JP4062432B2 - Circuit board and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a circuit board and a manufacturing method thereof, and more particularly to a multilayer circuit board formed by laminating a plurality of substrates via an adhesive layer and a manufacturing method thereof.
[0002]
[Prior art]
In response to demands for miniaturization and higher density of circuit devices, multilayer circuit boards tend to be used. Among such multilayer circuit boards, a method has been developed in which two circuit boards formed on only one side are bonded to each other via an adhesive layer. Such a circuit board is obtained by laminating a plurality of boards with an adhesive layer interposed therebetween, so that the circuit can be mounted at a higher density than a single-layer board.
[0003]
When manufacturing such a multilayer circuit board, the positional accuracy between the circuit forming surfaces is important. For example, before the entire surface of the board is bonded and laminated at once, precise positioning is performed. For alignment, the corner portions of the substrate are temporarily bonded after precise positioning, and then the main bonding is performed. That is, conventionally, when a plurality of substrates are stacked, bonding in two steps of temporary bonding and main bonding is sequentially performed.
[0004]
FIG. 7 shows a temporarily bonded state when such multilayer circuit boards are laminated. Here, the pair of substrates 11 and 12 are bonded via an adhesive sheet 13. One substrate 11 has a wiring pattern 26 formed in advance by etching the copper foil 22 on the surface in contact with the adhesive sheet 13. On the other hand, the copper foil 30 of the other board | substrate 12 is etched, and the wiring pattern 31 is formed in the part joined by this by the lamination sheet 13. FIG.
[0005]
In this manner, the pair of substrates 11 and 12 having the wiring patterns 26 and 31 formed on the bonding surfaces are overlapped with each other via the adhesive sheet 13. Then, the heating head 18 is applied to a temporary bonding region of the substrate, for example, a corner portion, and pressed, thereby melting the adhesive sheet 13 in the region corresponding to the heating head 18, thereby the upper and lower substrates 11, 12 are moved. They are bonded together temporarily.
[0006]
[Problems to be solved by the invention]
As shown in FIG. 7, when the pair of substrates 11 and 12 are temporarily bonded by the heating head 18 via the adhesive sheet 13, there is no method for transferring heat from the heating head 18 to the temporary bonding region of the adhesive sheet 13. For this reason, in order to raise the adhesive sheet 13 to a temperature at which the adhesive sheet 13 can be bonded, it usually takes 5 minutes or more, thereby increasing the time required for the process. And since it took time for such heating, productivity was falling.
[0007]
Further, as shown in FIG. 7, since it takes time to temporarily bond the corresponding temporary bonding region of the adhesive sheet 13 while being heated by the heating head 18, as shown by the arrow 40 in FIG. Heat is transmitted along the surface of the substrate 11 especially on the copper foil 22, and the adhesive sheet 13 is softened in the region other than the temporary adhesive region, whereby the upper and lower substrates 11, 12 are positioned relative to each other as shown in FIG. 7B. Misalignment was likely to occur. If the upper and lower substrates 11 and 12 are displaced from each other in the plane direction, the alignment accuracy is lowered, which adversely affects the quality of the circuit board, or a defective substrate is manufactured, resulting in a decrease in yield.
[0008]
The present invention has been made in view of such problems, and particularly reduces the time required for heating at the time of temporary bonding when a multilayer circuit board is manufactured by laminating a plurality of boards, It is an object of the present invention to provide a circuit board and a method of manufacturing the circuit board which prevent mutual positional deviation of the substrates to be joined to each other during temporary bonding to avoid a decrease in alignment accuracy .
[Means for Solving the Problems]
The main invention of this application is:
In a multilayer circuit board formed by laminating a plurality of substrates via an adhesive layer,
A plurality of small holes for transferring heat to the temporary bonding region of the substrate temporarily bonded by the bonding layer are formed so as to be close to each other, and a metal layer on the inner peripheral surface of these small holes is formed. The substrate surface is continuous with each other through a metal layer formed on the surface, and the metal layer in the temporary adhesion region on the surface of the substrate is independent of the metal layer in other regions of the substrate. The present invention relates to a characteristic circuit board.
[0009]
Here, the metal layer on the inner peripheral surface of the small hole is formed of plating formed on the inner peripheral surface of the small hole, and the metal layer and the adhesive layer are formed on the surface of the substrate and are temporarily bonded. It is preferable to contact via. Further, the small holes for transferring heat may be formed in a region where a wiring pattern is not formed. The small holes for transmitting heat are preferably formed in a region to be discarded after being divided.
[0010]
The main invention related to the manufacturing method is
In a manufacturing method for manufacturing a multilayer circuit board by laminating a plurality of substrates through an adhesive layer,
Forming a plurality of small holes penetrating each other in advance to transfer heat to a temporary bonding region for temporarily bonding a plurality of circuit boards through the adhesive layer,
A metal layer is formed on the inner peripheral surface of the small hole , and the metal layer is continuous with the surface of the substrate via the metal layer formed on the surface, and the temporary adhesion region on the surface of the substrate is The metal layer is independent of metal layers in other areas of the substrate ;
The present invention relates to a circuit board manufacturing method, wherein a plurality of substrates are temporarily bonded to each other by heating the adhesive layer through the small holes by a heating head.
[0011]
Here, the adhesive layer is preferably an adhesive sheet. The adhesive sheet is preferably a B-stage epoxy resin sheet in a semi-cured state. Further, it is preferable that the small hole for transmitting heat is a hole having a diameter of 0.1 to 1.0 mm. In addition, it is preferable that a temporary adhesion region including a plurality of small holes for transmitting heat is formed in the vicinity of the four corners on the surface of the circuit board. Further, it is preferable to perform main bonding after temporary bonding to bond the entire surface of the circuit board.
[0012]
In a preferred embodiment of the invention included in the present application, a rigid circuit board having a circuit configuration on one side is bonded via an adhesive sheet to manufacture a multilayer circuit board. A small hole for transferring heat composed of a thermal via for improvement is arranged. Here, the thermal via formed of a small hole has a metal layer of a conductor in which a metal layer on the inner peripheral surface is provided in the temporary adhesion region of the substrate and is independent from the metal layers in other regions. The thermal via is formed at the same time as the inner via hole including a through hole formed in the circuit board.
[0013]
According to such an aspect, the efficiency of heat conduction from the heating head to the bonding means is greatly improved by using the thermal via for spot bonding. Further, by forming a land made of a metal layer independent of other regions in the thermal via portion, diffusion of heat to regions other than the temporary adhesion region can be suppressed, and the same effect can be obtained. As a result, the period of the temporary bonding step is greatly shortened, and the productivity is greatly improved.
[0014]
In addition, the provision of the thermal vias shortens the process time of the temporary bonding process and makes it difficult to cause a shift in the surface direction between the temporarily fixed substrates during the temporary bonding process. This improves alignment accuracy and greatly improves the quality of the bonding process. Further, by forming the thermal via at the same time as the inner via hole formed of the through hole in another region, a special additional process is not required, and this does not increase the manufacturing cost.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to the illustrated embodiments. The present embodiment relates to a multilayer circuit board in which two rigid boards 11 and 12 made of various insulating materials such as glass epoxy resin and ceramic are bonded via an adhesive sheet 13 and a manufacturing method thereof.
[0016]
Here, the two substrates 11 and 12 are heated and temporarily bonded by the heating head 18 at the portions of the circular temporary bonding regions 16 formed in the corner regions of the substrates 11 and 12, for example. ing. A plurality of heating small holes 17 are formed close to the temporary adhesion region 16. As shown in FIG. 2, the temporary adhesion regions 16 formed in the four corner portions of the substrate 11 may be formed in unnecessary surrounding portions that are divided and discarded by the dividing slits 19, for example. preferable.
[0017]
The adhesive sheet 13 that is interposed between the two substrates 11 and 12 and joins the bonding surfaces of the substrates 11 and 12 to each other is preferably a semi-cured B-stage epoxy resin sheet. Such an epoxy resin sheet is a low flow type adhesive sheet that bonds substrates on both sides by heating and pressing.
[0018]
The temporary adhesion region 16 for heating the temporary adhesion region of the adhesive sheet 13 may be a substantially circular region having a diameter of 3 to 12 mm. The size of the temporary bonding region 16 can be arbitrarily changed according to the overall size and weight of the substrate 12, but generally the size of the temporary bonding region 16 is increased as the dimensions of the substrates 11 and 12 are increased. In contrast, when the size of the substrates 11 and 12 is small, the size of the temporary bonding region 16 is also small. In addition, in order to prevent the heat head 18 used for temporary bonding from contacting the outside of the temporary bonding area 16 to prevent heat diffusion of the heating head 18, the size of the temporary bonding area 16 is the same as the size of the heating head 18. It should be about the same or slightly larger. Further, the heating small hole 17 formed in the temporary adhesion region 16 may have a diameter in the range of 0.1 to 1.0 mm, and more preferably has a diameter of 0.2 to 0.5 mm. Within range. Further, it can be arbitrarily adjusted according to the size of the temporary adhesion region and the number of small holes 17. The number of small holes 17 is at least 5 or more, preferably 7 to 15. In general, a plurality of, for example, ten heating small holes 17 are gathered and formed in close proximity in the temporary bonding region 16 as shown in FIGS.
[0019]
Moreover, the copper foil 22 is joined to the both surfaces of the board | substrate 11 in which the temporary adhesion area | region 16 by the small hole 17 for heating is formed. In particular, a copper foil 23 is also bonded to the temporary bonding region 16. These copper foils 22 and 23 are both formed by etching a copper foil formed on the surface of the substrate 11, and a gap 24 is formed on the outer peripheral side of the copper foil 23 in the temporary bonding region 16. . This gap 24 constitutes a blocking portion, and is intended to prevent heat transfer to the outer peripheral side. Further, a plating layer 25 is formed on the inner peripheral surface of the heating small hole 17 as shown in FIG. 3C, and this plating layer 25 is in contact with or continuous with the copper foil 23 in the temporary bonding region 16.
[0020]
Next, the process of manufacturing the upper substrate 11 of the pair of upper and lower substrates 11 and 12 shown in FIG. 1 will be described with reference to FIG. A plate-like base material made of an insulating material having copper foils 22 bonded on both sides, that is, the substrate 11 is prepared as shown in FIG. 3A. Then, as shown in FIG. 3B, the heating hole 17 and the through hole 27 are formed in the substrate 11 by an NC drill. That is, the feature of this processing is that the through hole 27 and the heating small hole 17 constituting the through hole are formed simultaneously. This eliminates the need for a separate process for forming the heating small holes 17.
[0021]
Thereafter, as shown in FIG. 3C, the inner peripheral surface of the heating small hole 17 and the inner peripheral surface of the through hole 27 are plated. That is, at the time of through plating of the inner via hole formed of the through hole 27, the inner peripheral surface of the heating small hole 17 is simultaneously plated, and a plating metal is formed on the inner wall. Therefore, another process for forming a metal layer on the inner peripheral surface of the heating small hole 17 is not necessary.
[0022]
Thereafter, as shown in FIG. 3D, a wiring pattern 26 is formed on the surface to be bonded to the adhesive sheet 13 and opposite to the surface exposed to the outside after bonding. The wiring pattern 26 is formed by etching the copper foil 22 formed on the surface of the substrate 11. At the same time, the shielding portion 24 including the gap shown in FIG. 2 is formed by etching, and the copper foil 23 remains inside the shielding portion 24. The copper foil 23 is continuous with the plating layer 25 inside the small hole 17 for heating.
[0023]
Next, how to make the counterpart substrate 12 will be described with reference to FIG. As the substrate 12, as shown in FIG. 4A, a substrate made of a plate-like base material having copper foils 30 formed on both sides is used. Then, the copper foil on one surface of the substrate 12 which is bonded to the adhesive sheet 13 and opposite to the surface exposed to the outside after being bonded is etched, thereby forming the wiring pattern 31 in FIG. 4B. As shown in FIG.
[0024]
Thereafter, as shown in FIG. 4C, the adhesive sheet 13 is bonded to the surface of the substrate 11 on which the wiring pattern 31 is formed. Then, as shown in FIG. 4D, drilling is performed with an NC drill or the like to form a through hole 32. The through hole 32 penetrates not only the substrate 12 but also the adhesive sheet 13. At this stage, the inner peripheral surface of the through hole 32 is not yet plated.
[0025]
Next, a process of bonding and laminating the substrate 11 manufactured as shown in FIG. 3 and the substrate 12 manufactured as shown in FIG. 4 using the adhesive sheet 13 will be described with reference to FIG. The substrate 11 is positioned facing the substrate 12 on which the wiring pattern 31 is formed and the adhesive sheet 13 is bonded. At this time, the lower surface of the substrate 11 on which the wiring pattern 26 is formed is made to face the adhesive sheet 13. In this state, as shown in FIG. 5B, the upper and lower substrates 11 and 12 are bonded to each other via the adhesive sheet 13 in a state where the upper and lower substrates 11 and 12 are correctly positioned in the surface direction. That is, the substrate 11 on which the heating small holes 17 are formed and the substrate 12 to which the adhesive sheet 13 is bonded are aligned and fixed.
[0026]
After this, as shown in FIG. 5C, the heating head 18 is pressed against the pair of upper and lower substrates 11 and 12 after alignment against the temporary bonding region 16 of the upper substrate 11 and pressed. At this time, the heating temperature by the heating head 18 is set to 150 ° C. or higher. For example, in the case of a heating head having a diameter of 7 mm, a pressure of 1 to ³ kg / cm ² is applied.
[0027]
Thus, the adhesive sheet 13 below the temporary adhesion region 16 is melted and thermally cured using the heating small holes 17 in the temporary adhesion region 16. In particular, the heat from the heating head 18 is effectively transmitted to the adhesive sheet 13 through the plating layer 25 on the inner peripheral surface of the plurality of small heating holes 17 formed in the temporary adhesion region 16. Therefore, this process ensures that the upper and lower substrates 11 and 12 are securely fixed, particularly in the temporary bonding region 16, and there is almost no possibility of displacement.
[0028]
Thus, if the upper and lower substrates 11 and 12 are temporarily bonded to each other only in the temporary bonding region 16, the heating head 18 is gently retracted in this state. Then, the upper and lower substrates 11 and 12 are joined by temporary bonding as shown in FIG. 5D. In this state, the positions of the upper and lower substrates 11 and 12 are determined in the surface direction, and the two do not cause positional deviation.
[0029]
Thereafter, as shown in FIG. 6, the upper and lower substrates 11 and 12 temporarily bonded are placed on the base 35, and the substrates 11 and 12 are bonded to each other from the upper side while being heated by the pressing head 36 to perform the main bonding. The heating condition at this time is 150 ° C. or higher, for example, 175 ° C., and the pressing head 36 is applied with a pressure of ²⁰ to 50 kg / cm ² under vacuum. When the main bonding is completed, the pressure head 36 is raised and the stacked substrate is taken out from the base 35.
[0030]
Thereafter, a wiring pattern is formed by etching a portion of the copper foil 22 on the substrate 11 side which is the outer surface of the substrates 11 and 12 bonded to each other, and the copper foil 30 on the outer surface side of the substrate 12 is further etched. To form a wiring pattern. In addition, the inner surface of the through hole 32 on the substrate 12 side is plated, whereby the wiring patterns 26 and 31 are electrically connected to the wiring pattern newly formed on the outer surface of the substrate 12. Then, by mounting components on the outer surfaces of the substrates 11 and 12, an electronic circuit device is obtained.
[0031]
Although the invention included in the present application has been described above with reference to the illustrated embodiments, the invention included in the present application is not limited to the above-described embodiments, and various modifications are possible within the scope of the technical idea of the present invention. is there. For example, the above embodiment relates to a bonding structure of two substrates 11 and 12, but the present invention can be applied to bonding of three or more substrates. In the above-described embodiment, the temporary bonding region 16 is temporarily bonded by the heating head 18, but may be heated by a head that generates a heated gas instead of heat. In the above embodiment, the heating small holes 17 are formed in one of the substrates 11, but the heating small holes 17 can be formed in both the substrates 11 and 12.
[0032]
【The invention's effect】
The main invention of the present application is that, in a multilayer circuit board formed by laminating a plurality of substrates via an adhesive layer, a plurality of small holes for transferring heat to the temporary adhesion region of the substrate temporarily adhered by the adhesive layer are mutually connected. together they formed through in a state in which the assembled proximity, via the metal layer a metal layer of the inner peripheral surface of the small holes are formed on the surface at the surface of the substrate contiguous to each other, yet the surface of the substrate The metal layer in the temporary adhesion region is independent of the metal layer in other regions of the substrate .
[0033]
Therefore, according to such a circuit board, the temporary bonding is more reliably performed by the heat applied through the small holes, the time required for the temporary bonding is shortened, and the displacement in the surface direction at the time of the temporary bonding is prevented. It becomes possible to improve the accuracy.
[0034]
In a manufacturing method for manufacturing a multilayer circuit board by laminating a plurality of substrates via an adhesive layer, the main invention relating to the manufacturing method is a temporary bonding region where the plurality of substrates are temporarily bonded via an adhesive layer. A small hole for transferring heat is formed in advance through the substrate , a metal layer is formed on the inner peripheral surface of the small hole , and the metal layer is formed on the surface of the substrate on the surface. The metal layers in the temporary bonding region on the surface of the substrate are independent from the metal layers in other regions of the substrate, and the heating layer is used to heat the bonding layer through the small holes to form a plurality of circuit boards. They are temporarily bonded to each other.
[0035]
Therefore, according to such a manufacturing method, it becomes possible to heat the adhesive layer effectively through the small holes by the heating head to perform temporary bonding, thereby improving heat conduction and shortening time during temporary bonding. It becomes possible. Accordingly, the time for temporary bonding is shortened to improve the productivity, and the positional deviation at the time of temporary bonding is less likely to occur, thereby improving the quality.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a main part showing joining of circuit boards.
FIG. 2 is a plan view of the main part.
FIG. 3 is a longitudinal sectional view showing the production of a substrate having a small hole for heating.
FIG. 4 is a longitudinal sectional view of an essential part showing the production of a mating substrate.
FIG. 5 is a longitudinal sectional view of a main part showing a state of temporary bonding.
FIG. 6 is a longitudinal sectional view of a main part showing a state of main bonding.
FIG. 7 is a longitudinal sectional view of a main part showing the operation of conventional temporary bonding.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11, 12 ... Board | substrate, 13 ... Adhesive sheet, 16 ... Temporary adhesion | attachment area | region, 17 ... Heating small hole, 18 ... Heating head, 19 ... Dividing slit, 22, 23 ... Copper foil, 24 ...... Clearance (blocking part), 25 plating layer, 26 wiring pattern, 27 through hole, 30 copper foil, 31 wiring pattern. 32 ... Through hole, 35 ... Base, 36 ... Pressing head, 40 ... Arrow

Claims (10)

In a multilayer circuit board formed by laminating a plurality of substrates via an adhesive layer,
A plurality of small holes for transferring heat to the temporary bonding region of the substrate temporarily bonded by the bonding layer are formed so as to be close to each other, and a metal layer on the inner peripheral surface of these small holes is formed. The substrate surface is continuous with each other through a metal layer formed on the surface, and the metal layer in the temporary adhesion region on the surface of the substrate is independent of the metal layer in other regions of the substrate. Feature circuit board. The metal layer on the inner peripheral surface of the small hole is made of plating formed on the inner peripheral surface of the small hole, and the metal layer is formed on the surface of the substrate and is temporarily bonded to the region through the adhesive layer. The circuit board according to claim 1 , wherein the circuit board is in contact with each other.   The circuit board according to claim 1, wherein the small holes for transmitting heat are formed in a region where a wiring pattern is not formed.   The circuit board according to claim 1, wherein the small hole for transferring heat is formed in a region to be discarded after being divided. In a manufacturing method for manufacturing a multilayer circuit board by laminating a plurality of substrates through an adhesive layer,
Forming a plurality of small holes passing through the substrate in close proximity to each other for transferring heat in advance to a temporary bonding region for temporarily bonding a plurality of substrates through the adhesive layer,
A metal layer is formed on the inner peripheral surface of the small hole , and the metal layer is continuous with the surface of the substrate via the metal layer formed on the surface, and the temporary adhesion region on the surface of the substrate is The metal layer is independent of metal layers in other areas of the substrate ;
A method of manufacturing a circuit board, comprising: heating a plurality of substrates to each other by heating the adhesive layer through the small holes by a heating head. The circuit board manufacturing method according to claim 5 , wherein the adhesive layer is an adhesive sheet. The method for manufacturing a circuit board according to claim 6 , wherein the adhesive sheet is a semi-cured B-stage epoxy resin sheet. 6. The method for manufacturing a circuit board according to claim 5 , wherein the small hole for transmitting heat is a hole having a diameter of 0.1 to 1.0 mm. 6. The method of manufacturing a circuit board according to claim 5 , wherein a temporary adhesion region having a plurality of small holes for transmitting heat is formed in the vicinity of four corners on the surface of the circuit board. 6. The method for manufacturing a circuit board according to claim 5 , wherein the main bonding is performed after the temporary bonding to bond the entire surface of the circuit board.

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