JP4089671B2 - Circuit forming substrate manufacturing method and circuit forming substrate - Google Patents

Description

  The present invention relates to a method for manufacturing a circuit forming substrate and a circuit forming substrate used in various electronic devices.

  As electronic devices have become smaller and more dense in recent years, more and more circuits and components can be integrated on a circuit-forming board on which electronic components are mounted, instead of the conventional single-sided board. High-density substrates have been developed (for example, “Surface mount technology” published by Nikkan Kogyo Shimbun, January 1997 issue, Kiyoshi Takagi; “Remarkable development trend of build-up multilayer PWB”).

  A conventional example will be described below with reference to the drawings.

  A substrate material 1 shown in FIG. 3A is a so-called prepreg in which a glass fiber woven fabric as a reinforcing material used for a circuit forming substrate is impregnated with a thermosetting epoxy resin or the like to be in a B-stage state. A film 2 is attached to both surfaces of the substrate material 1 by a laminating method using a hot roll or the like.

  Next, as shown in FIG. 3B, via holes 3 are formed in the substrate material 1 by a processing method such as laser, and then conductive particles such as copper powder and a thermosetting resin, a curing agent, a solvent, and the like are kneaded. The conductive paste 4 made into a paste is filled to obtain the configuration shown in FIG.

  Thereafter, the film 2 is peeled to obtain a shape in which the conductive paste 4 protrudes as shown in FIG. 3D, and copper foils 5 are arranged on both sides thereof and heated by a hot press device (not shown). By applying pressure, the substrate material 1 is thermally cured as shown in FIG. 3E, the conductive paste 4 is compressed, and the copper foils 5 on the front and back sides are electrically connected. At that time, the impregnated epoxy resin in the substrate material 1 flows and flows out to form a flow-out portion 6.

Thereafter, excess portions at the ends are cut off to form the shape as shown in FIG. 3F, and the copper foil 5 is processed into a desired pattern by a method such as etching to form a circuit 7, which is shown in FIG. 3G. Such a double-sided circuit-formed substrate is obtained.
Kiyoshi Takagi, “Development Trend of Remarkable Build-up Multilayer PWB”, “Surface Mount Technology” January issue, Nikkan Kogyo Shimbun, 1997

  However, in the method of manufacturing a circuit forming substrate as described above, the electrical connection between the front and back circuits of the circuit forming substrate using a conductive paste, or the surface layer and inner layer circuits is unstable in the case of a multilayer circuit forming substrate. It may become a thing.

  In order to investigate the cause, the inventor conducted an experimental trial or analysis of the circuit-formed substrate produced, and as a result, the cause of the above-mentioned connection failure is the conductive particles in the conductive paste 4 as shown in the connection diagram 3E. It was confirmed that this is due to the generation of outflow particles 8 flowing out from the diameter of the via hole 3.

  That is, in order to realize an ideal electrical connection, the conductive paste 4 is compressed in the vertical direction in the figure, and the conductive particles in the conductive paste efficiently contact each other and the copper foil 5 also contacts firmly. There is a need to.

  However, as can be seen from the fact that the flow-out portion 6 is formed in the process from FIG. 3D to 3E, the thermosetting resin in the substrate material 1 is directed toward the outer open end during heat compression. To flow. At that time, the flowing thermosetting resin causes a phenomenon that the conductive particles in the conductive paste 4 are washed away in the horizontal direction in the figure. As a result, efficient compression of the conductive paste 4 is not performed, and the electrical connection by the conductive paste 4 becomes unstable.

  In the above description, the case of the substrate material using the glass woven fabric and the thermosetting resin has been described, but the case of using the inorganic fiber other than glass or the organic fiber such as aramid or the non-woven fabric reinforcing material other than the woven fabric. However, the same connection failure phenomenon was confirmed.

  In particular, when a woven fabric is used, the flow of the thermosetting resin described above becomes remarkable due to the small flow resistance due to the configuration using the woven fabric, and it is difficult to realize the electrical connection with the conductive paste. there were.

  The inventor repeatedly conducted various experiments and analyzed the periphery of the via hole portion with insufficient electrical connection. As a result, many outflow particles 8 as shown in FIG. 3E were observed on the surface side of the substrate material 1. I found out that Furthermore, the cause of the occurrence was examined and the following conclusions were obtained.

  When a prepreg using a glass fiber woven fabric is used as the substrate material, the substrate material has a cross-sectional shape as shown in FIG. That is, the substrate material 1 is impregnated with a glass fiber woven fabric 9 as a impregnating resin 10 with a thermosetting resin such as a varnish-like epoxy resin, and after adjusting the thickness of the impregnating resin 10 with a roll or the like so as to have a desired thickness, Manufactured by a process of drying and B-stage.

  Accordingly, the thickness of the substrate material 1 is obtained by adding the thickness of the impregnating resin 10 formed on the surface to the initial thickness of the glass fiber woven fabric 9. The layer of the impregnating resin 10 formed on the surface flows violently in the hot pressing step in the circuit forming substrate manufacturing process described above. Therefore, many outflow particles 8 are generated in the vicinity of the surface of the substrate material 1, and as a result, the connection between the layers by the conductive paste 4 becomes insufficient.

  In a circuit-formed substrate using a normal prepreg as a substrate material, the prepreg is completely cured by hot pressing, that is, after forming a C-stage, drilling is performed using a drill or the like, and a metal such as copper is plated between layers. Since the connection is established, the above-mentioned problem does not occur.

  In recent years, a method of filling a via hole formed in a substrate material in a B-stage state with a conductive substance, that is, a conductive paste has been developed for a high-density circuit forming substrate to form an interlayer connection means. The above problems have become apparent when manufacturing circuit-formed substrates.

  As the circuit forming substrate, various thicknesses are required for the insulating layer between the layers, but the types of the thickness of the reinforcing material used for the prepreg are limited, and the layer of the impregnating resin 10 shown in FIG. At present, a relatively thick substrate material is also used.

  From the results of many experiments and the analysis of prototype samples, the inventor has found that the conventional problems as described above are the thickness of the portion mainly composed of the impregnating resin near the surface of the substrate material, that is, above and below the reinforcing material, and the impregnating resin. Has found that it is important to maintain an appropriate ratio between the thickness of the central portion of the substrate material integrated with the reinforcing material. That is, when the ratio is inappropriate, a phenomenon occurs in which the interlayer connection means such as conductive particles flows out due to the flow of the substrate material components in the process such as hot pressing in the vicinity of the surface of the substrate material.

  In the method for producing a circuit-formed substrate of the present invention, the B-stage state substrate material includes a woven fabric or a non-woven fabric as a reinforcing material, or a mixed material of a woven fabric and a non-woven fabric, and the B-stage state substrate material after molding in a hot press process The thickness of the reinforcing material is not less than the thickness of the reinforcing material and not more than 1.5 times the thickness of the reinforcing material.

  According to the present invention, the electrical connection can be efficiently expressed by the interlayer connection means such as the conductive paste.

  Moreover, in the manufacturing material of the circuit formation board | substrate of this invention, it is set as the structure whose weight ratio in the board | substrate material of a reinforcing material is 30% or more and 60% or less.

  According to the present invention, electrical connection can be efficiently expressed by interlayer connection means such as conductive paste.

  As a result, the reliability of electrical connection between layers using a conductive paste or the like is greatly improved, and a circuit forming substrate having high density and excellent quality can be provided.

  As described above, in the circuit forming substrate manufacturing method and the circuit forming substrate of the present invention, the thickness of the substrate material of the layer where the interlayer connection means exists is not less than the thickness of the reinforcing material and not more than 1.5 times the thickness of the reinforcing material. The electrical connection by the interlayer connection means such as a conductive paste can be efficiently performed.

  In particular, when a woven fabric using fibers such as glass is used as a reinforcing material for a prepreg as a substrate material, taking advantage of the dimensional stability of the woven fabric and the strong peeling strength of copper foil or the like. However, the special effect that the connection between the layers can be stabilized is exhibited.

  Further, in the material for manufacturing a circuit-formed substrate of the present invention, the weight ratio of the reinforcing material in the substrate material is 30% or more and 60% or less, or the thickness of the reinforcing material is 50% or more and 90% or less of the substrate material thickness. By adopting a configuration such as setting, electrical connection can be efficiently expressed by an interlayer connection means such as a conductive paste.

  As a result, the reliability of the electrical connection between layers using a conductive paste or the like is greatly improved, and a high-density and high-quality circuit forming substrate can be provided.

The invention described in claim 1 of the present invention
(1) Metal foil, or metal foil affixed to a support, or metal foil affixed to a support and formed with a circuit pattern (2) B-stage substrate material provided with interlayer connection means (3) Circuit or B stage substrate material with metal foil and interlayer connection means (4) C stage state substrate material with circuit or metal foil or C stage state substrate material with circuit or metal foil and interlayer connection means,
A laminating step of laminating two or more metal foils or substrate materials including a B-stage substrate material provided with at least one or more types of interlayer connection means;
A hot press step of forming the laminate by heating and pressing;
And a step of cutting the laminate periphery comprising flowing out of the thermosetting resin flows from the substrate material during the heat pressing step,
The substrate material of B-stage is composed of a woven fiber glass thermosetting resin impregnated in the reinforcing material and the reinforcing material thickness T1,
The ratio of the reinforcing material in the substrate material in the B stage state is 30% or more and 60% or less by weight ratio,
The thickness T1 of the reinforcing material is adjusted to be 50% to 90% of the thickness of the B-stage substrate material,
The substrate material in the B stage state is molded by being compressed into a substrate material having a thickness T2 by forming a flow-out portion through the thermosetting resin in the substrate material flowing through the hot pressing step. ,
The hot pressing step is performed under heating and pressurizing conditions where the ratio T2 / T1 of the thicknesses T1 and T2 satisfies 1.17 or more and 1.31 or less ,
The interlayer connection means provided in the substrate material in the B stage state is composed of conductive particles filled in via holes and a conductive paste mainly composed of a resin component,
The conductive paste is a method for manufacturing a circuit-formed substrate, wherein the conductive paste is compressed in the thickness direction of the substrate material in the hot press process, and flows from the substrate material during the hot press process. By forming the flow-out portion of the thermosetting resin, the substrate material composed of the reinforcing material having the thickness T1 and the thermosetting resin is efficiently compressed into the substrate material having the thickness T2 after the heat pressing step. Can be molded. As a result, the interlayer connection means made of a conductive material or the like has an effect of realizing a low resistance interlayer connection.
Further, by setting the weight of the reinforcing material to be 30% or more and 60% or less of the weight of the substrate material, it is possible to control the flow of the substrate material in the hot press process and to stabilize the formation of the interlayer connection means. .

In addition, when glass fiber woven fabric is used as the reinforcing material, the connection between the layers can be stabilized while taking advantage of the dimensional stability of the woven fabric and the strong peeling strength of the copper foil. The effect of is demonstrated.

Further, the interlayer connecting means are shorted with be composed of a conductive paste mainly containing filled conductive particles and a resin component in the hole of the through, the filling work into the hole of the penetration of the conductive material can be performed conveniently At the same time, since the interlayer connection means to be formed has flexibility, it has an effect of improving reliability against thermal shock and mechanical repeated stress.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

(Embodiment 1)
1A to 1G are process cross-sectional views illustrating a method for manufacturing a circuit forming substrate and a material for manufacturing the circuit forming substrate according to the first embodiment of the present invention.

  As shown in FIG. 1A, a substrate material 1 is prepared in which a film 2 having a thickness of 20 μm is bonded to both surfaces. The substrate material 1 is a prepreg using a glass fiber woven fabric as a reinforcing material. In order to express the thickness of the glass fiber woven fabric as a reinforcing material, a numerical value called a nominal thickness that is usually used is used.

  For film 2, polyethylene terephthalate (PET) having a thickness of 20 μm was used. Instead of the PET film, a thermosetting resin such as an epoxy resin may be coated and used as the film 2.

  Next, as shown in FIG. 1B, a via hole 3 having a diameter of about 200 μm was processed using a carbon dioxide laser.

  Next, the conductive paste 4 was filled in the via hole 3 as shown in FIG. 1C by a method such as screen printing. The conductive paste 4 is obtained by kneading copper powder having a diameter of about 5 μm together with a thermosetting resin and a curing agent. It is also possible to add a solvent or the like to the conductive paste 4 for the purpose of adjusting the viscosity.

  Next, as shown in FIG. 1 (D), the film 2 on both sides of the substrate material 1 is peeled to obtain the substrate material 1 with the conductive paste 4 protruding corresponding to the thickness of the film 2, and then on both sides. Copper foil 5 is disposed.

  Next, a shape as shown in FIG. 1 (E) is obtained through a hot pressing step of heating and pressing in the substrate thickness direction. At that time, the thermosetting resin in the substrate material 1 flows and becomes a flow-out portion 6.

  Next, as shown in FIG. 1 (F), the peripheral portion of the substrate material 1 is cut into a desired size, and then the copper foil 5 is patterned by a method such as etching to form a circuit 7. FIG. A double-sided circuit-formed substrate as shown in FIG.

  When the circuit forming substrate is manufactured through the above-described steps, the electrical connection by the conductive paste 4 becomes insufficient due to the phenomenon that the conductive particles of the conductive paste 4 flow as described in the conventional example. In order to solve the problem, the inventor has studied various substrate materials and hot press process conditions.

  Three types of reinforcing materials having a thickness of 60, 80, and 100 μm are used in a plain woven glass fiber woven fabric for an ordinary printed wiring board, and the amount of thermosetting resin impregnated in the reinforcing material is expressed as a resin amount by weight ratio. . The impregnated thermosetting resin is B-staged with a dryer to produce a prepreg. The substrate thickness after hot pressing was measured, and the ratio with the glass woven fabric thickness was calculated.

  In addition, a test pattern in which 500 interlayer connection parts are connected in series with approximately 200 μm diameter via holes on the double-sided board was measured, and the circuit electrical resistance was measured to determine the connection resistance values of the front and back surfaces per location. That is, the average of the electrical resistance values of one interlayer connection portion connecting the front and back surfaces of the double-sided board was calculated as the via resistance value.

  The above results are summarized in (Table 1).

  As can be seen from the results of (Table 1), the thickness of the reinforcing material in the substrate material 1, that is, the thickness (T2) of the substrate material 1 after hot pressing in the first embodiment is 1. It can be seen that the via resistance value is stable when it is 5 times or less.

  In addition, although the sample of Experiment No. 1 has a low via resistance value, the peel strength for peeling the copper foil 5 from the substrate material 1 is lower than usual, and the resin amount is 66 when used for applications requiring peel strength. It is desirable to increase it from 67% to 67% to 68%.

  In addition, when the storage reliability test was performed on the sample of Experiment No. 2 under high temperature and high humidity, an increase in via resistance was observed.

  From the results of the above experiments, it has been found that it is generally preferable to form via resistances of 10 mΩ or less. Therefore, the thickness of the substrate after hot pressing was measured, and it was concluded that it was good to set the ratio of T2 / T1 to 1.5 or less.

  In order to obtain a better electrical connection, the post-press thickness of the substrate material 1 in the state of FIG. 1 (E) is more effective as the thickness is reduced. As a result of the experiment, it is necessary to have a post-press thickness that is at least greater than the thickness of the reinforcing material due to the moldability and the necessity of embedding the circuit irregularities of the inner circuit formation substrate when manufacturing the multilayer circuit formation substrate described later. Obtained.

  Furthermore, as a problem when the post-press thickness (T2) is made too thin, the fiber in the reinforcing material is in contact with the copper foil and easily causes problems such as copper migration. confirmed.

  Further, as means for achieving the post-pressing thickness (T2) of the substrate material, the ratio of the reinforcing material in the substrate material is 30% or more and 60% or less by weight, and the state of FIG. It is effective to set the thickness of the substrate material 1 at 2 to 1.1 times the thickness of the reinforcing material, that is, to adjust the thickness of the reinforcing material to be 50% to 90% of the thickness of the substrate material 1. It was confirmed as a result of the experiment.

(Embodiment 2)
In the first embodiment, the double-sided circuit formation substrate has been described. In the second embodiment, a case where a multilayer circuit formation substrate is manufactured as shown in FIG. 2 will be described.

  First, a double-sided circuit forming substrate 11 as shown in FIG. 2A is prepared. As shown in FIG. 2B, the substrate material 1 and the copper foil 5 filled with the conductive paste 4 are used as the double-sided circuit forming substrate 11. Align and place on the front and back. In this state, the substrate material 1 is molded and cured by heating and pressing with a hot press apparatus or the like to obtain a shape as shown in FIG. At that time, the flow-out portion 6 is formed by the component of the substrate material 1 that has flowed.

  Next, after cutting off an excess part of the periphery to obtain a shape as shown in FIG. 2D, the copper foil 5 is patterned by a method such as etching to form a circuit 7, and FIG. A four-layer circuit forming substrate as shown in FIG.

  Also in the manufacture of such a multilayer circuit forming substrate, the electrical connection between the layers could be satisfactorily formed by applying the manufacturing method and manufacturing material of the circuit forming substrate of the present invention.

  The double-sided circuit forming substrate 11 used in the present embodiment may be the one described in the first embodiment, but it is also possible to use a substrate in which an interlayer connection is formed by a normal plating method or the like. A configuration in which the substrate material 1 is temporarily press-bonded to the double-sided circuit forming substrate 11 at the stage shown in FIG.

  An example of the manufacturing method will be described. As shown in FIGS. 1A to 1G, the film 2, the substrate material 1, the circuit formation substrate 7, the substrate material 1, and the film are laminated on both sides of the circuit formation substrate shown in FIG. Paste them together so that they are in the order of 2. Next, after processing the via hole 3 by laser processing, the conductive paste 4 is filled in the via hole 3, then the film 2 is peeled off, and then the copper foil 5 is disposed on the outside and hot pressing is performed. Is possible.

  As an example of the material described as the substrate material, that is, the prepreg in the first and second embodiments described above, it is possible to use a normal glass fiber woven fabric or non-woven fabric impregnated with a thermosetting resin to form a B stage. In addition, organic fibers such as aramid can be employed instead of glass fibers.

  Moreover, it is also possible to use the material which mixed the woven fabric and the nonwoven fabric, for example, the material which inserted | pinched the glass fiber nonwoven fabric between two glass fibers as a reinforcing material.

  In addition, examples of the thermosetting resin in the portion described as the thermosetting resin in the embodiment of the present invention include an epoxy resin, an epoxy / melamine resin, an unsaturated polyester resin, a phenol resin, and a polyimide resin. , Cyanate resin, cyanate ester resin, naphthalene resin, urea resin, amino resin, alkyd resin, silicon resin, furan resin, polyurethane resin, aminoalkyd resin, acrylic resin, fluorine resin A resin, a polyphenylene ether resin, a cyanate ester resin, etc. can be used alone, or two or more thermosetting resin compositions or thermosetting resin compositions modified with a thermoplastic resin can be used. In addition, flame retardants and inorganic fillers can be added.

  Further, a circuit made of metal foil or the like temporarily fixed to a support can be used instead of copper foil.

  Further, although the conductive paste has been described as the interlayer connection means, the conductive paste is not limited to those obtained by kneading conductive particles such as copper powder in a thermosetting resin containing a curing agent, and suitable conductive particles. Various compositions such as a kneaded polymer material having a viscosity or a solvent can be used.

  In addition to the conductive paste, post-shaped conductive protrusions formed by plating or the like, or conductive particles having a relatively large particle size that are not made into a paste can be used alone as an interlayer connection means.

(A)-(G) is process sectional drawing which shows the manufacturing method of the circuit formation board | substrate of the 1st Embodiment of this invention. (A)-(E) is process sectional drawing which shows the manufacturing method of the circuit formation board | substrate of the 2nd Embodiment of this invention. (A)-(G) is process sectional drawing which shows the manufacturing method of the circuit formation board | substrate in a 1st prior art example. Sectional schematic diagram showing material for manufacturing circuit forming substrate in second conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate material 2 Film 3 Via hole 4 Conductive paste 5 Copper foil 6 Outflow part 7 Circuit 8 Outflow particle 9 Glass fiber woven fabric 10 Impregnation resin 11 Double-sided circuit formation board

Claims (1)

(1) Metal foil, or metal foil affixed to the support, or metal foil affixed to the support and formed with a circuit pattern (2) B-stage substrate material provided with interlayer connection means (3) Circuit or B stage substrate material with metal foil and interlayer connection means (4) C stage state substrate material with circuit or metal foil or C stage state substrate material with circuit or metal foil and interlayer connection means,
A laminating step of laminating two or more metal foils or substrate materials including a B-stage substrate material provided with at least one or more types of interlayer connection means;
A hot press step of forming the laminate by heating and pressing;
And a step of cutting the laminate periphery comprising flowing out of the thermosetting resin flows from the substrate material during the heat pressing step,
The substrate material of B-stage is composed of a woven fiber glass thermosetting resin impregnated in the reinforcing material and the reinforcing material thickness T1,
The ratio of the reinforcing material in the substrate material in the B stage state is 30% or more and 60% or less by weight ratio,
The thickness T1 of the reinforcing material is adjusted to be 50% to 90% of the thickness of the B-stage substrate material,
The substrate material in the B stage state is molded by being compressed into a substrate material having a thickness of T2 by forming a flow-out portion through the thermosetting resin in the substrate material flowing through the hot pressing step. ,
The hot pressing step is performed under heating and pressurizing conditions where the ratio T2 / T1 of the thicknesses T1 and T2 satisfies 1.17 or more and 1.31 or less ,
The interlayer connection means provided on the B-stage substrate material is composed of conductive particles filled in via holes and a conductive paste mainly composed of a resin component,
The method of manufacturing a circuit-formed substrate, wherein the conductive paste is compressed in the thickness direction of the substrate material in the hot pressing step .

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