JP2002043723A - Wiring board and electronic parts module using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board and an electronic parts module using the wiring board excellent in thermal hysteresis, thermal fatigue resistance in a heat cycle test and moisture resistance in high acceleration test (HAST) when mounted on. SOLUTION: On a wiring board 4, a wiring conductive layer 2 is formed by adhering the wiring conductive layer 2 on the surface of an insulating board 1. A solder resist layer 3 is adhered with covering a part of the wiring conductive layer 2. The solder resist layer 3 is comprised of a lower layer part 3a which principal constituent is photosensitive resin and an upper layer part 3b which principal constituent is thermosetting resin. The infiltrating amount of the upper layer part 3b is 20 to 150 g/m2 when it is measured by a method regulated by JIS Z 0208. Therefore, the wiring conductive layer 2 does not corrode in a reliability test of a moisture shelf test and the like, and the solder resist layer 3 does not separate from the insulating board 1 when soldering, which prevents the wiring conductive layer from disconnecting. The value of resistance does not fall in a short period of time, or electric short circuit does not occur in a short period of time, even when a high acceleration test (HAST) is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board having a solder resist layer and an electronic component module using the same, and more particularly to a heat history and a temperature cycle test (TCT) at the time of mounting on an external electric circuit board. The present invention relates to a wiring board excellent in heat fatigue resistance against) and moisture resistance against a high acceleration test (HAST), and an electronic component module using the same.

[0002]

2. Description of the Related Art Conventionally, an electronic component module such as a hybrid integrated circuit device in which a predetermined electronic circuit is constituted by active components such as a semiconductor device and passive components such as a capacitance device and a resistor is usually used.
On the surface of a wiring board manufactured by forming a plurality of wiring conductor layers made of a refractory metal powder such as tungsten and molybdenum on the inside and the surface of an insulating base made of a ceramic material such as an aluminum oxide sintered body, a semiconductor element or the like is formed. Capacitive element
It is formed by mounting and mounting a resistor and the like and electrically connecting these electrodes to each wiring conductor layer.

However, such a wiring board has been required to be reduced in size, thickness, and weight, as represented by components used in mobile communication devices in recent electronic component modules. On the other hand, a conductive paste made of a refractory metal powder such as tungsten or molybdenum is applied to an insulating substrate made of a ceramic material such as an aluminum oxide sintered body into a predetermined pattern by using a thick film technique such as screen printing. Since the wiring conductor layer is formed by printing and applying, it is difficult to miniaturize the wiring conductor layer and it is not possible to form the wiring conductor layer at a high density. As a result, the wiring board is reduced in size and weight. There is a problem that it is difficult to do so. In addition, since the wiring conductor layer made of a high melting point metal powder such as tungsten or molybdenum has a high resistance, it is difficult to process electric signals at high speed, and recent semiconductor devices that require high-speed processing of electric signals are required. There is a problem that it is difficult to apply to a storage package or the like.

In order to solve such problems, recently, a low-resistance metal has been adopted by adopting a thin film forming method on the surface of an insulating substrate made of glass woven fabric or aramid woven fabric and a thermosetting resin such as epoxy resin. A so-called printed board formed by forming a wiring conductor layer made of copper, gold, or the like is applied to a package or the like that houses a wiring board or a semiconductor element.

[0005] In such a printed circuit board, after a wiring conductor layer is formed on the surface of an insulating substrate by employing an etching method, a transfer method, a plating method, or the like, oxidation and corrosion of the wiring conductor layer are prevented and wiring is performed. In order to protect the insulating substrate from heat when mounting electronic components on the board, a solder resist layer is formed by covering the wiring conductor layer, and then the solder resist layer is opened using an exposure and development method. And a nickel / gold plating on the wiring conductor layer exposed from the opening, and further connecting an electrode of an electronic component such as a semiconductor element to the wiring conductor layer via a conductor bump made of solder or the like. And the like.

Incidentally, the solder resist layer generally comprises
It is formed using a photosensitive resin that has good adhesion to the wiring conductor layer and the insulating substrate, has flexibility, and does not cause peeling or cracking from the insulating substrate in a reliability test such as a temperature cycle test. .

In this wiring board, the wiring conductor layer is formed by employing a thin film forming method such as an etching method, a transfer method or a plating method, so that the wiring conductor layer can be miniaturized. Since it is made of woven or aramid woven fabric and a thermosetting resin such as epoxy resin, it is small and lightweight, and since the wiring conductor layer is made of low-resistance metal such as copper and gold, electric signals It is possible to perform high-speed processing.

However, this wiring board is inferior in moisture resistance because the photosensitive resin forming the solder resist layer contains a highly hygroscopic component such as a hydroxyl group or a carboxylic acid group. In a reliability test such as a wet test in which the board is left for a long time, moisture is easily absorbed, and as a result, this moisture corrodes the wiring conductor layer and lowers the reliability of electrical connection of the wiring board. Had the problem that

Further, in this wiring board, when an opening is formed in the solder resist layer and a nickel / gold plating is applied to the wiring conductor layer exposed from the opening, a strong basic solution of a plating solution swells the solder resist layer. As a result, the solder resist layer is peeled off from the insulating substrate, and as a result, there is a problem that the wiring conductor layer is peeled off from the insulating substrate and disconnected.

[0010] In order to solve such problems, the crosslinking density of the resin constituting the solder resist layer is increased,
A method has been proposed in which a filler is densely filled in a solder resist layer to increase the hardness of the solder resist layer and prevent the solder resist layer from swelling due to a plating solution.

However, when the crosslinking density of the resin is increased, the flexibility of the solder resist layer is reduced, and cracks are generated in the solder resist layer in a heat fatigue resistance test such as a temperature cycle test. There has been a problem that disconnection occurs in the wiring conductor layer and the reliability of electrical connection of the wiring board is reduced. Also, when the solder resist layer is filled with the filler at a high density, the amount of resin in the solder resist layer is reduced by the high density of the filler, and the adhesion between the solder resist layer and the insulating substrate is reduced. As a result, peeling occurs between the insulating substrate and the solder resist layer in a thermal fatigue test such as a temperature cycle test, and as a result, the wiring conductor layer is peeled from the insulating substrate and the wiring substrate is peeled off. Has a problem in that the reliability of the electrical connection is reduced.

In order to solve these problems, the surface of the solder resist layer is filled with a filler at a high density of 50 to 90% by weight to increase the hardness, and the region on the insulating substrate side is filled with the filler. (Japanese Patent Laid-Open Publication No. 2000-31628) has been proposed a solder resist layer in which the filling amount is as small as 0 to 30% by weight to lower the hardness as compared with the surface layer side. According to this solder resist layer, the surface layer side is filled with a high density of fillers to increase the hardness, so that the solder resist layer does not swell during plating, and the solder resist layer and the wiring conductor layer are removed from the insulating substrate. Can be prevented from being separated and the wiring conductor layer is disconnected. In addition, since the solder resist layer has a lower filler filling amount in the region on the insulating substrate side and has a lower hardness than the surface layer side, the flexibility of the solder resist layer is reduced and cracks or solder The adhesiveness between the resist layer and the insulating substrate is not reduced, so that peeling does not occur between the insulating substrate and the solder resist layer. As a result, disconnection of the wiring conductor layer can be prevented.

[0013]

However, in recent years,
Higher-density wiring boards used in network personal computers and supercomputers for space development are required to have higher reliability. Electronic components such as semiconductor elements are soldered to conventional wiring boards. An electronic component module mounted via conductive bumps is, for example, a high-temperature type in which a voltage of 5.5 V is continuously applied between terminals of a wiring board in a high-temperature and high-humidity chamber having a temperature of 130 ° C. and a relative humidity of 85%. When an acceleration test (HAST) is performed, by applying a voltage between terminals at high temperature and high humidity, the metal of the conductive bumps is ionized and ion migration occurs, and the resistance value between adjacent conductive bumps decreases in a short time. Or electrical short-circuiting occurs between the conductive bumps in a short time, and as a result, the reliability of the electrical connection of the wiring board is reduced. This is because moisture easily accumulates at the interface between the filler and the resin, and metal ions easily move along this interface.In the solder resist layer on the surface layer filled with filler at a high density, the filler may be located between the conductor bumps or the solder resist layer. This is because the front and back surfaces are cross-linked, and as a result, when a high acceleration test (HAST) is performed, metal ions easily move between the conductor bumps along the interface between the filler and the resin.

The solder resist layer filled with such a filler at a high density generally has a moisture permeability of JIS.
It has a high value of 200 g / m 2 or more as measured by the method specified in Z 0208.

The present invention has been devised in view of the above-mentioned problems of the prior art, and has as its object the purpose of heat resistance at the time of mounting on an external electric circuit board, heat resistance to temperature cycle test, and high acceleration test ( An object of the present invention is to provide a wiring board excellent in moisture resistance against HAST) and an electronic component module using the same.

[0016]

According to the present invention, there is provided a wiring board comprising: a wiring conductor layer formed on a surface of an insulating substrate;
A wiring board comprising a solder resist layer covering a part of the wiring conductor layer, wherein the solder resist layer is a lower layer mainly composed of a photosensitive resin and an upper layer mainly composed of a thermosetting resin. And the upper layer is JIS Z
20 to 150 g / m 2 measured by the method specified in 0208
It is characterized by being.

Further, in the wiring board of the present invention, the lower part of the solder resist layer is composed of 50 to 80% by weight of a photosensitive resin, 10 to 40% by weight of an elastomer, and 5 to 20% by weight of an inorganic insulating filler.
And the upper layer is composed of 50 to 80% by weight of a thermosetting resin, 10 to 40% by weight of an elastomer, and 5 to 5 parts of an inorganic insulating filler.
It is characterized by comprising 20% by weight.

An electronic component module according to the present invention is an electronic component module in which an electronic component is mounted on the wiring board, wherein an opening for exposing a wiring conductor layer is provided in a solder resist layer, and the wiring conductor in the opening is provided. An electrode of an electronic component is connected to the layer via a conductor bump.

The electronic component module according to the present invention is characterized in that, in the electronic component module, the opening diameter of the upper layer of the solder resist layer is 50 to 80% of the opening diameter of the lower layer. It is.

According to the wiring board of the present invention, the lower part of the solder resist layer covering the wiring conductor layer is made mainly of a photosensitive resin, so that the solder resist layer is excellent in compatibility with the insulating substrate and the wiring conductor layer. A wiring board having excellent adhesion and exhibiting excellent thermal fatigue resistance without peeling or cracking from an insulating substrate in a reliability test such as a temperature cycle test can be obtained. In addition, since the upper layer portion of the solder resist layer is mainly composed of a thermosetting resin, the crosslink density can be increased and the solder resist layer has good moisture resistance and the solder resist layer does not swell during plating. As a result, the wiring substrate does not corrode in a reliability test such as a standing test in a wet condition, or the wiring conductor layer does not break due to peeling of the solder resist layer from the insulating substrate during plating. It can be.

Further, according to the wiring board of the present invention, the moisture permeability of the upper layer portion of the solder resist layer is 20 to 150 g / m 2 as measured by the method specified in JIS Z 0208. An opening for exposing the wiring conductor layer is provided in the solder resist layer, and an electrode of the electronic component is connected to the wiring conductor layer in the opening via a conductor bump. Even if a high acceleration test (HAST), in which a voltage of 5.5 V is continuously applied between terminals of a wiring board in an 85% high-temperature and high-humidity chamber, is performed, the resistance value between adjacent conductor bumps decreases in a short time. An electrical short circuit does not occur in a short time between conductor bumps, and a wiring board having good moisture resistance can be obtained.

Further, according to the wiring board of the present invention, since the upper and lower layers of the solder resist layer contain 10 to 40% by weight of the elastomer, they have good flexibility and can be reliably used in a temperature cycle test or the like. It is possible to obtain a wiring board excellent in heat fatigue resistance without causing peeling or cracking from the insulating substrate in the resistance test. The upper part of the solder resist layer has a low content of the inorganic insulating filler of 5 to 20% by weight, so that the inorganic insulating filler is cross-linked between the front and back surfaces of the solder resist layer and between adjacent conductor bumps. As a result, the moisture permeation amount of the upper layer portion of the solder resist layer can be measured to a value of 20 to 150 g / m 2 by the method specified in JIS Z 0208.

According to the electronic component module of the present invention, an opening for exposing the wiring conductor layer is provided in the solder resist layer of the wiring board, and the electrode of the electronic component is connected to the wiring conductor layer in the opening via the conductor bump. Because of the connection, it is possible to provide an electronic component module that is excellent in heat fatigue resistance and moisture resistance against a high acceleration test (HAST).

Further, according to the electronic component module of the present invention, since the opening diameter of the upper layer of the solder resist layer is 50 to 80% of the opening diameter of the lower layer, the photosensitive resin is mainly used. The lower layer can be covered well with the upper layer mainly composed of a thermosetting resin having a high crosslinking density and good moisture resistance, and as a result, a wet storage test or a high acceleration test (H
AST) to provide an electronic component module having good moisture resistance.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a wiring board according to the present invention and an electronic component module using the same will be described in detail with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of an essential part showing an example of an embodiment of an electronic component module in which electronic parts such as semiconductor elements are mounted on a wiring board of the present invention, and FIG. It is an expanded sectional view.

In these figures, 1 is an insulating substrate, 2 is a wiring conductor layer, and 3 is a solder resist layer composed of a lower layer 3a and an upper layer 3b, and these mainly constitute the wiring board 4 of the present invention. You. Reference numeral 5 denotes an opening composed of an opening 5a in the lower layer 3a and an opening 5b in the upper layer 3b, 6 denotes a conductor bump, and 7 denotes an electronic component. The wiring board 4 mainly includes the opening 5, the conductor bump 6, and the electronic component 7. Thus, the electronic component module 8 of the present invention is configured.

In this embodiment, an example is shown in which the wiring conductor layers 2 formed on both surfaces of the insulating substrate 1 are electrically connected by the through conductors 10 formed in the through holes 9.

The insulating substrate 1 is made of a resin material generally used for a wiring board such as glass cloth-epoxy resin, glass cloth-bismaleimide triazine resin, glass cloth-polyphenylene ether resin, aramid fiber-epoxy resin, and the like. 2 and a support for the solder resist layer 3.

A wiring conductor layer 2 made of a thin metal film such as copper, gold, nickel, or aluminum is formed on both sides of the insulating substrate 1.
Are formed. The wiring conductor layer 2 functions as a conductive path for electrically connecting each electrode of the electronic component 7 such as a semiconductor element mounted on the insulating substrate 1 to an external electric circuit board (not shown).

Each electrode of an electronic component 7 such as a semiconductor element is connected to a portion of the wiring conductor layer 2 exposed on the upper surface of the insulating substrate 1 by flip-chip connection via a conductor bump 6 made of gold, solder or the like. By connecting the portion exposed on the lower surface of the insulating substrate 1 to the wiring conductor layer of the external electric circuit board via solder, the electronic component 7 such as a semiconductor element can be connected to the wiring conductor layer 2.
Is electrically connected to an external electric circuit board via the

The wiring conductor layer 2 is formed by attaching a metal foil such as a copper foil to the surface of the insulating substrate 1 with an adhesive and etching the metal foil to form the wiring conductor layer 2. 2 is formed by adopting a transfer method of transferring a metal foil such as a copper foil formed in the shape of 2 to the insulating substrate 1, a plating method of forming the wiring conductor layer 2 on the surface of the insulating substrate 1 by plating, and the like. Wiring conductor layer 2 using a transfer method
Is formed, the copper foil bonded to the transfer film via an adhesive is formed in advance in the shape of the circuit conductor layer 2 by etching, and then the transfer film is overlaid on the insulating substrate 1 to be the wiring board 4. In addition, by heating at a temperature of 60 to 200 ° C. for 30 minutes to 24 hours while applying a pressure of 4 to 6 MPa, a coating is formed on the surface of the insulating substrate 1.

The wiring conductor layer 2 has a thickness of 3 to 50.
μm, and preferably 3 μm or more from the viewpoint of transmitting a high-speed electric signal. When the wiring conductor layer 2 is applied to the insulating substrate 1, no large stress remains in the wiring conductor layer 2. In order to make it difficult for the wiring conductor layer 2 to peel off from the insulating substrate 1, the thickness is preferably set to 50 μm or less.

Further, a solder resist layer 3 is formed on the surface of the insulating substrate 1 so as to cover a part of the wiring conductor layer 2. The solder resist layer 3 has a function of preventing oxidation and corrosion of the wiring conductor layer 2 and a function of protecting the insulating substrate 1 from heat when the electronic component 7 is mounted on the wiring substrate 1.

In the wiring board 4 of the present invention, the solder resist layer 3 comprises a lower layer 3a mainly composed of a photosensitive resin and an upper layer 3b mainly composed of a thermosetting resin.
It is important that the moisture permeability of the upper layer portion 3b is 20 to 150 g / m 2 as measured by the method specified in JIS Z 0208.

Here, the amount of moisture permeability is defined as the amount of moisture permeating through a film when a film having a constant thickness is left in a constant temperature and humidity chamber for a certain period of time.
[0208] The method specified in the method is to cover the opening of a predetermined moisture-resistant container with a film having a thickness of 25 µm, leave the container in an environment at a temperature of 40 ° C and a relative humidity of 90% for 24 hours, and leave the container. The moisture permeability is determined from the weight difference between after and before standing.

According to the wiring board 4 of the present invention, since the lower layer 3a of the solder resist layer 3 covering the wiring conductor layer 2 is made mainly of a photosensitive resin, the solder resist layer 3 is The wiring board 4 exhibits excellent adhesion to the wiring board 2 and the wiring conductor layer 2 and does not peel off or crack from the insulating substrate 1 in a reliability test such as a temperature cycle test. Further, since the upper layer portion 3b of the solder resist layer 3 is mainly composed of a thermosetting resin, the crosslink density can be increased, the moisture resistance is good, and the solder resist layer 3 does not swell during plating. And as a result,
The wiring board 4 does not corrode the wiring conductor layer 2 in a reliability test such as a wet standing test or the like, and the wiring conductor layer 2 does not break due to the solder resist layer 3 peeling off from the insulating substrate 1 during plating. be able to.

According to the wiring board 4 of the present invention, the upper layer portion 3b of the solder resist layer 3 has a moisture permeability of 20 to 150 g / m 2 as measured by a method specified in JIS Z 0208. Therefore, an opening 5 for exposing the wiring conductor layer 2 is provided in the solder resist layer 3 of the wiring board 4, and the electrode of the electronic component 7 is connected to the wiring conductor layer 2 in the opening 5 via the conductor bump 6. The electronic component module 8 is mounted on the wiring board 4 in a high-temperature and high-humidity chamber having a temperature of 130 ° C. and a relative humidity of 85%.
Even if a high acceleration test (HAST) in which a voltage of 5.5 V is continuously applied between the terminals of the conductive bumps 6 is performed, the resistance value between the adjacent conductive bumps 6 decreases in a short time, or an electrical short circuit occurs between the conductive bumps 6. Does not occur in a short time, and the wiring board 4 having good moisture resistance can be obtained. When the moisture permeability of the upper layer portion 3b of the solder resist layer 3 is less than 20 g / m 2, the upper layer portion 3b has a high crosslinking density, and cracks easily occur in the upper layer portion 3b in a reliability test such as a temperature cycle test. If it exceeds 150 g / m 2, the resistance value between adjacent conductor bumps 6 decreases in a short time when a high acceleration test (HAST) is performed, or an electrical short circuit between the conductor bumps 6 occurs in a short time. Tend to occur. Therefore, the moisture permeability of the upper layer portion 3b of the solder resist layer 3 is 20 to 15 as measured by the method specified in JIS Z 0208.
It is preferable to be in the range of 0 g / m2.

The lower part 3a of the solder resist layer 3 is composed of 50 to 80% by weight of a photosensitive resin, 10 to 40% by weight of an elastomer, and 5 to 20% by weight of an inorganic insulating filler. The photosensitive resin improves the adhesion between the lower layer portion 3a of the solder resist layer 3 and the insulating substrate 1 or the wiring conductor layer 2, and prevents peeling or cracking from the insulating substrate 1 in a reliability test such as a temperature cycle test. Has a function to prevent. As such a photosensitive resin, a resin such as epoxy acrylate or modified polybutadiene / epoxy resin / bismaleimide triazine resin is used. When the amount of the photosensitive resin is less than 50% by weight, the crosslinking density of the lower layer 3a of the solder resist layer 3 tends to decrease, and the thermal fatigue resistance tends to decrease. And the temperature cycle test tends to cause cracks. Therefore, the content of the photosensitive resin is preferably in the range of 50 to 80% by weight.

The elastomer imparts flexibility to the lower layer portion 3a of the solder resist layer 3 and absorbs thermal stress generated when the electronic component 7 is mounted on the wiring board 4 or when a temperature cycle test is performed. It has a function of preventing the occurrence of cracks in the lower layer portion 3a. As such an elastomer, acrylic rubber, acrylonitrile-butadiene rubber, styrene-butadiene-styrene triblock elastomer, styrene-isoprene-styrene triblock elastomer, or the like is used. When the amount of the elastomer is less than 10% by weight, the flexibility of the lower layer portion 3a is reduced, and cracks tend to easily occur in a reliability test such as a temperature cycle test. The crosslinking density of the lower layer portion 3a tends to decrease, and the moisture resistance and plating resistance tend to decrease. Therefore, the content of the elastomer is 10 to
Preferably it is in the range of 40% by weight.

Further, the inorganic insulating filler has a function of increasing the strength of the lower layer 3a of the solder resist layer 3 and matching the thermal expansion coefficient of the lower layer 3a with the thermal expansion coefficients of the insulating substrate 1 and the wiring conductor layer 2. Have. As such an inorganic insulating filler, an inorganic insulating powder such as silicon oxide, aluminum oxide, aluminum nitride, silicon carbide, and calcium titanate is used. If the amount of the mechanical insulating filler is less than 5% by weight, the flatness of the lower layer portion 3a tends to be poor, and if it exceeds 20% by weight, the workability of the lower layer portion 3a such as the opening of the opening 5a is increased. Tend to be worse. Therefore, the content of the inorganic insulating filler is preferably in the range of 5 to 20% by weight. In addition, the inorganic insulating filler,
The average particle diameter is preferably 5 μm or less from the viewpoint of the moldability of the lower layer portion 3a, and a substantially spherical particle having an average particle diameter of 2 μm or less is preferable from the viewpoint of the filling property of the inorganic insulating filler.

The upper layer portion 3b of the solder resist layer 3 is composed of 50 to 80% by weight of a thermosetting resin, 10 to 40% by weight of an elastomer, and 5 to 20% by weight of an inorganic insulating filler.

The thermosetting resin has a function of increasing the crosslink density of the upper layer 3b of the solder resist layer 3 and preventing moisture from penetrating into the upper layer 3b and swelling of the upper layer 3b during plating. As such a thermosetting resin, a resin such as an epoxy resin, a bismaleimide triazine resin, a polyphenylene ether, a modified polyethylene, or a norbornene resin is used. When the amount of the thermosetting resin is less than 50% by weight, the crosslink density of the upper layer 3b of the solder resist layer 3 tends to decrease, and the moisture resistance of the upper layer 3b tends to decrease, and more than 80% by weight. In addition, the flexibility of the upper layer portion 3b is reduced, and cracks tend to easily occur in a reliability test such as a temperature cycle test. Therefore, the content of the thermosetting resin is preferably in the range of 50 to 80% by weight.

The elastomer imparts flexibility to the upper layer portion 3b of the solder resist layer 3 and absorbs thermal stress generated when the electronic component 7 is mounted on the wiring board 4 or when a temperature cycle test is performed. It has a function of preventing the occurrence of cracks in the upper layer portion 3b. As such an elastomer, acrylic rubber, acrylonitrile-butadiene rubber, styrene-butadiene-styrene triblock elastomer, styrene-isoprene-styrene triblock elastomer, or the like is used. When the amount of the elastomer is less than 10% by weight, the flexibility of the upper layer portion 3b is reduced, and cracks tend to be easily generated in a reliability test such as a temperature cycle test. The crosslinking density of the upper layer portion 3a tends to decrease, and the moisture resistance and plating resistance tend to decrease. Therefore, the content of the elastomer is 10 to
Preferably it is in the range of 40% by weight.

Furthermore, the inorganic insulating filler has a function of increasing the strength of the upper layer 3b of the solder resist layer 3 and matching the thermal expansion coefficient of the upper layer 3b with the thermal expansion coefficients of the insulating substrate 1 and the wiring conductor layer 2. Have. As such an inorganic insulating filler, an inorganic insulating powder such as silicon oxide, aluminum oxide, aluminum nitride, silicon carbide, and calcium titanate is used. When the amount of the inorganic insulating filler is less than 5% by weight, the flatness of the upper layer portion 3b tends to deteriorate, and when it exceeds 20% by weight, the upper layer portion 3b such as a hole 5b to be described later is formed. Workability tends to be poor. Therefore, the content of the inorganic insulating filler is preferably in the range of 5 to 20% by weight. The inorganic insulating filler preferably has an average particle size of 5 μm or less from the viewpoint of moldability of the upper layer portion 3b, and has a substantially spherical shape with an average particle size of 2 μm or less from the viewpoint of filling the inorganic insulating filler. preferable.

In the wiring board 4 of the present invention, since the content of the inorganic insulating filler in the upper layer portion 3b of the solder resist layer 3 is as low as 5 to 20% by weight, the inorganic insulating filler is in the upper layer portion. No cross-linking occurs between the front and back surfaces of 3b and between the adjacent conductor bumps 6, and as a result, the moisture permeability of the upper layer portion of the solder resist layer is measured by a method specified in JIS Z 0208 to 20 to 150 g / m 2. Value.

The lower layer 3a and the upper layer 3b of the solder resist layer 3 are formed on the insulating substrate 1 by the following method.

First, a liquid varnish obtained by adding a suitable solvent, plasticizer, dispersant, etc. to a photosensitive resin, an elastomer, and an inorganic insulating filler is applied onto the insulating substrate 1 and the wiring conductor layer 2 by a screen printing method. Or apply uniformly so that the thickness after curing adopts a roll coating method to a thickness of 10 to 25 μm, and after drying at a temperature of 60 to 80 ° C. for 10 to 100 minutes to remove the solvent, 1 to 3 J The lower layer portion 3a is formed by performing a UV irradiation treatment at an intensity of / cm and a curing treatment at a temperature of 150 to 180 ° C for 1 to 3 hours. Next, on the lower layer 3a, a liquid varnish obtained by adding a suitable solvent, plasticizer, dispersant, etc. to a thermosetting resin, an elastomer, an inorganic insulating filler, etc. is employed by a screen printing method or a roll coating method. The thickness after curing is uniformly applied to a thickness of 10 to 40 μm,
After drying at a temperature of 80 ° C for 10-100 minutes to remove the solvent, 1
The upper layer 3b is formed by performing a curing treatment at a temperature of 50 to 180C for 1 to 3 hours.

Instead of applying the liquid varnish uniformly on the insulating substrate 1 by using a screen printing method or a roll coating method, a sheet-like lower layer 3a and an upper layer 3b are manufactured in advance, and a vacuum laminator is used. The sheet-like lower layer portion 3a and upper layer portion 3b may be formed on the insulating substrate 1 by using them.

The lower part 3a of the solder resist layer 3
Is preferably in the range of 10 to 25 μm from the viewpoint of workability and moisture resistance. When the thickness of the lower layer portion 3a is less than 10 μm, the thermal fatigue resistance in a reliability test such as a temperature cycle test tends to be inferior. When the thickness exceeds 25 μm, when forming the opening 5a by exposure and development described below, A large amount of resin remains at the bottom of the opening 5a, and the reliability of the electrical connection between the wiring conductor layer 2 and the conductor bump 6 tends to decrease. Therefore, the thickness of the lower layer portion 3a of the solder resist layer 3 is 10 to 25.
The range of μm is preferred.

Further, the upper layer 3 of the solder resist layer 3
The thickness b is preferably in the range of 10 to 40 μm from the viewpoint of workability and moisture resistance. When the thickness of the upper layer portion 3b is less than 10 μm, the moisture resistance in the wet storage test tends to decrease, and when it exceeds 40 μm, when forming the opening 5b with the laser in the upper layer portion 3b described later, A large amount of resin remains at the bottom of the opening 5b, and the reliability of the electrical connection between the wiring conductor layer 2 and the conductor bump 6 tends to decrease. Therefore, the thickness of the upper layer portion 3b of the solder resist layer 3 is preferably in the range of 10 to 40 μm.

The lower layer 3a of the solder resist layer 3
If the ratio of the thickness of the upper layer portion 3b is set to a value in the range of 50:50 to 80:20, the reliability of electrical connection, moisture resistance, and workability can be further improved.

Thus, according to the wiring board 4 of the present invention, the wiring conductor layer 2 is formed on the surface of the insulating substrate 1 and a part of the wiring conductor layer 2 is covered with a thermosetting resin. The solder resist layer 3 comprising an upper layer 3b of 20 to 150 g / m2 and a lower layer 3a mainly composed of a photosensitive resin is coated with a component as well as a moisture permeability measured by a method specified in JIS Z 0208. The solder resist layer 3 protects the insulating substrate 1 from heat when the electronic component 7 is mounted on the wiring board 1 and protects the wiring conductor layer 2 from oxidation and corrosion due to moisture. The wiring board 4 having excellent properties and moisture resistance can be obtained.

Further, the electronic component module 8 of the present invention
An opening 5 for exposing the wiring conductor layer 2 is provided in the solder resist layer 3, and each electrode of the electronic component 7 is connected to the wiring conductor layer 2 in the opening 5 via a conductor bump 6.

The opening 5 is formed by an opening 5a provided in the lower layer 3a of the solder resist layer 3 and an opening 5b provided in the upper layer 3b.

The openings 5a and 5b are formed in the insulating substrate 1
Lower layer 3a and upper layer 3 on the surface of the solder resist layer 3
It is formed at the same time as b is formed. The opening 5a of the lower layer 3a is formed by applying a liquid varnish made of a photosensitive resin or the like to the surface of the insulating substrate 1 and drying it at a temperature of 60 to 80 ° C. for 10 to 100 minutes to remove the solvent. It is formed by exposing with an intensity of 400 to 600 mJ / cm through a glass mask and then developing with an aqueous solution of about 1% sodium carbonate. The opening 5b of the upper layer 3b is connected to the lower layer 3a by one.
After UV irradiation treatment at a strength of ~ 3 J / cm and curing treatment at a temperature of 150-180 ° C for 1-3 hours, a liquid varnish made of a thermosetting resin or the like is applied on the lower layer 3a, Dry at temperature for 10-100 minutes to remove the solvent, then 150-18 more
After performing a hardening treatment at a temperature of 0 ° C. for 1 to 3 hours, the output of the carbon dioxide gas laser is set to 5 to 7 A, the pulse width is set to 50 to 100 μs, and the laser light is passed through a mask having a predetermined diameter.
The upper layer portion 3b on the opening 5a of FIG.

The openings 5a and 5b have a diameter of usually 30 to 300 μm. If the diameter is larger than 300 μm, the pitch of the wiring conductor layer 2 becomes large and the wiring board 4 tends to become large. If it is smaller than 30 μm, the reliability of electrical connection tends to decrease. Therefore, the diameter of the openings 5a and 5b is preferably in the range of 30 to 300 μm.

The diameter of the opening 5b of the upper layer 3b is
If the opening 5a is 50 to 80% of the diameter, the upper layer 3
b can cover the lower layer portion 3a satisfactorily, and when the electronic component 7 such as a semiconductor element is mounted on the wiring board 4 via the conductive bumps 6 such as solder, the electronic component module 8 is formed. In the HAST), the electronic component module 8 has good electrical connection reliability without reducing the resistance value between the adjacent conductor bumps 6 in a short time or causing an electric short circuit in a short time. Can be. The diameter of the opening 5b of the upper layer 3b is 50% of the diameter of the opening 5a of the lower layer 3a.
If it is less than 3 mm, the area of the opening 5 b of the upper layer portion 3 b will be extremely small, and it will be difficult to make a good connection between the wiring conductor layer 2 and the conductor bumps 6. The position of the opening 5b of the lower layer 3a and the position of the opening 5a of the lower layer 3a may cause a location where the thickness of the upper layer 3b covering the lower layer 3a becomes extremely thin. It tends to decrease. Therefore, it is preferable that the diameter of the opening 5b of the upper layer portion 3b be in a range of 50 to 80% of the diameter of the opening 5a of the lower layer portion 3a.

Normally, the wiring conductor layer 2 exposed in the opening 5 is provided with nickel on its exposed surface in order to prevent oxidation corrosion of the wiring conductor layer 2 and to improve the connection with the conductor bump 6. It is preferable to apply a metal having good conductivity and excellent corrosion resistance, such as gold, to a thickness of 1 to 20 μm by plating.

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

Such a conductive bump 6 is made of gold or lead-tin.
It is made of a conductive material such as tin-zinc, tin-silver-bismuth,
For example, when the conductive material is made of lead-tin, this paste is printed in the opening 5 by screen printing or a metal ball made of lead-tin is placed in the opening 5 and then passed through a reflow furnace. It is formed in the opening 5 in a semicircular shape.

Further, the electronic component 7 is mounted on the conductor bumps 6 and the wiring conductor layer 2 and the respective electrodes of the electronic component 7 are electrically connected through a reflow furnace, whereby the electronic component module 8 of the present invention is provided. Becomes In order to protect the conductor bumps 6 and firmly fix the electronic component 7 and the wiring board 4,
An underfill material composed of a thermosetting resin and a filler may be injected between the electronic component 7 and the wiring board 4.

Thus, the electronic component module 8 of the present invention
According to the method, the lower layer portion 3a mainly composed of a photosensitive resin on the surface of the wiring board 4 and the thermosetting resin as a main component, and the amount of moisture permeation is 20 to 15 measured by a method specified in JIS Z 0208.
An opening 5 for exposing the wiring conductor layer 2 is provided in the solder resist layer 3 composed of the upper layer portion 3b and the upper part 3b of the electronic component 7 via the conductor bumps 6 in the opening 5. Is connected, it is possible to obtain the electronic component module 8 having excellent heat resistance fatigue resistance and moisture resistance against a high acceleration test (HAST).

The wiring board and the electronic component module according to the present invention are not limited to the above-described embodiment.
Various changes can be made without departing from the scope of the present invention. For example, a build-up substrate formed by alternately laminating a wiring conductor layer and an insulating layer on an insulating substrate may be used as the wiring substrate.

FIG. 3 is a sectional view of an essential part showing an example of an embodiment of an electronic component module in which electronic components are mounted on such a build-up board. In this figure, 11 is an insulating substrate, and 12 is a through hole. , 13 is a through-hole conductor, 14 is an insulating layer, 15 is a wiring conductor layer, 16 is a through hole, 17 is a through conductor,
Reference numeral 18 denotes a solder resist layer composed of a lower layer portion 18a and an upper layer portion 18b, and these mainly constitute a wiring board 19. Reference numeral 20 denotes an opening, reference numeral 21 denotes a conductor bump, and reference numeral 22 denotes an electronic component. The electronic component module 23 mainly includes the wiring board 19 and the opening 20, the conductor bump 21, and the electronic component 22.

In this example, the wiring board 19 has a structure in which the wiring conductor layers 15 and the insulating layers 14 are alternately laminated on both the front and back surfaces of the insulating substrate 11,
Further, it is constituted by forming a solder resist layer 18 by applying.

In the above-described example, a semiconductor element is shown as an example of an electronic component mounted on the electronic component module. However, an electronic component such as a resistor, a capacitor, or a piezoelectric element may be mounted. Further, a heat radiating plate such as a stiffener may be attached to the wiring board in order to dissipate heat generated when the electronic component operates.

[0068]

EXAMPLE In order to evaluate the characteristics of the wiring board of the present invention and the electronic component module using the same, the following electronic component module was manufactured.

Example 1 First, 60% by weight of an epoxy resin was used as a thermosetting resin, and styrene was used as an elastomer.
30% by weight of butadiene-styrene triblock elastomer, 10% by weight of silicon oxide as an inorganic insulating filler,
A liquid varnish obtained by kneading a mixture comprising a solvent and the like,
Using a screen printing method, uniformly apply and print on the release film so that the cured thickness becomes 25 μm, dry at 80 ° C. for 30 minutes to remove the solvent, and remove the solvent at 150 ° C. A time-curing treatment was performed, and then the release film was peeled off to obtain a solder resist layer 3b mainly composed of a film-like thermosetting resin. At this time, the amount of moisture permeation of the solder resist layer 3b was 50 g / m2 as a result of measurement according to JIS Z 0208.

Next, an insulating substrate 1 having a wiring conductor layer 2 formed on the surface thereof is prepared. On the insulating substrate 1 and the wiring conductor layer 2, first, 50% by weight of epoxy acrylate and 50% by weight of epoxy resin are formed. Liquid varnish obtained by kneading a mixture of 60% by weight of a photosensitive resin, 30% by weight of a styrene-butadiene-styrene triblock elastomer as an elastomer, 10% by weight of silicon oxide as an inorganic insulating filler, and a solvent. The lower layer 3a of the solder resist layer 3 was formed by applying a uniform printing and coating so that the thickness after curing was 10 μm by employing a screen printing method.

Further, after this layer was dried at a temperature of 80 ° C. for 30 minutes to remove the solvent, 500 mJ was passed through a glass mask.
Exposure was performed at an intensity of 5 cm / cm, followed by development with an approximately 1% aqueous sodium carbonate solution to form an opening 5a having a diameter of 100 µm. After the opening 5a is formed, the layer to be the lower layer portion 3a of the solder resist layer 3 is UV-cured at an intensity of 1 J / cm.
The resin was cured by irradiation treatment and heat treatment at a temperature of 150 ° C. for 1 hour. Thereafter, the solder resist layer 3b having the above composition was uniformly formed on the lower layer portion 3a by screen printing so that the thickness after curing became 30 μm. Next, this layer was dried at a temperature of 80 ° C. for 40 minutes to remove the solvent, and then cured by performing a curing treatment at a temperature of 170 ° C. for 1 hour. Further, the output of the carbon dioxide laser is set to 5 A, the pulse width is set to 100 μs, and the laser beam is applied to the upper layer 3b on the opening 5a of the lower layer 3a three times through a mask having a predetermined diameter.
The opening 5b having a diameter of 70 μm was formed by irradiating the hole.

Further, nickel / gold plating is sequentially applied to the exposed surface of the wiring conductor layer 2 in the opening 5b, and thereafter, a solder paste made of lead-tin is printed on this portion, and the conductor bump is formed by passing through a reflow furnace. 6 was formed. Further, the electronic component 7 is placed on the conductor bump 6 and the wiring conductor layer 2 and each electrode of the electronic component 7 are electrically connected through a reflow furnace. The underfill was injected into the gap of No. 1 to produce a reliability evaluation module A.

The reliability test items include a temperature cycle test (T
CT) and a high acceleration test (HAST), the TCT evaluated the appearance such as cracks and peeling and the rate of change in resistance, and the HAST evaluated the migration and insulation resistance.

In the TCT, a module for reliability evaluation A was allowed to stand in a gas phase at temperatures of -55 ° C. and 125 ° C. for 30 minutes for each of 30 minutes using a gas phase cooling / heating tester. The resistance change rate was calculated by measuring the resistance before and after the test.

In the HAST, a high acceleration tester was used. After applying a voltage of 5.5 V for 300 hours in an atmosphere at a temperature of 130 ° C. and a relative humidity of 85%, ion migration of the conductive bumps 6 was performed. The insulation resistance was measured.

The module A for reliability evaluation of the present invention
No cracks occurred even after 2000 cycles of CT, and the rate of change in resistance was as low as 8%. Even after 300 hours of HAST, ion migration did not occur, and the insulation resistance was a high value of 1010Ω or more.

Example 2 First, 60% by weight of a bismaleimide triazine resin as a thermosetting resin, 25% by weight of a styrene-butadiene-styrene triblock elastomer as an elastomer, and 15% by weight of silicon oxide as an inorganic insulating filler. , A liquid varnish obtained by kneading a mixture comprising a solvent and the like, and employing the same method as in Example 1 to form a solder resist layer 3b having a film-shaped thermosetting resin having a thickness of 25 μm as a main component. Obtained. At this time, the amount of moisture permeation of the solder resist layer 3b was 45 g / m 2 as a result of measurement according to JIS Z 0208.

Next, the insulating substrate 1 having the wiring conductor layer 2 formed on the surface thereof is prepared. On the insulating substrate 1 and the wiring conductor layer 2, first, 55% by weight of epoxy acrylate and 45% by weight of epoxy resin are mixed. A liquid varnish obtained by kneading a mixture comprising 60% by weight of a photosensitive resin, 25% by weight of a styrene-butadiene-styrene triblock elastomer as an elastomer, 15% by weight of silicon oxide as an inorganic insulating filler, and a solvent. The lower layer 3a of the solder resist layer 3 was formed by uniformly printing and applying so that the thickness after curing was 15 μm by employing a screen printing method.

Next, using the same method as in the first embodiment,
An opening 5a having a thickness of 100 μm was formed, and after curing the lower layer portion 3a, a solder resist layer 3b having the above composition was uniformly formed thereon by screen printing so that the thickness after curing was 25 μm. After drying and curing this layer,
An opening 5b having a diameter of 80 μm was formed in the same manner as in Example 1. Further, the electronic components 7 were mounted and connected in the same manner as in Example 1, and a reliability evaluation module B was created.

Using this reliability evaluation module B,
As a result of performing the same reliability test and evaluation as in Example 1, no crack occurred in the reliability evaluation module B even after 2000 cycles of TCT, and the resistance value change rate was as low as 8%. Even after 300 hours of HAST, ion migration did not occur, and the insulation resistance was as high as 1010Ω or more.

(Comparative Example) First, epoxy acrylate 50
Photosensitive resin 60% by weight and 50% by weight of epoxy resin
% By weight and 40% by weight of silicon oxide as an inorganic insulating filler
Using a liquid varnish obtained by kneading a mixture consisting of a solvent and a solvent, a similar solder resist layer having a thickness of 25 μm was obtained by employing the same method as in Example 1. At this time, the moisture permeation amount of the solder resist layer was 250 g / m2 as a result of measurement according to JIS Z 0208.

Next, an insulating substrate having a wiring conductor layer formed on the surface thereof is prepared, and a solder resist layer having the above composition is uniformly formed on the insulating substrate and the wiring conductor layer so that the cured thickness becomes 40 μm. Formed. Further, an opening having a diameter of 80 μm was formed by employing the exposure and development method. After the opening was formed, the solder resist layer was cured by performing a UV irradiation treatment at an intensity of 1 J / cm and a heat treatment at a temperature of 150 ° C. for one hour. Furthermore, electronic components were mounted and connected in the same manner as in Example 1 to prepare a comparative module C.

Using this comparative module C, the same reliability test and evaluation as in Example 1 were carried out. As a result, the comparative module C had cracks after 1500 TCT cycles, and the rate of change in resistance value was reduced to 50%. Increased. Also, HAST25
After 0 hour, ion migration occurred, and the insulation resistance also dropped to 3 × 107Ω.

[0084]

According to the wiring board of the present invention, since the upper layer portion of the solder resist layer covering the wiring conductor layer is made mainly of a thermosetting resin, the crosslink density can be increased and good. It has moisture resistance and can prevent the solder resist layer from swelling during plating.As a result, the wiring conductor layer corrodes in reliability tests such as a wet test, and the solder resist layer becomes The wiring substrate can be prevented from being peeled off from the wiring conductor layer and being disconnected. In addition, since the lower layer portion of the solder resist layer is made mainly of a photosensitive resin, it has excellent thermal fatigue resistance without peeling or cracking from the insulating substrate in a reliability test such as a temperature cycle test. It can be a wiring board.

According to the wiring board of the present invention, the moisture permeability of the upper layer portion of the solder resist layer is 20 to 150 g / m 2 as measured by the method specified in JIS Z 0208. An opening for exposing the wiring conductor layer is provided in the solder resist layer, and an electrode of the electronic component is connected to the wiring conductor layer in the opening via a conductor bump. Even if a high acceleration test (HAST), in which a voltage of 5.5 V is continuously applied between terminals of a wiring board in an 85% high-temperature and high-humidity chamber, is performed, the resistance value between adjacent conductor bumps decreases in a short time. An electrical short circuit does not occur in a short time between conductor bumps, and a wiring board having good moisture resistance can be obtained.

Further, according to the wiring board of the present invention, since the upper and lower layers of the solder resist layer contain 10 to 40% by weight of the elastomer, they have good flexibility and can be reliably used in a temperature cycle test or the like. It is possible to obtain a wiring board excellent in heat fatigue resistance without causing peeling or cracking from the insulating substrate in the resistance test. The upper part of the solder resist layer has a low content of the inorganic insulating filler of 5 to 20% by weight, so that the inorganic insulating filler is cross-linked between the front and back surfaces of the solder resist layer and between adjacent conductor bumps. As a result, the moisture permeation amount of the upper layer portion of the solder resist layer can be measured to a value of 20 to 150 g / m 2 by the method specified in JIS Z 0208.

According to the electronic component module of the present invention, an opening for exposing the wiring conductor layer is provided in the solder resist layer of the wiring board, and the electrode of the electronic component is connected to the wiring conductor layer in this opening via the conductor bump. Because of the connection, it is possible to provide an electronic component module that is excellent in heat fatigue resistance and moisture resistance against a high acceleration test (HAST).

According to the electronic component module of the present invention, since the opening diameter of the upper layer of the solder resist layer is 50 to 80% of the opening diameter of the lower layer, the photosensitive resin is mainly used. The lower layer can be covered well with the upper layer mainly composed of a thermosetting resin having a high crosslinking density and good moisture resistance, and as a result, a wet storage test or a high acceleration test (H
AST) to provide an electronic component module having good moisture resistance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an essential part showing an example of an embodiment of an electronic component module in which an electronic component is mounted on a wiring board according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of the electronic component module shown in FIG.

FIG. 3 is a sectional view of a main part showing another example of the embodiment of the electronic component module of the present invention.

[Explanation of symbols]

 1 Insulating substrate 2 Wiring conductor layer 3 Solder resist layer 3a ..Lower layer portion 3b of the solder resist layer 3b Upper layer portion of the solder resist layer 4 Wiring board 5 Opening 5a Opening in lower layer 5b Opening in upper layer 6 Conductor bump 7 .... Electronic components 8 ... Electronic component modules

Claims (4)

[Claims] 1. A wiring board comprising: a wiring conductor layer formed on a surface of an insulating substrate; and a solder resist layer covering a part of the wiring conductor layer. Is composed of a lower layer mainly composed of a photosensitive resin and an upper layer mainly composed of a thermosetting resin, and the amount of moisture permeation of the upper layer is 20 to 20 measured by a method specified in JIS Z 0208. A wiring substrate having a weight of 150 g / m2. 2. The method according to claim 1, wherein the lower layer portion of the solder resist layer comprises 50 to 80% by weight of a photosensitive resin and 10 to 40% by weight of an elastomer.
% By weight and 5 to 20% by weight of an inorganic insulating filler, and the upper layer portion is 50 to 80% by weight of a thermosetting resin,
2. The wiring board according to claim 1, comprising 10 to 40% by weight of an elastomer and 5 to 20% by weight of an inorganic insulating filler. 3. An electronic component module comprising an electronic component mounted on the wiring board according to claim 1 or 2, wherein an opening for exposing the wiring conductor layer is provided in the solder resist layer. An electronic component module, wherein an electrode of the electronic component is connected to a wiring conductor layer inside via a conductor bump. 4. The electronic component according to claim 3, wherein an opening diameter of the upper layer portion of the solder resist layer is 50 to 80% of an opening diameter of the lower layer portion. module.