JP2003043675A - Solder resistant resin layer and wiring board using the same and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solder resistant resin layer having the thermal fatigue resistance to a heat history and temperature cycle test(TCT) in packaging, the moisture resistance to a high acceleration test (HAST), etc., and a wiring board using the same and an electronic device. SOLUTION: The solder resistant resin layer 3 is formed by curing a resin composition containing an epoxy resin mixture, thermal stress absorption particles A formed by using elastomer particles not compatible with the epoxy resin mixture as cores and coating the cores with the resin compatible with the epoxy resin mixture as a shell layer and inorganic insulative fillers of 0.1 to 2 μm in average grain size and the Erichsen value thereof is 5 to 15 mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder-resistant resin layer having excellent heat resistance and moisture resistance, a wiring board using the same, and an electronic device, and more particularly, to a heat history during mounting and a temperature cycle test (TCT). To a solder-resistant resin layer excellent in heat fatigue resistance and moisture resistance against a high acceleration test (HAST), a wiring board using the same, and an electronic device.

[0002]

2. Description of the Related Art Generally, current electronic devices are required to be small, thin, lightweight, high-performance, high-performance, high-quality and highly reliable as represented by mobile communication devices. Electronic devices mounted on various electronic devices are also required to be small and have high density. Therefore, wiring boards that make up electronic devices are also required to be small, thin, and have multiple terminals. To achieve this, the widths of wiring conductors such as signal conductors are made narrower and the intervals between them are reduced. High-density wiring is achieved by multilayering wiring conductors.

A wiring board manufactured by adopting a build-up method is known as a wiring board capable of such high-density wiring. The build-up method is, for example, a core material obtained by impregnating a reinforcing material such as a glass cloth or an aramid non-woven fabric with a thermosetting resin typified by an epoxy resin having heat resistance and chemical resistance and curing the epoxy resin. A varnish made of a thermosetting resin such as a resin is applied and cured by heating to form an insulating layer, and then a via hole having a diameter of about 50 to 200 μm is formed in the insulating layer by laser light. The inner wall of the via hole is chemically roughened with a roughening solution such as potassium permanganate solution, and thereafter, a wiring conductor is formed on the inner wall of the via hole and the surface of the insulating layer by using an electroless copper plating method and an electrolytic copper plating method. This is a method of manufacturing a wiring board in which the same steps as described above are repeated on the insulating layer to form an insulating layer and a wiring conductor. In addition, this wiring board has solder bonding pads functioning as connection terminals for the electronic components to be mounted and solder bonding pads connected to the wiring conductors of the external electric circuit board on the outermost insulating layer surface. And
Further, on the surface of the insulating layer including the outer peripheral portion of the solder joint pad, a solder resistant resin layer having an opening for exposing the central portion of the solder joint pad is adhered and formed.

Such a solder-resistant resin layer is formed by using a roll coater method or a screen printing method with an uncured resin liquid composed of a photosensitive resin, an inorganic insulating filler, and a photoinitiator to form an outermost insulating layer or wiring conductor.・ Apply to a predetermined thickness on the entire surface of the solder bonding pad, and dry it to adhere to the surface of the insulating layer. Then, the solder resistant resin layer is exposed and developed to form a solder bonding pad. It is formed by forming an opening and finally by photo-curing and heat-curing. Furthermore, on the exposed solder joint pad surface,
Nickel / gold plating with good wettability with solder is applied.

Then, the openings on the solder bonding pads are filled with the solder paste by screen printing, and the solder paste is melted and solidified by passing through a reflow oven to form solder bumps. An electronic device is manufactured by electrically connecting the solder joint pads of the wiring board and the connection terminals of the electronic component via the interposer, and then bonding the wiring board and the electronic component with an underfill material. The electronic device is mounted on the external electric circuit board by connecting the solder joint pads for connecting the external terminals to the wiring conductors of the external electric circuit board via the solder bumps.

[0006] In general, such a wiring board contains an elastic body such as an elastomer or rubber in the solder-resistant resin layer in order to improve thermal history at the time of mounting and thermal fatigue resistance to a temperature cycle test (TCT). (See Japanese Patent Laid-Open No. 2001-57446). Note that these elastomers, rubbers, and other elastic bodies are microphase-separated in the solder-resistant resin layer so as to form a sea-island structure, and absorb the stress generated by the difference in thermal expansion between the solder bonding pad and the solder-resistant resin layer. -It is relaxed and the generation of cracks is suppressed.

[0007]

However, in the above-mentioned wiring board, the particle size of the elastic body such as elastomer or rubber which is microphase-separated in the solder resistant resin layer is not uniform and the solder resistant resin layer surface is Since it is easily unevenly distributed, and the elastic body such as an elastomer or rubber easily sticks to the glass mask during exposure, there is a problem that the appearance becomes poor.

Further, the solder resistant resin layer contains 30 to 80% by weight of an inorganic insulating filler having an average particle diameter of 5 to 20 .mu.m in order to match the coefficient of thermal expansion with that of the insulating layer and the wiring conductor.
Although contained, moisture easily accumulates at the interface between the inorganic insulating filler and the resin and impurity ions easily move along this interface, and the solder-resistant resin layer is 5 to 20 μm as the wiring board becomes thinner. When the thickness of the solder-resistant resin layer is reduced, the particles of the inorganic insulating filler having a particle size larger than the thickness of the solder-resistant resin layer crosslinks both the front and back surfaces of the solder-resistant resin layer, resulting in a high acceleration test (HAST). ), The impurity ions easily move along the interface between the inorganic insulating filler and the resin on both the front and back surfaces of the solder-resistant resin layer, and the insulation resistance sharply decreases, causing an electrical short circuit. Had the problem.

The present invention has been completed in view of the above problems of the prior art, and an object thereof is thermal fatigue at the time of mounting and thermal fatigue resistance to a temperature cycle test (TCT) and moisture resistance to a high acceleration test (HAST). An object is to provide a solder-resistant resin layer having excellent properties, a wiring board using the same, and an electronic device.

[0010]

The solder-resistant resin layer of the present invention comprises an epoxy resin mixture, elastomer particles incompatible with the epoxy resin mixture as a core, and a resin compatible with the epoxy resin mixture as a shell layer. It is formed by curing a resin composition containing heat stress absorbing particles and an inorganic insulating filler having an average particle diameter of 0.1 to 2 μm, and has an Erichsen value of 5 to 15 mm.

In the solder-resistant resin layer of the present invention, the epoxy resin mixture is an acrylic modified epoxy resin 40 to 80% by weight.
And 20 to 60% by weight of an epoxy resin, and 20 to 60% by weight of heat stress absorbing particles and 5 to 20% by weight of an inorganic insulating filler with respect to the epoxy resin mixture. To do.

In the wiring board of the present invention, the above-mentioned solder-resistant resin layer is adhered and formed on the insulating substrate on which the solder-bonding pad is adhered, and an opening is formed in the solder-resistant resin layer on the solder-bonding pad. It is characterized by consisting of.

The electronic device of the present invention is characterized in that the electrodes of the electronic component are connected to the solder joint pads in the openings formed in the solder-resistant resin layer of the wiring board through solder.

According to the solder-resistant resin layer of the present invention, thermal stress absorbing particles obtained by coating an epoxy resin mixture with a shell layer of a resin that is compatible with the epoxy resin mixture and has a core of elastomer particles that are incompatible with the epoxy resin mixture. Since it is contained, the thermal stress absorption particles can be uniformly dispersed in the solder-resistant resin layer, and as a result, the thermal stress absorption particles are not unevenly distributed on the surface of the solder-resistant resin layer and the glass mask can be exposed at the time of exposure. It is possible to form a solder-resistant resin layer having good appearance without sticking. Also, the average particle size is 0.1 ~
Since it contains an inorganic insulating filler of 2 μm,
Solder resistant resin layer is 5 to 20μ as wiring board becomes thinner
Even if the thickness is reduced to m, the inorganic insulating filler particles do not crosslink both the front and back surfaces of the solder-resistant resin layer, and as a result, ion migration does not occur even in the high acceleration test (HAST) and heat resistance -A photosensitive solder resin layer having excellent moisture resistance can be formed. Furthermore, since the Erichsen value is set to 5 to 15 mm, it occurs due to the difference in thermal expansion between the solder-resistant resin layer and the solder joint pad when mounting an electronic component on the wiring board or when performing a temperature cycle test (TCT). The thermal stress can be relaxed, and the solder-resistant resin layer is not cracked. As a result, the solder-resistant resin layer can be excellent in electrical connection reliability without breaking the wiring conductor layer. Further, since it contains the epoxy resin mixture, it is possible to form a solder-resistant resin layer having good adhesion to the solder joint pad or the insulating substrate due to the polarity of the epoxy group.

Further, according to the solder-resistant resin layer of the present invention, since the epoxy resin mixture is composed of 40 to 80% by weight of the acrylic modified epoxy resin and 20 to 60% by weight of the epoxy resin, it is resistant to chemicals such as plating solutions. It is possible to obtain a solder-resistant resin layer which has excellent properties and does not cause cracks. Furthermore, for the epoxy resin mixture, heat stress absorbing particles are added.
Since it contains 20 to 60% by weight, it has flexibility, heat resistance, and
It has excellent moisture resistance, and since it contains 5 to 20% by weight of an inorganic insulating filler, the solder-resistant resin layer can be formed flat and exposed by exposure and development. No filler remains when forming the part.

According to the wiring board of the present invention, the solder resistant resin layer is deposited on the insulating substrate on which the solder bonding pad is deposited, and the opening is formed in the solder resistant resin layer on the solder bonding pad. Since it is formed, the solder-resistant resin layer can protect the insulating layer from heat when mounting electronic components on the wiring board and protect the solder joint pads from oxidation and corrosion due to moisture, resulting in heat resistance and A wiring board having excellent moisture resistance can be obtained.

Further, according to the electronic device of the present invention, since the electrode of the electronic component is connected to the solder joint pad in the opening formed in the solder-resistant resin layer of the wiring board through the solder, the temperature cycle test is performed. Even in (TCT), no crack or peeling occurs, and an electronic device having excellent heat resistance and humidity resistance can be obtained.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a solder-resistant resin layer of the present invention, a wiring board using the same, and an electronic device will be described in detail.

The solder-resistant resin layer of the present invention comprises an epoxy resin mixture, thermal stress absorbing particles obtained by coating a core of elastomer particles incompatible with the epoxy resin mixture with a resin compatible with the epoxy resin mixture as a shell layer. Average particle size is
It is formed by curing a resin composition containing an inorganic insulating filler of 0.1 to 2 μm. The epoxy resin mixture is composed of 40 to 80% by weight of an acrylic modified epoxy resin and 20 to 60% by weight of an epoxy resin.
.About.60% by weight and 5 to 20% by weight of an inorganic insulating filler.

Since such an epoxy resin mixture has a carboxylic acid or a hydroxyl group, it has the function of improving the adhesion to the solder joint pad of the wiring board and the insulating substrate, and the crosslinking density of the solder-resistant resin layer is high. However, it has a function of suppressing molecular cutting of the resin due to heat and permeation of water into the resin.

The content of the acrylic modified epoxy resin is 40% by weight or more from the viewpoint that it is difficult for resin residue or undercut to occur when an opening is formed in the solder resistant resin layer described later by exposure and development. Is preferable, and it is preferably 80% by weight or less from the viewpoint of excellent chemical resistance to plating solutions and the like. Therefore, the content of the acrylic modified epoxy resin is preferably in the range of 40 to 80% by weight. If the content of the epoxy resin is less than 20% by weight, the crosslink density of the solder-resistant resin layer becomes low,
Heat resistance and chemical resistance tend to decrease, and if it exceeds 60% by weight, the crosslink density of the solder resistant resin layer becomes high and flexibility decreases, and cracks tend to occur easily. Therefore, the content of the epoxy resin is preferably in the range of 20 to 60% by weight.

As such an acrylic-modified epoxy resin, a photosensitive resin such as an acrylated cresol novolac type epoxy resin or an acrylated phenol novolac type epoxy resin is used, and has a molecular weight of several hundreds from the viewpoint of exposure and developability. Thousands are preferable. As the epoxy resin, a thermosetting resin such as a bisphenol A type epoxy resin or a bisphenol F type epoxy resin is used. From the viewpoint of heat resistance and chemical resistance, a resin having a molecular weight of about several hundreds is preferable. Further, an α-aminoketone-based photopolymerization initiator or a benzophenone-based photosensitizer may be added to the resin composition in order to accelerate exposure and development.

In the solder-resistant resin layer of the present invention, 100% by weight of the epoxy resin compound is coated with elastomer particles which are incompatible with the epoxy resin mixture as a core and a resin which is compatible with the epoxy resin mixture as a shell layer. It contains 20 to 60% by weight of heat stress absorbing particles. Such thermal stress absorbing particles have a function of absorbing thermal stress generated when an electronic component is mounted on a wiring board or when performing a temperature cycle test (TCT), and prevent cracks in the solder-resistant resin layer. .
Further, since the core elastomer particles are coated with a resin compatible with the epoxy resin mixture, they can be uniformly dispersed in the solder-resistant resin layer, and as a result, uneven distribution on the solder-resistant resin layer surface may occur. In addition, the solder-resistant resin layer has a good appearance without sticking to the glass mask during exposure.

The content of such thermal stress absorbing particles is
If it is less than 20% by weight, the flexibility of the solder-resistant resin layer is reduced and the solder-resistant resin layer tends to be cracked,
Also, if it exceeds 60% by weight, the cross-linking density decreases and heat resistance
Moisture resistance tends to decrease. Therefore, the content of the heat stress absorbing particles is preferably in the range of 20 to 60% by weight.

The average particle size of the heat stress absorbing particles is 1 to 5
The range of μm is preferable, 1 μm or more is preferable in order to suppress the increase in viscosity at the time of mixing, and 5 μm or less is preferable in order to improve the appearance of the surface of the solder-resistant resin layer. The range of ˜5 μm is preferable.

As the elastomer serving as the core of such heat stress absorbing particles, any elastic material which is incompatible with the epoxy resin mixture may be used. For example, styrene-ethylene-butylene-styrene triblock polymer (SEB).
S) -Styrene-ethylene-isoprene-styrene triblock polymer (SEPS) -Polyether-polyester multiblock polymer thermoplastic elastomers, acrylic rubber (ACM), hydrogenated acrylonitrile-butadiene rubber (HNBR), etc. Rubber is used. The resin for the shell layer may be any resin that is compatible with the epoxy resin mixture. For example, epoxy resin, acrylonitrile-styrene resin (AS), or the like is used.

As a method of producing the heat stress absorbing particles, for example, an elastomer such as SEBS is uniformly dispersed in an organic solvent with a homogenizer or the like, and a resin to be a shell layer such as AS is dissolved in the organic solvent. After mixing and mixing, a method of coating the resin by drying with a spray dryer, or after synthesizing elastic particles such as acrylic rubber by emulsion polymerization or suspension polymerization, further adding acrylonitrile monomer and styrene monomer. There is a method of coating elastic particles with AS resin by seed polymerization.

The solder-resistant resin layer of the present invention contains an inorganic insulating filler having an average particle size of 0.1 to 2 μm.
The inorganic insulating filler has a function of increasing the strength of the solder-resistant resin layer and matching the thermal expansion coefficient of the solder resin layer with the thermal expansion coefficient of the insulating layer or the wiring conductor. According to the solder-resistant resin layer of the present invention, the average particle size of the inorganic insulating filler is 0.1 to
Since the thickness of the solder-resistant resin layer is 2 μm, even if the thickness of the solder-resistant resin layer is reduced to 5 to 20 μm as the wiring board is made thinner, the inorganic insulating filler particles do not crosslink both the front and back surfaces of the solder-resistant resin layer. As a result, high acceleration test (HA
Even in ST), ion migration does not occur, and a solder-resistant resin layer having excellent heat resistance and humidity resistance can be obtained.

The inorganic insulating filler has an average particle size of 0.
If it is less than 1 μm, the bulk density tends to be high, and the viscosity of the solder-resistant resin layer at the time of molding tends to increase, making it difficult to control the thickness. When the thickness is reduced, a plurality of inorganic insulating filler particles are connected in a row to crosslink both the front and back surfaces of the solder-resistant resin layer, and ion migration occurs along the interface between the inorganic insulating filler and the resin to prevent soldering. The insulation resistance of the resin layer tends to decrease. Therefore,
The average particle size of the inorganic insulating filler is preferably in the range of 0.1 to 2 μm. Further, the content of the inorganic insulating filler is preferably 5% by weight or more from the viewpoint of ensuring the flatness at the time of forming the solder resistant resin layer.
It is preferably 20% by weight or less from the viewpoint that the residual inorganic insulating filler is less likely to be generated when the opening is formed by development. Therefore, the content of the inorganic insulating filler is preferably in the range of 5 to 20% by weight based on the epoxy resin mixture.

As such an inorganic insulating filler,
Inorganic insulating particles such as silicon oxide, aluminum oxide, aluminum nitride, silicon carbide, calcium titanate, titanium oxide, and zeolite are used, and silicon oxide is preferable from the viewpoint of controlling the thermal expansion coefficient. Further, in order to improve the wettability with the resin, it may be used after being treated with a silane coupling agent or the like.

Furthermore, since the solder-resistant resin layer of the present invention has an Erichsen value of 5 to 15 mm after the above resin composition is cured, it can be used for mounting electronic parts on a wiring board or in a temperature cycle test (TCT). ), The solder-resistant resin layer absorbs the difference in thermal expansion between the solder-resistant resin layer and the insulating layer well, and the solder-resistant resin layer does not crack. As a result, the wiring conductor is disconnected. It is possible to obtain a solder-resistant resin layer having excellent electrical connection reliability.

Here, the Erichsen value of the solder-resistant resin layer is such that a solder-resistant resin layer is adhered to an iron plate of 1 mm and an iron ball having a diameter of 10 mm is pressed from the back side to raise the solder-resistant resin layer and raise cracks. Expressed in height.

Such a solder-resistant resin layer is formed, for example, by adding an epoxy resin mixture consisting of 60% by weight of an acrylic-modified cresol novolac type epoxy as an acrylic-modified epoxy resin and 40% by weight of a bisphenol A type epoxy as an epoxy resin to a heat-resistant epoxy resin mixture. As the stress absorbing particles, the core is acrylic rubber and the shell layer is AS resin, and the average particle size is 3μ.
A liquid varnish is prepared by adding 50% by weight of m particles, 10% by weight of silicon oxide having an average particle size of 0.1 to 2 μm as an inorganic insulating filler, and an organic solvent, and kneading.
This is applied by uniformly applying it onto a predetermined insulating substrate by employing a screen printing method or a roll coating method, further drying to remove the organic solvent, and then U
Manufactured by V and heat curing. Further, the solder-resistant resin layer may be used as a film-shaped solder-resistant resin obtained by applying the above liquid varnish on a release film and drying it. In this case, the film-shaped solder-resistant resin should use a vacuum laminator. To be deposited on the insulating substrate.

Thus, the solder-resistant resin layer of the present invention can be made excellent in heat resistance and moisture resistance without cracking even in the temperature cycle test (TCT).

The solder-resistant resin layer of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention. For example, the above solder-resistant resin layer may contain an organic dye such as phthalocyanine green for facilitating visual inspection and a lubricant such as higher fatty acid ester for improving moldability.

Next, a wiring board and an electronic device using the solder-resistant resin layer of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an example of an embodiment of an electronic device in which an electronic component such as a semiconductor element is mounted on a wiring board using a solder-resistant resin layer of the present invention. In this figure, 1 is an insulating substrate, 2 is a solder bonding pad, 3 is a solder-resistant resin layer, and these mainly constitute the wiring substrate 4 of the present invention.
Further, 5 is an opening, 6 is a solder bump, 7 is an electronic component, and the electronic device 8 of the present invention is mainly composed of the wiring board 4, the solder bump 6 and the electronic component 7. In this example, the solder joint pads 2 adhered and formed on both surfaces of the insulating substrate 1 are electrically connected by the through conductors 10 formed in the through holes 9.

Further, FIG. 2A is an enlarged sectional view of an essential part of FIG. 1, and FIG. 2B is an enlarged sectional view of an essential part of a conventional wiring board. In these figures, A is a thermal stress absorbing particle, B is
Are elastic particles such as elastomer and rubber.

The insulating substrate 1 is made of glass cloth-epoxy resin, glass cloth-bismaleimide triazine resin, glass cloth-polyphenylene ether, aramid fiber-.
It is made of epoxy resin or the like, has a function as a support for the solder bonding pad 2 and the solder-resistant resin layer 3, and is manufactured by a conventional method.

On both front and back surfaces of the insulating substrate 1, solder joint pads 2 made of a metal thin film of copper, nickel, aluminum or the like are provided.
Has been formed.

The solder joint pads 2 are a part of wiring conductors formed on both front and back surfaces of the insulating substrate 1. At the front surface side of the insulating substrate 1, each electrode of the electronic component 7 is a conductive bump 6 such as solder. And a wiring conductor (not shown) of the external electric circuit board is electrically connected to the rear side portion via conductor bumps 6 such as solder.

Such a solder bonding pad 2 is obtained by, for example, depositing a metal foil made of copper on the insulating substrate 1 via an adhesive, patterning it with a dry film resist, and then wiring conductors and It is formed by etching and removing a portion other than the portion to be the solder joint pad 2.

The thickness of the wiring conductor / solder joint pad 2 is preferably 3 μm or more from the viewpoint of preventing the wiring conductor / solder joint pad 2 from peeling off from the insulating substrate 1. Further, the thickness of the wiring conductor / solder joint pad 2 is set to the insulating substrate 1. It is preferable that the thickness is 50 μm or less from the viewpoint that a large stress does not remain in the wiring conductor / solder joint pad 2 when it is adhered and formed, and the wiring conductor / solder joint pad 2 is less likely to be separated from the insulating substrate 1. Therefore, the thickness of the wiring conductor / solder joint pad 2 is 3
It is preferably in the range of ˜50 μm.

On the surface of the insulating substrate 1, a solder resistant resin layer 3 having an opening 5 at the center of the solder bonding pad 2 is adhered and formed.

The solder-resistant resin layer 3 has a function of protecting the insulating substrate 1 from heat when mounting the electronic component 7 on the wiring substrate 4 and protecting the wiring conductor and the solder joint pad 2 from oxidation and corrosion due to moisture. Have. In addition, the solder-resistant resin layer 3
Has a good adhesion to the wiring conductor / solder joint pad 2 and the insulating substrate 1 due to the polarity of the epoxy group. Further, in the conventional example, the elastic body particles B are likely to be unevenly distributed on the surface of the solder resistant resin layer 30 as shown in FIG.
In order to form the thermal stress absorbing particles A by coating the resin compatible with the epoxy resin mixture as the shell layer with the elastomer particles not compatible with the epoxy resin mixture as the core, as shown in FIG. The thermal stress absorbing particles A are not evenly dispersed in the solder-resistant resin layer and unevenly distributed on the surface of the solder-resistant resin layer 3. As a result, the thermal stress absorbing particles A do not adhere to the glass mask during exposure, and the appearance It is possible to obtain a good solder-resistant resin layer 3. Furthermore, the average particle size is 0.
Since it contains the inorganic insulating filler of 1 to 2 μm, even if the solder resistant resin layer 3 is thinned to a thickness of 5 to 20 μm as the wiring board 4 is made thinner, the inorganic insulating filler particles are Does not crosslink both the front and back surfaces of the solder-resistant resin layer 3, and as a result, the solder-resistant resin layer 3 is excellent in heat resistance and humidity resistance without ion migration even in a high acceleration test (HAST). it can.

Such a solder-resistant resin layer 3 is, for example, an epoxy resin mixture composed of 60% by weight of acrylic-modified cresol novolac type epoxy as an acrylic-modified epoxy resin and 40% by weight of bisphenol A type epoxy as an epoxy resin. 50% by weight of particles having an average particle diameter of 3 μm and 50% by weight of particles of silicon oxide having an average particle diameter of 0.1 to 2 μm as an inorganic insulating filler, and 10% by weight of silicon oxide as an inorganic insulating filler. % And an organic solvent are added and kneaded to form a liquid varnish, which is applied by uniformly applying it onto a predetermined insulating substrate 1 by employing a screen printing method or a roll coating method. After further drying to remove the organic solvent, the opening 5 is formed on the solder joint pad 2 by exposure and development, and UV and thermosetting are performed. It is formed by performing. The solder-resistant resin layer 3 may be used as a film-shaped solder-resistant resin obtained by applying a liquid varnish on a release film and drying it. In this case, the film-shaped solder-resistant resin is insulated by using a vacuum laminator. The openings 5 are formed by being adhered to the substrate 1 and the solder bonding pads 2 and by irradiating the solder resistant resin layer 3 on the solder bonding pads 2 with a laser.

The diameter of the opening 5 is usually 30 to 30.
When the diameter is 300 μm and the diameter is larger than 300 μm, the diameter of the solder bonding pad 2 tends to be large and the wiring board 4 tends to be large, and when it is smaller than 30 μm, the electrical connection reliability tends to be deteriorated. . Therefore, the diameter of the opening 5 is preferably 30 to 300 μm.

Normally, on the exposed surface of the solder joint pad 2 in the opening 5, nickel / gold is used to prevent oxidation and corrosion of the solder joint pad 2 and to improve the connection with the conductor bump 6. It is preferable to deposit a metal having good electrical conductivity and excellent corrosion resistance such as, for example, a thickness of 1 to 20 μm by a plating method.

Thus, according to the wiring board 4 of the present invention,
Since the solder resistant resin layer 3 is deposited on the insulating substrate 1 on which the solder bonding pad 2 is deposited, and the opening 5 is formed in the solder resistant resin layer 3 on the solder bonding pad 2, The solder resin layer 3 can protect the insulating substrate 1 from heat when the electronic component 7 is mounted on the wiring board 4, and can protect the solder joint pads 2 from oxidation and corrosion due to moisture, and as a result, heat resistance and moisture resistance. The wiring board 4 having excellent properties can be obtained.

A conductor bump 6 is fixedly formed on the exposed surface of the solder joint pad 2 in the opening 5.
The conductor bump 6 has a function of electrically and mechanically connecting the solder joint pad 2 and the electronic component 7.

Such conductive bumps 6 are made of gold, lead-tin,
Made of a conductive material such as tin-zinc, tin-silver-bismuth,
For example, when the conductive material is solder made of lead-tin, the paste is printed in the opening 5 by a screen printing method or a solder ball made of lead-tin is placed in the opening 5 and then a reflow furnace is used. By passing through, it is fixedly formed in the opening 5 in a semicircular shape.

Then, the electronic component 7 is placed on the conductor bump 6, and the solder bonding pad 2 and each electrode of the electronic component 7 are electrically connected through a reflow furnace, whereby the electronic device 8 of the present invention is obtained. Become. In order to protect the conductor bumps 6 and firmly fix the electronic component 7 and the wiring board 4, an underfill material F composed of a thermosetting resin and a filler is provided between the electronic component 7 and the surface layer of the wiring board 4. May be injected.

Thus, according to the electronic device 8 of the present invention,
Opening 5 formed in the solder-resistant resin layer 3 of the wiring board 4
Since the electrode of the electronic component 7 was connected to the solder joint pad 2 in the interior through the conductor bump 6, the temperature cycle test (TC
Even in T), the electronic device 8 has excellent heat resistance and moisture resistance without cracking or peeling.

The electronic device of the present invention is not limited to the above embodiment, and for example, a built-up wiring board in which wiring conductors and insulating layers are alternately laminated on an insulating board is used as the wiring board. May be.

FIG. 3 is a sectional view showing an example of an embodiment of an electronic device in which electronic components are mounted on such a build-up wiring board. In this figure, 11 is an insulating substrate, 12 is a through hole, and 13 is a through hole. Is a through-hole conductor, 14 is an insulating layer, 15
Is a solder joint pad, 16 is a through hole, 17 is a through conductor, and 18 is a solder-resistant resin layer. These mainly constitute the wiring board 20 of the present invention. Further, 19 is an opening, 21 is a conductor bump, 22 is an electronic component, and mainly the wiring board 20 and the opening 19.
The conductor bump 21 and the electronic component 22 form an electronic device 23 of the present invention.

In this example, the wiring board 20 is constructed by alternately laminating the wiring conductors 15 and the insulating layers 14 on both front and back surfaces of the insulating substrate 11 and forming the solder-resistant resin layer 18 by adhesion.

In the above example, a semiconductor element is shown as an electronic component to be mounted in the electronic device, but electronic components such as a resistor, a capacitor and a piezoelectric element may be mounted. Further, a heat dissipation plate such as a stiffener may be attached to the wiring board in order to dissipate heat generated during the operation of the electronic component.
Further, an underfill material F composed of a thermosetting resin and a filler may be injected between the electronic component 22 and the surface layer of the wiring board 20.

[0058]

According to the solder-resistant resin layer of the present invention, the epoxy resin mixture is coated with a resin that is compatible with the epoxy resin mixture as a shell layer, and a core layer is made of elastomer particles that are incompatible with the epoxy resin mixture. Since the particles are contained, the thermal stress absorption particles can be uniformly dispersed in the solder-resistant resin layer, and as a result, the thermal stress absorption particles do not become unevenly distributed on the surface of the solder-resistant resin layer and the glass is exposed at the time of exposure. The solder-resistant resin layer has a good appearance without sticking to the mask. The average particle size is 0.1
Since it contains an inorganic insulating filler with a thickness of ~ 2 μm, the solder-resistant resin layer is used as the wiring board becomes thinner.
Even if the thickness is reduced to 20 μm, the inorganic insulating filler particles do not crosslink both sides of the solder-resistant resin layer, and as a result, ion migration does not occur even in high acceleration test (HAST) and heat resistance -A photosensitive solder resin layer having excellent moisture resistance can be formed. further,
Since the Erichsen value is set to 5 to 15 mm, thermal stress generated by the difference in thermal expansion between the solder-resistant resin layer and the solder joint pad when mounting electronic components on the wiring board or when performing a temperature cycle test (TCT). Can be alleviated and cracks do not occur in the solder-resistant resin layer, and as a result, a solder-resistant resin layer having excellent electrical connection reliability without disconnection of the wiring conductor layer can be obtained. Further, since it contains the epoxy resin mixture, it is possible to form a solder-resistant resin layer having good adhesion to the solder joint pad or the insulating substrate due to the polarity of the epoxy group.

Further, according to the solder-resistant resin layer of the present invention, since the epoxy resin mixture is composed of 40 to 80% by weight of the acrylic modified epoxy resin and 20 to 60% by weight of the epoxy resin, it is resistant to chemicals such as plating solution. It is possible to obtain a solder-resistant resin layer which has excellent properties and does not cause cracks. Furthermore, for the epoxy resin mixture, heat stress absorbing particles are added.
Since it contains 20 to 60% by weight, it has flexibility, heat resistance, and
It has excellent moisture resistance, and since it contains 5 to 20% by weight of an inorganic insulating filler, the solder-resistant resin layer can be formed flat and exposed by exposure and development. No filler remains when forming the part.

According to the wiring board of the present invention, the above-mentioned solder-resistant resin layer is adhered and formed on the insulating substrate on which the solder-bonding pad is adhered, and an opening is formed in the solder-resistant resin layer on the solder-bonding pad. Since it is formed, the solder-resistant resin layer can protect the insulating layer from heat when mounting electronic components on the wiring board and protect the solder joint pads from oxidation and corrosion due to moisture, resulting in heat resistance and A wiring board having excellent moisture resistance can be obtained.

Further, according to the electronic device of the present invention, since the electrode of the electronic component is connected to the solder joint pad in the opening formed in the solder-resistant resin layer of the wiring board through the solder, the temperature cycle test is performed. Even in (TCT), no crack or peeling occurs, and an electronic device having excellent heat resistance and humidity resistance can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an embodiment of an electronic device in which an electronic component is mounted on a wiring board of the present invention.

FIG. 2 (a) is an enlarged cross-sectional view of a main part of FIG.
(B) is an enlarged cross-sectional view of a main part of a conventional wiring board.

FIG. 3 is a cross-sectional view showing another example of the embodiment of the electronic device in which the electronic component is mounted on the wiring board of the present invention.

[Explanation of symbols]

1, 11 ... Insulating substrate 2, 15 ...- Solder joint pads 3, 18 ... Solder resistant resin layer 4, 20 ... Wiring board 5, 19 ... ・ Opening 6, 21 ... Conductor bumps 7,22 ... Electronic parts 8 ・ 23 ・ ・ ・ ・ ・ ・ Electronic device A ・ ・ Thermal stress absorption particles

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 23/12 501 H01L 23/12 501B 23/14 H05K 3/28 C H05K 3/28 H01L 23/14 R F-term (reference) 2H025 AA02 AA10 AA20 AB15 AC01 AD01 BC13 BC42 BC74 BJ03 CB30 CC08 CC20 4J038 CQ012 DB061 DB071 DB451 KA08 KA15 NA04 NA14 PB09 5E314 AA24 AA25 AA27 AA32 AA42 BB05 CC11 CC01 FF15

Claims (4)

[Claims] 1. An epoxy resin mixture, thermal stress absorption particles coated with a shell layer of a resin compatible with the epoxy resin mixture, the core being made of elastomer particles incompatible with the epoxy resin mixture, and an average particle size of 0. A solder resistant resin layer, which is formed by curing a resin composition containing 1 to 2 μm of an inorganic insulating filler and has an Erichsen value of 5 to 15 mm. 2. The epoxy resin mixture comprises 40 to 80% by weight of an acrylic modified epoxy resin and 20 to 20% of the epoxy resin.
60 wt% of the epoxy resin mixture, and 20 to 60 wt% of the thermal stress absorbing particles and 5 to 20 wt% of the inorganic insulating filler with respect to the epoxy resin mixture. 1. The solder-resistant resin layer according to 1. 3. The solder resistant resin layer according to claim 1 or 2 is deposited on an insulating substrate on which a solder bonding pad is deposited, and an opening is formed in the solder resistant resin layer on the solder bonding pad. A wiring board formed by forming a portion. 4. An electronic device, wherein an electrode of an electronic component is connected to the solder joint pad in the opening formed in the solder-resistant resin layer of the wiring board according to claim 3 via a conductor bump.