JP2016046458A - Chip resistor and packaging structure therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire bonding connection type chip resistor which improves heat dissipation and surge resistance, and a packaging structure therefor.SOLUTION: A chip resistor 1 includes: an insulation substrate 2 in a rectangular parallelepiped shape; a pair of front-side electrodes 3 and 4 which are formed along sides 2a and 2b opposing each other on a front face of the insulation substrate 2; and a resistive element 5 which is formed to be connected to the front-side electrodes 3 and 4. A planar shape of the pair of front-side electrodes 3 and 4 is formed in a trapezoidal shape that occupies one side (2a or 2b) of the insulation substrate 2, and inclined side parts 3a and 4a of the front-side electrodes 3 and 4 are disposed oppositely in parallel with each other while interposing the resistive element 5 therebetween. In a portion where an interval between the sides 2a and 2b of the insulation substrate 2 and the inclined side parts 3a and 4a becomes substantially maximum in the front-side electrodes 3 and 4, two parts which are positioned on a diagonal on the front face of the insulation substrate 2 are defined as connection parts C for a bonding wire, respectively.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wire bonding connection type chip resistor excellent in surge resistance and a mounting structure in which such a chip resistor is mounted on a circuit board.

  Conventionally, a chip resistor having a structure as shown in FIG. 8 has been proposed as a chip resistor having excellent surge resistance (see, for example, Patent Document 1). In the figure, reference numeral 100 denotes a rectangular parallelepiped insulating substrate, and surface electrodes 101 are respectively formed at two corners on the diagonal line on the surface of the insulating substrate 100. These surface electrodes 101 are formed in a triangular shape in plan view with the corners of the insulating substrate 100 as vertices, and the inclined side portions 101a of the two surface electrodes 101 forming the bases of the triangles face each other in parallel. In addition, a resistor 102 having a rectangular shape in plan view is formed on the surface of the insulating substrate 100, and two corners facing each other of the resistor 102 are connected to the surface electrode 101.

  In the chip resistor configured as described above, the inclined side portions 101a of the pair of front electrodes 101 are arranged to face each other in parallel with the resistor 102 interposed therebetween, and the resistor exists in the region sandwiched between the inclined side portions 101a. As for 102, since current flows in a direction perpendicular to the inclined side portion 101a in any part, current concentration on a specific part of the front electrode 101 can be reduced. Further, the resistor 102 is also formed in the remaining two corner side regions where the surface electrode 101 does not exist on the surface of the insulating substrate 100, that is, the region outside the portion sandwiched between the two inclined side portions 101a. In this case, the resistor 102 can have a large area and is a chip resistor having excellent surge resistance.

Japanese Patent No. 4594117

  In the above-described chip resistor according to the conventional example, the inclined side portions 101a of the both surface electrodes 101 facing each other with the resistor 102 interposed therebetween are formed in a straight line having no corners, and the distance between the electrodes of both surface electrodes 101 is Since it becomes constant over the entire area along the inclined side portion 101a, it is possible to reduce to some extent the deterioration of load characteristics that current concentrates on a portion where the distance between the electrodes is short and the temperature of the portion increases.

  However, as shown in FIG. 9, in addition to the current flowing in the direction orthogonal to the inclined side portion 101a (see arrow A) in the resistor 102 sandwiched between both surface electrodes 101, the resistor 102 formed outside thereof There is a current (see arrow B) that wraps around the front electrode 101, and the latter current B is an edge portion (reference symbol E) that is the intersection of the inclined side portion 101a of the front electrode 101 and the outer side of the resistor 102. 4), the temperature of the resistor 102 located in the vicinity of the edge portion E rises due to load concentration. In particular, if the area of the resistor 102 is increased in order to improve surge resistance, the area of the surface electrode 101 decreases in inverse proportion to this, so that the temperature rise in the vicinity of the edge portion E increases and the load characteristics are increased. In the worst case, the chip resistor may be destroyed by heat generation.

  The present invention has been made in view of such a state of the art, and its first object is to provide a wire bonding connection type chip resistor excellent in heat dissipation and surge resistance, A second object is to provide such a chip resistor mounting structure.

  In order to achieve the first object, the present invention provides a rectangular parallelepiped insulating substrate, a pair of surface electrodes formed along opposite sides on the surface of the insulating substrate, and both the surface electrodes. In a chip resistor comprising a resistor formed to be connected and the pair of front electrodes being wire bonding electrodes, the pair of front electrodes are inclined with respect to the sides of the insulating substrate, respectively. Inclined sides extending to each other, and the two inclined sides are arranged opposite to each other in parallel through the resistor, and the distance between the side of the insulating substrate and the inclined sides of the surface electrode The portion located on the diagonal line on the surface of the insulating substrate is the bonding wire connecting portion.

  In the chip resistor configured as described above, the planar shape of the pair of front electrodes is formed in a trapezoidal shape (or a right triangle) that occupies one side of the insulating substrate, and the inclined sides of the front electrodes are arranged between each other. Since they are arranged opposite to each other in parallel via resistors, there is only one portion where current concentrates due to current wrapping for each surface electrode, and the area of the resistor is increased to improve surge resistance. Thus, it is possible to suppress the deterioration of the load characteristics due to the temperature rise. The temperature rise due to current concentration is the portion of the surface electrode where the distance between the side of the insulating substrate and the inclined side is the largest, and this portion is used as a bonding wire connecting portion. By mounting on the circuit board and wire bonding connection, the elevated temperature is dissipated to the circuit board side via the bonding wire, realizing a wire bonding connection type chip resistor with excellent heat dissipation and surge resistance Can do.

  In the above configuration, the shape of the resistor is not particularly limited as long as the resistor is connected to the surface electrode with the connection portion exposed, but the planar shape of the resistor is a parallelogram, If the opposite side of the resistor is connected to the inclined side portion of the surface electrode with substantially the same width, the resistor can be printed easily and with high accuracy.

  In the above configuration, if a heat dissipation electrode is formed on almost the entire back surface of the insulating substrate, when the chip resistor is mounted on the circuit board and wire-bonded, the temperature rise of the resistor and the surface electrode is bonded. Not only is the heat radiated to the circuit board side via the wire, but the heat transmitted through the inside of the insulating substrate is also radiated from the heat radiation electrode to the circuit board side, so the heat dissipation can be improved more effectively.

  In order to achieve the second object, according to the present invention, a chip resistor includes a rectangular parallelepiped-shaped insulating substrate and a pair of front electrodes formed along opposite sides of the surface of the insulating substrate. And a resistor formed so as to be connected to both surface electrodes. The chip resistor is mounted on the circuit board, and the wiring pattern provided on the circuit board and the chip resistor are provided. In a chip resistor mounting structure in which the surface electrode of the device is connected via a bonding wire, a pair of the surface electrodes is formed with inclined sides extending in an inclined direction with respect to the side of the insulating substrate. In addition, the two inclined side portions are arranged opposite to each other in parallel through the resistor, and the insulating substrate has a maximum interval between the side of the insulating substrate and the inclined side portion of the surface electrode. Table The site located diagonally in the connecting portion of the bonding wire.

  In the mounting structure configured as described above, the surface electrodes are formed along two opposite sides of the insulating substrate provided in the chip resistor, and the planar shape of these surface electrodes is one of the insulating substrates. The trapezoidal (or right triangle) shape that occupies the sides, and the inclined sides of both surface electrodes are arranged opposite to each other in parallel through resistors, so that the current concentrated portions by the current wraparound Only one surface electrode is provided, and the area of the resistor is increased to improve the surge resistance, and the deterioration of the load characteristics due to the temperature rise can be suppressed. The temperature rises due to the current concentration at the part of the surface electrode where the distance between the side of the insulating substrate and the inclined side is the largest, and the chip resistor is attached to the circuit board with this part as the connecting part of the bonding wire. Since it is mounted, the rising temperature generated in the chip resistor is radiated to the circuit board side through the bonding wire, and the surge resistance and heat dissipation of the chip resistor can be improved.

  In this case, a heat radiation electrode is formed on almost the entire back surface of the insulating substrate, and a connection land portion having an outer shape larger than the heat radiation electrode is formed on the wiring pattern, and the heat radiation electrode is soldered to the connection land portion. When the chip resistor is mounted on the circuit board in this state, the temperature rise of the resistor and the surface electrode is not only radiated to the circuit board side via the bonding wire, but also the heat transmitted inside the insulating board Since heat is radiated also from the heat radiation electrode to the circuit board side, the heat dissipation can be improved more effectively.

  According to the present invention, it is possible to provide a wire bonding connection type chip resistor excellent in heat dissipation and surge resistance.

It is a top view of the chip resistor concerning the example of an embodiment of the present invention. It is sectional drawing which follows the II-II line of FIG. It is sectional drawing which follows the III-III line of FIG. It is sectional drawing which follows the IV-IV line of FIG. It is explanatory drawing of the surface electrode and resistor which are provided in this chip resistor. It is sectional drawing which shows the mounting structure which mounted this chip resistor on a circuit board. It is explanatory drawing which shows the manufacturing process of this chip resistor. It is a top view of the chip resistor concerning a conventional example. It is explanatory drawing which shows the distribution state of the electric current in this chip resistor.

  DESCRIPTION OF EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 4, a chip resistor 1 according to an embodiment of the present invention includes a rectangular parallelepiped insulating substrate 2 and the insulating substrate 2. A pair of surface electrodes 3, 4 formed along opposite sides 2a, 2b on the surface, a resistor 5 formed so as to be connected to both surface electrodes 3, 4, and both surface electrodes 3 , 4 and the protective coating 6 formed so as to cover the resistor 5, and the back electrode 7 formed almost entirely on the back surface of the insulating substrate 2.

  The insulating substrate 2 is made of ceramic (alumina 96 or alumina 99) or the like, and this insulating substrate 2 is obtained by dividing a large aggregate substrate along vertical and horizontal dividing grooves and taking a large number.

  The pair of front electrodes 3 and 4 is obtained by screen-printing Ag (or Ag / Pd) paste, dried and fired, and both front electrodes 3 and 4 correspond to the side edges 2a and 2b of the corresponding insulating substrate 2. And inclined side portions 3a and 4a extending in the inclined direction. The inclined side portions 3 a and 4 a face each other in parallel, and both the surface electrodes 3 and 4 have a trapezoidal shape that is point-symmetric with respect to the center of the insulating substrate 2.

  The resistor 5 is a resistor paste such as ruthenium oxide screen-printed, dried and fired. This resistor 5 is formed in a parallelogram shape in which two pairs of opposite sides are parallel to each other, and one pair of opposite sides located in the left-right direction has a substantially constant width with the inclined sides 3a and 4a of the surface electrodes 3 and 4, respectively. Are overlapping.

  Here, as shown in FIG. 5, of the resistor 5 sandwiched between the inclined sides 3a and 4a of the surface electrodes 3 and 4, two straight lines L and 2 orthogonal to the inclined sides 3a and 4a are provided. A rectangular region S1 (hatched portion) surrounded by the two inclined sides 3a and 4a is a portion where the distance between the electrodes is constant and there is no corner where current is concentrated. Triangular regions S2 and S3 that are vertically adjacent to each other are portions where current flows toward the surface electrodes 3 and 4 located at the apexes of the triangle. As a result, when the left surface electrode 3 is viewed, the intersection of one straight line L and the inclined side portion 3a becomes the edge portion E, and when the right front electrode 4 is viewed, the other straight line L and the inclined side portion 4a. The point of intersection with the edge part E becomes an edge part E, and the vicinity of the edge part E becomes a part where the temperature rises with load concentration.

  The protective coat 6 is obtained by screen-printing and baking a glass paste, but other than that, an epoxy-based resin paste may be screen-printed and heat-cured. The protective coat 6 is formed so as to cover the entire resistor 5, and the resistor 5 is protected from the external environment by the protective coat 6. Further, the protective coat 6 is formed so as to cover both the front electrodes 3 and 4 except for the vicinity of the edge portion E described above, and a portion of the front electrodes 3 and 4 that is not covered by the protective coat 6 will be described later. This is a bonding wire connection C. These connecting portions C are portions where the distance between the side edges 2a, 2b of the insulating substrate 2 and the inclined side portions 3a, 4a is substantially maximized (rectangular white portions shown in FIG. 1). The upper corner portion of the front electrode 3 and the lower corner portion of the front electrode 4 located on the diagonal line on the surface of the substrate 2 are connection portions C, respectively.

  The back electrode 7 is obtained by screen-printing Ag paste, Cu paste or the like, drying and firing, and this back electrode 7 is formed on almost the entire back surface except the outer edge portion of the insulating substrate 2. Although not shown in the drawing, the connection portion C of both the front electrodes 3 and 4 exposed from the back electrode 7 and the protective coat 6 is subjected to Ni plating, Ni / Au plating, Pd plating or the like. The type is appropriately selected according to the material of the bonding wire that is ultrasonically connected to the connection portion C. In the case where both the front electrodes 3 and 4 are formed of a dense thick film rather than porous, for example, in the case of an Ag-based thick film with a small glass component and a large amount of metal component (Ag), the above-described plating treatment is performed. Can be omitted.

  As shown in FIG. 6, the chip resistor 1 configured as described above is used in a state where it is mounted on the circuit board 8, and two places of the wiring pattern 9 provided on the circuit board 8 and the chip resistor 1 are arranged. Both surface electrodes 3 and 4 are connected via a bonding wire 10.

  The circuit board 8 is a DBC board based on ceramics such as alumina and aluminum nitride, and a copper circuit plate to be a wiring pattern 9 is bonded to both front and back surfaces by a eutectic reaction. It is also possible to use an epoxy substrate. A part of the wiring pattern 9 provided on the surface of the circuit board 8 forms a connection land portion 9a, and the chip resistor 1 is mounted on the connection land portion 9a.

  The procedure for mounting the chip resistor 1 on the circuit board 8 will be described. First, a solder paste (solder paste) 10 is printed on the connection land portion 9 a of the circuit board 8. Next, after the chip resistor 1 is mounted on the solder paste 11 with the back electrode 7 facing downward, the chip resistor 1 is carried into the reflow furnace as it is, and the solder paste 11 is melted and solidified. The electrode 7 and the connection land portion 9a of the circuit board 8 are soldered.

  Thereafter, both ends of one bonding wire 10 are connected to the connection portion C of the surface electrode 3 and the wiring pattern 9 by ultrasonic welding, and both ends of another bonding wire 10 are connected to the connection portion C of the surface electrode 4. Connect to wiring pattern 9. Here, since the connection part C is set in a wide part of the both surface electrodes 3 and 4 formed in the trapezoidal shape, the connection work of the bonding wire 10 can be easily performed.

  In addition, in the case where electronic components such as a CPU and a power transistor other than the chip resistor 1 are mounted on the circuit board 8, paste-like heat radiation grease is formed on the wiring pattern 9 provided on the back surface of the circuit board 8. It is preferable that the circuit board 8 is attached to a heat sink (not shown) through this heat radiation grease.

  Next, the manufacturing process of the chip resistor 1 configured as described above will be described with reference to FIG.

  First, an aggregate substrate 2A from which a large number of insulating substrates 2 are taken is prepared. In this aggregate substrate 2A, primary division grooves and secondary division grooves (both not shown) are provided in a lattice shape in advance, and each square divided by both division grooves is one chip. It becomes an area. In FIG. 7, the collective substrate 2A corresponding to one chip region is representatively shown. However, in reality, each process described below is performed on the collective substrate 2A corresponding to many chip regions. It is done in a lump.

  That is, as shown in FIG. 7A, after the Ag-based paste is screen-printed on the back surface of the collective substrate 2A, the back electrode 7 is formed on the back surface of the collective substrate 2A by drying and baking this (back surface). Electrode forming step).

  Next, before and after the back electrode formation step, Ag (or Ag / Pd) paste is screen-printed on the surface of the aggregate substrate 2A, and then dried and fired, as shown in FIG. 7B. Then, a pair of front electrodes 3 and 4 are formed on the left and right sides of the collective substrate 2A (surface electrode forming step). As described above, the surface electrodes 3 and 4 are formed in a trapezoidal shape that is point-symmetric with respect to the center of the insulating substrate 2, and the inclined sides 3a and 4a of the surface electrodes 3 and 4 face each other in parallel. .

  Next, after a resistor paste such as ruthenium oxide is screen-printed on the surface of the aggregate substrate 2A, this is dried and fired, so that the left and right opposite sides are inclined side portions 3a, 3a, A parallelogram-shaped resistor 5 superimposed on 4a is formed (resistor forming step).

  Thereafter, a glass paste is screen-printed on a region covering the entire resistor 5 and most of the surface electrodes 3 and 4 and baked, as shown in FIG. A protective coat 6 in which a part of the protective coat 6 is exposed as the connection portion C is formed (protective coat forming step). As described above, these connection portions C are portions where the distances between the side edges 2a, 2b of the insulating substrate 2 and the inclined sides 3a, 4a of the surface electrodes 3, 4 are substantially maximized. One end of the wire 10 is connected.

  Next, after applying Ni plating, Ni / Au plating, or the like to the connecting portion C and the back electrode 7 of the front electrodes 3 and 4 as necessary, the collective substrate 2A is moved along the primary divided grooves and the secondary divided grooves. Then, the chip resistor 1 as shown in FIGS. 1 to 4 is obtained by dividing into pieces.

  As described above, in the chip resistor 1 according to this embodiment, the planar shape of the pair of front electrodes 3 and 4 is formed in a trapezoidal shape that occupies one side (2a or 2b) of the insulating substrate 2. In addition, since the inclined sides 3a and 4a of the surface electrodes 3 and 4 are arranged to face each other in parallel with each other via the resistor 5, a portion where current concentrates due to current wraparound is related to each of the surface electrodes 3 and 4. Only one location (edge portion E) is provided, and the area of the resistor 5 is increased to improve surge resistance, and deterioration of load characteristics due to temperature rise can be suppressed. The periphery of the edge portion E where the temperature rises due to the current concentration is a portion where the distance between the side edges 2a, 2b of the insulating substrate 2 and the inclined side edges 3a, 4a of the surface electrodes 3, 4 is substantially maximum. Since this portion is used as the connection portion C of the bonding wire 10, in the mounting structure in which the chip resistor 1 is mounted on the circuit board 8 and wire bonding is connected, the temperature that rises around the edge portion E is passed through the bonding wire 10. It is possible to realize the wire bonding connection type chip resistor 1 that is radiated to the circuit board 8 side and is excellent in heat dissipation and surge resistance.

  Further, in the chip resistor 1 according to the present embodiment example, since the back electrode 7 is formed on almost the entire back surface of the insulating substrate 2, when the chip resistor 1 is mounted on the circuit substrate 8 and wire-bonded. The temperature rise of the resistor 5 and the front electrodes 3 and 4 is not only radiated to the circuit board 8 side via the bonding wires 10, but the heat transmitted through the inside of the insulating substrate 2 is transferred from the back electrode 7 to the circuit board 8 side. Since heat is also radiated, heat dissipation can be improved more effectively.

  In the above embodiment, the planar shape of the pair of front electrodes 3 and 4 is a trapezoid that occupies one side of the insulating substrate 2, but the planar shape of these front electrodes 3 and 4 is a right angle instead of the trapezoid. In short, the pair of front electrodes 3 and 4 have inclined side portions 3a and 4a extending in the inclined direction with respect to the side sides 2a and 2b of the insulating substrate 2, and these inclined side portions. It suffices that 3a and 4a face each other in parallel through the resistor 5.

  Further, in the above embodiment, since a pair of opposite sides of the resistor 5 formed in a parallelogram shape is superimposed on the inclined sides 3a and 4a of the surface electrodes 3 and 4, a printing mask having a simple structure is used. Although the resistor 5 can be printed and formed easily and with high accuracy, the resistor 5 can be formed in a shape other than a parallelogram. For example, the planar shape of the resistor 5 can be formed in the same manner as the protective coat 6 by changing the portion of the resistor 5 that overlaps the inclined sides 3a and 4a from a linear shape to a stepped shape. The connection part C set to a pair of surface electrodes 3 and 4 should just be exposed without being covered with the resistor 5 and the protective coat 6.

  In the above embodiment, the back electrode 7 as a heat radiation electrode is formed on almost the entire back surface of the insulating substrate 2, and the back electrode 7 is soldered to the connection land portion 9 a of the circuit board 8. However, the back electrode 7 can be omitted. In this case, the chip resistor 1 may be mounted on the circuit board 8 using an adhesive.

  Further, in the above embodiment, the resistor 5 is formed by screen printing the resistor paste, but the resistor material is not limited to the thick film paste, but a metal plate such as nichrome or copper nickel, It may be a metal foil or a thin film.

DESCRIPTION OF SYMBOLS 1 Chip resistor 2 Insulation board | substrate 2a, 2b Side 2A Collective board 3, 4 Front electrode 3a, 4a Inclined side part 5 Resistor 6 Protective coating 7 Back electrode (heat dissipation electrode)
8 Circuit board 9 Wiring pattern 9a Connection land portion 10 Bonding wire 11 Solder paste C Connection portion E Edge portion

Claims (5)

A rectangular parallelepiped insulating substrate, a pair of surface electrodes formed along opposite sides of the surface of the insulating substrate, and a resistor formed so as to be connected to both surface electrodes, In the chip resistor in which the surface electrode is an electrode for wire bonding,
The pair of front electrodes are formed with inclined side portions extending in the inclined direction with respect to the side sides of the insulating substrate, and both the inclined side portions are arranged opposite to each other in parallel through the resistor, A chip resistor characterized in that, among the electrodes, a portion located on a diagonal line on the surface of the insulating substrate is a bonding wire connecting portion having a maximum distance between the side of the insulating substrate and the inclined side. vessel.   2. The chip resistor according to claim 1, wherein a planar shape of the resistor is a parallelogram, and opposite sides of the resistor are overlapped with the inclined side portion of the surface electrode with substantially the same width.   3. The chip resistor according to claim 1, wherein a heat radiation electrode is formed on substantially the entire back surface of the insulating substrate. A chip resistor includes a rectangular parallelepiped insulating substrate, a pair of surface electrodes formed along opposite sides of the surface of the insulating substrate, and a resistor formed so as to be connected to both surface electrodes. The chip resistor is mounted on the circuit board, and the wiring pattern provided on the circuit board and the surface electrode of the chip resistor are connected via a bonding wire. In the resistor mounting structure,
The pair of front electrodes are formed with inclined side portions extending in the inclined direction with respect to the side sides of the insulating substrate, and both the inclined side portions are arranged opposite to each other in parallel through the resistor, Of the electrodes, the chip is characterized in that a portion located on a diagonal line on the surface of the insulating substrate is used as a connecting portion of the bonding wire, with the gap between the side of the insulating substrate and the inclined side portion being substantially maximum. Resistor mounting structure.   5. The heat radiation electrode according to claim 4, wherein a heat radiation electrode is formed on substantially the entire back surface of the insulating substrate, and a connection land portion having an outer shape larger than the heat radiation electrode is formed on the wiring pattern. A chip resistor mounting structure, wherein the chip resistor is mounted on the circuit board in a state where the chip resistor is soldered to the connection land portion.