JP2004342766A - Circuit board and electronic component mounted body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board which can restrain a short circuit between electronic component installation electrodes and between wiring patterns when the electronic components are mounted, and an electronic component mounted body of high reliability which uses the circuit board. <P>SOLUTION: The circuit board in which a plurality of wiring patterns 13 are arranged on one main surface of an insulating substrate 11 and the one main surface includes an electrode formation region 10 which turns to an electronic component installation electrode by arranging conductive adhesive agent, is characterized by including a flow prevention projection 12 of the conductive adhesive agent arranged at a part of ambients at least of an electrode formation region 10. The circuit board is arranged inside, includes via including resin further, and one end of the via may expose in the electrode formation region 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a circuit board and an electronic component mounted body on which electronic components such as a semiconductor package component, a chip component, and a connector are mounted.
[0002]
[Prior art]
2. Description of the Related Art In recent years, regulations on lead in solder alloys have been regulated in the field of electronics mounting due to increasing awareness of environmental issues. Therefore, there is an urgent need to establish a technology for electrically connecting an electronic component to a circuit board using a lead-free material (lead-free material). Lead-free materials mainly include lead-free solder and conductive adhesives, but conductive adhesives that are expected to have advantages such as flexibility at the junction between electronic components and circuit boards and lower mounting temperatures Is attracting attention.
[0003]
The conductive adhesive usually contains, for example, a resin composition containing a thermosetting resin and a conductive filler dispersed in the resin composition. To mount an electronic component using this conductive adhesive, first, a conductive adhesive is applied by screen printing onto a land electrode (electrode for mounting electronic components) formed on a circuit board, and the printed conductive adhesive is applied. The electrode part of the electronic component is arranged on the upper side and heated to cure the thermosetting resin contained in the conductive adhesive. The curing causes the thermosetting resin to shrink, and the conductive fillers to come into contact with each other to ensure conduction between the electronic component and the circuit board, and to join the circuit board and the electronic component with a predetermined strength. (For example, see Patent Document 1).
[0004]
Since the conductive adhesive has a curing temperature of the thermosetting resin of about 100 to 200 ° C., the heating temperature is extremely low as compared with the lead-free solder made of tin-silver-copper having a melting temperature of 220 ° C. It can also be used to mount inexpensive electronic components with low heat resistance. Also, since the conductive adhesive contains a resin, the joint between the electronic component and the circuit board is more flexible than when solder is used, and has the advantage that cracks due to heat or external force are less likely to occur. .
[0005]
[Patent Document 1]
JP-A-10-303517 (pages 2-3)
[0006]
[Problems to be solved by the invention]
The mounting of electronic components using the conductive adhesive has the following problems.
[0007]
As the mounting density increases, the size of the electronic component installation electrode becomes smaller, so that it becomes difficult to stably print the conductive adhesive on the electronic component installation electrode. To improve the printability of the conductive adhesive, adjusting the size of the opening of the printing plate used for screen printing and adjusting the viscosity of the conductive adhesive are effective, but reducing the size of the opening, Alternatively, when the viscosity of the conductive adhesive is increased, the conductive adhesive cannot be removed from the printing plate, resulting in a problem of insufficient printing amount. Increasing the size of the opening or lowering the viscosity of the conductive adhesive causes a problem that the conductive adhesive flows out of the electrodes for electronic component installation, and a short circuit occurs between the electrodes for electronic component installation and between the wiring patterns. is there.
[0008]
In addition, the conductive adhesive has good wettability with respect to the electrode for mounting electronic components, or is pressurized for mounting and bonding of the electronic component when mounting the electronic component on the electrode for mounting electronic components. As a result, it may flow out of the electrode for electronic component installation. After the conductive adhesive is screen-printed on the electrode for electronic component installation, shear stress is applied to the conductive adhesive when the printing plate is removed, so that the viscosity of the conductive adhesive decreases and the conductive adhesive is used for the electronic component. In some cases, it flowed from the installation electrode. Further, the viscosity of the conductive adhesive may be reduced by heat at the time of curing, and the conductive adhesive may flow out of the electrode for electronic component installation.
[0009]
[Means for Solving the Problems]
The circuit board of the present invention is a circuit board in which a plurality of wiring patterns are arranged on one main surface of an insulating substrate, and the one main surface is provided with a conductive adhesive so that electronic components are installed. And an electrode forming region serving as an electrode for use, and a protrusion for preventing the conductive adhesive from flowing, which is disposed at least partially around the electrode forming region.
[0010]
The electronic component mounted body of the present invention is characterized in that the electronic component and the circuit board of the present invention are electrically connected via the conductive adhesive.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
In the circuit board of the present embodiment, one main surface of the insulating substrate includes an electrode forming region serving as an electronic component installation electrode by disposing a conductive adhesive, and at least the periphery of the electrode forming region. Includes the conductive adhesive flow prevention projections disposed in a part, for example, increasing the size of the opening of the printing plate used when applying the conductive adhesive to the electrode forming region by screen printing. Alternatively, even if the viscosity of the conductive adhesive is reduced, the electrodes for mounting electronic components can be formed in a desired region (electrode formation region), and the formed electrodes for mounting electronic components and one of the insulating substrates can be formed. Short circuit between the wiring patterns arranged on the main surface can be suppressed. In addition, the degree of freedom in selecting a conductive adhesive in the design of the electronic component package can be increased.
[0012]
It is preferable that the insulating substrate includes a resin, and a region including the resin exists in at least a part of the electrode formation region. Since the conductive adhesive contains a resin, if the electrode forming region contains a resin, the adhesiveness between the electrode forming region and the conductive adhesive is good, and the electronic component is mounted on the circuit board of the present embodiment. This is because the reliability of the mounted electronic component mounting body is improved.
[0013]
In the circuit board of the present embodiment, wherein the insulating substrate includes a resin, and at least a part of the electrode forming region includes a region including the resin, the circuit substrate further includes a via that includes a resin and is disposed therein. Preferably, one end of the via is exposed in the electrode formation region. Generally, the bonding strength between resin and resin is higher than the bonding strength between resin and metal. Since the conductive adhesive containing the resin and the via containing the resin can be directly bonded to each other, adhesion between the resin and the resin can be obtained, and a highly reliable electronic component mounted body can be obtained.
[0014]
In the electronic component mounted body of the present embodiment, since the circuit board of the present embodiment described above is used, a short circuit between the electronic component installation electrodes and the wiring pattern due to the outflow of the conductive adhesive is suppressed. ing.
[0015]
In the electronic component package of the present embodiment, it is preferable that the conductive adhesive contains the same resin as the resin contained in the electrode formation region. When the conductive adhesive contains the same resin as that of the electrode forming region, the compatibility is good, the adhesiveness between the electrode forming region and the conductive adhesive is good, and the reliability of the electronic component mounted body is increased. .
[0016]
Hereinafter, an example of the circuit board of the present invention and an example of the electronic component mounted body of the present invention will be specifically described with reference to the drawings.
[0017]
(Embodiment 1)
FIG. 1 is a partial plan view of an example of the circuit board of the present invention. As shown in FIG. 1, the circuit board of the present embodiment is a circuit board in which a plurality of wiring patterns 13 are arranged on one main surface of an insulating substrate 11, and one main surface has a conductive adhesive. A conductive adhesive flow preventing projection 12 (hereinafter referred to as a “protrusion 12”) that includes an electrode forming region 10 that becomes an electrode for electronic component installation by disposing an agent, and is disposed at least partially around the electrode forming region 10. Abbreviated).
[0018]
The circuit board of the present embodiment includes an electrode forming region 10 that is to be an electronic component installation electrode by disposing a conductive adhesive, and a protrusion 12 that is disposed at least partially around the electrode forming region 10. For example, the size of the opening of the printing plate used when applying the conductive adhesive to the electrode forming region 10 by screen printing or the viscosity of the conductive adhesive is reduced, (Electrode formation region 10), the electronic component installation electrode can be formed, and a short circuit between the formed electronic component installation electrode and the wiring pattern 13 can be suppressed.
[0019]
The insulating substrate 11 may be made of any material including a reinforcing material such as glass fiber or aramid fiber in an epoxy resin, a polyimide resin, a ceramic material containing alumina as a main component, and the like. In particular, it is preferable that the insulating substrate 11 contains a resin and that a region containing the resin exists in at least a part of the electrode formation region 10. Since the conductive adhesive contains a resin, if the electrode forming region 10 contains a resin, the adhesiveness between the electrode forming region 10 and the conductive adhesive is good, and the electronic component is mounted on the circuit board of the present embodiment. This is because the reliability of the electronic component mounted body on which is mounted is increased.
[0020]
The material of the projection 12 is not particularly limited, and may be any of a conductive material and an insulating material. When the protrusion 12 is formed of, for example, a conductive material, the protrusion 12 and the wiring pattern 13 may be integrated, and the protrusion 12 and the wiring pattern 13 may be formed simultaneously. When the insulating substrate 11 is formed of a material containing glass fiber in the epoxy resin, the protrusions 12 and the wiring patterns 13 are formed by bonding a copper foil to one surface of the insulating substrate 11 and then etching unnecessary portions. It can be formed by removing and leaving the surface of the copper foil with nickel and gold plating. In the case where the insulating substrate 11 is made of a ceramic material, a material in which tungsten is dispersed in glass and which exhibits conductivity when heated to 800 ° C. to 1000 ° C. and fired is screen-printed on the insulating substrate 11. Thereby, the protrusions 12 and the wiring patterns 13 can be formed simultaneously.
[0021]
Note that, even when the protrusion 12 is formed from a conductive material, it is not always necessary to form the protrusion 12 and the wiring pattern 13 at the same time. Even when the protrusion 12 and the wiring pattern 13 are not formed at the same time, the protrusion 12 can be formed by a method such as etching and printing.
[0022]
When the material of the protrusion 12 is an insulating material such as an epoxy resin, the protrusion 12 can be formed by forming a thin epoxy resin layer on the insulating substrate 11 and removing unnecessary portions by photolithography.
[0023]
In the example shown in FIG. 1, the protrusions 12 are formed all around the electrode forming region 10. However, the present invention is not limited to this. As shown in FIG. May be formed only in a part of the periphery of a region surrounded by a circle, for example, only in a place where the interval between the electrode forming regions 10 is narrow.
[0024]
Next, an example of a method for manufacturing an electronic component mounted body of the present invention will be described.
[0025]
As shown in FIG. 3, first, a conductive adhesive 14 is screen-printed on the electrode formation region 10 of the circuit board. When the protrusions 12 are formed of a conductive material, the conductive adhesive 14 is printed such that a part of the conductive adhesive 14 is disposed on the protrusions 12, and the protrusions 12 are formed of an insulating material. If it is formed, it is necessary to perform printing so that a part of the conductive adhesive 14 is arranged on the wiring pattern 13. This is because the conductive adhesive 14 and the wiring pattern 13 need to be electrically connected.
[0026]
In printing, a printing plate having a thickness greater than the thickness of the projections 12 is used, and the conductive adhesive 14 is printed such that the upper surface of the printed conductive adhesive 14 is slightly higher than the upper surface of the projections 12. Is preferred. As shown in FIG. 4B, since the terminal electrode 16 of the electronic component 15 and the conductive adhesive 14 can be sufficiently contacted, the resistance of the electrical connection between the electronic component 15 and the circuit board can be reduced. is there.
[0027]
As the conductive adhesive, one obtained by kneading a resin composition containing a conductive filler and a thermosetting resin can be used. For the thermosetting resin, for example, an epoxy resin, a phenol resin or the like can be used, and for the conductive filler, at least one selected from the group consisting of Ag, Pd, Ni, Au, Cu, C, Pt and Fe Metal particles can be used. The resin composition may contain a thermoplastic resin such as an acrylic resin or a polyester resin instead of the thermosetting resin, or may contain a mixture of the thermosetting resin and the thermoplastic resin. And may further contain a solvent. In particular, the conductive adhesive 14 preferably contains the same resin as the resin contained in the electrode formation region 10. If the electrode forming region 10 and the conductive adhesive 14 contain the same resin, the compatibility is good, so that the adhesiveness between the electrode forming region 10 and the conductive adhesive 14 is good, and the reliability of the electronic component mounted body is high. Is increased.
[0028]
The method of applying the conductive adhesive may be potting using a syringe in addition to screen printing.
[0029]
Next, as shown in FIG. 4A and FIG. 4B, the terminal electrodes 16 of the electronic component 15 are aligned with the conductive adhesive 14 so as to be in contact with each other, and the electronic component 15 is mounted on a circuit board. The conductive adhesive 14 is cured by heating to about ° C.
[0030]
As described above, in the circuit board according to the present embodiment, the electrode forming region 10 (see FIG. 1) which becomes the electrode for electronic component installation by disposing the conductive adhesive 14 and at least the periphery of the electrode forming region 10. Since it includes the protrusions 12 disposed in a part, short-circuiting between the electrodes for installing electronic components and between the wiring patterns 13 due to the outflow of the conductive adhesive 14 can be suppressed.
[0031]
In addition, the presence of the protrusions 12 facilitates the adjustment of the viscosity of the conductive adhesive 14. The properties required of the conductive adhesive 14 include a number of viscosities at the time of screen printing, a viscosity at the time of removing the printing plate, and a viscosity at the time of heating and pressing. In the circuit board of the present embodiment, the presence of the projections 12 alleviates the required characteristics of the conductive adhesive 14 and increases the degree of freedom in designing the conductive adhesive. Specifically, when the conductive adhesive has a shear rate of 1.0 sec ⁻¹ at a temperature of 30 ° C., the viscosity is conventionally 500 Pa · s to 1500 Pa · s. For the substrate, a conductive adhesive having a viscosity of 30 Pa · s to 1500 Pa · s can be used, and the degree of freedom in selecting the conductive adhesive in designing an electronic component package can be increased.
[0032]
(Embodiment 2)
FIG. 5 shows another example of the circuit board of the present invention. 5, constituent members having the same functions as the constituent members shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.
[0033]
As shown in FIG. 5, in the circuit board of the present embodiment, the insulating substrate 11 contains a resin, and at least a part of the electrode forming region 10 has a region containing the resin. Further, the circuit board further includes a via 17 including a resin disposed therein, and one end of the via 17 is exposed in the electrode formation region 10. The via 17 can be formed, for example, from a conductive resin composition obtained by mixing metal particles and a thermosetting resin. As the metal particles, for example, gold, silver, copper or nickel can be used, and as the thermosetting resin, for example, an epoxy resin, a phenol resin, an isocyanate resin, or the like can be used.
[0034]
For example, an electric path of an electronic component mounted body in which an electronic component is mounted on a conventional circuit board on which an electronic component installation electrode is formed by copper foil (plated with nickel and gold as necessary) is an electronic component. Electrode → conductive adhesive → electrode for mounting electronic parts on circuit board → via on circuit board. As a result of conducting a connection reliability test such as a heat cycle test and a humidity resistance test on such an electronic component mounted body, peeling between the conductive adhesive and the electrode for mounting the electronic component is considered to be the first cause of electrical connection failure. Was the factor. This is because the adhesive strength between the conductive adhesive and the electronic component installation electrode made of a metal material (copper foil) is low.
[0035]
When the circuit board of the present embodiment is used, the conductive adhesive 14 containing a resin and the via 17 containing a resin can be directly bonded to each other, so that the resin / resin bonding can be obtained. Since the bonding between the resin and the resin has a higher bonding strength than the bonding between the resin and the metal, the circuit board according to the present embodiment can suppress an electrical connection failure due to peeling or the like, and can provide a highly reliable electronic component mounted body. Can be obtained.
[0036]
Although FIG. 4 shows an electronic component mounted body in which electronic components are mounted only on one surface of the circuit board, the electronic component mounted body of the present invention is not limited to this, and the circuit board is provided on both main surfaces. An electronic component mounted body including a wiring pattern, an electrode formation region, and a projection, and electronic components mounted on both main surfaces may be used.
[0037]
【The invention's effect】
According to the present invention, it is possible to provide a circuit board capable of suppressing a short circuit between electrodes for mounting electronic components and between wiring patterns when mounting electronic components, and a highly reliable electronic component mounted body using the same. In addition, the degree of freedom in selecting a conductive adhesive in the design of the electronic component package can be increased.
[Brief description of the drawings]
1 is a partial plan view showing an example of the circuit board of the present invention; FIG. 2 is a partial plan view showing another example of the circuit board of the present invention; FIG. 3 is a conductive adhesive on the circuit board shown in FIG. FIG. 4A is a partial plan view showing an example of the electronic component package of the present invention, and FIG. 4B is a cross-sectional view taken along the line II ′ of FIG. Partial plan view showing another example of substrate [Explanation of reference numerals]
DESCRIPTION OF SYMBOLS 10 Electrode formation area 11 Insulating substrate 12 Protrusion preventing protrusion 13 of conductive adhesive 13 Wiring pattern 14 Conductive adhesive 15 Electronic component 16 Terminal electrode 17 of electronic component 17 Via

Claims (5)

A circuit board in which a plurality of wiring patterns are arranged on one main surface of an insulating substrate, wherein the one main surface is an electrode forming region that becomes an electrode for mounting electronic components by disposing a conductive adhesive. A circuit board, comprising: a protrusion for preventing the flow of the conductive adhesive, which is disposed on at least a part of a periphery of the electrode forming region. The circuit board according to claim 1, wherein the insulating substrate includes a resin, and a region including the resin exists in at least a part of the electrode formation region. The circuit board according to claim 2, wherein the circuit board further includes a via disposed inside and including a resin, and one end of the via is exposed in the electrode formation region. An electronic component mounted body, wherein the electronic component and the circuit board according to any one of claims 1 to 3 are electrically connected via the conductive adhesive. The electronic component package according to claim 4, wherein the conductive adhesive contains the same resin as a resin contained in the electrode formation region.

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