JP4312545B2 - Multilayer circuit board manufacturing method and circuit board material - Google Patents

Description

  The present invention relates to a technique for manufacturing a multilayer circuit board, and more particularly to a circuit board manufacturing method and a circuit board material that use conductive bumps to provide conduction between front and back layers of an insulating resin layer.

  Conventionally, when a high-density multilayer substrate is manufactured, the following process is performed. First, a copper foil with an insulating resin is bonded onto the patterned lower substrate. Next, a mask corresponding to the pattern of the lower substrate is prepared, and an opening is formed in the copper foil using this mask. Then, the insulating resin in the opening is removed by irradiating a laser through the opening. Thereafter, the upper and lower conductive portions are formed by performing metal plating on the surface of the portion excluding the insulating resin, and the upper copper foil is further patterned. Thus, a multilayer circuit board is obtained.

As a cost reduction measure for the manufacturing method of this multilayer circuit board, what is called B ² it technology as shown in Patent Documents 1 and 2 has been developed. This is done by preparing a metal foil with conductive bumps formed on the surface, and contacting the bumps of this metal foil with another patterned metal foil via an insulating resin to form a conductive part. Further, the copper foil is patterned to form a circuit of a multilayer substrate.
Japanese Patent Laid-Open No. 06-342977 JP 2001-1111189 A

  In the production of a circuit board in which conductive protrusions on the bumps formed on the conductor layer penetrate the film-like insulating resin to perform interlayer electrical bonding with the opposing conductor layer, the insulating resin penetration of the protrusions is It depends on the mechanical strength of the resin film, the shape and mechanical strength of the protrusions, and the temperature and pressure during pressing.

  And when a resin film is a thing with big mechanical strength, a protrusion may be difficult to penetrate. For example, when a resin film having excellent mechanical strength such as a polyimide film is to be penetrated by a protrusion having a flat top portion and a circular planar shape and a size of about 100 μm, the film thickness is about 25 μm. In some cases, it is technically difficult to penetrate all of several hundreds of protrusions arranged in one press.

  As countermeasures, mechanical operations such as scraping off the resin in the through-hole part, methods of disassembling and removing the resin by dry etching, etc., or exposing the bump tops, or opening the through part by laser processing or NC drill, etc. Repair work such as improving the penetrability of bumps has been carried out.

  However, with these methods, it is difficult to avoid contamination of the circuit board due to problems such as the bump itself being scraped off or loss of the insulating resin, and residual bumps or abrasives from the bump. . In addition, there are problems such as considerable time and processing time and the need for precise alignment technology.

  The present invention has been made in consideration of the above points, and in order to avoid a repair process or a pretreatment process with precise alignment as much as possible, a method for manufacturing a circuit board that can easily improve resin penetration of bumps and It aims at providing the raw material for circuit boards used for the method.

In order to achieve the above object, in the present invention,
Claim 1
A film made of an insulating resin is layered on an interlayer connection bump provided on a circuit board, and the bump touches the film and presses it, so that the bump penetrates the film and connects to another layer. In the method of manufacturing a circuit board,
The pretreatment scratches the film surface by mechanical processing;
A method of manufacturing a circuit board, characterized by forming a crack occurrence portion having a shape that causes crack growth in the film by pressing the bump against the film;
Claim 2
A film made of an insulating resin is layered on an interlayer connection bump provided on a circuit board, and the bump touches the film and presses it, so that the bump penetrates the film and connects to another layer. In the method of manufacturing a circuit board,
Prepare a filler-added film by adding a filler that does not chemically bond with the insulating resin and causes delamination,
Instead of the film, using the filler-added film
A method of manufacturing a circuit board, characterized by forming a crack occurrence portion having a shape that causes crack growth in the filler-added film by pressing the bump against the filler-added film ;
And claim 3,
In order to form a multilayer circuit board, an insulating resin film through which an interlayer connection bump formed on the circuit board passes,
An insulating resin film formed by adding a filler that does not chemically bond to the insulating resin and causes delamination;
I will provide a.

  The present invention, as described above, is used in the manufacture of a circuit board in which bumps penetrate through a resin film and perform interlayer bonding by pressing using bumps having edges that are shaped to easily cause cracks in the resin film. The penetrability can be significantly improved.

  In the present invention, it is important how the bumps easily penetrate the resin film. In order to penetrate, the resin film is caused to crack by abutting the bumps, and the crack is developed. An embodiment for this will be described with reference to FIGS.

  1 to 4, a conductor layer 2 is disposed on a substrate 1, and an interlayer bonding bump 3 is provided on the conductor layer 2. The insulating resin film 4 and the cushion material 5 are overlaid on the interlayer bonding bumps 3, and the substrate 1 or the cushion material 5 is sandwiched and pressed between the press end plates 6a and 6b.

  FIG. 1 shows a state immediately before pressing, in which a cushion material 5 is inserted between the bumps 3 so as to penetrate only the resin film 4 and sandwiched between end plates 6a and 6b.

  FIG. 2 shows the next state of FIG. 1, where the portion of the resin film 4 where the top surface of the bump 3 abuts is curved and deformed upward in the drawing, and the resin at the top edge of the bump 3 is pressed. A stress concentration portion A is generated on the surface of the film 4.

  FIG. 3 shows a state in which cracks are generated on the surface of the resin film 4 due to the stress concentration.

  In general, since the resin film 4 is processed by a coater, the surface thereof is flat. However, as is well known in fracture mechanics, when a stress concentration portion A has a crack, if the stress intensity factor at that portion is greater than a certain value, the crack progresses destructively. The stress intensity factor greatly depends on the shape of the crack, and the value of the stress intensity factor increases as the crack edge becomes acute.

  Therefore, as shown in FIG. 3, if the surface of the resin is formed in advance so as to form an acute crack end, the resin penetration of the bump 3 can be remarkably improved.

  This surface shape may be on the entire surface of the resin as long as it includes a surface that directly contacts the bump 3. Therefore, the resin surface shape changing step as the pretreatment is not caught by the position accuracy, and it is only necessary to process the surface unit.

  FIG. 4 shows the top structure of the bump 3 for facilitating the generation of cracks. As shown in FIG. 4, if the edge of the bump top is finished at an acute angle, this becomes the starting point of crack propagation, and the penetrability can also be improved.

  As another method, a filler that has a sharp corner and is not chemically bonded to the resin film 4 is added to the resin film 4, and the interface peeling between the filler and the resin film 4 at the stress concentration portion A in FIG. The penetration can be improved by forming cracks by forming cracks B.

  In addition, by using a thermoplastic resin for the resin film 4, even when cracks propagate due to the dense arrangement of bumps after penetration, by thermocompression bonding at a temperature equal to or higher than the Tg of the resin with the opposing conductor layer, The scratches or the like attached in advance are embedded by the flow of the resin itself, and no wrinkles are generated in the resin as the insulating layer.

(Example of pretreatment to facilitate cracking of resin film)
In order to facilitate the generation of cracks, it is effective to form a surface shape having a sharp end face on the surface of the resin film 4 in advance.
(1) Mechanically scratch with abrasives, abrasive paper, etc.
(2) Make a cut with a sharp blade to a depth that will not break the film 4.
(3) Roll presses the resin film 4 with a roll that has been subjected to gravure processing, etc., and heated and pressed to transfer the unevenness of the roll to the surface, forming a surface state with a sharp end face.
Etc.

And to make the top edge of the bump 3 an acute angle,
(1) Mark with a punch, etc.
(2) Roughening by etching, etc.
(3) Electroplating is used to grow plating locally on the edges using the phenomenon of electrodeposition concentration on the edges to form sharp edges. In order to further increase the penetrability, Ni plating is used to increase the mechanical strength of the end,
Etc.

As a filler that causes delamination as a starting point of rupture in resin,
(1) Inorganic compounds such as talc and alumina,
(2) Organic compounds with excellent releasability such as PTFE,
(3) The filler shape is preferably plate-like, thread-like, or needle-like, and its size is preferably several μm or less.
Etc.

(Example)
The following materials (i) to (iii) were prepared, and through-pressing was performed at room temperature to confirm the effect of the present invention.
(i) Insulating resin as the material to be penetrated:
Kapton 50H (trade name; resin thickness 12.5μm)
(ii) Bump as penetrating material:
Bumps made of oxygen-free copper with φ100μm and height of 100μm
(iii) Cushion material:
Silicon rubber mat having a thickness of 2 mm Penetration conditions: 30 mm square sample was pressed with a 5-t press. Penetration rate was 5% when the insulating resin was pressed while purchased.

  On the other hand, the surface of the insulating resin in the purchased state is rubbed vertically and horizontally to the extent that the surface of the resin film 4 is lightly touched 5 to 6 times with a # 1200 sandpaper so that the surface of the resin film 4 is thinly scratched. I scratched it.

  When this resin film 4 was used for penetration pressing under the same pressing conditions, the penetration rate was 45%. Thus, as a result of conducting the penetration test of the bump 3 using the resin film 4 having a scratched surface, the penetration rate was remarkably improved.

  And the technique performed in order to improve penetrability is comparatively easy to implement, it is easy to implement industrially, and the effect is also great.

  In addition, when a thermoplastic resin is used as the resin, even if the film is scratched, the scratch disappears by self-bonding by thermocompression bonding at Tg or higher, so that the insulating layer of the completed circuit board has a defect. It does not cause.

The schematic diagram at the time of a penetration press start time. Schematic diagram during penetration press. The figure which shows the mode of penetration at the time of scratching the film surface. The figure which shows the mode of penetration at the time of forming an acute angle part in the edge of a bump top part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Conductor layer 3 Interlaminar bonding bump 4 Insulating resin film 5 Cushion material 6 Press end plate A Stress concentration part B Breaking part

Claims (3)

A film made of an insulating resin is layered on an interlayer connection bump provided on a circuit board, and the bump touches the film and presses it, so that the bump penetrates the film and connects to another layer. In the method of manufacturing a circuit board,
The pretreatment scratches the film surface by mechanical processing;
A method of manufacturing a circuit board, comprising forming a crack occurrence portion having a shape that causes crack growth in the film by pressing the bump against the film . A film made of an insulating resin is layered on an interlayer connection bump provided on a circuit board, and the bump touches the film and presses it, so that the bump penetrates the film and connects to another layer. In the method of manufacturing a circuit board,
Prepare a filler-added film by adding a filler that does not chemically bond with the insulating resin and causes delamination,
Instead of the film, using the filler-added film
A method of manufacturing a circuit board, comprising forming a crack occurrence portion having a shape that causes crack propagation in the filler-added film by pressing the bump against the filler-added film . In order to form a multilayer circuit board, an insulating resin film through which an interlayer connection bump formed on the circuit board passes,
An insulating resin film obtained by adding a filler that does not chemically bond to an insulating resin and causes delamination.

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