JP2008071869A - Wiring substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring substrate which suppresses the occurrence of breakage of a low melting point brazing material and a connecting pad by the progress of crack generated from the outer rim of a region which is not covered by an insulating film. <P>SOLUTION: The wiring substrate is constituted of a wiring conductor 2 formed in an insulating substrate 1, a connecting pad 6 provided on the lower surface of the insulating substrate 1 so as to be connected to the wiring conductor 2 and an insulating film 8 covering a region from the insulating substrate 1 around the connecting pad 6 to a region approximated to the peripheral rim of lower surface of the connecting pad 6. In this case, the connecting pad 6 is constituted of a flat plate shape connecting a pad main body 61 and a projected part 62 formed on the upper surface side so as to be opposed to the outer rim of the region not covered by the insulating film on the lower surface side of the connecting pad 61 while the projected part 62 is buried in the insulating substrate 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wiring substrate used for a semiconductor element storage package on which a semiconductor element is mounted and stored.

  A wiring substrate on which a semiconductor element is mounted includes an insulating base having a mounting portion on which the semiconductor element is mounted on the upper surface, a wiring conductor led out from the semiconductor element mounting portion of the insulating base or its periphery to the lower surface, and the lower surface of the insulating base. And a plurality of connection pads electrically connected to the wiring conductor. In addition, as will be described later, the low melting point brazing material used when joining the connection pads to the circuit wiring of the external circuit board flows out around the connection pads, and the adjacent connection pads are short-circuited or the operation of the semiconductor element is performed. In order to prevent the connection pad from being peeled off from the outer edge due to repeated thermal stress caused by the heat generated from time to time, an insulating film is coated from the lower surface of the insulating base around the connection pad to a region close to the periphery of the connection pad. (For example, refer to Patent Document 1).

  Then, the semiconductor element is bonded to the mounting portion of the insulating base with an adhesive made of glass, resin, brazing material, metal, etc., and each electrode of the semiconductor element and the wiring conductor are electrically connected via an electrical connection means such as a bonding wire. After that, the semiconductor element is hermetically sealed with a lid or a sealing resin as necessary, so that a semiconductor device is obtained.

Such a semiconductor device is mounted on the external circuit board so that the circuit wiring of the external circuit board and the connection pad on the lower surface of the insulating base are opposed to each other with a low melting point solder such as tin-lead solder sandwiched therebetween. The low melting point brazing material is heated and melted at a temperature of 150 to 350 ° C., so that it is mounted on the circuit board of the external circuit board.
JP-A-6-53648

In the above wiring board, the insulating base is formed of a ceramic material such as an aluminum oxide sintered body or a glass ceramic sintered body, and its thermal expansion coefficient is about 4 × 10 ⁻⁶ / ° C. to 12 × 10 ^−6. / ° C. On the other hand, the external circuit board is generally formed of a resin material such as glass epoxy resin, and has a thermal expansion coefficient of about 15 × 10 ⁻⁶ / ° C. to 50 × 10 ⁻⁶ / ° C., which is greatly different. To do.

  Therefore, when the heat generated during the operation of the semiconductor element repeatedly acts on the wiring board and the external circuit board, a large thermal stress is repeatedly generated in the horizontal direction due to the difference in thermal expansion between the two, and the repetition of the thermal stress reduces the connection pad and the external circuit board. Thermal stress concentrates on the edge near the interface with the melting point brazing material (the outer edge of the non-insulating region), and cracks form from this part. The semiconductor device and the external circuit board are disconnected from each other in a short period of time. In particular, when lead-free solder such as tin-silver-copper is used instead of conventional tin-lead solder as the low melting point brazing material, the bonding strength to the connection pad due to the influence of embrittlement due to thermal load, etc. Is likely to be low, and the occurrence of breakage becomes more prominent. Note that a crack occurs in the connection pad from the outer edge of the insulating film non-covering region because the insulating film covering region of the connection pad is thinner than the insulating film non-covering region due to pressurization during insulating film coating. This is because stress tends to concentrate on the outer edge of the uncovered area.

  The present invention has been devised in view of the above problems, and a wiring board that suppresses the occurrence of breakage in a low melting point brazing material and a connection pad due to the development of cracks generated from the outer edge of an insulating film non-covering region. The purpose is to provide.

  In the present invention, a wiring conductor is formed inside an insulating base, and a connection pad connected to the wiring conductor is provided on the lower surface of the insulating base, and the lower surface of the connection pad is formed from the insulating base around the connection pad. A wiring board in which an insulating film is coated over a region close to a peripheral edge, and the connection pad is opposed to a flat connection pad main body and an outer edge of an insulating film non-covering region on a lower surface side of the connection pad main body. The protrusion is formed on the upper surface side, and the protrusion is embedded in the insulating base.

  According to the present invention, a wiring conductor is formed inside the insulating base, and a connection pad connected to the wiring conductor is provided on the bottom surface of the insulating base, and the bottom surface of the connection pad is formed from the insulating base around the connection pad. A wiring board in which an insulating film is coated over a region close to the periphery of the substrate, wherein the connection pad is opposed to the outer edge of the flat connection pad main body and the insulating film non-covering region on the lower surface side of the connection pad main body And the upper surface of the connection pad main body and the lower surface of the insulating base are bonded to each other inside the protruding portion via a bonding layer. To do.

  According to the wiring board of the present invention, the protrusion formed on the upper surface side facing the outer edge of the insulating film non-covering region on the lower surface side of the connection pad main body is softer and more easily deformed than the insulating substrate, so that stress It exhibits an effect like a cushion that absorbs heat, and cracks that develop from the end of the joint surface between the low melting point brazing material and the connection pad (outer edge of the insulating film non-covering region) where thermal stress is concentrated develops, resulting in a low melting point It is possible to suppress breakage of the brazing material and the connection pad.

An embodiment of the present invention will be described.
1 is a schematic cross-sectional view of a package for housing a semiconductor element using the wiring board of the present invention, FIG. 2 is an enlarged cross-sectional view of a connection pad as an embodiment of the wiring board of the present invention, and FIG. 3 is a connection shown in FIG. It is explanatory drawing of the state which looked at the pad from the lower side.

  In the present invention, a wiring conductor 2 is formed inside an insulating base 1, a connection pad 6 connected to the wiring conductor 2 is provided on the lower surface of the insulating base 1, and the connection pad 6 extends from the insulating base 1 around the connection pad 6. The wiring board 4 is coated with an insulating film 8 over a region close to the periphery of the lower surface of the substrate. The connection pad 6 includes a flat-shaped connection pad main body 61 and an insulating film non-covering region on the lower surface side of the connection pad main body 61. It is comprised from the protrusion 62 formed in the upper surface side facing the outer edge of this, and the protrusion 62 is embed | buried under the insulating base | substrate 1. It is characterized by the above-mentioned. The wiring board 4 is employed as a part of a package for housing a semiconductor element, for example.

  The insulating substrate 1 is made of, for example, an electrically insulating material such as an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body, a silicon carbide sintered body, or a glass ceramic sintered body. The upper surface of the insulating substrate 1 has a storage portion 1a on which the semiconductor element 3 is mounted and stored, and the semiconductor element 3 is bonded and fixed to the bottom surface of the storage portion 1a via an adhesive such as glass, resin, brazing material, or metal. The

  When the insulating substrate 1 is made of an aluminum oxide sintered body, first, a suitable organic binder and solvent are added to and mixed with raw material powders such as aluminum oxide, silicon oxide, calcium oxide, and magnesium oxide to produce a slurry ceramic slurry. . Then, a sheet-shaped ceramic green sheet (ceramic green sheet) is obtained from the ceramic slurry by employing a conventionally known sheet molding technique such as a doctor blade method or a lip coater method. Thereafter, the ceramic green sheet is punched and printed, and a plurality of these are laminated, and then cut into an appropriate shape by cutting. Finally, the laminated ceramic green sheets are produced by firing at a temperature of about 1600 ° C. in a reducing atmosphere.

  A large number of wiring conductors 2 are formed on the insulating base 1 from the periphery of the storage portion 1a to the lower surface, and each electrode of the semiconductor element 3 is bonded to the wiring conductor 2 exposed at the peripheral portion of the storage portion 1a. It is electrically connected via. In addition, a plurality of connection pads 6 that are electrically connected to the wiring conductor 2 are formed in a portion led out to the lower surface of the insulating base 1, and serve as external terminals for mounting the wiring board 4 on the external circuit board. I'm in charge. At the time of mounting, it is joined to the circuit wiring of the external circuit board through the low melting point brazing material, and thereby the electrode of the semiconductor element 3 is electrically connected to the circuit wiring of the external circuit board. The diameter of the connection pad 6 is about 300 to 1000 μm, although it depends on the size of the insulating substrate 1.

  The wiring conductor 2 and the connection pad 6 are preliminarily screen-printed on a ceramic green sheet serving as the insulating base 1 by using a metal paste obtained by adding an appropriate organic binder or solvent to a refractory metal powder such as tungsten, molybdenum or manganese. It is formed by printing and applying a predetermined pattern by the method.

  Further, as shown in FIG. 2, an insulating film 8 made of ceramic, glass, resin, or the like is coated from the lower surface of the insulating base 1 around the connection pad 6 to a region close to the periphery of the lower surface of the connection pad 6. The insulating film 8 prevents the low melting point brazing material from flowing out around the connection pads and short-circuits the adjacent connection pads, and is connected by thermal stress repeated by heat generated during operation of the semiconductor element. The pad 6 is provided to prevent the pad 6 from peeling from the outer edge. Therefore, in order to exhibit such an effect, the region where the insulating film 8 covers the connection pad 6 is a region close to the periphery of the lower surface of the connection pad 6, in other words, from the periphery of the lower surface of the connection pad 6 to the inside. This is a region up to a part (about 50 to 300 μm) separated by a predetermined distance.

  The connection pad 6 is composed of a flat connection pad main body 61 and a protrusion 62 formed on the upper surface side facing the outer edge of the non-covering region of the insulating film 8 on the lower surface side of the connection pad main body 61. . Here, the region where the insulating film 8 of the connection pad body 61 is covered by the formation pressure of the insulating film 8 is thin, and the outer edge of the non-insulating region of the connection pad body 61 is easily broken by stress concentration. ing. Therefore, the protrusion 62 is provided opposite to the outer edge of the insulating film 8 non-covering region so that the thickness of the protruding portion 62 is softer and easier to deform than the insulating base, and provides cushioning for absorbing stress. In addition, it is possible to compensate for the decrease in strength due to the reduction in thickness due to the formation of the insulating film 8 and to suppress the progress of breakage due to thermal stress. As shown in FIG. 3, when the connection pad main body 61 is circular in plan view, the non-covering region of the insulating film 8 is also circular, and the protrusion 62 is formed in an annular shape (ring shape). Has been. FIG. 3 shows a state in which the connection pad 6 is viewed from the lower surface side, and shows a circular connection pad main body 61 and an annular (ring-shaped) ridge portion 62 whose inner edge and outer edge are represented by dotted lines. ing. Here, the insulating film 8 is removed for the description of the connection pad 6, and the position (inner edge and outer edge) of the insulating film 8 is virtually represented by a one-dot chain line.

  The protrusion 62 only needs to be formed on the upper surface side so as to face the outer edge of the insulating film 8 non-covering region on the lower surface side of the connection pad main body 61, and the shape thereof is not particularly limited. For example, when the connection pad main body 61 is a square and the non-covering region of the insulating film 8 is also a square, one that is shaped into a square by four linear protrusions may be employed. In addition, it is preferable that the protrusion 62 is formed so as not to be interrupted on the upper surface side so as to face the outer edge of the non-covering region of the insulating film 8, but may be interrupted at several places. The protrusion 62 is formed on the upper surface side so as to be opposed to the outer edge of the insulating film 8 non-covering region on the lower surface side of the connection pad main body 61 when the inner edge and the outer edge of the protrusion 62 are viewed from above and below. It means that the outer edge of the insulating film 8 non-covering region is located between them, and it is preferable that the outer edge of the insulating film 8 non-covering region is located approximately between the inner edge and the outer edge of the protrusion 62.

  The protrusion 62 can be formed by printing and applying a metal paste by a screen printing method, and can be formed so as to be embedded in the insulating substrate 1 by a pressure treatment. Here, the thickness of the protrusion 62 is preferably in the range of 5 to 30 μm. When formed with this thickness, it is easy to control the thickness during formation by a screen printing method or the like, and it is possible to prevent an increase in internal stress during pressurization and to maintain the flatness of the connection pad 6 (connection pad body 61). . Moreover, it is preferable that the width | variety of the protrusion part 62 shall be the range of about 100-300 micrometers. By setting it as this range, the area of the thick part of the connection pad 6 can be reduced as much as possible, and generation | occurrence | production of curvature can be suppressed. The outer edge of the protrusion 62 may coincide with the periphery of the connection pad 6, but the outer edge of the protrusion 62 is connected to the effect of the formation of the insulating film 8. It is preferable to be inside a predetermined distance (about 25 to 200 μm) from the periphery.

  In addition, it is preferable that the thickness of the connection pad main body 61 is 10-30 micrometers from a viewpoint of conductor strength and flatness.

  The protrusion 62 can also be formed by press-forming a recess at a position where each connection pad is provided, and printing and applying the recess using a screen printing method or the like. Further, it can be formed by embedding a metal fitting or the like having a desired shape in a position where each connection pad is provided by pressure treatment.

  Thus, the protrusion 62 is provided to face the outer edge of the non-covering region of the insulating film 8, so that the end portion (insulating film) of the bonding surface between the low melting point brazing material and the connection pad main body 61 where thermal stress is most concentrated. It is possible to suppress the cracks generated from the outer edge of the non-covered region 8) from progressing and breakage of the low melting point brazing material and the connection pad main body 61. Specifically, the heat generated during the operation of the semiconductor element mounted on the wiring board repeatedly acts on the insulating base of the wiring board and the external circuit board, and is greatly increased in the horizontal direction due to the difference in thermal expansion coefficient between the two. Even if the thermal stress is repeatedly generated, the protrusion 62 works like a cushion to relieve the stress and suppress the breakage of the low melting point brazing material and the connection pad main body 61. Therefore, the connection between the connection pad 6 and the circuit wiring of the external circuit board can be maintained for a long time.

Next, another embodiment of the present invention will be described with reference to FIG.
In the wiring board shown in FIG. 4, the upper surface of the connection pad main body 61 and the lower surface of the insulating base 1 are bonded via the bonding layer 9 inside the protrusion 62. The bonding layer 9 is made of an insulating material whose main component or subcomponent is the material for forming the insulating base 1, or a conductor material having a composition different from that of the material for forming the connection pad 6. Other configurations are the same as those shown in FIG.

  In this embodiment, the protrusion 62 is formed by printing and applying a metal paste by a screen printing method and pressurizing, and the bonding layer 9 is an insulating material or connection pad whose main component or subcomponent is a material for forming an insulating substrate. A conductive material having a different composition can be formed by printing and applying pressure to the inside of the protrusion 62 so as to be at the same height as the protrusion 62 and pressurizing. In FIG. 4, the insulating base 1 is shown as having a recess, but this is embedded by the pressurizing process when forming the protrusion 62 and the bonding layer 9. This formation is preferable in terms of reduction in height and manufacturing.

  The protrusion 62 and the bonding layer 9 are preferably formed with a thickness of 5 to 30 μm. If it is this range, the thickness control at the time of formation by a screen printing method etc. will become easy, the increase in the internal stress at the time of pressurization, etc. will be prevented, and the flatness of the connection pad 6 surface can be maintained. Moreover, it is preferable that the thickness of the connection pad main body 61 is 10-30 micrometers from a viewpoint of conductor intensity | strength and flatness.

  When an insulating material whose main component or subcomponent is the forming material of the insulating substrate 1 is used as the bonding layer 9, the surface state becomes rough by forming the bonding layer 9 in this portion by screen printing or the like, and the anchor effect There is an effect of improving the bonding strength rather than directly bonding to the insulating substrate 1 by the (wedge effect). Further, in the vicinity of the connection pad 6 of the insulating base 1, the conductor of the connection pad 6 is easily diffused into the insulating base and obstructs the sinterability of the insulating base 1. By filling the insulating material with an increased amount of binder and improved sinterability, the bonding strength (conductor adhesive strength) of the connection pad 6 can be improved.

  Further, when a conductive material having a composition different from that of the connection pad 6 is used as the bonding layer 9, a conductor having a low conductor adhesion strength to ceramic, such as copper, silver, or gold, is generally used for the connection pad 6. Is particularly effective. As a conductive material having a composition different from that of the connection pad 6, for example, by using a conductive composite material of metal and ceramic, the difference in thermal expansion between the connection pad 6 and the insulating substrate 1 can be gradually reduced, and bonding can be performed. The force (conductor adhesive strength) can be improved.

  Although not shown in FIGS. 2 and 4, since it is preferable to join the connection pad main body 61 and the wiring conductor 2 (via-hole conductor) almost at the center of the connection pad 6 (connection pad main body 61), FIG. As shown in FIG. 2, a projection 63 for joining to the wiring conductor 2 (via hole conductor) is usually formed.

  In addition, the wiring conductor 2 and the connection pad 6, and the plating layer which consists of the metal excellent in the wettability and bonding property with respect to low melting-point brazing materials, such as nickel, copper, palladium, silver, gold | metal | money, for example in the exposed area | region Can be effectively prevented from oxidative corrosion of the wiring conductor 2 and the connection pad 6 by sequentially depositing a plating layer of about 1 to 10 μm and a thickness of about 0.05 to 5 μm. The low melting point brazing material and the bonding wire 5 can be firmly bonded and bonded. Therefore, the wiring conductor 2 and the connection pad 6 are preferably formed by depositing a plating layer of nickel, copper, palladium, silver, gold or the like on the surface thereof with a thickness of about 1 to 15 μm.

  Thus, according to the wiring board of the present invention, the semiconductor element 3 is bonded and fixed to the bottom surface of the housing portion 1a of the insulating base 1 via an adhesive such as glass, resin, brazing material, and the electrodes of the semiconductor element 3 are wired. Electrically connected to the conductor 2 via a bonding wire 5, and then a lid 7 made of metal or ceramics is joined to the upper surface of the insulating substrate 1 via a sealing material such as glass, resin, metal or brazing material. Then, the semiconductor element storage package is completed by airtightly storing the semiconductor element 3 in the container composed of the insulating base 1 and the lid 7.

  The wiring board of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the wiring board of the present invention can be changed. Although an example in which the substrate is used for a package for a semiconductor storage element has been described, this may be used for a hybrid integrated circuit substrate or the like.

  In order to evaluate the mounting reliability of the embodiment of the present invention, an evaluation board was produced. This evaluation board is formed by laminating an insulating layer having a width of 47.5 mm × 47.5 mm and a thickness of 2.0 mm, applying a daisy pattern with a line width of 0.1 mm to the inner layer, and bonding a 0.12 mm via, thereby forming a surface layer The connection pad is joined.

Below, it shows about the manufacturing method of an evaluation board | substrate.
First, a green sheet constituting an insulating substrate was produced. A glass powder, a quartz powder, and a CaZrO ₃ powder containing SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, and ZnO are prepared. These are 57% by mass of glass, 40% by mass of quartz powder, and CaZrO _2. 3% by mass of the powder was weighed and an organic binder and a plasticizer were added to prepare a glass-ceramic composition slurry.

  This glass ceramic composition slurry was molded by a doctor blade method to produce a green sheet having a thickness of 200 mmSQ and a thickness of 125 μm. Here, a through hole having a diameter of 120 μm was formed in the green sheet by punching.

  A copper conductor was used as the wiring conductor, and a copper paste was prepared by adding an acrylic resin as a copper powder and an organic binder and a plasticizer as a solvent, and kneading to obtain a copper conductor. The via paste and pattern paste produced by this method were filled into a green sheet by screen printing and printed.

  First, the connection pad 6 is formed by using a screen printing method to form an annular ridge 62 along a position on the upper surface side that faces the outer edge of the insulating film non-covering region on the lower surface side of the connection pad body. Then, after being embedded in the insulating substrate 1 by pressure treatment, the connection pad main body 61 was formed by a screen printing method. Both had a printing thickness of about 10 to 20 μm.

Next, glass powder, quartz powder, and CaZrO ₃ powder constituting the insulating substrate 1 are prepared for the insulating film 8, and these are weighed 57% by mass of glass, 40% by mass of quartz powder, and 3% by mass of CaZrO ₂ powder. Then, an organic binder and a plasticizer were added and kneaded to prepare a glass ceramic coating paste. The insulating film paste produced by this method was printed and applied by screen printing.

  The insulating film 8 was applied so that the inner peripheral edge thereof was positioned between the outer peripheral edge and the inner peripheral edge of the protrusion 62 in a plan view, and the printing thickness was about 10 to 20 μm.

  Specifically, the connection pad 6 is first formed to have a circular shape with a diameter of 800 μm, and a circular insulating film non-covering region with a diameter of 600 μm is formed by covering 100 μm from the outer periphery with an insulating film in a ring shape. The The protrusion 62 is a ring-shaped protrusion as shown in FIGS. 2 and 3, and has a conductor width of 150 μm, an inner edge dimension of 400 μm in diameter, and an outer edge dimension of 700 μm in diameter.

  Using the green sheet on which the wiring pattern thus obtained was formed, a laminate was produced. The evaluation substrate was formed by stacking 20 layers of green sheets on which via conductors and wiring patterns were arranged. At this time, an adhesive was uniformly applied between the green sheets, and pressure lamination was performed under the conditions of 40 ° C. and 20 MPa.

  Subsequently, these laminates are placed on a base plate made of an aluminum oxide sintered body and subjected to heat treatment at 750 ° C. in a nitrogen atmosphere to decompose and remove organic components such as an organic binder, and then nitrogen. Firing was performed in an atmosphere at 900 ° C. for 1 hour.

  The evaluation substrate after firing was formed by sequentially depositing nickel in a thickness of about 3 to 5 μm and gold in a thickness of about 0.1 to 0.5 μm as a plating layer made of a metal having excellent wettability to the low melting point brazing material. .

  The evaluation board thus obtained was measured for ball pull strength when mounted on a solder ball, and joined to a glass epoxy resin printed board via a solder ball, and then subjected to a temperature cycle test (0 to 100 ° C., air To evaluate the mounting reliability. In addition, in this evaluation, the thing which does not provide the protrusion part 62 (the shape without a protrusion part, comparative example) was also produced simultaneously, and comparative evaluation was performed.

First, the ball pull strength when solder balls were mounted was measured. Solder ball diameter is φ0.76mm eutectic solder, connection pad diameter is φ0.6mm, bond tester 4000 is used as a measuring machine, chuck jig is JAW0.80DIA, chuck pressure is 1.5bar, holding time is 2s, speed is 83μm / Measured in s. Further, the fracture mode of the sample for measuring the ball pull strength was confirmed using a 10 × microscope. The results are shown in Table 1.

The ball pull strength is a shape in which the protrusion 62 is provided on the upper surface of the connection pad main body 61 of the present invention (an embodiment of the present invention), an average value of 7.0 kg / mm ² , and a shape without the protrusion 62 (the protrusion). No part, comparative example), the average value was 5.6 kg / mm ² , confirming an increase in strength of about 25% compared to the conventional case. Further, when compared with the minimum value of the ball pull strength, the minimum value is 6.1 kg / mm ² with the protrusion on the upper surface (invention example), and the minimum value is 4.1 kg / without the protrusion (comparative example). It was mm ² , and an increase in strength of about 50% compared to the conventional value was confirmed, and a high increase in strength was confirmed compared to the above average value.

  When the destruction mode is compared, the one with the protrusions on the upper surface (invention example) has a solder destruction (neck breakage) mode of 100%, but without the protrusions (comparative example), Solder breakage (neck breakage) mode was 45%, breakage between the solder and the connection pad was 30%, and breakage at the interface between the connection pad and the insulating base was 25%. In general, the ball pull strength breaks down starting from the weakest part, and the break between the solder and the connection pad and between the connection pad and the insulating substrate is positioned as a weak mode. From this, by providing the protrusion 62 on the connection pad 6, a crack is generated from the outer edge of the insulating film non-covering region, which is the starting point of the breakdown, and it is possible to suppress the progress of the crack and the progress of the breakdown. I confirmed that it led to the rise.

  Subsequently, the wiring board was joined to a printed board of glass epoxy resin via solder balls, and a temperature cycle test was conducted to confirm the mounting reliability.

  The temperature cycle conditions were evaluated in a gas phase atmosphere of 0 to 100 ° C. under the condition of raising and lowering 0 ° C. to 100 ° C. at intervals of 20 minutes. As the solder balls, lead-free solder balls having a diameter of 0.6 mm (Sn / Ag / Cu = 96.5 / 3.0 / 0.5 [wt%]) were used. The connection pad diameter was 0.6 mm, the pad pitch was 1 mm, and the number of pads was 2116.

As confirmation items at this time, it was taken out every 1000 cycles after 1000 cycles, and the presence or absence of electrical connection, the presence or absence of cracks due to cross-sectional polishing, and the progress state were confirmed by resistance measurement. For electrical connection evaluation, a judgment of NG (x) was made when one package failed in 20 packages as a judgment criterion. Regarding the crack evaluation, as a judgment criterion, OK (◯) if the crack has not progressed more than half of the connection pad by cross-sectional polishing, △ if it has progressed more than half, and NG (× ) Was made. The results are shown in Table 2.

  In the electrical connection evaluation, electrical connection was observed up to 4500 cycles with protrusions on the upper surface of the connection pad body (Example of the present invention), while electrical connections were observed with 3500 cycles without protrusions (Comparative Example). The connection was NG, and a mounting reliability of about 30% was confirmed as compared with no protrusion (comparative example).

  In addition, when comparing the progress of cracks, with the protrusions (invention example), the crack progresses to about 4500 cycles, although the progress of cracks of about half of the connection pad is seen in 3500 cycles or more, No breakage was seen, but without the conventional ridge (comparative example), the crack started to develop about half of the connection pad from 2500 cycles, and the crack was completely removed after 3500 cycles. The ones that progressed and broke were confirmed.

  For this reason, by providing the protrusion 62 on the upper surface (insulating base side) of the connection pad 6, it is possible to suppress the progress of the breakage due to the development of a crack from the outer edge of the insulating film non-covering region that is the starting point of the breakage. It was confirmed.

It is sectional drawing of the package for semiconductor element accommodation containing the wiring board of this invention. It is an expanded sectional view of the connection pad as one embodiment of the present invention. It is explanatory drawing of the state which looked at the connection pad shown in FIG. 2 from the lower side. It is an expanded sectional view of the connection pad as other embodiments of the present invention. It is explanatory drawing of the connection pad shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulation base | substrate 1a ... Storage part 2 ... Wiring conductor 3 ... Semiconductor element 4 ... Wiring board 5 ... Bonding wire 6 ... Connection pad 61- ··· Connection pad body 62 ··· Projection 63 ··· Protrusion 7 ··· Lid 8 ··· Insulating film 9 ··· Bonding layer

Claims (2)

A wiring conductor is formed inside the insulating base, and a connection pad connected to the wiring conductor is provided on the lower surface of the insulating base, and is adjacent to the periphery of the lower surface of the connection pad from the insulating base around the connection pad. A wiring board formed by covering an area with an insulating film,
The connection pad is composed of a flat connection pad main body and a ridge formed on the upper surface side opposite to the outer edge of the insulating film non-covering region on the lower surface side of the connection pad main body. Is embedded in the insulating substrate. A wiring conductor is formed inside the insulating base, and a connection pad connected to the wiring conductor is provided on the lower surface of the insulating base, and is adjacent to the periphery of the lower surface of the connection pad from the insulating base around the connection pad. A wiring board formed by covering an area with an insulating film,
The connection pad includes a plate-shaped connection pad main body, and a protrusion formed on the upper surface side opposite to the outer edge of the insulating film non-covering region on the lower surface side of the connection pad main body. The wiring board is characterized in that the upper surface of the insulating substrate and the lower surface of the insulating base are bonded to each other inside the protruding portion via a bonding layer.

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