JP2009094159A - Chip resistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chip resistor extremely favorable in heat radiation properties. <P>SOLUTION: The chip resistor 1 comprises: a rectangular parallelepiped ceramic substrate 2; a pair of terminal electrodes 3 disposed on both longitudinal ends of the ceramic substrate 2; a resistor 4 bridging the pair of terminal electrodes 3 on one surface (opposed to a printed substrate 50) of the ceramic substrate 2; insulating protection layers 5, 6 provided in a region covering the resistor 4; a heat radiation electrode 7 disposed to cross the surface of the protection layer 6 and insulated from the resistor 4 and the terminal electrodes 3; and a plating layer 8 covering the heat radiation electrode 7 and the terminal electrodes 3. The heat radiation electrode 7 is extended from one surface of the ceramic substrate 2 to the midst of both latitudinal end surfaces. The chip resistor 1 is face-down packaged by soldering the terminal electrodes 3 and the heat radiation electrode 7 to a plurality of lands 51, 52 isolated from one another on the printed substrate 50. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a chip resistor in which a resistor is provided on one side of a rectangular parallelepiped ceramic substrate, and in particular, a chip provided with a heat radiation electrode to release heat generated by the resistor when power is applied. Related to resistors.

  A conventional general rectangular chip resistor is provided with a pair of terminals in which a resistor and an insulating protective layer covering the resistor are provided on one side of a rectangular parallelepiped ceramic substrate, and a plating layer is attached. Electrodes are provided at both ends in the longitudinal direction of the ceramic substrate, and the pair of terminal electrodes are bridged by a resistor. This type of chip resistor is usually surface-mounted on a mounting board such as a printed circuit board with the resistor side facing up, and each terminal electrode is soldered to a land disposed on the mounting board. However, if miniaturization of chip resistors is promoted, problems such as resistance changes due to the heat generated by the resistors when power is applied and solder joints are likely to melt. Become.

Therefore, conventionally, an auxiliary electrode is extended to the terminal electrode, and the auxiliary electrode is configured to cover a part of the resistor through an insulating protective layer, and the face where the resistor exists is faced down. A chip resistor that is surface-mounted on a mounting substrate is proposed (for example, see Patent Document 1). In such a conventional chip resistor, if the land (electrode pad) on the mounting substrate to which the terminal electrode is soldered is formed large and the auxiliary electrode is soldered to the land, the resistor of the resistor is applied when power is applied. Since the generated heat is quickly transmitted to the mounting substrate via the auxiliary electrode, the heat dissipation is improved and the temperature rise of the chip resistor can be suppressed.
JP 2007-53218 A

  However, as in the prior art described above, the chip resistor in which the auxiliary electrode is extended to the terminal electrode and face-down mounted has a problem that heat cannot be efficiently released using a heat sink or the like. That is, since the auxiliary electrode is soldered to the common land together with the terminal electrode, the reliability of the chip resistor is significantly impaired if the land is in conduction with a metal heat sink or thermal via. It will be. For this reason, the conventional technology expects that the heat generated by the resistor when power is applied is released through the mounting substrate such as a printed circuit board. However, the substrate material (for example, glass epoxy) of the mounting substrate is particularly heat radiating. Therefore, the effect of suppressing the temperature rise of the chip resistor was insufficient.

  The present invention has been made in view of such a state of the prior art, and an object thereof is to provide a chip resistor with extremely good heat dissipation.

  In order to achieve the above object, a chip resistor of the present invention is provided with a rectangular parallelepiped ceramic substrate, a pair of terminal electrodes provided at both ends in the longitudinal direction of the ceramic substrate, and one surface of the ceramic substrate. A resistor that bridges the pair of terminal electrodes, an insulating protective layer provided in a region covering the resistor, and a surface of the protective layer that crosses the surface of the protective layer between the pair of terminal electrodes. A heat-dissipating electrode and a plating layer deposited on the heat-dissipating electrode and the terminal electrode, the heat-dissipating electrode extending from the one side of the ceramic substrate to the middle of both end surfaces in the lateral direction. In addition, the heat-radiating electrode and the terminal electrode are soldered to a plurality of lands separated from each other on the mounting substrate, so that face-down mounting is performed.

  The chip resistor configured in this manner has a heat radiation electrode that overlaps with the resistor via a protective layer on the surface facing the mounting substrate such as a printed circuit board, and this heat radiation electrode is provided on the resistor and the terminal electrode. Insulation with respect to the terminal electrode lands can be provided on the mounting substrate separately from the terminal electrode lands, and the terminal electrodes and the radiating electrodes can be soldered to the lands, respectively. This makes it easy for the heat generated by the resistor when power is applied to be transferred to the heat dissipation electrode and the heat dissipation electrode land on the mounting board, and to transmit heat efficiently from the heat dissipation electrode land to the thermal via, heat sink, etc. As a result, the heat dissipation can be remarkably improved, and the temperature rise of the chip resistor can be effectively suppressed. In addition, since the heat dissipation electrode extends from the lower surface of the ceramic substrate to both end surfaces in the short direction, this chip resistor is not only in the longitudinal direction where the terminal electrode exists but also in the short direction where the heat dissipation electrode exists. Soldering is performed on the mounting board in a state in which solder fillets are formed at both ends, and therefore the mounting strength of the chip resistor to the mounting board is greatly improved.

  According to the chip resistor of the present invention, the heat radiation electrode that overlaps the resistor via the protective layer is provided on the surface facing the mounting substrate such as a printed circuit board, and this heat radiation electrode is connected to the resistor and the terminal electrode. Therefore, the radiating electrode lands that are electrically isolated from the land for the terminal electrodes can be provided on the mounting substrate, and the terminal electrodes and the radiating electrodes can be soldered to the lands, respectively. Therefore, the heat generated by the resistor when power is applied can easily be transferred to the heat dissipation electrode or the heat dissipation electrode land of the mounting substrate, and heat can be transferred from the heat dissipation electrode land to the thermal via or heat sink to efficiently dissipate heat. Therefore, it is possible to remarkably improve the heat dissipation and effectively suppress the temperature rise of the chip resistor. In addition, since the heat dissipation electrode extends to both end surfaces in the short direction of the ceramic substrate, this chip resistor can form solder fillets at both ends in the short direction, and the mounting strength to the mounting substrate can be increased. Rise.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view along the longitudinal direction showing a state immediately before mounting a chip resistor according to an embodiment of the present invention, and FIG. FIG. 3 is a top view of a principal part of a printed circuit board on which the chip resistor is mounted, and FIGS. 4 to 7 are process diagrams for explaining a method of manufacturing the chip resistor. FIG. 8 is a perspective view of an individual piece obtained during the manufacture of the chip resistor.

  The chip resistor 1 shown in FIGS. 1 and 2 is provided on a rectangular parallelepiped ceramic substrate 2, a pair of terminal electrodes 3 provided at both ends in the longitudinal direction of the ceramic substrate 2, and the lower surface of the ceramic substrate 2 in the figure. Crossing the surface of the second protective layer 6, the resistor 4 bridging the pair of terminal electrodes 3, the insulating first protective layer 5 and the second protective layer 6 provided in the region covering the resistor 4 The heat radiation electrode 7 provided so as to be insulated from the terminal electrode 3 and the resistor 4 and the two-layered plating layer 8 attached to the heat radiation electrode 7 and the terminal electrode 3 are mainly configured. Yes. The chip resistor 1 is mounted on a printed circuit board 50, which is a mounting substrate, so that the resistor 4 is formed facing downward, so-called face down, and the terminal electrode 3 and the heat radiation electrode 7 are respectively connected to the corresponding lands 51, 52. It is designed to be surface-mounted by soldering. That is, as shown in FIG. 3, a pair of lands 51 for soldering the pair of terminal electrodes 3 and lands 52 for soldering the heat radiation electrode 7 are spaced apart from each other on the printed circuit board 50. The land 52 for the heat radiation electrode 7 is designed to efficiently transfer heat to the heat sink 55 via the thermal via 53 and the heat radiation silicon 54. In addition, the code | symbol 40 in FIG. 2 has shown the solder.

  The ceramic substrate 2 is an alumina substrate, which is obtained by dividing a large-sized substrate, which will be described later, into a plurality of vertical and horizontal portions. Each terminal electrode 3 includes a surface electrode 31 formed on one surface (lower surface) of the ceramic substrate 2 and a back electrode 32 formed on the other surface (upper surface) of the ceramic substrate 2 on the side end surface of the ceramic substrate 2. It is connected via the end electrode 33 formed. Both the front electrode 31 and the back electrode 32 are made of Ag / Pd, and the end face electrode 33 is made of nickel chrome (Ni / Cr). The resistor 4 is made of ruthenium oxide or the like, and both ends in the longitudinal direction of the resistor 4 are connected to a pair of surface electrodes 31. The resistor 4 has a trimming groove 4a (see FIG. 5) for adjusting the resistance value. The first protective layer 5 is a pre-glass coat that covers the resistor 4, and narrow portions 15 a (see FIG. 5) are extended from the four corners to the middle of both end faces of the ceramic substrate 2 in the short direction. The second protective layer 6 is an overcoat made of resin or glass that covers the first protective layer 5. The plating layer 8 having a two-layer structure is for preventing electrode cracking and improving the reliability of soldering. The underlying Ni plating layer 9 and Sn deposited on the Ni plating layer 9 are used. It consists of a plating layer 10.

  The heat radiation electrode 7 is for releasing the heat generated by the resistor 4 to the outside when power is applied, and is electrically isolated between the pair of terminal electrodes 3. The heat radiation electrode 7 is made of Ag, and covers the central portion of the second protective layer 6 on the lower surface side of the ceramic substrate 2 as shown in FIG. It is the extension part 7a extended to the middle of both the end surfaces. As will be described later, the heat radiating electrode 7 is formed by printing Ag paste in a band-shaped region that extends across the surface of the second protective layer 6 into the secondary dividing groove 12 at the stage of a large substrate. It is.

  The chip resistor 1 having such a configuration is manufactured by the following procedure.

  First, as shown in FIG. 4 (a), a large substrate (alumina substrate) 13 for multi-cavity in which a primary dividing groove 11 and a secondary dividing groove 12 extending vertically and horizontally are engraved is prepared. The Ag-Pd paste is sequentially screen-printed and fired on the back surface and the front surface of 13 to form a large number of front surface electrodes 31 and back surface electrodes 32 corresponding to the individual chip resistors 1. The large substrate 13 becomes the ceramic substrate 2 of the chip resistor 1 after the division, and the surface electrode 31 and the back electrode 32 are formed across the primary division groove 11. However, either the front electrode 31 or the back electrode 32 may be formed first.

  Next, as shown in FIG. 4B, a resistor paste such as ruthenium oxide is screen-printed and fired on the surface of the large substrate 13 (the surface on which the surface electrode 31 is formed). A number of resistors 4 extending along the secondary dividing grooves 12 and bridging adjacent surface electrodes 31 are formed.

  Thereafter, as shown in FIG. 5 (a), a glass paste is screen-printed on the surface of the large substrate 13 to cover each resistor 4 and baked to open along the primary dividing grooves 11. A strip-shaped glass coat 15 having 14 is formed. The strip-shaped glass coat 15 becomes the first protective layer (pre-glass coat) 5 after the division, but a part of the strip-shaped glass coat 15 enters the secondary divided groove 12 and is a narrow portion adjacent to the opening 14. 15a.

  Next, as shown in FIG. 5B, the trimming groove 4a is formed by performing laser trimming on each resistor 4 in order to adjust the resistance value in the state of the large substrate 13. In this laser trimming, the strip-shaped glass coat 15 is also trimmed at a location corresponding to the trimming groove 4a of the resistor 4.

  Next, as shown in FIG. 6A, a resin paste (or glass paste) is screen-printed and baked (or baked) on the surface of the large substrate 13 where the band-shaped glass coat 15 is substantially covered. 2 Many protective layers (overcoat) 6 are formed. The second protective layer 6 covers the first protective layer 5 together with the trimming groove 4a. However, the narrow portion 15 a formed in the secondary dividing groove 12 is exposed without being covered by the second protective layer 6.

  Thereafter, as shown in FIG. 6B, a resin-based (or glass-based) Ag paste is screen printed on the surface of the large substrate 13 covering the second protective layer 6 and the central portion of the opening 14 and baked. By performing (or firing), a strip-shaped heat radiation electrode 16 that is narrower than the strip-shaped glass coat 15 and extends along the primary dividing groove 11 is formed. The strip-shaped heat radiation electrode 16 becomes the heat radiation electrode 7 after the division, and the portion that enters the secondary division groove 12 and is exposed in the opening 14 becomes the extension portion 7a after the division. The Ag paste for the belt-shaped heat radiation electrode 16 is blocked by the narrow portion 15a of the belt-shaped glass coat 15 even if it flows to the surface electrode 31 side in the secondary dividing groove 12, so that the belt-shaped heat radiation electrode 16 and the surface There is no possibility that the electrode 31 is short-circuited.

  Next, as shown in FIG. 7A, the large substrate 13 is divided along the primary dividing grooves 11 to form a large number of strip-shaped divided pieces 17. Thereafter, the end face electrode 33 is formed by sputtering nickel chrome (Ni / Cr) on the dividing surface 17 a of the strip-shaped divided piece 17. Thereby, the terminal electrode 3 in which the front surface electrode 31 and the back surface electrode 32 are bridged by the end surface electrode 33 is obtained.

  Thereafter, as shown in FIG. 7B, the strip-shaped divided pieces 17 are subdivided along the secondary divided grooves 12 to obtain a large number of chip-sized pieces 18 as shown in FIG. . Thereby, the strip-shaped glass coat 15 is divided into the first protective layer 5, the strip-shaped heat radiation electrode 16 is divided into the heat radiation electrodes 7, and the extended portion 7 a of the heat radiation electrode 7 and the narrow portion 15 a of the belt-shaped glass coat 15 are formed. The ceramic substrate 2 is exposed on both end surfaces in the short direction. Then, by putting these pieces 18 into a barrel (not shown) and performing electrolytic plating (barrel plating), the Ni plating layer 9 and the Sn plating layer 10 are sequentially formed. That is, first, electrolytic plating is performed in a Ni plating barrel, and then electrolytic plating is performed in a Sn plating barrel, thereby depositing a plating layer 8 having a two-layer structure on the surfaces of the terminal electrode 3 and the heat dissipation electrode 7. Thus, a large number of chip resistors 1 as shown in FIGS. 1 and 2 are obtained.

  As described above, the chip resistor 1 according to this embodiment includes a resistor on the lower surface of the ceramic substrate 2 (the surface on the side facing the printed circuit board 50) via the first and second protective layers 5 and 6. 4 is provided, and the heat dissipation electrode 7 is insulated from the resistor 4 and the terminal electrode 3, so that it is electrically separated from the land 51 for the terminal electrode 3 on the printed board 50. An isolated land 52 for the heat radiation electrode 7 is provided, and the terminal electrode 3 and the heat radiation electrode 7 can be soldered to the plurality of lands 51 and 52, respectively. Therefore, the heat generated by the resistor 4 when electric power is applied can be easily transferred to the heat radiation electrode 7 and the land 52, and the heat can be transferred from the land 52 to the heat sink 55 through the thermal via 53 and the like to be efficiently radiated. Therefore, the chip resistor 1 can remarkably improve the heat dissipation and effectively suppress the temperature rise, thereby improving the reliability.

  Further, in this chip resistor 1, since the extending portions 7 a of the heat radiation electrode 7 are extended from the lower surface of the ceramic substrate 2 to both end surfaces in the short direction, only the both end portions in the longitudinal direction where the terminal electrodes 3 exist are provided. In other words, both ends in the short direction where the extending portion 7a exists are soldered onto the printed circuit board 50 in a state in which solder fillets are formed (see FIG. 2). Therefore, the chip resistor 1 for the printed circuit board 50 is used. The mounting strength is greatly improved. Although the heat radiation electrode 7 is electrically isolated, it extends to both end surfaces of the ceramic substrate 2 in the short direction, so that the plating layer 8 (Ni plating layer 9 and Sn plating layer 10) is formed. Therefore, there is no possibility that the heat conduction to the heat radiation electrode 7 will be hindered during the barrel plating, and therefore it is easy to deposit the plating layer 8 having a desired thickness on the heat radiation electrode 7.

  In the above embodiment, in the manufacturing stage of the chip resistor 1, by providing the narrow glass portion 15 that becomes the first protective layer 5 after the division, the narrow portion 15a that enters the secondary division groove 12 is provided after the division. Although the possibility that the Ag paste for the strip-shaped heat radiation electrode 16 to be the heat radiation electrode 7 reaches the surface electrode 31 by capillary action is excluded, it is possible to adopt a configuration in which the narrow portion 15a is not provided. It is also possible to provide an opening similar to the opening 14 in the substrate 13.

It is sectional drawing which follows the longitudinal direction which shows the state just before mounting of the chip resistor which concerns on the example of embodiment of this invention. It is sectional drawing which follows the transversal direction of this chip resistor of the mounting state. It is a principal part top view of the printed circuit board with which this chip resistor is mounted. It is process drawing for demonstrating the manufacturing method of this chip resistor. It is process drawing for demonstrating the manufacturing method of this chip resistor. It is process drawing for demonstrating the manufacturing method of this chip resistor. It is process drawing for demonstrating the manufacturing method of this chip resistor. It is a perspective view of the piece obtained in the middle of manufacture of this chip resistor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chip resistor 2 Ceramic substrate 3 Terminal electrode 4 Resistor 4a Trimming groove 5 1st protective layer (pre-glass coat)
6 Second protective layer (overcoat)
7 Radiation electrode 7a Extension part 8 Plating layer 9 Ni plating layer 10 Sn plating layer 11 Primary division groove 12 Secondary division groove 13 Large format board 50 Printed circuit board (mounting board)
51 Land (for terminal electrode) 52 Land (for heat radiation electrode) 53 Thermal via 55 Heat sink

Claims (1)

A rectangular parallelepiped ceramic substrate, a pair of terminal electrodes provided at both ends in the longitudinal direction of the ceramic substrate, a resistor provided on one side of the ceramic substrate to bridge the pair of terminal electrodes, and the resistance An insulating protective layer provided in a region covering the body, a heat dissipation electrode provided so as to cross the surface of the protective layer in a short direction between the pair of terminal electrodes, and the heat dissipation electrode and the terminal A plating layer deposited on the electrode,
The heat dissipation electrode extends from the one surface of the ceramic substrate to the middle of both end surfaces in the short direction, and the heat dissipation electrode and the terminal electrode are soldered to a plurality of lands spaced apart from each other on the mounting substrate. A chip resistor characterized by being mounted face down.

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