JP5706186B2 - Chip resistor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a chip resistor that is mounted face-down on a circuit board using a conductive adhesive, and a manufacturing method thereof.

  A chip resistor face-down mounted on a circuit board is provided with a resistor covered with a protective film and a pair of electrodes that overlap both ends of the resistor on the surface facing the circuit board. .

  As a conventional example of this type of chip resistor, a resistor and a pair of main electrodes that cover both ends of the resistor in the longitudinal direction are provided on one side (surface facing the circuit board) of a rectangular parallelepiped insulating substrate. And a protective film covering the resistor exposed between the main electrodes, and having end face electrodes on both end faces in the longitudinal direction of the insulating substrate, and the end face electrodes are closely bonded to the main electrodes. (For example, refer to Patent Document 1). In such a conventional example, the surface of the main electrode and the end face electrode is plated for reasons such as improving solder wettability. When this chip resistor is mounted face-down, it is provided on the circuit board. A main electrode is mounted on the wiring pattern and soldered, and a solder fillet is formed by the end face electrode.

  However, in this conventional example, since two or more plating layers (Ni plating layer, solder plating layer, etc.) must be formed on the surface of the main electrode and the end face electrode, the plating process is complicated and cannot be manufactured at low cost. There were difficulties. In recent years, it has been recommended to use lead-free solder that does not contain lead in consideration of the environment when soldering, but it is necessary to heat the lead-free solder to about 260 ° C. in order to melt it. Therefore, when trying to cope with solder bonding using lead-free solder, the heat resistance of the chip resistor must be greatly increased, and the manufacturing cost of the chip resistor inevitably increases.

  On the other hand, a technique of mounting a chip resistor on a circuit board using a conductive adhesive instead of solder has been conventionally known (see, for example, Patent Document 2). This conductive adhesive is obtained by dispersing a conductive material such as metal powder in an epoxy-based resin material, and curing it at a temperature of 200 ° C. or lower to connect an unplated electrode of a chip resistor to a circuit. It can be bonded to the wiring pattern on the substrate. Therefore, if a conductive adhesive is used for face-down mounting, it is not necessary to form a plating layer on the surface of the chip resistor electrode, and it is not necessary to particularly increase the heat resistance of the chip resistor. Chip resistors can be manufactured at low cost.

  However, since the surface of the electrode of the chip resistor is generally formed to be relatively smooth, it is difficult to obtain a desired adhesive strength even if the conductive adhesive is directly attached to the electrode of the chip resistor. Yes. For this reason, in the chip resistor disclosed in Patent Document 2, a conductive material in which a conductive material is dispersed in a resin material in a relatively wide region that covers the electrode and wraps the end portion of the insulating substrate. By providing an external electrode made of a connecting material and selecting a resin material with good adhesion to the resin material of the conductive adhesive used during mounting as the resin material for this external electrode, The adhesive strength of the adhesive is increased.

JP 2007-88162 A JP 2010-225660 A

  If the electrode is previously covered with an external electrode made of a conductive connecting material as in the chip resistor disclosed in Patent Document 2, a complicated plating process is not required, and the manufacturing cost can be easily reduced and the conductive property can be reduced. It becomes possible to mount face down on a circuit board using an adhesive. However, in such a conventional chip resistor, in order to form an external electrode made of a conductive connection material, a dipping step of immersing the divided end face of the insulating substrate in an uncured conductive connection material, and the uncured material Therefore, it has been difficult to significantly reduce the manufacturing cost of the chip resistor. In addition, the resin material of the conductive adhesive used at the time of mounting is not necessarily good adhesion with the resin material of the external electrode, depending on the type of conductive adhesive, it is not possible to obtain the desired adhesive strength, There is a possibility that the reliability of conduction between the external electrode of the chip resistor and the conductive adhesive is impaired.

  The present invention has been made in view of the actual situation of the prior art, and a first object thereof is to provide a chip resistor suitable for face-down mounting using a conductive adhesive and having high conduction reliability. There is to do. A second object of the present invention is to provide a manufacturing method capable of manufacturing such a chip resistor at a low cost.

In order to achieve the first object described above, in the present invention, a resistor, a pair of electrodes overlapping both ends of the resistor, and a protective film covering the resistor are provided on one surface of the insulating substrate. In the chip resistor mounted face down with the one side of the insulating substrate facing the circuit board, the electrode is provided in a region away from the outer edge of the one side of the insulating substrate, Rutotomoni to expose the surface of the electrode, the exposed surface is a configuration that has been surface-roughened to be rougher than at least the surface of the insulating substrate.

The chip resistor configured in this way has a large number of fine concave portions formed on the exposed surface of the electrode by the roughening treatment, and the surface area of the exposed surface of the electrode is wide due to the presence of the concave portion. The adhesive strength of the conductive adhesive to the exposed surface can be greatly increased. Therefore, this chip resistor can be mounted face-down on the circuit board using a conductive adhesive without using solder, and the conduction reliability between the electrode of the chip resistor and the conductive adhesive is also good. It becomes. Further, this chip resistor does not require a plating layer covering the electrode, an external electrode, or the like, and it is not necessary to particularly increase the heat resistance of the chip resistor, so that the manufacturing cost can be greatly reduced. Furthermore, the electrode is provided in a region away from the outer edge of one side of the insulating substrate, and the peripheral wall of the exposed portion of the electrode can be surrounded by the non-printing region on one side of the insulating substrate. When face-down mounting, the conductive adhesive can be easily attached to all the peripheral walls, and the exposed surface of the electrode can be reliably covered with the conductive adhesive. Therefore, oxidation and sulfurization of the electrode can be prevented and stable performance can be easily maintained. In addition, if the electrodes are separated from the ridgeline (outline) of the insulating substrate in this way, the electrodes overlap the dividing grooves of the large substrate for taking a large number of insulating substrates in the manufacturing process of the chip resistor. Therefore, workability at the time of division work is improved and the manufacturing yield is easily increased.

  In the chip resistor having the above configuration, the height dimension from one side of the insulating substrate to the exposed surface of the electrode is equal to or greater than the height dimension from one side of the insulating substrate to the surface of the protective film. If it is set, there is no possibility that the chip resistor mounted face-down will be inclined with the protective film as a fulcrum, so that even if an external force acts on the mounted chip resistor from above, cracks and the like are less likely to occur. In this case, if an insulating layer is provided on both ends of one side of the insulating substrate and an electrode is provided so as to cover the insulating layer, the height position of the electrode can be easily raised by the film thickness of the insulating layer.

  Further, in the chip resistor having the above configuration, when a magnetic layer made of a magnetic material is provided on the surface opposite to the one surface of the insulating substrate, when the chip resistor is taped and automatically mounted, The posture of the chip resistor can be stabilized by the magnet.

In order to achieve the second object described above, in the present invention, a resistor, a pair of electrodes overlapping both ends of the resistor, and a protective film covering the resistor are provided on one surface of the insulating substrate. In the method of manufacturing a chip resistor face-down mounted with the one side of the insulating substrate facing the circuit board, the electrode is formed by thick-film printing an electrode paste on the one side of the insulating substrate. In addition, by including a plurality of types of glass materials having different softening points in the electrode paste, the surface of the electrode is exposed after being roughened so as to be rougher than at least the surface of the insulating substrate. I made it.

Thus, when the surface of the chip resistor electrode is roughened and exposed, the exposed surface of the electrode having a large number of fine recesses and a large surface area ensures the adhesive strength with the conductive adhesive. It can function as an easy adhesive surface. Therefore, the chip resistor manufactured in this way can be mounted face-down on the circuit board using a conductive adhesive without using solder, and the conduction reliability between the electrode of the chip resistor and the conductive adhesive Will also be good. In addition, the chip resistor manufactured in this way does not require a plating layer covering the electrode, an external electrode, or the like, and it is not necessary to particularly improve the heat resistance of the chip resistor, so that the manufacturing cost can be greatly reduced. In addition, since the electrodes of the chip resistor are roughened by including a plurality of types of glass materials having different softening points in the electrode paste, the roughening treatment can be performed in the electrode forming step.

  According to the chip resistor of the present invention, the surface of the roughened electrode is exposed, and the adhesive strength of the conductive adhesive to the exposed surface of the electrode can be greatly increased. Therefore, this chip resistor can be mounted face-down on a circuit board using a conductive adhesive without using solder, and the conduction reliability between the electrode of the chip resistor and the conductive adhesive is also good. Become. Further, this chip resistor does not require a plating layer covering the electrode, an external electrode, or the like, and it is not necessary to particularly increase the heat resistance of the chip resistor, so that the manufacturing cost can be greatly reduced.

  According to the manufacturing method of the chip resistor of the present invention, the surface of the electrode of the chip resistor is exposed after being roughened, so that the exposed surface of the electrode is secured with a conductive adhesive. It can function as an easy-to-use adhesive surface. Therefore, the chip resistor manufactured in this way can be mounted face-down on the circuit board using a conductive adhesive without using solder, and the conduction reliability between the electrode of the chip resistor and the conductive adhesive is also improved. It becomes good. In addition, the chip resistor manufactured in this way does not require a plating layer covering the electrode, an external electrode, or the like, and it is not necessary to particularly improve the heat resistance of the chip resistor, so that the manufacturing cost can be greatly reduced.

It is a top view of the chip resistor concerning a 1st embodiment of the present invention. It is sectional drawing which shows the state which mounted the chip resistor shown in FIG. 1 face down. It is process drawing which shows the state which formed the electrode in the large format board | substrate in the manufacture process of the chip resistor shown in FIG. It is process drawing which shows the state which formed the resistor in the large format board | substrate in the manufacture process of the chip resistor shown in FIG. It is process drawing which shows the state which formed the protective film which covers a resistor in the manufacture process of the chip resistor shown in FIG. It is sectional drawing of the chip resistor which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the chip resistor which concerns on the 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, a chip resistor according to a first embodiment of the present invention will be described with reference to FIGS. Further, a manufacturing method of this chip resistor will be described with reference to FIGS.

  A chip resistor 1 shown in FIGS. 1 and 2 includes a rectangular parallelepiped insulating substrate 2, a resistor 3 provided in a strip shape at the center of one surface 2a of the insulating substrate 2, and one surface 2a of the insulating substrate 2. And a protective film 4 that covers the resistor 3 exposed between the electrodes 5 and a pair of electrodes 5 that are provided in a region near both ends in the longitudinal direction of the resistor 3 and that overlaps both ends in the longitudinal direction of the resistor 3. The surface of each electrode 5 is exposed. As shown in FIG. 2, the chip resistor 1 is mounted face-down with one side 2 a of the insulating substrate 2 facing the circuit board 10, and a wiring pattern 11 provided on the circuit board 10 and the chip resistor. Each electrode 5 is electrically and mechanically connected by a conductive adhesive 12. That is, the chip resistor 1 is designed to be face-down mounted by making the exposed surface of each electrode 5 an adhesive surface with respect to the conductive adhesive 12. Therefore, the surface of the electrode 5 (including the exposed surface) is roughened so that it is at least rougher than the surface of the insulating substrate 2.

  The structure of the chip resistor 1 will be described in detail. The insulating substrate 2 is, for example, an alumina substrate. The resistor 3 is made of ruthenium oxide or the like, and the protective film 4 is made of an epoxy resin or the like. Although not shown, a thin glass coat layer is provided between the resistor 3 and the protective film 4, and a trimming groove (not shown) for adjusting the resistance value is formed in the resistor 3 and the glass coat layer covering the resistor 3. Is formed. The electrode 5 is made of an Ag-based conductive material (Ag, Ag / Pd, or the like). The electrode 5 is covered with the resistor 3 and the protective film 4 at one end portion on the resistor 3 side, but most of the electrode 5 is exposed, and the peripheral wall of the exposed portion is the insulating substrate 2. It is surrounded by a non-printing area on one side 2a. That is, the electrode 5 is provided in a region away from the outer edge of the one surface 2 a of the insulating substrate 2. Further, since the surface of the electrode 5 is blasted at the manufacturing stage, the entire surface of the electrode 5 is roughened to form a large number of fine recesses 5a as shown in FIG. However, in FIG. 2, the roughened state of the electrode 5 is exaggerated.

  Next, a manufacturing method of the chip resistor 1 configured as described above will be described. First, as shown in FIG. 3, a large number of electrodes 5 are formed by printing and baking an electrode paste on a predetermined position of a large-sized substrate 20 that is an aggregate of insulating substrates 2. This electrode paste is a known one containing an Ag-based conductive material, a glass material, or the like. In addition, the large substrate 20 is formed with division grooves 21 extending in a lattice shape in advance, and each electrode 5 is formed along the division grooves 21 in a region near the division grooves 21.

  As the next step, the surface of each electrode 5 is roughened by performing blasting such as sand blasting on each electrode 5. Thereafter, as shown in FIG. 4, a resistor paste containing ruthenium oxide or the like is printed in a thick film and fired in a band-like region that bridges the electrodes 5 arranged in parallel at a predetermined interval. Thus, a large number of resistors 3 are formed. As a result, each electrode 5 is electrically connected to the resistor 3 with one end thereof overlapping the resistor 3.

  As the next step, a large number of glass coat layers are formed by printing and baking a glass paste on the regions covering the respective resistors 3. Then, the resistance value is adjusted by irradiating each glass coat layer with a laser to form the trimming groove in a part of each resistor 3.

  After that, as shown in FIG. 5, protection is provided by printing a thick film of epoxy-based resin paste on the strip-shaped region covering the plurality of glass coat layers arranged in a row including the trimming grooves, and baking it. A continuum of film 4 is formed. The protective film 4 of the chip resistor 1 is obtained by dividing this continuous body. That is, as the next step, the large substrate 20 is divided into a large number of insulating substrates 2 by dividing the large substrate 20 along the vertical and horizontal dividing grooves 21, so that a large number of chip resistors separated into individual pieces. 1 is obtained collectively.

  The chip resistor 1 manufactured in this way has a large number of fine recesses 5 a formed on the surface of the electrode 5 roughened by blasting, and these recesses 5 a increase the surface area of the electrode 5. Since most of the roughened surface of the electrode 5 is exposed, the exposed surface of the electrode 5 can function as an adhesive surface that can easily secure the adhesive strength with the conductive adhesive 12. . Therefore, as shown in FIG. 2, the chip resistor 1 can be mounted face-down on the circuit board 10 using the conductive adhesive 12.

  Specifically, after applying a conductive adhesive 12 on a predetermined wiring pattern 11 on the circuit board 10, the wiring pattern corresponding to each electrode 5 is arranged with the one side 2 a side of the chip resistor 1 facing the circuit board 10. 11 is mounted. Thereby, since the conductive adhesive 12 enters the recess 5a of the exposed surface of the electrode 5, a sufficient contact area of the conductive adhesive 12 with respect to the exposed surface of the electrode 5 can be ensured, and the adhesion degree is also good. Moreover, since the peripheral wall of the exposed part of the electrode 5 is surrounded by the non-printing region of the one surface 2a of the insulating substrate 2, the conductive adhesive 12 is easily attached to all the peripheral wall, and the exposed surface of the electrode 5 Can be reliably covered with the conductive adhesive 12. Therefore, the chip resistor 1 can be reliably face-down mounted on the circuit board 10 by heating and curing the conductive adhesive 12 at about 100 to 200 ° C.

  As described above, the chip resistor 1 according to this embodiment has a number of fine recesses 5a formed on the exposed surface of the electrode 5 by the roughening process (blasting). Since the surface area is also wide due to the presence of the recess 5a, the adhesive strength of the conductive adhesive 12 to the exposed surface of the electrode 5 can be significantly increased. Therefore, the chip resistor 1 can be mounted face-down on the circuit board 10 using the conductive adhesive 12 without using solder, and the electrode 5 of the chip resistor 1 and the conductive adhesive 12 The conduction reliability is also improved. Further, the chip resistor 1 does not require a plating layer covering the electrode 5, an external electrode, or the like, and it is not necessary to particularly improve the heat resistance of the chip resistor 1, so that the manufacturing cost can be greatly reduced.

  In the chip resistor 1 according to this embodiment, the electrode 5 is provided in a region away from the outer edge of the one surface 2a of the insulating substrate 2, and the exposed surface of the electrode 5 is electrically conductive adhesive 12 when face-down mounting. Therefore, it is possible to prevent the electrode 5 from being oxidized or sulfided and to maintain stable performance. In addition, the chip resistor 1 in which the electrode 5 is separated from the ridge line (outline) of the insulating substrate 2 in this way is divided because the electrode 5 does not overlap the dividing groove 21 of the large substrate 20 in the manufacturing process. The workability during work is improved and the manufacturing yield is easily increased.

  In the present embodiment, when the chip resistor 1 is manufactured, the surface of the large number of electrodes 5 is blasted and roughened in the state of the large-sized substrate 20, so that the roughening can be efficiently performed in a short time. Processing can be performed.

  However, another method may be employed to roughen the electrode 5 of the chip resistor 1. For example, it is possible to roughen the electrode 5 by incorporating a plurality of types of glass materials (bismuth glass or the like) having different softening points into the electrode paste. Since the exposed surface can be roughened in the step, a step of separately performing the roughening treatment after the formation of the electrode 5 can be omitted. For example, three kinds of glass materials having softening points of 400 ° C., 600 ° C., and 700 ° C. may be mixed and contained in the electrode paste. Further, as another method, the electrode 5 can be roughened by including a plurality of types of metal powders (Ag / Pd, etc.) having different particle sizes in the electrode paste. A metal powder having a diameter of 1 μm or less and a metal powder having a particle diameter of about 10 μm may be mixed in the same amount and contained in the electrode paste.

  In the present embodiment, since the resistor 3 and the protective film 4 are printed after the entire surface of the electrode 5 is roughened in the manufacturing process of the chip resistor 1, the resistor paste or protective film for the resistor 3 is formed. The dripping of the resin paste for 4 is suppressed by the fine recesses 5 a of the electrode 5. Therefore, there is an additional effect that the resistor 3 and the protective film 4 can be printed with high positional accuracy.

  In the above embodiment, only one layer of the electrode 5 of the chip resistor 1 is formed on the insulating substrate 2. However, it is possible to increase the thickness of the electrode 5 by forming a laminated structure of two or more layers. In this case, the surface of the uppermost layer of the electrode 5 may be roughened.

  FIG. 6 shows a chip resistor according to the second embodiment of the present invention, and portions corresponding to those in FIG. 1 and FIG. In the chip resistor 1 shown in FIG. 6, the magnetic layer 6 made of a magnetic material is provided on the back surface 2b opposite to the one surface 2a of the insulating substrate 2, and the other configuration is the first embodiment described above. It is the same. The magnetic layer 6 can be formed by an appropriate method such as sputtering, electroless plating, or printing.

  When the magnetic layer 6 is provided on the back surface 2b of the insulating substrate 2 as in the second embodiment, the chip resistor 1 is automatically mounted on the circuit board 10 when the chip resistor 1 is taped and packaged. When doing so, the posture of the chip resistor 1 can be stabilized by attracting the magnetic layer 6 with a magnet (not shown).

  FIG. 7 shows a chip resistor according to the third embodiment of the present invention, and portions corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals. The chip resistor 1 shown in FIG. 7 is provided with an insulating layer 7 for raising the height position of the electrode 5, and the electrode 5 and the insulating layer 7 extend to the outer edge of the one surface 2 a of the insulating substrate 2. It extends. That is, since the insulating layer 7 is provided at both longitudinal ends of the one surface 2a of the insulating substrate 2 and the electrode 5 is provided so as to cover the insulating layer 7, the height position of the exposed surface of the electrode 5 and the protection are provided. The height position of the surface of the film 4 is substantially the same. The insulating layer 7 can be formed by thickly printing an epoxy-based resin paste and baking it before forming the electrode 5.

  By providing the insulating layer 7 as in the third embodiment, the height dimension from the one surface 2a which is the resistor forming surface of the insulating substrate 2 to the exposed surface of the electrode 5 is protected from the one surface 2a. If the height of the film resistor 4 is approximately the same as the height of the film 4, the chip resistor 1 mounted face-down will not be inclined with the protective film 4 as a fulcrum. Even if an external force is applied, cracks and the like are less likely to occur. In addition, the chip resistor 1 in which the electrodes 5 and the insulating layer 7 extend to the outer edge of the one surface 2a of the insulating substrate 2 has two electrodes 5 and two insulating layers 7 on the dividing line of the large substrate at the time of manufacture. Therefore, printing of the electrodes 5 and the insulating layer 7 can be performed relatively easily. Since the height of the electrode 5 can be easily raised by the film thickness of the insulating layer 7, the insulating layer 7 is formed thicker so that the electrode 5 is exposed at a position slightly higher than the surface of the protective film 4. Also good.

DESCRIPTION OF SYMBOLS 1 Chip resistor 2 Insulating board | substrate 2a Single side | surface 3 Resistor 4 Protective film 5 Electrode 5a Recess 6 Magnetic layer 7 Insulating layer 10 Circuit board 11 Wiring pattern 12 Conductive adhesive 20 Large format board 21 Divided groove

Claims (5)

A resistor, a pair of electrodes overlapping both ends of the resistor, and a protective film covering the resistor are provided on one side of the insulating substrate, and the one side of the insulating substrate is opposed to the circuit board. In chip resistors mounted face down,
The electrode is provided in a region remote from the one side of the outer edge of the insulating substrate, Rutotomoni to expose the surface of the electrode, crude as the exposed surface is rougher than at least the surface of the insulating substrate A chip resistor that is surface-treated.   The height dimension from the one surface of the insulating substrate to the exposed surface of the electrode is equal to or greater than the height dimension from the one surface of the insulating substrate to the surface of the protective film. Chip resistor characterized by being set to the size of   3. The chip resistor according to claim 2, wherein an insulating layer is provided at both ends of the one surface of the insulating substrate, and the electrode is provided so as to cover the insulating layer. In the description of any one of claims 1 to 3 chip resistor, wherein a magnetic layer made of a magnetic material to the surface of the one side and opposite side of the insulating substrate is provided. A resistor, a pair of electrodes overlapping both ends of the resistor, and a protective film covering the resistor are provided on one side of the insulating substrate, and the one side of the insulating substrate is opposed to the circuit board. In the manufacturing method of the chip resistor to be face-down mounted,
  The electrode paste is formed by thick film printing on one side of the insulating substrate to form the electrode, and a plurality of types of glass materials having different softening points are included in the electrode paste, whereby at least the surface of the electrode is insulated. A method of manufacturing a chip resistor, characterized by being exposed after being roughened so as to be rougher than the surface of the conductive substrate.

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