JP4256719B2 - Electronic component mounting body and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a circuit board and an electronic component mounting body in which electronic components such as a semiconductor package component, a chip component, and a connector are mounted on the circuit board.
[0002]
[Prior art]
In recent years, due to increasing awareness of environmental issues, regulations regarding lead in solder alloys are being implemented in the field of electronics packaging. Therefore, there is an urgent need to establish a technique for electrically connecting electronic components 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 benefit from the flexibility of joints between electronic components and circuit boards and lower mounting temperatures. Attention has been gathered.
[0003]
The conductive adhesive usually contains, for example, a resin composition containing a thermosetting resin and a conductive filler dispersed in the resin composition. When mounting electronic components using this conductive adhesive, first, conductive adhesive is applied to the land electrodes (electrodes for installing electronic components) formed on the circuit board by screen printing, and the printed conductive adhesive is used. The electrode part of an electronic component is arrange | positioned on it, it heats, and the thermosetting resin contained in a conductive adhesive is hardened. By curing, the thermosetting resin contracts, the conductive fillers come into contact with each other to ensure electrical connection between the electronic component and the circuit board, and the circuit board and the electronic component are bonded with a predetermined strength. (For example, refer to Patent Document 1).
[0004]
Since the conductive adhesive has a curing temperature of about 100 to 200 ° C., the heating temperature is extremely low compared to a 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. In addition, since the conductive adhesive contains a resin, the joint between the electronic component and the circuit board is more flexible than the case where solder is used, and has an advantage that cracking due to heat or external force hardly occurs. .
[0005]
[Patent Document 1]
JP-A-10-303517 (page 2-3)
[0006]
[Problems to be solved by the invention]
The mounting of electronic components using the above conductive adhesive has the following problems.
[0007]
As the mounting density becomes higher, the electrodes for installing electronic parts become smaller, and it becomes difficult to stably screen-print the conductive adhesive on the electrodes for installing electronic parts. In order to improve the printability of the conductive adhesive, the size adjustment of the opening of the printing plate used for screen printing and the viscosity adjustment of the conductive adhesive are effective, but the size of the opening is reduced, Alternatively, when the viscosity of the conductive adhesive is increased, there is a problem that the conductive adhesive cannot be removed from the printing plate and the printing amount is insufficient. If the size of the opening is increased or the viscosity of the conductive adhesive is lowered, the conductive adhesive will flow out of the electronic component installation electrodes, causing a short circuit between the electronic component installation electrodes and between the wiring patterns. is there.
[0008]
In addition, the conductive adhesive exhibits good wettability with respect to the electrode for installing the electronic component, or pressurization for weighting or joining the electronic component when the electronic component is mounted on the electrode for installing the electronic component. As a result, the liquid may flow out of the electronic component installation electrode. After screen printing the conductive adhesive on the electrode for electronic component installation, when the printing plate is removed, the conductive adhesive is subjected to shear stress, so the viscosity of the conductive adhesive is reduced and the conductive adhesive becomes an electronic component. Sometimes it flowed out of the electrode for installation. In addition, the viscosity of the conductive adhesive is lowered due to heat at the time of curing, and the conductive adhesive sometimes flows out from the electrode for installing the electronic component.
[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 an electronic component by arranging a conductive adhesive. It includes an electrode forming region serving as a working electrode, and includes a flow prevention protrusion of the conductive adhesive disposed at least at a part of the periphery of the electrode forming region.
[0010]
The electronic component mounting 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]
DETAILED DESCRIPTION OF THE INVENTION
In the circuit board according to the present embodiment, one main surface of the insulating substrate includes an electrode formation region that becomes an electrode for installing an electronic component by disposing a conductive adhesive, and at least around the electrode formation region. Since the conductive adhesive flow prevention protrusion is disposed in part, for example, the size of the opening of the printing plate used when applying the conductive adhesive to the electrode forming region by screen printing is increased. Alternatively, even if the viscosity of the conductive adhesive is lowered, the electrodes for installing electronic components can be formed in a desired region (electrode forming region), and between the formed electrodes for installing electronic components or one of the insulating substrates Short-circuiting between wiring patterns arranged on the main surface can be suppressed. Moreover, the freedom degree of selection of the conductive adhesive in the design of an electronic component mounting body can be raised.
[0012]
It is preferable that the insulating substrate contains a resin and a region containing the resin exists in at least a part of the electrode formation region. Since the conductive adhesive contains resin, if the resin is contained in the electrode formation region, the adhesion between the electrode formation region and the conductive adhesive is good, and the electronic component is mounted on the circuit board of this embodiment. This is because the reliability of the mounted electronic component is increased.
[0013]
In the circuit board according to the present embodiment, in which the insulating substrate includes a resin, and the region including the resin exists in at least a part of the electrode formation region, the circuit substrate further includes a via disposed in the circuit substrate. It is preferable that one end of the via is exposed in the electrode formation region. In general, the adhesion between resin / resin has higher adhesive strength than the adhesion between resin / metal. Since the conductive adhesive containing the resin and the via containing the resin can be directly adhered, the resin / resin adhesion can be obtained, and a highly reliable electronic component mounting body can be obtained.
[0014]
In the electronic component mounting body according to the present embodiment, since the circuit board according to the present embodiment described above is used, a short circuit between the electrodes for installing the electronic components and between the wiring patterns due to the flow of the conductive adhesive is suppressed. ing.
[0015]
In the electronic component mounting body according to the present embodiment, it is preferable that the conductive adhesive contains the same resin as that contained in the electrode formation region. This is because if the conductive adhesive contains the same resin as the electrode forming region, the compatibility is good, so the adhesive property between the electrode forming region and the conductive adhesive is good, and the reliability of the electronic component mounting body is increased. .
[0016]
Hereinafter, an example of a circuit board of the present invention and an example of an electronic component mounting 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 a 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 is made of conductive adhesive. The conductive adhesive flow prevention protrusions 12 (hereinafter referred to as “protrusions 12”) that include the electrode forming region 10 that becomes an electrode for installing an electronic component when the agent is disposed, and are disposed at least partially around the electrode forming region 10. Abbreviated).
[0018]
The circuit board according to the present embodiment includes an electrode forming region 10 that becomes an electrode for installing an electronic component by disposing a conductive adhesive, and a protrusion 12 disposed at least at a part of the periphery of the electrode forming region 10. Therefore, for example, even if the size of the opening of the printing plate used when applying the conductive adhesive to the electrode forming region 10 by screen printing is increased or the viscosity of the conductive adhesive is decreased, it is desirable. In this region (electrode formation region 10), the electrodes for installing the electronic components can be formed, and short circuits between the formed electrodes for installing the electronic components and between the wiring patterns 13 can be suppressed.
[0019]
The insulating substrate 11 may be formed of any material of a material containing a reinforcing material such as glass fiber or aramid fiber in an epoxy resin, a polyimide resin, a ceramic material mainly composed of alumina, or the like. In particular, it is preferable that the insulating substrate 11 includes a resin, and at least a part of the electrode formation region 10 includes a region including the resin. Since the conductive adhesive contains a resin, if the resin is contained in the electrode formation region 10, the adhesion between the electrode formation region 10 and the conductive adhesive is good, and the circuit board of this embodiment has an electronic component. This is because the reliability of the electronic component mounting body on which is mounted increases.
[0020]
There is no restriction | limiting in particular about the material of the processus | protrusion 12, Either of a conductive material and an insulating material may be sufficient. When the protrusion 12 is made 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 at the same time. When the insulating substrate 11 is formed of a material containing glass fiber in an epoxy resin, the protrusion 12 and the wiring pattern 13 are formed by etching unnecessary portions after bonding a copper foil to one surface of the insulating substrate 11. It can be formed by removing and applying nickel and gold plating to the surface of the remaining copper foil. When the insulating substrate 11 is made of a ceramic material, tungsten is dispersed in the glass, and a material that exhibits conductivity by heating and baking at 800 ° C. to 1000 ° C. is screen-printed on the insulating substrate 11. Thus, the protrusion 12 and the wiring pattern 13 can be formed simultaneously.
[0021]
Even when the protrusion 12 is formed of 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 simultaneously, the protrusion 12 can be formed by a method such as etching or printing.
[0022]
When the material of the protrusion 12 is, for example, 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 on the entire periphery of the electrode formation region 10. However, the present invention is not limited to this, and as shown in FIG. 2, the electrode formation region 10 (dotted line in FIG. 2). May be formed only in a part of the periphery of the region), for example, in a place where the interval between the electrode forming regions 10 is narrow.
[0024]
Next, an example of the manufacturing method of the electronic component mounting body of this invention is demonstrated.
[0025]
As shown in FIG. 3, first, the conductive adhesive 14 is screen-printed on the electrode forming region 10 of the circuit board. When the protrusion 12 is made of a conductive material, the conductive adhesive 14 is printed so that a part of the conductive adhesive 14 is disposed on the protrusion 12, and the protrusion 12 is made of an insulating material. When formed, it is necessary to print so that a part of the conductive adhesive 14 is disposed 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 thicker than the protrusion 12 is used, and the conductive adhesive 14 is printed such that the upper surface of the printed conductive adhesive 14 is slightly above the upper surface of the protrusion 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 brought into contact with each other, the resistance of the electrical connection between the electronic component 15 and the circuit board can be reduced. is there.
[0027]
What knead | mixed the conductive filler and the resin composition containing a thermosetting resin can be used for a conductive adhesive. For example, an epoxy resin, a phenol resin, or the like can be used as the thermosetting resin, and the conductive filler can be 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. Further, it may contain a solvent. In particular, the conductive adhesive 14 preferably contains the same resin as that 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. Therefore, the adhesion between the electrode forming region 10 and the conductive adhesive 14 is good, and the reliability of the electronic component mounting body This is because it increases.
[0028]
The method for applying the conductive adhesive may be potting using a syringe in addition to screen printing.
[0029]
Next, as shown in FIGS. 4A and 4B, the terminal electrode 16 of the electronic component 15 and the conductive adhesive 14 are aligned so that the electronic component 15 is mounted on the circuit board, and then 150 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) that becomes the electrode for installing the electronic component by disposing the conductive adhesive 14, and at least the periphery of the electrode forming region 10 Since the projections 12 arranged in part are included, short-circuits between the electrodes for installing electronic components and between the wiring patterns 13 due to the flow-out of the conductive adhesive 14 can be suppressed.
[0031]
Further, the presence of the protrusion 12 makes it easy to adjust the viscosity of the conductive adhesive 14. The properties required for the conductive adhesive 14 are many such as the viscosity at the time of screen printing, the viscosity at the time of removing the printing plate, the viscosity at the time of heating and the pressure. In the circuit board according to the present embodiment, the presence of the protrusion 12 reduces 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 has conventionally been 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 of selection of the conductive adhesive in the design of the electronic component mounting body can be increased.
[0032]
(Embodiment 2)
FIG. 5 shows another example of the circuit board of the present invention. In FIG. 5, constituent members having the same functions as those shown in FIG.
[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 formation region 10 has a region containing the resin. In addition, 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 from, for example, a conductive resin composition in which metal particles and a thermosetting resin are mixed. As the metal particles, for example, gold, silver, copper, nickel, or the like can be used. As the thermosetting resin, for example, an epoxy resin, a phenol resin, or an isocyanate resin can be used.
[0034]
For example, an electrical path of an electronic component mounting body in which an electronic component is mounted on a conventional circuit board in which an electrode for installing an electronic component is formed by copper foil (plated with nickel and gold if necessary) is an electronic component Electrode → conductive adhesive → circuit board electronic component installation electrode → circuit board via. 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 mounting body, peeling between the conductive adhesive and the electronic component installation electrode is the first of the poor electrical connection. It was a factor. This is due to the low adhesive strength between the conductive adhesive and the electronic component installation electrode made of a metal material (copper foil).
[0035]
If the circuit board of this Embodiment is used, the conductive adhesive 14 containing resin and the via | veer 17 containing resin can be adhere | attached directly, and adhesion | attachment between resin / resin can be obtained. Since the resin / resin adhesion has higher adhesive strength than the resin / metal adhesion, the circuit board of this embodiment can suppress electrical connection failure due to peeling and the like, and has a highly reliable electronic component mounting body. Can be obtained.
[0036]
4 shows the electronic component mounting body in which the electronic component is mounted only on one surface of the circuit board. However, the electronic component mounting body of the present invention is not limited to this, and the circuit board is mounted on both main surfaces. An electronic component mounting body that includes a wiring pattern, an electrode formation region, and a protrusion and has 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 installing electronic components and between wiring patterns when mounting an electronic component, and a highly reliable electronic component mounting body using the circuit board. Moreover, the freedom degree of selection of the conductive adhesive in the design of an electronic component mounting body can be raised.
[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 an electronic component mounting body according to the present invention, and B is a cross-sectional view taken along line II ′ of A. FIG. 5 is a circuit according to the present invention. Partial plan view showing another example of substrate [Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Electrode formation area 11 Insulating substrate 12 Flow prevention protrusion 13 of conductive adhesive 13 Wiring pattern 14 Conductive adhesive 15 Electronic component 16 Terminal electrode 17 of electronic component Via

Claims (2)

An electronic component and a circuit board are electronic component mounting bodies that are electrically connected via an electronic component installation electrode,
The circuit board is a circuit board disposed a plurality of wiring patterns on one principal surface of the insulating substrate, wherein the one main surface, the electronic component installed by electrically conductive adhesive is disposed includes an electrode formation region where the electrodes Ru is formed, seen including at least a part disposed a flow prevention protrusions of the conductive adhesive around the electrode formation region,
The conductive adhesive comprises an epoxy resin;
The insulating substrate contains an epoxy resin, and there is a region containing the epoxy resin in at least a part of the electrode formation region,
The circuit board further includes a via disposed inside and including an epoxy resin, and one end of the via is exposed in the electrode formation region,
The electronic component mounting body, wherein the electrode forming region and the via are directly bonded to the conductive adhesive . It is a manufacturing method of the electronic component mounting object according to claim 1,
The conductive adhesive containing a solvent is applied to the electrode forming region, the electronic component is mounted on the circuit board via the conductive adhesive, and then the conductive adhesive is cured to install the electronic component. The manufacturing method of the electronic component mounting body characterized by including the process used as the electrode for an object.

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