JP2004031500A - Method for punching multi-layer printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily punch holes whose diameter is small at the time of forming through-holes in a multi-layer printed wiring board integrated into various electronic equipment. <P>SOLUTION: Insulating layers 2, 3, and 4 and conductor layers 7, 8, 9, and 10 are alternately laminated on a multi-layer printed wiring board 1; and a hole forming part 15 of a multi-layer printed wiring board 1 is irradiated with a quadruple wave ultraviolet laser whose mean energy density ranges from 5 to 20J/cm<SP>2</SP>at a 1kHz or more repeat frequency. Thus, the configuring elements of the multi-layer printed wiring board 1 are ablated in a molecular level by the four-time wave ultraviolet laser, and a through-hole 5 or a stop hole 6 whose diameters D1 and D2 are small, that is, about 10 to 20 μm are formed. In this case, the working of glass fibers and conductor layers 7, 8, 9, and 10 in the insulating layer 2 is not accompanied with any difficulty. Also, the debris of the resin of the insulating layers 2, 3, and 4 can be prevented from staying at the bottom of the stop hole 6, and from disturbing the conduction of the conductive hole. Also, at the time of forming a plurality of conductive holes, productivity can be increased by improving the punching speed, if a multistage cyclic perforation is employed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drilling method for a multilayer printed wiring board incorporated in various electronic devices.
[0002]
[Prior art]
Conventionally, when forming a conduction hole in this type of multilayer printed circuit board, after using a miniature drill or carbon dioxide laser to make a hole (through hole or stop hole), a conductor is formed on the inner surface by various methods. Was.
[0003]
[Problems to be solved by the invention]
However, drilling using a miniature drill cannot easily make a hole with a small diameter of 100 μm or less.
[0004]
On the other hand, drilling with a carbon dioxide laser cannot easily drill holes with a diameter of 50 μm or less, and simultaneously processes conductor layers (copper foil, etc.) and glass fibers that are components of a multilayer printed wiring board. It becomes difficult. Also, if a stop hole is made in a multilayer printed wiring board with a carbon dioxide laser, resin residues may accumulate at the bottom of the hole, which may hinder conduction between the conductor formed in the hole and the conductor layers on both sides of the insulating layer. There was an inconvenience.
[0005]
In view of such circumstances, the present invention can easily make a hole having a small diameter of about 10 to 20 μm, and does not involve difficulty in simultaneous processing of the conductor layer and the glass fiber, and does not hinder the conduction of the conduction hole. An object of the present invention is to provide a method for drilling a wiring board.
[0006]
[Means for Solving the Problems]
First, the invention according to claim 1 of the present invention provides a predetermined ultraviolet laser beam focused to a predetermined size at a hole forming portion of a multilayer printed wiring board in which insulating layers and conductor layers are alternately laminated. The hole is formed with a predetermined diameter by irradiation at a repetition frequency of Here, the hole in the multilayer printed wiring board may be a through hole or a stop hole. With this configuration, the ultraviolet laser acts to ablate the components of the multilayer printed wiring board at the molecular level.
[0007]
Further, the invention according to claim 2 of the present invention is an ultraviolet ray focused to a predetermined size with respect to a plurality of hole forming portions of a multilayer printed wiring board in which insulating layers and conductor layers are alternately laminated. When a plurality of holes having a predetermined diameter are formed by irradiating a laser at a predetermined repetition frequency, first, the first stage of the circular perforation is performed by sequentially irradiating each of the hole forming portions with a predetermined number of pulses. Next, a second step of circular perforation is performed by sequentially irradiating each hole forming portion with a predetermined number of pulses of ultraviolet laser, and then the necessary number of steps of circular perforation for each hole forming portion are performed in the same procedure. It is constructed in this way.
[0008]
By adopting such a configuration, in addition to the ultraviolet laser ablating the components of the multilayer printed wiring board at the molecular level, the repetition frequency for each hole forming portion becomes a fraction of the total number of hole forming portions by circular drilling, Since the evaporated material of the multilayer printed circuit board generated by the laser processing is sufficiently discharged from the laser light path, the evaporated material acts so as to suppress the wasteful absorption of the ultraviolet laser.
[0009]
Moreover, the invention which concerns on Claim 3 among this invention is comprised using the 4th harmonic ultraviolet laser in the range whose average energy density is 5-20 J / cm < ² > as said ultraviolet laser.
[0010]
The invention according to claim 4 of the present invention is configured so that the repetition frequency of the ultraviolet laser is 1 kHz or more.
[0011]
Furthermore, the invention which concerns on Claim 5 among this invention is comprised by the diameter of the said hole being 50 micrometers or less.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a multilayer printed wiring board processed by an embodiment of a method for drilling a multilayer printed wiring board according to the present invention, wherein (a) is a perspective view before conductor formation, and (b) is a conductor. It is an expanded sectional view after formation.
[0013]
As shown in FIG. 1, the multilayer printed wiring board 1 has an insulating layer 2 made of a resin reinforced with glass fibers, and conductor layers 7 and 8 are arranged on both front and back surfaces of the insulating layer 2, respectively. Yes. An insulating layer 3 made of resin is pasted on the surface of the insulating layer 2 above the conductor layer 7, and a conductor layer 9 is disposed on the surface of the insulating layer 3. In addition, an insulating layer 4 made of a resin is pasted below the conductor layer 8 on the back surface of the insulating layer 2, and a conductor layer 10 is disposed on the back surface of the insulating layer 4. The multilayer printed wiring board 1 has a predetermined thickness T1 (for example, T1 = 350 μm).
[0014]
When a plurality of (for example, 25) conduction holes are formed in the multilayer printed wiring board 1, first, holes (through holes 5 and stop holes 6) are formed in these forming portions. For that purpose, the fourth harmonic wave of Nd: YAG, Nd: YLF, Nd: YVO ₄ or the like having an average energy density within the range of 5 to ²⁰ J / cm ² with respect to each hole forming portion 15 of the multilayer printed wiring board 1. An ultraviolet laser is irradiated at a repetition frequency of 1 kHz or more (preferably 10 kHz or more). At this time, the first-stage circular perforation is performed by sequentially irradiating each hole forming portion 15 with a 4th-wave ultraviolet laser in a predetermined number of times (for example, once, three times, etc.), and then each hole forming portion 15. Then, the second-stage circular perforation is performed by sequentially irradiating a fourth-frequency ultraviolet laser with a predetermined number of times (for example, once, three times, etc.), and then the circular perforation for each hole forming portion 15 is performed in the same procedure. Perform as many steps as necessary (for example, 10 steps). As a method of this circular perforation, a method of changing the irradiation direction of the ultraviolet laser with a plurality of galvanometer mirrors or AOM elements (not shown) of a laser processing apparatus is simple.
[0015]
Then, as shown in FIG. 1, this quadruple wave ultraviolet laser is formed from above the multilayer printed wiring board 1 with the conductor layer 9, the insulating layer 3, the conductor layer 7, the insulating layer 2, the conductor layer 8, the insulating layer 4 and the conductor. The through hole 5 is formed by drilling the layer 10, and the stop hole 6 is formed by drilling the conductor layer 9 and the insulating layer 3 from above the multilayer printed wiring board 1.
[0016]
At this time, the quadruple wave ultraviolet laser is focused to the same size as the processing hole diameter by the optical system, and the components (conductor layer 9 and the like) of the multilayer printed wiring board 1 are ablated at the molecular level, Since the processing is less affected by heat, small diameter holes (through holes 5 and stop holes 6) having diameters D1 and D2 of about 10 to 20 μm can be easily formed, and the glass fibers and conductor layers in the insulating layer 2 There is no difficulty in processing 7, 8, 9, and 10. In addition, there is no problem that the resin residue constituting the insulating layers 2, 3, 4 accumulates at the bottom of the stop hole 6.
[0017]
In addition, as a result of the circular perforation, the repetition frequency for each hole forming portion 15 becomes 1 / total number of the hole forming portions 15, and the evaporated material of the multilayer printed wiring board 1 generated due to laser processing is sufficient from the laser beam path. Therefore, the situation in which the evaporant absorbs the ultraviolet laser wastefully is suppressed, and it is possible to increase the productivity by increasing the drilling speed by the ultraviolet laser.
[0018]
Thus, when all the through holes 5 and the stop holes 6 are formed, conductors 12 and 13 are formed on the inner surfaces of the through holes 5 and the stop holes 6 as shown in FIG. Then, a conduction hole is formed in the multilayer printed wiring board 1. Here, since the resin residue does not accumulate at the bottom of the stop hole 6 as described above, there is no risk of hindering conduction of the conduction hole, and the yield of the multilayer printed wiring board 1 is improved.
[0019]
In the above-described embodiment, the case of using a fourth harmonic ultraviolet laser has been described. However, other ultraviolet lasers (for example, a third harmonic ultraviolet laser and a fifth harmonic ultraviolet laser) can be substituted. .
[0020]
【The invention's effect】
As described above, according to the first, third, fourth, and fifth aspects of the invention, the ultraviolet laser ablate the constituent elements of the multilayer printed wiring board at the molecular level, so that a hole with a small diameter of about 10 to 20 μm can be easily formed. Therefore, it is possible to provide a method for drilling a multilayer printed wiring board that does not impede the conduction of the conductive holes without difficulty in processing the conductor layer and the glass fiber.
[0021]
In addition, according to the inventions according to claims 2, 3, 4, and 5, since the ultraviolet laser ablate the constituent elements of the multilayer printed wiring board at the molecular level, it is possible to easily form a small-diameter hole of about 10 to 20 μm. In addition to having no difficulty in processing the conductor layer and the glass fiber, in addition to not hindering the conduction of the conduction hole, the repetition frequency for each hole formation portion is reduced to a fraction of the total number of the hole formation portions by circular drilling, and laser processing As the evaporated material of the multilayer printed circuit board generated along with this is sufficiently discharged from the optical path of the laser, the situation where this evaporated material absorbs the ultraviolet laser is suppressed, so drilling with an ultraviolet laser is performed. It is possible to provide a method for drilling a multilayer printed wiring board that can increase the speed and increase the productivity.
[Brief description of the drawings]
1A and 1B are diagrams showing a multilayer printed wiring board processed by an embodiment of a method for drilling a multilayer printed wiring board according to the present invention, wherein FIG. 1A is a perspective view before conductor formation, and FIG. It is an expanded sectional view after conductor formation.
[Explanation of symbols]
1 ... Multilayer printed circuit board 2, 3, 4 ... Insulating layer 5 ... Hole (through hole)
6 ... Hole (stop hole)
7, 8, 9, 10 ... conductor layer 15 ... hole formation location

Claims (5)

A hole having a predetermined diameter is formed by irradiating an ultraviolet laser beam focused to a predetermined size at a predetermined repetition frequency to a hole forming portion of a multilayer printed wiring board in which insulating layers and conductor layers are alternately laminated. A method for drilling a multilayer printed wiring board, characterized in that: A plurality of hole formation locations in a multilayer printed wiring board in which insulating layers and conductor layers are alternately laminated are irradiated with an ultraviolet laser focused to a predetermined size at a predetermined repetition frequency to have a predetermined diameter. When making multiple holes,
First, each hole forming portion is sequentially irradiated with a predetermined number of pulses of ultraviolet laser to perform the first round of perforation,
Next, a second round of perforation is performed by sequentially irradiating a predetermined number of pulses with an ultraviolet laser in order to each hole forming location,
Thereafter, a perforating method for a multilayer printed wiring board, wherein a necessary number of steps of circular perforation are performed for each of the hole forming locations in the same procedure. 3. The method for punching a multilayer printed wiring board according to claim 1, wherein a quadruple wave ultraviolet laser having an average energy density in the range of 5 to ²⁰ J / cm ² is used as the ultraviolet laser. . The multi-layer printed wiring board drilling method according to any one of claims 1 to 3, wherein a repetition frequency of the ultraviolet laser is 1 kHz or more. The diameter of the said hole was 50 micrometers or less, The drilling method of the multilayer printed wiring board in any one of Claim 1 to 4 characterized by the above-mentioned.

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