vertical direction on the side surface of the insulating substrate 1. A second groove 5 having a trapezoidal cross-sectional shape is formed so as to be continuous with the first groove 4, and a side conductor 3 a electrically connected to the wiring conductor 3 on the inner surface of the second groove 5. Is attached.

  The first groove 4 and the second groove 5 are formed such that the lower base (longer base) of the trapezoid is located outside and the upper base (shorter base) is located inside. . In this case, the cross-sectional shape of the first groove 4 and the second groove 5 is not limited to a complete trapezoidal shape, and may be a shape close to an elliptical arc shape with a corner portion formed into an arc shape.

  The side conductor 3a is made of the same metal material as that of the wiring conductor 4. For example, a metal paste similar to that for forming the wiring conductor 3 is previously extended in the vertical direction on the side surface of the green sheet to be the insulating base 1. It is formed by printing on the inner surface of the second groove 5 provided. For example, the side conductor 3a is electrically connected to the wiring conductor 3 by contacting a portion of the wiring conductor 3 that is led out to the side surface or the lower surface of the insulating substrate 1, and the electronic component mounted on the mounting portion 1a. By electrically connecting the electrode (not shown) to the wiring conductor 3, the electrode of the electronic component is led out to the outside through the wiring conductor 3 and the side conductor 3a.

  In other words, an electronic component (not shown) is mounted on the mounting portion 1a of the wiring board 9, and the electrode of the electronic component is electrically connected to a portion of the wiring conductor 3 exposed to the mounting portion 1a via a bonding wire, solder, or the like. And a lid (not shown) is joined to the upper surface of the insulating frame 2 to close the mounting portion 1a, whereby an electronic component is hermetically sealed in the mounting portion 1a to complete the electronic device. By electrically connecting the lower end portion of 3a to an electric circuit (not shown) of an external electric circuit board via a bonding material such as solder, the electrode of the electronic component is externally connected via the wiring conductor 3 and the side conductor 3a. It is electrically connected to the electrical circuit. In this case, a bonding material such as solder is formed over the side conductor 3a and the electric circuit of the external electric circuit board, and the connection of the wiring board 9 to the external electric circuit board can be made stronger.

  In order to secure a bonding area between the side conductor 3a and a bonding material such as solder, the radius of the second groove 5 is preferably set to 300 μm or more. Further, in order to prevent the bonding material from spreading too much and form a certain meniscus in the bonding material to ensure the bonding strength, the radius of the second groove 5 is more preferably set to 300 μm to 600 μm.

  The first groove 4 is also formed on the outer peripheral surface of the insulating frame 1 for grounding by extending the side conductor 3a on the inner surface and electrically connecting the side conductor 3a to the lid. In the case where protective plating such as nickel or gold is applied to the exposed surface of the side conductor 3a, the plating solution can easily enter the first groove 4 to prevent defects such as lack of plating. Because.

  If a plating layer such as nickel or gold is applied to the exposed surface of the wiring conductor 3 or the side conductor 3a, the bonding property of the bonding wire to the wiring conductor 3 or the connection of the side conductor 3a to an external electric circuit is achieved. Solder wettability and the like can be improved.

  In the wiring board of the present invention, the first and second grooves 4 and 5 have the same width, and the depth of the first groove 4 from the side surface of the insulating substrate 2 is shallower than that of the second groove 5. . As a result, although a slight step is generated between the second groove 5 and the first groove 4, the step is smaller than the width of the insulating frame 2, and the first groove on which a large amount of stress acts. 4, the step between the first and second grooves 4 and 5 gradually decreases as the distance between the two ends increases, so that the mechanical strength of the insulating frame 2 at the upper portion of the step is prevented from being lowered. It is possible to prevent stress from being concentrated along the portion where the lower surface of the body 2 and the upper end portion of the second groove 5 are in contact with each other, and prevent the occurrence of cracks in the insulating frame 2 and hermetic sealing. The reliability can be made excellent.

  Further, since the depth of the first groove 4 from the outer peripheral surface of the insulating frame 2 is shallow, a sufficient width of the insulating frame 2 is secured even in the portion where the groove 4 is formed, and the insulating frame 2 and the lid The body can be firmly joined.

  As a result, the bonding area between the insulating frame 2 and the lid is ensured, and the insulating frame 2 is effectively prevented from being mechanically broken such as cracks. A small wiring board 9 can be provided.

  The first groove 4 and the second groove 5 are formed, for example, in a so-called multi-chip form in which a large number of wiring board regions are arranged in a matrix on a ceramic mother board. A through hole having a circular cross section is formed along the boundary of the region, and then the ceramic mother substrate is divided along the boundary of the wiring substrate region. A cross section in which the divided circular through-holes are formed on the side surface of each wiring board 9 is the trapezoidal second groove 5.

  Further, the radius and the punching position of the through hole at this time are as follows at the above boundary for the through hole to be the first groove 4 and the through hole to be the second groove 5 that are continuous up and down when the green sheets are laminated. The width is the same, and the depth in the green sheet main surface direction from the boundary of the through hole serving as the first groove 4 is set smaller than the depth of the through hole serving as the second groove.

  When the side conductor 3a is extended to the inner surface of the first groove 4, if the wiring conductor 3 is for grounding, the side conductor 3a is extended to reach the upper surface of the insulating frame 2, and the insulating frame It is preferable to form a metal layer such as a metallized layer on the upper surface of 2. In that case, the grounding of the electronic component can be more reliably performed.

  Moreover, it is preferable that the depth of the 1st groove | channel 4 is 200 micrometers or less. When the depth exceeds 200 μm, it becomes difficult to ensure a bonding width with the lid on the upper surface of the insulating frame 2, and the reliability of hermetic sealing may be deteriorated.

  Further, the first groove 4 has a shape in which at least one of the width and the depth is gradually increased from the upper end to the lower end to ensure the ease of entering the plating solution as described above and the like in the insulating frame 2. The area occupied by the upper end portion may be reduced so that the joining width of the lid body is more effectively secured and the reliability of the hermetic sealing is further increased.

  Note that the present invention is not limited to the embodiments described above, and various changes and improvements can be made without departing from the scope of the present invention. For example, the second groove 5 on the side surface of the insulating substrate 1 is provided with a convex portion or a concave portion on a part of its inner surface to ensure a larger bonding area with respect to the side conductor 3a, so You may make it make the reliability of the connection with respect to a board | substrate more favorable.

It is a top view which shows an example of embodiment of the wiring board of this invention. It is a side view which shows an example of embodiment of the wiring board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulation base | substrate 1a ... Mounting part 2 ... Insulation frame 3 ... Wiring conductor 3a ... Side conductor 4 ... 1st groove | channel 5 ... 2nd groove | channel 9 ...・ Wiring board

Claims (1)

A rectangular insulating substrate having an electronic component mounting portion on the upper surface, a rectangular frame-shaped insulating frame attached to the outer peripheral portion of the upper surface of the insulating substrate so as to surround the mounting portion, and the mounting portion A wiring conductor led out to at least one of a side surface and a lower surface of the insulating substrate; a first groove having a trapezoidal cross-sectional shape formed on the outer peripheral surface of the insulating frame so as to extend vertically; The wiring conductor is attached to the inner surface of the second groove having a trapezoidal cross-sectional shape formed so as to extend in the vertical direction on the side surface of the substrate and to be continuous with the first groove. And the first and second grooves have the same width, and the depth of the first groove from the side surface of the insulating substrate is the second conductor. A wiring board characterized in that it is shallower than the groove.

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