JP2007059529A - Manufacturing method of circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a circuit board in which thermoplastic resin and thermosetting resin, which are used as interlayer insulating resin, are not peeled from a conductive projection, without depending on a temporary adhesion condition at the time of manufacturing the circuit board by connection using the conductive projection. <P>SOLUTION: For manufacturing the circuit board where a circuit substrate having metal foil in which the conductive projection is erected at least on one face, and an insulating resin layer stuck to one face of metal foil by pressure in a state where the conductive projection passes through the insulating resin layer is laminated with another circuit substrate or with a metal foil; the insulating resin layer is stuck by pressure to metal foil where the conductive projection is erected. The top of the conductive projection is pressurized, and the size of the top of the conductive projection is made larger than the hole through which the conductive projection passes in the insulating resin layer. The circuit substrate is laminated with the other circuit member or metal foil. Circuit layers are connected by the conductive projection. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a circuit board, and more particularly to a method for manufacturing a circuit board in which layers are connected by conductive protrusions.

  In recent years, downsizing and higher functionality of electronic devices have been promoted more and more, and therefore, there is an increasing demand for higher density of circuit boards. In view of this, the circuit board is made to be a multi-layer circuit board from one side to both sides or three or more layers to increase the density of the circuit board.

  In these circuit boards, conventionally, for interlayer connection, a technique of performing a plating process after opening by laser, NC drill, plasma etching, chemical etching or the like is employed. However, it has the disadvantage that the yield of the plating process itself is poor and the process for conducting the insulating resin layer is complicated.

  Therefore, a method has been developed in which the electrical connection between the circuit board layers is replaced with a connection using a conductive protrusion such as a printing bump by a conductive paste or a metal bump by plating or etching instead of a conventional via hole connection by a plating method. Yes.

  The interlayer insulating material of the circuit board by the connection using the conductive protrusion described above can be roughly divided into a thermoplastic resin and a thermosetting resin. Examples of the thermoplastic resin include thermoplastic polyimide and liquid crystal polymer. As the thermosetting resin, an epoxy prepreg is widely used as a substrate material.

  These interlayer insulating resins are temporarily bonded to the copper foil surface on which the conductive protrusions stand, and the conductive protrusions are formed by mechanical polishing such as roll polishing or chemical polishing such as CMP as described in Patent Document 1. The following problems arise when a circuit substrate is formed such that the top is exposed from the interlayer insulating resin.

  Regardless of whether a thermoplastic resin or thermosetting resin is used, the adhesive strength at the time of temporary bonding described above is weak, and the interlayer insulating resin may float or peel off from the conductive protrusion due to handling to the next process, etc. In some cases, the yield may be affected, and if the repair is possible, the repair may be performed to deteriorate the productivity. In addition, inspection between processes becomes difficult.

  Therefore, when trying to increase the temporary adhesive force, in the case of a thermoplastic resin, a temperature at which the actual adhesive force is exhibited, for example, a very high process temperature of about 300 ° C. for a thermoplastic polyimide and about 250 ° C. for a liquid crystal polymer is required. Thus, productivity is impaired. Further, when the temperature at which adhesiveness is manifested is low, the heat resistance as a substrate is poor, and problems arise when exposed to a high temperature atmosphere of 200 ° C. or higher such as solder heat resistance or reflow during component mounting. In the case of a thermosetting resin, it is possible to increase the temporary adhesive force at a lower temperature than the thermoplastic resin, but the higher the temporary adhesive force, the lower the actual adhesive force. It was difficult to obtain a sufficient temporary adhesive force with a cured resin.

  3 and 4 are manufacturing process diagrams of a double-sided flexible circuit board by connection using conductive protrusions according to the conventional methods described in Patent Documents 1 and 2. FIG. When manufacturing the double-sided flexible circuit board, as shown in FIG. 3 (1), the copper foil 21 (for example, 100 μm in thickness) / nickel foil 22 (for example, 2 μm in thickness) described in Patent Documents 1 and 2 ) / A metal substrate 24 having a three-layer structure of copper foil 23 (for example, 18 μm thick) is prepared.

  Next, as shown in FIG. 3B, conductive protrusions 25 are formed on the copper foil 23 by an etching method. As the etching solution at this time, the etching solution having selectivity described in Patent Documents 1 and 2 is used.

  Next, as shown in FIG. 3 (3), in the process of exposing the polyimide film 26 having thermoplastic polyimide on both surfaces and the subsequent conductive protrusion tops, a protective film 27 for protecting the conductive protrusion is provided with the conductive protrusion. Affixed to the surface with a press or laminator.

  Next, as shown in FIG. 3 (4), in order to expose the top portion 28 of the conductive protrusion from the polyimide film 26, mechanical polishing such as roll polishing or chemical polishing such as CMP is performed. Although it is described in Patent Document 4 that the conductive protrusion 25 penetrates the polyimide film depending on the type of the polyimide film, even if such a polyimide film is used, the flat conductivity at the top formed by etching is described. Since the polyimide film always remains on the top of the protrusion 25, a step of exposing the top of the conductive protrusion as described above is necessary. The so-called protrusion amount from the polyimide film 26 to the top 28 of the conductive protrusion at this time is substantially equal to the thickness of the protective film 27 when mechanical polishing such as roll polishing or chemical polishing such as CMP is performed as described above. Will be equal.

  Next, as shown in FIG. 3 (5), the polished protective film 29 is peeled off. The circuit substrate 30 in which the conductive protrusion 25 penetrates the polyimide film 26 is obtained through the steps so far.

  However, as shown in FIG. 4 (1), in the case where the temporary adhesion force of the polyimide film 26 is not so strong, the polyimide film 26 partially peels off or floats, and the subsequent process is selected. The inspection to be performed may be difficult, and this peeling or lifting may reduce the yield.

  Next, as shown in FIG. 4 (2), the circuit base material 30 in which the conductive protrusions 25 penetrate the polyimide film 26 is laminated on the copper foil 31.

Thereafter, as shown in FIG. 4 (3), a circuit pattern 32 is formed on the laminated copper foil of the base material. Further, the cover film and the solder resist layer are formed, electroless nickel, gold plating and the like are performed by a conventional method to obtain the double-sided flexible circuit board 33.
JP 2002-141629 A JP 2003-129259 A JP-A-7-245479 Japanese Patent No. 3348004

  In the present invention, when manufacturing a circuit board by connection using conductive protrusions, a circuit in which the thermoplastic resin and thermosetting resin used as an interlayer insulating resin do not peel from the conductive protrusions regardless of temporary bonding conditions. It is an object to provide a method for manufacturing a substrate.

  In order to achieve the above object, the present application provides the following invention.

  According to the present invention, a circuit substrate having a metal foil having conductive protrusions standing on at least one surface, and an insulating resin layer that is pressure-bonded in a state where the conductive protrusions penetrate the one surface of the metal foil; In a method of manufacturing a circuit board in which another circuit substrate or a metal foil is laminated, after the insulating resin layer is pressure-bonded to the metal foil on which the conductive protrusions are erected, the top portion of the conductive protrusions is pressurized. The conductive protrusion is deformed to have a larger diameter at the top of the conductive protrusion than the hole penetrating the insulating resin layer, and is then laminated with another circuit member or a metal foil, and the conductive protrusion is used between the circuit layers. Connect.

  Due to these features, the present invention has the following effects.

  According to the present invention, a circuit substrate having a metal foil having conductive protrusions standing on at least one surface, and an insulating resin layer that is pressure-bonded in a state where the conductive protrusions penetrate the one surface of the metal foil; In a method of manufacturing a circuit board in which another circuit substrate or a metal foil is laminated, after the insulating resin layer is pressure-bonded to the metal foil on which the conductive protrusions are erected, the top portion of the conductive protrusions is pressurized. Since the conductive protrusion deforms the diameter of the top portion of the conductive protrusion larger than the hole penetrating the insulating resin layer, the conductive protrusion is physically formed regardless of the type of interlayer insulating resin and the temporary bonding condition. The top portion can prevent peeling of the interlayer insulating resin. This improves the productivity and facilitates inspection between processes without the interlayer insulating resin floating or peeling off from the conductive protrusion during handling to the next process.

  As a result, according to the present invention, when manufacturing a circuit board by connection using conductive protrusions, the thermoplastic resin and thermosetting resin used as the interlayer insulating resin are peeled off from the conductive protrusions regardless of the temporary bonding conditions. A circuit board manufacturing method that does not occur and a circuit base material suitable therefor can be provided inexpensively and stably.

  Hereinafter, the present invention will be further described with reference to the illustrated embodiments.

  FIG. 1 and FIG. 2 are manufacturing process diagrams of a circuit board according to the present invention. First, as shown in FIG. 1 (1), it is described in Patent Document 2 when a double-sided flexible circuit board is manufactured. A metal substrate 4 having a three-layer structure of copper foil 1 (for example, thickness 100 μm) / nickel foil 2 (for example, thickness 2 μm) / copper foil 3 (for example, thickness 18 μm) is prepared.

  Next, as shown in FIG. 1 (2), conductive protrusions 5 are formed on the copper foil 3 by an etching technique. As an etchant at this time, an etchant having selectivity described in Patent Document 3 is used.

  Next, as shown in FIG. 1 (3), a polyimide film 6 having thermoplastic polyimide on both sides and a first protective film 7 for protecting the conductive protrusions in the subsequent step of exposing the conductive protrusion tops are provided. Affixed to the surface where the conductive protrusions are erected with a press, laminator or the like.

  Next, as shown in FIG. 1 (4), in order to expose the top 8 of the conductive protrusion from the polyimide film 6, mechanical polishing such as roll polishing or chemical polishing such as CMP is performed. Although it is described in Patent Document 4 that the conductive protrusion 5 penetrates the polyimide film depending on the kind of the polyimide film, even if such a polyimide film is used, the flat conductivity at the top formed by etching is described. Since the polyimide film always remains on the top of the protrusion 5, a step of exposing the top of the conductive protrusion as described above is necessary. The so-called pop-out amount from the polyimide film 6 to the top 8 of the conductive protrusion at this time is the thickness of the first protective film 7 when mechanical polishing such as roll polishing or chemical polishing such as CMP is performed as described above. Almost equal to

  Next, as shown in FIG. 1 (5), the polished first protective film 9 is peeled off. The circuit substrate 10 in which the conductive protrusions 5 penetrate the polyimide film 6 is obtained through the steps so far.

  However, as shown in FIG. 2A, the second protective film 11 is formed on the circuit substrate 10 by a laminating method or the like. The thickness of the second protective film 11 is preferably from about half the thickness of the protrusion of the conductive protrusion of the circuit substrate 10 to about twice the thickness. The material of the second protective film 11 is preferably a synthetic resin such as a polyimide film or a pet film, a metal foil such as a copper foil or an aluminum foil, or paper such as kraft paper, and these are used alone or in combination. Here, a polyimide film having a thickness of 12.5 μm was used.

  Next, as shown in FIG. 2 (2), pressure is applied from above the second protective film 11 with a flat plate press or the like through a stainless steel plate or the like, so that the diameter of the top of the conductive protrusion is larger than the hole penetrating the insulating resin layer. Deform it greatly. At this time, when the thickness of the second protective film 11 is too thick compared to the protruding amount of the conductive protrusions of the circuit substrate 10, the deformation of the conductive protrusions hardly occurs, and the diameter of the top of the conductive protrusions Is not deformed to a greater extent than a hole penetrating the insulating resin layer. Moreover, when the thickness of the second protective film 11 is too thin compared to the protruding amount of the conductive protrusions of the circuit substrate 10, the conductive protrusions are crushed too much. There is a possibility that the connection reliability when laminated is impaired.

  The temperature at the time of pressurization is preferably from room temperature to around 50 ° C. If this temperature is high, the conductive projections are likely to be deformed, but the second protective film 11 and the interlayer insulating resin such as the polyimide film 6 are bonded to each other. There is a risk. Here, pressurization was performed at room temperature. Further, when the first protective film 9 is used as it is without using the second protective film 11, the top of the conductive protrusion is deformed into a rivet shape, and when the first protective film is peeled off, the rivet shape is formed. Since the top part of the deformed conductive protrusion is crowned, it is not preferable. Even if it presses in the state which peeled the 1st protective film 9 without using the 2nd protective film 11, although the top part of an electroconductive protrusion deform | transforms, control of the deformation amount is difficult.

  In addition, the connection using the conductive protrusion is conducted by the method of forming the conductive protrusion as described in Patent Documents 1 and 2, and the method of printing the conductive paste as described in Patent Document 3. In order to expose the top of the conductive protrusion from the interlayer insulating resin in the formation method of the conductive protrusion, since the mechanical polishing method such as roll polishing and the chemical polishing method such as CMP are used, the top of the conductive protrusion is scratched. Judgment in later inspection process becomes difficult. If it is a mere scratch, it should be a good product, but if foreign matter is attached or if it is poorly polished, it cannot flow to the next process and must be cleaned or repaired. If there are many conductive protrusions, these judgments also become a huge load, which not only impairs productivity but also leads to the outflow of defective products.

  So far, in order to prevent the conductive protrusions from becoming too deeply scratched, the count of the abrasive is increased to eliminate the scratches, or an abrasive with a higher count is used from the beginning. However, high count abrasives are expensive and have the disadvantage that productivity is deteriorated because clogging is likely to occur. On the other hand, as described above, pressure is applied from above the second protective film 11 with a flat plate press or the like through a stainless steel plate or the like, and the diameter of the top portion of the conductive protrusion is deformed larger than the hole penetrating the insulating resin layer. In order to smooth the scratches on the top of the conductive protrusions in the polishing process without using expensive high count abrasives, it is easy to make a decision in the subsequent inspection process, increasing productivity at a low cost, Defect outflow can be reduced.

  Further, as shown in FIG. 2 (3), the amount of protrusion of the conductive protrusions in FIG. 2 (1), the thickness of the second protective film, and the pressure when pressing with a flat plate press or the like are controlled. It is also possible to deform it into a rivet shape.

  Next, as shown in FIG. 2 (4), the second protective film 11 is peeled off to obtain a circuit substrate 13 in which the tops of the conductive protrusions are deformed into rivets. Since the shape of the top portion of the conductive protrusion is deformed in this way, even when the temporary adhesion force of the polyimide film 6 is not so strong, the polyimide film 6 is not partially peeled off or floated. There is no possibility that the polyimide film 6 is peeled off or lifted to reduce the inspection and the yield for selecting the process.

  Next, as shown in FIG. 2 (5), the circuit substrate 13 is laminated on the copper foil 14. Although not shown in the figure, when the circuit base 13 is built up on an inner layer circuit board or the like, the amount of protrusion of the conductive protrusion is small, so that the conductive protrusion described in Patent Document 4 is erected. There is also an effect that “damage to the inner layer circuit board”, which is a problem when building up the circuit base material to be built on the inner layer circuit board or the like, can be reduced.

  Thereafter, as shown in FIG. 2 (6), a circuit pattern 15 is formed on the laminated copper foil of the base material. Further, the cover film and the solder resist layer are formed, electroless nickel, gold plating and the like are performed by a conventional method to obtain the double-sided flexible circuit board 16.

The manufacturing process figure of the double-sided flexible circuit board in one Example of this invention. The manufacturing process figure following FIG. The manufacturing process figure of the double-sided flexible circuit board by a conventional construction method. Manufacturing process figure following FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Copper foil 2 Nickel foil 3 Copper foil 4 Metal base material 5 Conductive protrusion 6 Polyimide film 7 First protective film 8 Top part of conductive protrusion 9 Polished first protective film 10 Circuit base material 11 Second protection Film 12 Conductive protrusion 13 deformed larger than hole penetrating insulating resin layer Circuit substrate 14 having conductive protrusion deformed larger than hole penetrating insulating resin layer Copper foil 15 Circuit pattern 16 Flexible circuit board

Claims (1)

  A circuit substrate having a metal foil with conductive protrusions standing on at least one surface, and an insulating resin layer that is pressure-bonded with the conductive protrusions penetrating on the one surface of the metal foil, and another circuit substrate or In the method of manufacturing a circuit board in which a metal foil is laminated, after the insulating resin layer is pressure-bonded to the metal foil on which the conductive protrusion is erected, the top of the conductive protrusion is pressed, and the conductive protrusion is The diameter of the top portion of the conductive protrusion is deformed larger than the hole penetrating the insulating resin layer, and then laminated with another circuit member or a metal foil, and the circuit layer is connected by the conductive protrusion. A method for manufacturing a circuit board.

Images