JP3728059B2 - Multilayer wiring board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer wiring board suitable for, for example, a multilayer wiring board and a package for housing a semiconductor element.
[0002]
[Prior art]
Conventionally, a printed circuit board has been proposed in which a copper foil is bonded to the surface of an insulating substrate containing an organic resin, and then this is etched to form a fine wiring circuit. . Moreover, in such a printed circuit board, in order to increase its strength, a material in which a cloth-like glass woven fabric is dispersed in an organic resin is often used.
[0003]
In recent years, a substrate using an aramid woven fabric or a non-woven fabric instead of the glass woven fabric has been proposed. When an aramid nonwoven fabric is used, it has an advantage that a drilling process for forming via-hole conductors connecting wiring circuit layers can be easily performed as compared with a case where a glass woven fabric is used. That is, in the conventional glass woven fabric, drilling is generally performed by a micro drill, but the drill diameter is about 0.15 mm at the minimum, and when this drill is used, it is easy to break during drilling. It was not suitable for the required microfabrication. On the other hand, when an aramid nonwoven fabric is used, laser processing becomes easy and fine holes can be formed at high speed.
[0004]
[Problems to be solved by the invention]
However, the aramid resin has a nature that is inherently easy to absorb moisture. While the moisture absorption of organic resins such as epoxy, BT resin, and PPE used for ordinary printed circuit boards is 0.1 to 0.2%, aramid resin is 2 to 3% and more than 10 times moisture absorption. do. For this reason, if a printed circuit board containing an aramid resin is left in a high-temperature and high-humidity atmosphere, the wiring board becomes fragile due to expansion due to moisture absorption, and it is clear that there is a problem in long-term reliability.
[0005]
As one method for solving this problem, it is conceivable to newly form a moisture-proof resin layer on the surface of the wiring board. However, even if any resin is used, a small amount of moisture is absorbed, so that the effect of preventing moisture absorption is obtained. In order to fully exhibit, it is necessary to form with the thickness of at least 50 micrometers.
[0006]
However, if such a thick moisture-proof resin layer is formed after fine wiring required in the future, the wiring circuit is also covered, and as a result, there are restrictions when mounting electronic components on the wiring circuit. Not practical. In addition, since the wiring board is completely cured by heat treatment, there is a problem in that sufficient adhesion strength cannot be obtained even if a thick film is formed on the cured resin surface, and thus the wiring board is easily peeled off. It was.
[0007]
Thus, it is difficult to sufficiently prevent moisture absorption on a wiring board containing an aramid nonwoven fabric, and a highly reliable product has not been obtained.
[0008]
Accordingly, the present invention provides a multilayer wiring board that prevents the long-term stability from being hindered by the hygroscopic property of the aramid resin while taking advantage of the via processability of the aramid resin.
[0009]
[Means for Solving the Problems]
As a result of earnestly examining the above problems, the inventor formed the outermost insulating layer of the insulating substrate containing the aramid resin by an insulating layer having a high moisture resistance not containing the aramid resin. It has been found that the above-described problem in the case of containing an aramid resin can be solved by causing the wiring layer to function as a moisture-proof layer, resulting in the present invention.
[0010]
That is, the multilayer wiring board of the present invention comprises an insulating substrate formed by laminating a plurality of insulating layers containing at least an organic resin, a wiring circuit layer disposed on and inside the insulating substrate, and the wiring circuit layer. In a multilayer wiring board having a via-hole conductor for electrical connection, a via-hole conductor formed by filling an inner layer of the insulating substrate with at least an aramid resin and filling a through-hole with a paste containing metal powder A plurality of insulating layers having a laminated structure, and an outermost layer comprising an organic resin not containing an aramid resin and a powdered inorganic filler, and comprising an insulating layer functioning as a moisture-proof layer for the inner layer It is a feature.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view for explaining a multilayer wiring board according to the present invention.
[0012]
In the multilayer wiring board of the present invention, a plurality of wiring circuit layers 2 are deposited on the surface and inside of an insulating substrate 1 in FIG. The wiring circuit layers 2 are electrically connected by via-hole conductors 3. The insulating substrate 1 is composed of an insulating material containing at least an organic resin, and the insulating substrate 1 is composed of a laminated body of a plurality of insulating layers 1a to 1f as shown in FIG.
[0013]
According to the present invention, the inner layers in the insulating substrate 1, that is, the insulating layers 1b, 1c, 1d, and 1e are constituted by an insulating layer containing at least an aramid resin. More specifically, the aramid resin is desirably contained in the insulating layer at a ratio of 30 to 70% by volume, and in particular, the aramid resin is desirably contained as a nonwoven fabric or a woven fabric. In the case of using an aramid nonwoven fabric or a woven fabric, the insulating layer is formed by impregnating the nonwoven fabric or the woven fabric with an organic resin.
[0014]
As the organic resin impregnated at this time, for example, PPE (polyphenylene ether), BT resin (bismaleimide triazine), epoxy resin, polyimide resin, fluororesin, phenol resin, polyamide bismaleimide, and the like are desirable. A thermosetting resin that is liquid at room temperature is desirable.
[0015]
According to the multilayer wiring board of the present invention, the outermost insulating layer, that is, the insulating layers 1a and 1f, of the insulating substrate 1, is formed of an insulating material made of an organic resin other than an aramid resin and an inorganic filler. It is important to. If the aramid resin is contained in the outermost layer, as described above, the high absorptivity of the aramid resin itself causes problems such as expansion and deformation of the insulating substrate when stored for a long time in high humidity.
[0016]
Examples of organic resins other than the aramid resin constituting the outermost insulating layer include resins such as PPE (polyphenylene ether), BT resin (bismaleimide triazine), epoxy resin, polyimide resin, fluorine resin, phenol resin, and polyaminobismaleimide. Is desirable. In addition, it is necessary to approximate the thermal expansion characteristics of the inner layer with the insulating layer by blending an inorganic filler in the insulating layer. As the inorganic filler used at this time, SiO ₂ , Al ₂ O ₃ , AlN and the like are suitable, and the filler has a substantially spherical powder having an average particle size of 20 μm or less, particularly 10 μm or less, and optimally 7 μm or less. Is used. This inorganic filler is mixed in a ratio range of 15:85 to 5:95 in a volume ratio of organic resin: inorganic filler.
[0017]
More specifically, it is desirable that the thermal expansion coefficient of the outermost insulating layer from room temperature to 150 ° C. is 30 ppm / ° C. or less, particularly 20 ppm / ° C. or less. If the temperature exceeds 30 ppm / ° C., the thermal expansion coefficient of the aramid resin itself is low, so that the thermal expansion coefficient of the inner insulating layer is also 10 ppm / ° C. or less. Therefore, the inner insulating layer and the outermost insulating layer This is because, when a thermal cycle is applied to the wiring board on which the layers are stacked, problems such as peeling of the outermost insulating layer occur.
[0018]
Moreover, since most of the general organic resins contained in the outermost insulating layer have a high thermal expansion coefficient of 50 to 60 ppm / ° C. or higher, an appropriate amount of an inorganic filler having a thermal expansion coefficient of 20 ppm / ° C. or lower is appropriate. It can mix | blend and it can control to said thermal expansion characteristic.
[0019]
Accordingly, the outermost insulating layers 1a and 1f include an organic resin other than an aramid resin, and in some cases, are formed by a composite of an organic resin and an inorganic filler. The organic resin, the kind of the inorganic filler used here, and the blending ratio of the organic resin and the inorganic filler are as described above.
[0020]
The outermost layer functions as a moisture-proof layer with respect to the inner layer of the insulating substrate containing the aramid resin, but the thickness of the insulating layers 1a and 1f that do not contain the aramid resin in order to exhibit moisture-proof properties. Is preferably 10 to 300 μm, particularly 40 to 100 μm.
[0021]
Furthermore, in order to ensure the moisture resistance of the inner layer in the insulating substrate 1, it is desirable to coat the side surface of the wiring substrate with the organic resin.
[0022]
On the other hand, the wiring circuit layer 2 and the via-hole conductor 3 in the present invention are preferably made of at least one selected from the group consisting of copper, aluminum, gold, and silver, or two or more alloys, in particular, copper or copper. The alloy containing is most desirable. The wiring circuit layer 2 may be any one of the above-described metal foils, plating layers, and printed patterns using conductive ink, and the via-hole conductor 3 may be either filled with conductive ink or plated.
[0023]
Next, a method for producing the multilayer wiring board of the present invention will be described.
First, an insulating sheet containing an aramid resin is formed as an inner layer of the insulating substrate.
[0024]
For example, the insulating sheet for the inner layer is impregnated into the woven fabric or the nonwoven fabric after the organic resin or the mixture of the organic resin and the inorganic filler is made into a slurry in the aramid woven fabric or the nonwoven fabric.
[0025]
The slurry is a fluid having a viscosity of 100 to 3000 poise by adding a solvent such as toluene, butyl acetate, methyl ethyl ketone, isopropyl alcohol, methanol, etc. to the above-described organic resin or composite of organic resin-inorganic filler. It is good to consist of. In addition, after organic resin impregnation, it heat-processes and makes it semi-cure.
[0026]
On the other hand, an insulating sheet for forming the outermost insulating layer is produced. The outermost layer insulating sheet is prepared by thoroughly mixing an organic resin or a composition comprising an organic resin and an inorganic filler by means of a kneader or a three-roller, and using a rolling method, an extrusion method, an injection method, a doctor blade After forming into a sheet by a method or the like, the organic resin is semi-cured. For semi-curing, if the organic resin is a thermoplastic resin, the mixture mixed under heating is cooled. In the case of a thermosetting resin, the organic resin is heated to a temperature slightly lower than a temperature sufficient for complete solidification. That's fine.
[0027]
Then, via holes are formed by punching, laser processing, plasma etching, or the like in the inner layer insulating sheet and outermost layer insulating sheet produced as described above, and a conductor paste is filled in the holes. The conductor paste is a resin powder added with a resin component such as epoxy or cellulose and kneaded with a solvent such as butyl acetate. The metal powder blended in the conductor paste includes copper, aluminum, silver, gold It is desirable to consist of at least one low resistance metal. If desired, after filling in the hole, heat treatment can be performed at 60 to 140 ° C. to decompose and volatilize and remove the solvent and resin content in the paste.
[0028]
Next, a conductor circuit layer is formed on the surface of each insulating sheet filled with via-hole conductors. For the formation of the conductor circuit layer, a metal foil such as copper is attached to the insulating layer with an adhesive, and then a resist for the circuit pattern is formed and an unnecessary part of the metal is etched away with an acid or the like, or a metal that has been punched in advance Stick the foil. Another method is to form a conductor paste on the surface of the insulating layer by screen printing or photo resist method, etc., dry, and pressurize to embed the wiring circuit on the surface of the insulating layer and adhere to the insulating layer. Can be formed. Also, the wiring circuit is plated on a film, glass or metal plate, a metal foil is formed, a circuit pattern is formed by etching, and the wiring circuit is embedded on the surface of the insulating layer by transferring it while pressing on the insulating layer. It can also be formed.
[0029]
Then, the inner layer insulating sheet containing the aramid resin prepared as described above and the outermost layer insulating sheet not containing the aramid resin are aligned and bonded in a desired number of layers as shown in FIG. The organic resin of the insulating layer is completely cured by heating at a curing temperature of 150 to 300 ° C. Thus, since the inner layer and the outermost layer of the insulating substrate are both bonded in a semi-cured state and are simultaneously cured, the outermost layer not containing an aramid resin does not peel from the inner layer, A multilayer wiring board as shown in FIG. 1 can be produced.
[0030]
【Example】
Example 1
A slurry containing polyimide resin was impregnated into an aramid nonwoven fabric, and then a prepreg heated at 60 ° C. and semi-cured was produced. The content ratio was set to 50% by volume of polyimide resin and 50% by volume of non-woven fabric of aramid resin. A via hole having a diameter of 0.1 mm is formed in the prepreg with a carbon dioxide laser, and a copper paste containing copper powder plated with silver is filled in the hole to form a via hole conductor. ) Was produced.
[0031]
On the other hand, varnished resin and powder were mixed at a ratio of 50% by volume of polyimide resin and 50% by volume of silica powder to produce an insulating sheet by a doctor blade method, and heated at 60 ° C. to be semi-cured. A via hole having a diameter of 0.1 mm is formed in the insulating sheet by punching, and a copper paste containing copper powder plated with silver is filled in the hole to form a via hole conductor, and the outermost insulating sheet (B) Was made.
[0032]
On the other hand, an adhesive was applied to the surface of a transfer sheet made of polyethylene terephthalate (PET) resin to give tackiness, and a copper foil having a thickness of 12 μm and a surface roughness of 0.8 μm was adhered to one surface. Then, after apply | coating a photoresist and performing exposure development, this was immersed in the ferric chloride solution, the non-pattern part was etched away, and the wiring circuit layer was formed. The produced wiring circuit layer is a fine pattern having a line width of 60 μm and a distance between the wirings of 60 μm.
[0033]
Then, the transfer sheet on which the wiring pattern was formed as described above was superimposed on the surface of the inner layer insulating sheet (A) and pressed, and only the transfer sheet was peeled off to transfer the wiring circuit layer. Similarly, the wiring circuit layer was transferred to the surface of the outermost insulating sheet (B) in the same manner as described above.
[0034]
Then, with the three insulating sheets for the inner layer on which the wiring circuit layers are formed as described above, the outermost insulating sheet is laminated on the upper and lower sides thereof and pressure-bonded at a pressure of 50 kg / cm ² , and 1 at 200 ° C. The multilayer wiring board was produced by heating for a period of time and completely curing. The thickness of the outermost insulating layer not containing an aramid resin was 50 μm. Further, the thermal expansion coefficient of this outermost layer from room temperature to 150 ° C. was 25 ppm / ° C.
[0035]
As a result of observing the vicinity of the formation of the wiring circuit layer and via-hole conductor in the cross section of the obtained multilayer wiring board, the wiring circuit layer and the via-hole conductor are in a good connection state, and a continuity test between each wiring was performed. As a result, disconnection of the wiring was not recognized.
[0036]
The obtained multilayer wiring board was left in a high-temperature and high-humidity atmosphere having a humidity of 85% and a temperature of 85 ° C. for 100 hours. After leaving for 1000 hours, slight peeling of the insulating layer was observed in the peripheral part.
[0037]
Moreover, as a result of conducting a thermal cycle test from room temperature to 150 ° C., no change was observed after 200 cycles.
[0038]
Comparative Example 1
An insulating sheet for an inner layer was produced in the same manner as in Example 1, and via holes were formed in the same manner, and a via paste was produced by filling a conductor paste. Furthermore, a 12 μm thick copper foil was bonded to the sheet on one side, and the resin was cured by a vacuum laminator. Thereafter, a photoresist was applied to the copper foil portion and exposed and developed, and then this was immersed in a ferric chloride solution to remove the non-patterned portion by etching to form a wiring circuit layer. The produced wiring circuit layer is a fine pattern having a line width of 60 μm and a distance between the wirings of 60 μm.
[0039]
Then, as described above, 7 layers of the insulating sheet on which the via-hole conductor and the wiring circuit layer are formed are laminated, laminated and pressure-bonded at a pressure of 50 kg / cm ² , and heated at 200 ° C. for 1 hour to be completely cured. Thus, a multilayer wiring board was produced.
[0040]
As a result of observing the vicinity of the formation of the wiring circuit layer and via-hole conductor in the cross section of the obtained multilayer wiring board, the wiring circuit layer and the via-hole conductor are in a good connection state, and a continuity test between each wiring was performed. As a result, disconnection of the wiring was not recognized.
[0041]
When the obtained multilayer wiring board was left in a high-temperature and high-humidity atmosphere at a humidity of 85% and a temperature of 85 ° C. for 100 hours, separation occurred between the insulating layers, and the whole was deformed so as to wave. After leaving for 1000 hours, the multilayer wiring board did not retain its original shape. Moreover, as a result of conducting a thermal cycle test from room temperature to 150 ° C., no change was observed after 200 cycles.
[0042]
Example 2
In the same manner as in Example 1, a prepreg was prepared by impregnating an aramid non-woven fabric with BT resin so as to comprise 55% by volume of polyaminobismaleimide resin and 45% by volume of an aramid non-woven fabric. Then, a via hole having a diameter of 0.1 mm is formed in the prepreg by a carbon dioxide laser, and a copper paste made of copper powder plated with silver having a particle diameter of about 5 μm is filled in the hole to form an insulating sheet for inner layer (A). Produced.
[0043]
On the other hand, a via hole having a diameter of 0.1 mm is punched on a sheet-like insulating layer prepared by a doctor blade method by mixing a resin and a powder in a varnish state so that a ratio of 50% by volume of polyaminobismaleimide resin and 50% by volume of silica powder is obtained. The outermost insulating sheet (B) was prepared by filling the hole with a copper paste containing copper powder plated with silver to form a via-hole conductor.
[0044]
Thereafter, in the same manner as in Example 1, after the wiring circuit layer was transferred from the transfer sheet to each insulating sheet (A) and (B), three insulating sheets (A) were formed at the center, and the upper and lower outermost layers. Two insulating sheets (B) were laminated on each other, pressure-bonded at a pressure of 50 kg / cm ² , and heated at 200 ° C. for 1 hour to be completely cured to produce a multilayer wiring board. The thickness of the outermost insulating layer not containing an aramid resin was 75 μm. The thermal expansion coefficient of this outermost layer from room temperature to 150 ° C. was 20 ppm / ° C.
[0045]
As a result of observing the vicinity of the formation of the wiring circuit layer and via-hole conductor in the cross section of the obtained multilayer wiring board, the wiring circuit layer and the via-hole conductor are in a good connection state, and a continuity test between each wiring was performed. As a result, disconnection of the wiring was not recognized.
[0046]
The obtained multilayer wiring board was left in a high-temperature and high-humidity atmosphere having a humidity of 85% and a temperature of 85 ° C. for 100 hours. After leaving for 1000 hours, slight peeling of the layer was observed at the periphery. Moreover, as a result of conducting a thermal cycle test from room temperature to 150 ° C., no change was observed after 200 cycles.
[0047]
Comparative Example 2
A moisture absorption preventing layer made of a photosensitive imide resin having a thickness of 10 μm was formed on the surface of the wiring substrate manufactured according to Comparative Example 1 to manufacture a multilayer wiring substrate having seven insulating layers.
[0048]
As a result of observing the vicinity of the formation of the wiring circuit layer and via-hole conductor in the cross section of the obtained multilayer wiring board, the wiring circuit layer and the via-hole conductor are in a good connection state, and a continuity test between each wiring was performed. As a result, disconnection of the wiring was not recognized.
[0049]
When the obtained multilayer wiring board was left in a high-humidity atmosphere having a humidity of 85% and a temperature of 85 ° C. for 100 hours, separation occurred in some insulating layers, and the whole was slightly deformed. After leaving for 1000 hours, the substrate was deformed and the whole shape did not remain. In addition, as a result of performing a thermal cycle test at a temperature from room temperature to 150 ° C., peeling of the moisture absorption preventing layer was observed after 200 cycles.
[0050]
Comparative Example 3
A polyimide resin in a varnish state was formed into an insulating sheet by a doctor blade method and heated at 60 ° C. to be semi-cured. A via hole having a diameter of 0.1 mm is formed in the insulating sheet by punching, and a copper paste containing copper powder plated with silver is filled in the hole to form a via hole conductor. A wiring circuit layer was formed to produce an outermost layer insulating sheet.
[0051]
Then, in Example 1, the above-mentioned outermost layer insulating sheets are laminated on the upper and lower sides of the three inner layer insulating sheets provided with the via-hole conductor and the wiring circuit layer on the surface, and pressure-bonded at a pressure of 50 kg / cm ^2. Then, the multilayer wiring board was manufactured by heating at 200 ° C. for 1 hour to be completely cured. The thickness of the outermost insulating layer that does not contain an aramid resin was 50 μm. The coefficient of thermal expansion of this outermost layer from room temperature to 150 ° C. was 55 ppm / ° C.
[0052]
As a result of observing the vicinity of the formation of the wiring circuit layer and via-hole conductor in the cross section of the obtained multilayer wiring board, the wiring circuit layer and the via-hole conductor are in a good connection state, and a continuity test between each wiring was performed. As a result, disconnection of the wiring was not recognized.
[0053]
The obtained multilayer wiring board was left in a high-temperature and high-humidity atmosphere having a humidity of 85% and a temperature of 85 ° C. for 100 hours. After leaving for 1000 hours, slight peeling of the insulating layer was observed in the peripheral part.
[0054]
As a result of the thermal cycle test, it was found that the outermost layer was peeled after 200 cycles and lacked stability.
[0055]
【The invention's effect】
As described above in detail, according to the present invention, the surface of the multilayer wiring board containing an aramid resin functions as a moisture-proof layer for the inner layer made of an organic resin not containing an aramid resin and a powdered inorganic filler. By forming the insulating layer, the moisture resistance of the multilayer wiring board can be greatly improved, and the long-term stability of the multilayer wiring board can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a multilayer wiring board according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Insulating substrate 1a-1f Insulating layer 2 Wiring circuit layer 3 Via-hole conductor

Claims (3)

An insulating substrate formed by laminating a plurality of insulating layers containing at least an organic resin, and the wiring circuit layer disposed inside and insulating substrate surface, and via-hole conductors for electrically connecting the wiring circuit layers A multilayer wiring board comprising: a plurality of insulating layers having via-hole conductors formed by filling a through-hole with a paste containing metal powder at least in the inner layer of the insulating substrate; A multilayer wiring board characterized in that the outermost layer is constituted by an insulating layer made of an organic resin not containing an aramid resin and a powdery inorganic filler and functioning as a moisture-proof layer for the inner layer .   2. The multilayer wiring board according to claim 1, wherein the aramid resin is made of an aramid nonwoven fabric or a woven fabric.   2. The multilayer wiring board according to claim 1, wherein the outermost insulating layer has a thermal expansion coefficient of 30 ppm / ° C. or less from room temperature to 150 ° C.

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