JPH11121902A - Method for manufacturing double-sided carrier tape - Google Patents

Abstract

(57) [Problem] To solve the above-mentioned problems in forming a via hole having a high density and a small hole diameter in the production of a double-sided carrier tape, and to easily and efficiently form a highly accurate via hole on both sides. Provided is a method for manufacturing a carrier tape. SOLUTION: In a method for manufacturing a double-sided carrier tape obtained by laminating a first conductor layer, an insulating resin layer mainly composed of polyimide, and a second conductor layer, the surface conductor layer is etched to form holes. Drilling and then drilling the insulating resin layer with a Q-switched carbon dioxide laser to form a via hole reaching the conductor layer below the opening,
A method for producing a double-sided carrier tape in which a conductor layer is formed by electrolytic plating or electroless plating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a double-sided carrier tape used as an electronic component.

[0002]

2. Description of the Related Art Double-sided carrier tapes used as electronic components generally have wiring patterns such as inner leads arranged on the surface of a tape-shaped insulating substrate, and these patterns are formed into ground patterns on the back surface of the substrate by via holes, device holes, and the like. Connecting.

A via hole is a through hole that penetrates through an insulator and reaches a lead portion. The wall surface of the via hole forms copper plating and plays a role of electrically connecting a pattern on a front surface to a rear surface. A wet etching method is used as a processing method of the via hole, in which a photoresist is formed on a copper foil surface, a desired via hole pattern is patterned using a photolithography technique, and the exposed copper foil is etched. After that, if the photoresist is removed, a via hole pattern is formed in the copper foil, so that the insulator is exposed at a desired via hole formation position. Next, using the copper foil layer on which the via hole pattern is formed as an etching mask, the base material is immersed in a strong alkaline solution to etch the exposed insulator and completely remove the insulator at this portion until the pattern is reached, By forming a through hole, a desired via hole can be obtained.

However, as the demand for higher density has increased, the number of pins having a narrower pattern width has been increased in the wiring portion formed on the surface.
Since products having a narrow pitch such that the pattern gap is 30 μm with respect to μm are also manufactured, the via holes must be formed on such an extremely narrow pattern. In addition, since via holes are not allowed to be formed outside the pattern, it is necessary to dissolve and remove the insulator on the pattern when etching the insulator, taking into account the accuracy of the alignment between the front and back surfaces. It is necessary to form a via hole having a smaller diameter than the pattern width.

However, in the conventional wet etching method, since the lateral etching called side etching also proceeds at the same time, the wall surface of the opening is not formed vertically but is tapered to form a mortar. The diameter of the opening on the body surface is larger than the diameter of the bottom. The density of via holes must be increased with the increase in the density of wiring patterns. However, since the distance between adjacent via holes is naturally reduced, the increase in the opening diameter of the insulator surface portion due to the side etching described above is due to the increase in via hole density. It becomes a hindrance factor. In addition to this, the etching solution ages due to an increase in the amount of dissolved insulator, and the etching ability is reduced, so that the time-dependent change in the processing size of the via hole cannot be avoided, and has a subtle effect on the processing accuracy. Therefore, it is necessary to control the etching time, which has also been an obstacle to increasing the density of via holes and reducing the diameter of fine holes.

On the other hand, methods for drilling holes in a circuit board using a carbon dioxide laser are known from Japanese Patent Application Laid-Open Nos. 5-55724 and 3-210894. In an ordinary carbon dioxide laser, discharge excitation is performed in a laser gas such as carbon dioxide gas whose pressure is adjusted to several tens toor, and oscillation starts when the gain reaches an oscillation threshold within several tens μs after the start of discharge excitation. Therefore, the oscillation of the carbon dioxide laser is only a natural process, and the oscillation timing and laser intensity are irregular.

In general, in resin drilling with a laser, the magnitude of the peak output of the laser beam and the pulse repetition frequency are important factors. In other words, the resin removal at the time of resin opening is performed by rapid heating and evaporation by pulsed laser beam absorption and repulsion of the vaporized gas, so that a laser pulse with a fast rise is preferable, and therefore a peak output is large. Is desirable. However, the conventional carbon dioxide laser does not have a sufficient peak output and conditions suitable for resin drilling, and there is a problem in ultra-precision processing.

[0008]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to solve the above-mentioned problems in increasing the density of a double-sided carrier tape and forming a via hole with a small hole size, and to achieve easy and efficient precision. It is an object of the present invention to provide a method for manufacturing a double-sided carrier tape which can form a via hole having a high level.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, in the production of a double-sided carrier tape, a Q-switched carbon dioxide laser was used as a laser processing device. It has been found that a repetitive pulse having a high peak output and regularity is obtained, and is suitable for forming a microporous via hole made of a resin.

That is, the present invention provides a method for manufacturing a double-sided carrier tape, comprising laminating a first conductor layer, an insulating resin layer mainly composed of polyimide, and a second conductor layer. And then forming a via hole reaching the conductor layer below the opening by using a Q-switched carbon dioxide laser to form an insulating resin layer, followed by electrolytic plating or electroless plating. A method for producing a double-sided carrier tape, comprising forming a conductor layer.

Hereinafter, the present invention will be described in detail. The method for producing a double-sided carrier tape of the present invention is characterized in that when a hole is formed in an insulating resin layer to form a via hole, precision processing and high-speed processing are performed by using a Q-switched carbon dioxide laser as a laser processing apparatus. It is made possible.

This Q-switched carbon dioxide laser is a carbon dioxide laser equipped with a Q switch device and operates as follows. First, the Q value of the laser resonator is lowered so that laser oscillation does not occur for a while even after discharge excitation starts. When the Q value is rapidly increased after sufficient energy has been accumulated in the laser gas, the laser pulse rises explosively, and the operation ends in a manner in which the energy accumulated up to that point is extracted all at once. The time width of the pulse is several tens to
Since it is several hundred ns and the light energy is packed in a very short time, its peak output reaches several tens of kW to several hundreds of Mw. The start timing of the Q-switch oscillation can be controlled artificially, and a repetitive pulse with regularity can be obtained. The pulse repetition frequency does not depend on the discharge power source.
It depends on the repetition frequency of the switching device. For example,
In a rotary chopper switch, a pulse repetition frequency of about several hundred KHz is possible.

In the present invention, a laminate having conductor layers on both sides of an insulating resin layer is used as a base material. The insulating resin may be any resin containing polyimide as a main component, and examples thereof include polyimide and modified polyimide resin. In consideration of dimensional stability after processing, it is preferable that the coefficient of thermal expansion be 3 × 10 ⁻⁵ / ° C. or less. If the coefficient of thermal expansion is larger than this, the difference between the conductor layer and the coefficient of thermal expansion increases, which causes warpage or the like after processing the conductor layer. The thickness of the insulating resin layer is 5 to 100 μm, and preferably 10 to 50 μm in consideration of the balance between workability by laser and insulation.

Further, as the metal used for the conductor layer,
For example, copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, or an alloy thereof can be given, and copper is preferred.

In the present invention, one conductor layer is processed in advance by wet etching or the like, and is used as a metal master for forming the next through hole for forming a via hole.

[0016]

FIG. 7 is a view schematically showing an example of a laser processing apparatus used in the present invention, FIG. 8 is a partially enlarged view of a Q switch, and FIG. 9 is a front view of a chopper disk. . Lens 1 inside the resonator of carbon dioxide laser 11
A telescope lens 15 is formed by using the 3 and the rear mirror 14 (total reflection mirror), and a beam waist 16 is provided between the telescope lenses 15. Then, a rotary chopper 17 is installed at the position of the beam waist 16 to make a Q switch. The rotating chopper 17 includes a chopper disk 18.
And a rotation driving device 19, and the rotation driving device 19 is rotated at a predetermined rotation speed and chopping is performed at a predetermined repetition frequency, whereby a Q-switch pulse oscillation is obtained. The Q switch pulse has a time width of 200 ns to 1 μm.
s, an initial spike component having a peak power of 5 to 100 kw, followed by a tail component having a time width of 0.9 to 29 μs and a peak power of 2 to 5 kw. Laser light having a high peak output due to Q-switch pulse oscillation advantageously contributes to rapid heating of the resin.

Chopper disk 18 used for Q switch
The material is preferably a metal, but the type is not particularly limited. As the shape of the chopper disk 18, a disk in which slits having a predetermined width are arranged on the circumference can be used. Rotary drive device 19 for chopper disk 18
, A high-speed spindle motor or the like may be used. When arranging the chopper disk 18 on the beam waist 16, it is preferable to make a slight angle with respect to the laser oscillation optical axis so as not to make regular reflection. In addition, as a material of the front mirror 12 (partially reflecting mirror), the rear mirror 14 and the lens 13, Ge or the like other than Zn and Se can be used.

A carbon dioxide laser has a wavelength of about 10.6 μm (wave number up to 940 cm ⁻¹ ) and 10.3 μm (wave number up to 970 c- ¹ ).
It has nearly 100 oscillation lines in the vicinity of (m ^-1 ), 9.6 μm (wave number -1040 cm ^-1 ) and 9.3 μm (wave number -1075 cm ^-1 ). On the other hand, as shown in FIG. 10, an insulating resin, particularly a resin containing a polyimide resin (eg, Espanex, manufactured by Nippon Steel Chemical Co., Ltd.) has strong absorption around 9.3 μm and at shorter wavelengths. Is shown. Therefore, by adjusting the oscillation wavelength of the carbon dioxide gas laser to the high absorption band of the resin, efficient and local rapid heating can be performed, so that a beautiful laser beam with a low output can provide a beautiful processed cross-section without dripping. This also advantageously contributes to improving the productivity of the subsequent plating step.

As shown in FIG. 10, the absorbance of the polyimide resin tends to further increase at a wavelength of 9.3 μm or less.
However, in the 9.3 μm band oscillation line of the carbon dioxide laser,
Wavelength 9.22 to 9.33 μm (wave number 1071.87 to 1
In the range of 084.63 cm ^-1 ), the oscillation efficiency is highest, and in consideration of this, the range of the wavelength of 9.22 to 9.33 μm is most suitable for processing. Here, the optimal oscillation wavelength has been described using a polyimide-based insulating resin as an example,
Since the wavelength absorption characteristics are slightly different depending on the type of the resin to be processed, it is desirable to investigate the light absorption characteristics of the resin and select an optimal laser wavelength in this case.

In order to selectively irradiate a laser beam having a wavelength in the range of 9.22 to 9.33 μm, the reflectivity of the front mirror 12 is set to 2% or less around a wavelength of 10.6 μm.
The reflectance of the rear mirror 14 is in the range of 9.22 to 9.33 μm.
, 40% at 9.6 μm or less
The following is assumed. In addition, 9.22-
Apply a non-reflective film in the range of 9.33 μm.

In processing the double-sided carrier tape, a mask pattern is formed on the surface of the conductor layer on one side of the double-sided carrier tape by screen printing or a photosensitive resin.
Using this as an etching mask, the conductor layer is selectively removed with an appropriate etching solution, and then the mask pattern is removed to form an opening in one conductor layer. Next, carbon dioxide laser is applied to the entire surface on the side where the opening is formed, using the conductor layer having the opening formed as a metal mask. The insulating resin absorbs the laser that has passed through the opening of the metal mask, and is rapidly heated and evaporated, thereby removing the insulating resin in the opening, exposing the conductor layer on the opposite surface, and forming a via hole. A hole is formed.

[0022]

【Example】

Example 1 First, a non-adhesive copper-clad laminate ESPANEX SB18-50-18WE manufactured by Nippon Steel Chemical Co., Ltd.
(Trade name) was used. A photosensitive dry film was laminated on the copper foil on the A side of the substrate 1 and irradiated with ultraviolet rays through a mask pattern to expose and develop the photosensitive film. Next, after the developed substrate was etched with a ferric chloride solution, the dry film used at the time of etching was removed to form an opening 2 shown in FIG.

Further, the entire surface of the substrate 1 on which the openings 2 were formed was irradiated with a carbon dioxide laser. As shown in FIG.
Via holes 4 can be formed by drilling holes in the insulator with the laser beam 3 passing through the openings. The laser processing conditions at this time were as follows: a Q switch pulsed carbon dioxide laser was used, and the peak output of the pulsed laser was 6.4 kW.
Pulse energy is 30mJ, pulse time width is 20μ
s, the pulse repetition frequency is 12 kHz. The laser was used at a wavelength of 9.3 μm, and the light was collected at a diameter of 500 μm. The number of irradiation pulses to the same point is about 4 pulses.

Next, a copper film was formed on the entire surface including the wall surface of the via hole forming hole 4 using an electroless steel plating solution, and the blind through hole 5 of FIG. 4 was formed. Further, using the copper coating as a cathode and an electrolytic plating solution,
/ Dcm ² . The copper plating thickness at this time was 10 μm.

Next, a photosensitive dry film is laminated on both sides of the base material, and ultraviolet rays are irradiated through a double-sided pattern mask provided with signal lines such as inner leads and outer leads on the front surface and a ground pattern on the back surface. After exposing and developing this, the developed substrate was etched on both sides with a ferric chloride solution, and the dry film used at the time of etching was removed to obtain a circuit pattern of the double-sided carrier tape shown in FIG.

Next, a protective resist is applied by screen printing from the wiring lead portions on the front surfaces of the circuit patterns on both sides, and after drying the protective resist, the protective resist is applied to the ground pattern side on the rear surface in the same process. Finally, the wiring leads were subjected to surface treatment such as gold plating or tin plating to complete the double-sided carrier tape shown in FIG.

[0027]

According to the method of the present invention described above,
Via holes can be formed with extremely high precision,
It is possible to easily achieve a high density of via holes and a small hole diameter due to the increase in the number of pins of the double-sided carrier tape, and it is possible to provide a double-sided carrier tape with high added value. Further, by using a carbon dioxide gas laser having a Q-switch, the repetition frequency of the laser pulse can be increased, and the processing can be performed at a high speed.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an adhesive-free copper-clad laminate used in the present invention.

FIG. 2 is a side cross-sectional view of a non-adhesive copper-clad laminate in which an opening in a copper foil portion has been etched.

FIG. 3 is a side sectional view of a non-adhesive copper-clad laminate having via holes formed in an insulator by carbon dioxide laser processing.

FIG. 4 is a side sectional view of a non-adhesive copper-clad laminate having blind holes formed by plating.

FIG. 5 is a side sectional view of a double-sided carrier tape on which a pattern is formed by circuit processing.

FIG. 6 is a plan view of a double-sided carrier pattern subjected to circuit processing.

FIG. 7 is a schematic diagram illustrating a configuration of a laser processing apparatus.

FIG. 8 is a partially enlarged view of a Q switch.

FIG. 9 is a front view of the chopper disk.

FIG. 10 is a graph showing light absorption characteristics of a resin containing polyimide.

[Explanation of symbols]

 1: Base material 2: Copper foil opening 3: Carbon dioxide gas laser beam 4: Via hole forming hole 5: Blind through hole 6: Double-sided carrier tape 11: Carbon dioxide laser 12: Front mirror 13: Lens 14: Rear mirror 15: Telescope lens 16 : Beam waist 17: Rotary chopper 18: Chopper disk 19: Rotary drive

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Katsuhiro Minami 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Tatsuhiko Sakai 20-1 Shintomi, Futtsu-shi, Chiba Made in New Japan Inside the Technology Development Division, Steel Corporation

Claims (4)

[Claims] In a method for manufacturing a double-sided carrier tape comprising a first conductor layer, an insulating resin layer mainly composed of polyimide, and a second conductor layer, the conductor layer on the surface is etched. After drilling and then drilling the insulating resin layer with a Q-switched carbon dioxide laser to form a via hole reaching the conductor layer below the opening,
A method for producing a double-sided carrier tape, comprising forming a conductor layer by electrolytic plating or electroless plating. 2. A Q-switched carbon dioxide laser having a time width of 200 ns to 1 μs and a peak power of 5 to 10 μs.
0kw initial spike component and time width 0.9-29μ
2. The method for producing a double-sided carrier tape according to claim 1, wherein a laser pulse comprising s and a tail spike component having a peak power of 2 to 5 kW is generated. 3. The carbon dioxide laser is operated in a range of 9.22 to 9.33.
3. A carbon dioxide laser having an oscillation wavelength of μm.
A method for producing the double-sided carrier tape according to the above. 4. The method for producing a double-sided carrier tape according to claim 1, wherein the insulating resin layer is a polyimide or a modified polyimide resin having a coefficient of thermal expansion of 3 × 10 ⁻⁵ / ° C. or less.