JP2003347747A - Method of manufacturing multilayer wiring board and multilayer wiring board using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a multilayer wiring board performing ultraviolet laser drilling by a machining technique that is optimized by each layer material at the time of forming a hole part for connecting upper and lower wiring layers (blind via-hole machining) in a multilayer wiring board having adhesive layers interposed and wiring layers stacked. <P>SOLUTION: A hole part for a via hole is machined by using an ultraviolet laser drill having the energy densities of laser beams (the energy density and processing pulse number) different in a wiring layer and an insulation layer. The ultraviolet laser drill has an uniform energy density distribution within ±10%, and the insulation layer comprises a first insulation layer and a second insulation layer. The second insulation layer has a bonding function and includes stacking of the wiring layers. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a hole for a via hole formed for interlayer connection of metal wiring layers sandwiching a resin insulation layer, and a multilayer wiring board using the method. More specifically, the present invention relates to a method for manufacturing a multilayer wiring board such as a rigid or flexible printed wiring board or a printed circuit for high-density mounting, in which an insulating layer and a wiring layer are connected by a via hole.

[0002]

[0002] In recent years, the performance of semiconductors has dramatically improved,
Semiconductors are becoming more terminals. However, since the printed wiring board (mother board) in the hard disk of the computer and the printed wiring board in the portable terminal and the mobile phone have a limited area, the size of the wiring board (semiconductor package) on which the semiconductor is mounted is limited.

In order to mount a multi-terminal semiconductor, the wiring board is also required to have fine wiring (high density).
Since it is difficult to form wiring with a size of about μm or less in mass production technology, measures are taken to reduce the thinning of the wiring by increasing the number of wiring layers. When multilayered, a hole is formed in the resin insulation layer, and a conductive metal material is coated in the hole to provide interlayer connection between the upper and lower metal wiring layers sandwiching the resin insulation layer, resulting in a multilayer wiring board. .

Conventionally, when a hole for interlayer connection is formed, machining with a metal drill has been the mainstream. However, if the hole becomes finer, naturally the drill to be processed becomes smaller,
In addition, micro drills were expensive to manufacture and were a consumable item that suffered severe wear during drilling. In recent years, instead of machining a metal drill, laser drilling, in which high-energy laser light is irradiated and absorbed by a workpiece, has been used to form a microhole.

Laser light used for laser drilling is a CO ₂ laser (wavelength of 9.3 to 10.6 μm) in the infrared region, YAG
Laser (fundamental wavelength 1.06μm), YA in the ultraviolet region
G, YLF, YAP, YVO ₄ laser (third harmonic wavelength 355nm,
4th harmonic wavelength 266nm) and excimer laser (XeC)
l wavelength 308nm, KrF wavelength 248nm, ArF wavelength 193nm) are currently used as laser light for processing machines. Laser drilling using wavelengths in the infrared region is thermal processing or pyrolysis processing compared to machining in metal drills.
Laser drilling using a wavelength in the ultraviolet region is called photolysis using a photochemical reaction.

[0006] The mainstream of machining with a metal drill is the formation of a through hole (through hole) in a multilayer wiring board. However, laser drilling, which is a pulse oscillation, uses only an insulating layer by adjusting the energy density of laser light. Processing is possible. For this reason, laser drilling is mainly used for blind hole processing of a wiring board. Currently, the CO ₂ laser has a diameter of 50 to 150 μm.
m, the ultraviolet laser is φ30-80 μm. Excimer lasers can be processed to smaller diameters such as φ20μm, but they are not suitable for mass production due to the high cost of consumables such as highly reflective metal oxide masks and laser medium gas maintenance. However, in the above-described segregation, the formation of a hole by an ultraviolet laser having good maintainability is promising as the wiring board is densified.

Further, since an ultraviolet laser has a high energy density and a light condensing property, it can be laser drilled even with a minute diameter. And since the absorption to resin is also high, there is almost no residue remaining in the hole for a via hole. Ultraviolet lasers are processed per hole, and the current processing throughput is lower than that of CO ₂ lasers. However, in recent years, the frequency for laser oscillation has increased, and multi-axis processing heads have been developed. There is a high possibility that it will soon surpass the CO ₂ laser on site.

For the formation of the wiring layer, for example, when the material of the wiring layer is copper, a manufacturing method (subtractive method) in which wiring is formed from the entire copper foil layer and a reverse pattern of the wiring are formed on the insulating layer with a resin resist or the like. A manufacturing method (semi-additive method) in which a copper wiring is deposited by an electrochemical method is promising. In general, it is said that the semi-additive method is superior to miniaturization. However, in recent years, it has been reported that the thinning approaching that of the semi-additive method can be achieved by improving the technology of the subtractive method. .

On the other hand, in the via hole for interlayer conduction formed in the insulating layer, a columnar (bump) conduction portion is formed by screen printing or other than the method of forming the via hole by coating the inside of the hole with a metal substance after the formation of the hole portion. A method has also been proposed in which etching is performed, a resin insulating layer is laminated, a surface-conditioning process such as polishing is performed, and the wiring layer is pressed (in some cases, a thermal effect is given) to achieve interlayer conduction. Yes. However, the possibility that the resin film is interposed in the via hole at the time of pressure welding is not completely wiped out, and the mechanism of pressure welding is not yet elucidated, and there is a concern in the latter method that the reliability of interlayer connection is guaranteed. There is also a case.

After the hole is formed by laser drilling, a residue treatment (desmear) is performed by a potassium permanganate in the wet method and a fluorine-containing oxygen plasma treatment in the dry method. This is because the residue residue significantly reduces the connection reliability of the via hole. However, when the hole is formed by the ultraviolet laser beam, there is almost no residue because the absorption to the insulating layer (resin film) is high. In addition, the hole is usually filled by electroplating using an electrochemical method. However, since the metal thin film is covered throughout the hole in the plating pretreatment, the bottom of the hole is in close contact with the metal, and connection reliability is improved. .

When forming a circuit of a multilayer wiring board by hole formation by laser drilling and wiring formation by a subtractive method, the manufacturing order is diverse, but CO ₂ laser cannot be absorbed into metal, so etching is performed by etching. It is necessary to perform laser processing (conformal method) after circular patterning on the metal wiring layer. If blackening treatment is performed to increase the absorption rate of the laser beam, the laser beam is absorbed into the metal wiring layer, but in any case, the number of steps increases.

Therefore, the above problem is solved by selecting ultraviolet laser light for laser drilling. Because the wavelength of ultraviolet rays overlaps with the absorption wavelength of metal,
For example, when the wavelength is 355 nm, about 70 to 80% is absorbed by the metal wiring layer (copper). That is, with the ultraviolet laser beam, the metal wiring layer and the resin insulating layer can be processed simultaneously (direct processing). Selecting direct machining significantly reduces the number of processes and improves productivity.

Further, the absorption rate of ultraviolet laser light differs depending on the material to be processed. For example, about 70 to 80% for copper widely used in the wiring layer described above, 80 to 90% for epoxy type insulating film, 80 to 90% for polyimide type insulating film, plastic type typified by polyolefin type In the insulating film, the laser light absorption characteristics in the ultraviolet region depend on about 10 to 20% and various materials.

When blind via processing is performed on a multilayer wiring board laminated with an adhesive layer interposed, the processing order is as follows: wiring layer → first insulating layer (for example, polyimide insulating film) → second insulating layer (adhesion function) Insulating film). Since the absorption rate of the ultraviolet laser beam varies depending on the material of each layer, the laser beam having the energy density optimized for each layer material should be selected as the processing conditions for the blind via processing. This is because photolytic processing can be expected with materials with high absorption, but even with organic materials with low absorption, thermal processing elements are stronger than with photolytic processing even with organic materials, and flow, drooling, cracks, etc. due to overload heat are generated. Because of concern, a good processed shape cannot be obtained unless the laser light energy density per pulse is optimized.

When blind via processing is attempted only under a single processing condition, for example, a hole that should not be penetrated penetrates due to high energy density, or is processed only halfway through the insulating film. There is a concern that it may not. Further, if the processing pulse is not optimized, the above problem is similarly derived, and if the number of pulses is small, the residual residue of the adhesive layer becomes a problem.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-described problems. The upper and lower wiring layers are formed on a multilayer wiring board in which wiring layers are laminated with an adhesive layer interposed therebetween. It is an object of the present invention to provide a method for manufacturing a multilayer wiring board in which ultraviolet laser drilling is performed by a processing method optimized for each layer material when forming a hole for connecting (blind via processing).

[0017]

In order to achieve the above object in the present invention, first, the invention of claim 1 is a circuit in which a wiring layer made of a conductor film and an insulating layer made of a resin insulating film are laminated, and then a wiring layer is formed. In addition, in the method for manufacturing a multilayer wiring board in which the hole for the via hole is processed in the insulating layer, the hole for the via hole is processed by using an ultraviolet laser drill in which the laser beam energy density is different between the wiring layer and the insulating layer. A manufacturing method of a multilayer wiring board characterized by being processed. The invention according to claim 2 is the method for producing a multilayer wiring board according to claim 1, wherein the ultraviolet laser drill for processing the insulating layer has a uniform energy density distribution within ± 10%. The invention of claim 3 is characterized in that the processing using the ultraviolet laser drill is drill processing combining punching processing or trepanning processing that is a spiral locus, or a combination of both processing methods. It is a manufacturing method of the multilayer wiring board of Claim 1 or 2. In the invention of claim 4, the processing using the ultraviolet laser drill is either burst processing in which drilling of each layer is performed at the same coordinate or cycle processing in which the coordinates of all via hole holes are performed for each wiring layer and insulating layer. 4. The method for manufacturing a multilayer wiring board according to claim 1, wherein at least one of them is used. According to a fifth aspect of the present invention, there is provided a blind hole (blind via) in which a diameter of a hole for a via hole when machining using the ultraviolet laser drill is 50 μm or less and a ratio of a hole bottom diameter to a hole opening diameter is 0.6 or more. 5) The method for producing a multilayer wiring board according to any one of claims 1 to 4. The invention according to claim 6 is characterized in that the insulating layer comprises a first insulating layer and a second insulating layer, the second insulating layer has an adhesion function, and a wiring layer is laminated. Item 1-5
The method for producing a multilayer wiring board according to any one of the above. A seventh aspect of the invention is a multilayer wiring characterized in that a conductive material is filled in the via hole hole processed by the method according to any one of the first to sixth aspects, and the upper and lower wiring layers are electrically connected. It is a substrate.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a multilayer wiring board according to the present invention will be described below. In manufacturing a multilayer wiring board, a subtractive method is used for wiring formation, and direct processing using an ultraviolet laser beam is selected for interlayer connection. The semi-additive method increases the number of wiring forming steps, and the CO ₂ laser has a high processing throughput but is not suitable for direct processing, so it is necessary to select an ultraviolet laser. In addition, various types of insulating resin layers have been proposed as electronic materials (for example, glass epoxy type, polyimide type, liquid crystal polymer type, etc.), but as wiring layers, wiring and interlayer connection wiring (via holes) can be easily performed by electrochemical methods. Formable copper is widely used.

The ultraviolet laser drilling machine can vary the energy density of laser light per unit area in optical design or in controlling pulse oscillation. That is, by adjusting the energy density per pulse between the wiring layer (copper layer) and the insulating layer (resin), it is possible to perform the hole stop processing (blind via) as shown in FIG.

For example, the third harmonic of YAG (wavelength 355n
m) the the wiring layer processing using 20 J / cm ² or more, the insulating resin processing is required 1~5J / cm ² about energy. If the insulating layer is processed after the zero-wire layer processing using this energy density difference, the blind via can be formed by changing the energy density of the laser beam.

Here, the energy density of laser light is
Divide the output (W) of the laser beam focused on the processing point by the pulse oscillation frequency (Hz), and further process the spot diameter (cm ² )
Corresponds to the value divided by (J / cm ² ). The energy density can be changed (changed) when the output of the laser beam is changed on the optical design, when the oscillation frequency is changed on the pulse control, or by using both together. This is different from the case of forming holes by controlling the number of pulses using a single energy density in the conventional method. If the object to be processed is only one layer (for example, only an insulating layer), an optimal energy density is investigated in advance, and a good hole shape can be obtained by considering only the control of the number of pulses with that energy density. However, it cannot be handled when the processing target is a multilayer (for example, a wiring layer, an insulating layer, an adhesive layer). Therefore, if the energy density is varied in multiple steps according to the processing target and processing is performed with the optimum energy density in each layer, a good processing shape can be obtained even if the processing target is a multilayer.

An outline of a conventional multilayer wiring board (rigid type multilayer wiring board) is represented by FIG. A through hole (through hole 8) is formed in the core base material 7, and after the conduction treatment, for example, an epoxy resin is laminated on the surface of the core base material, and interlayer connection (via hole formation) with the core base material is performed. In some cases, a layer having an adhesive function is interposed, and in some cases, a material having an adhesive function is laminated on the laminated resin layer. Since the core substrate is a rigid material, there are several lamination methods, for example, thermocompression can be performed by a flat plate press. In general, it is manufactured by a single-wafer method in which a plurality of substrates are provided on a wide substrate.

As shown in FIG. 1, in the flexible multilayer wiring board, the wiring layer 5, the first insulating layer 2 and the second insulating layer laminated with the adhesive layer 3 (second insulating layer) interposed therebetween. Since it consists of layer 3, it is necessary to process in that order. For the flexible electronic substrate, polyimide is widely used as the first insulating layer because of its heat resistance, low dielectric constant, and ease of synthesis. It has a bonding function and satisfies the required characteristics of electronic materials.
Examples of the insulating layer 2 include, but are not particularly limited to, an epoxy type, an elastomer type, a polyimide type, a polyolefin type, and an acrylic type. In particular, a thermosetting adhesive having an epoxy curing component in the system can be laminated by using thermocompression bonding such as a rubber roll or a hot press.

Whatever system the second insulating layer is, laser drilling is possible if the main component in the system absorbs wavelengths in the ultraviolet region. Epoxy and polyimide systems can be expected to have a high absorption rate of 70 to 90%, and can be processed under almost the same processing conditions as the first insulating layer. However, elastomers, polyolefins, and acrylic systems have a few percent to 20%. Only absorption is allowed. That is, if the processing conditions are not optimized at the time of processing the second insulating layer, problems such as residue residue occur, so care must be taken. In addition, with such a low absorptivity material, it is almost impossible to expect a photolytic process element that dissociates the molecular chain of the resin, and it is necessary to devise a processing method in order to improve laser drilling processability.

Furthermore, if the second insulating layer is made of a material that absorbs less than ultraviolet laser light, the processing of the second insulating layer on the land may become non-uniform as shown in FIG. . The laser beam has an energy density distribution with respect to the via diameter. Since the energy density is lower at the bottom end of the via than the central portion of the bottom of the via, the residue remaining condition becomes worse. So second
It can be considered that the insulating layer is processed with a uniform energy band. By irradiating a uniform energy density within ± 10%, it is possible to finish the same degree of processing at the center of the via bottom and the end of the via bottom as shown in FIG.
A material having an adhesive function (particularly a soft material having a low elastic modulus) has a thermal expansion coefficient about 5 to 100 times larger than that of copper and polyimide. That is, if there is a residue in the adhesive layer, for example, in the thermal shock reliability test, the effect of peeling off the interface between the bottom of the via and the land is caused by the difference in thermal expansion coefficient, and the connection reliability of the via hole is significantly reduced. There is also danger. In other words, the processing state of the bottom of the via greatly affects the connection reliability after the subsequent via hole formation,
Even if the second insulating layer is a low-absorption material for ultraviolet laser light, it is necessary to be processed all the way.

The via hole is formed by burst processing in which the hole opening diameter is optically condensed at a processing point by mask transfer and the hole is formed by a punching method, and a condensing spot smaller than the hole opening diameter. There is a trepanning process (which may be referred to as a spiral process depending on the trajectory). Here, when the energy density distribution of the ultraviolet laser beam irradiated for processing with respect to the hole opening diameter 10 is not uniform as shown in FIG. This is because the processing energy density is lower at the bottom of the via than at the center of the bottom of the via.

If the inside of the hole is covered with a metal substance while maintaining the hole shape of FIG. 3A, the via bottom area is reduced by the amount of processing residue at the via bottom. The via hole interlayer connection reliability greatly affects the contact area between the via bottom and the land, and the reliability decreases when the via bottom area is small. When the ratio of the hole opening diameter to the via bottom diameter is 1, the hole shape is a straight shape, and when it is 1 or less, a forward tapered shape is obtained. When forming a via hole by a wet process as a post process, a shape with a forward taper to some extent is more suitable for fluid flow, but from the viewpoint of interlayer connection reliability, the via bottom area is larger if closer to 1. It can be said that the connection reliability is high.

That is, in order to prevent the processing residue as shown in FIG. 3 (a) from occurring, the insulating layer processing generated in a wedge shape by irradiating laser light having a uniform energy density distribution as shown in FIG. 3 (b). The rest can be eliminated. This is because by using a uniform energy band, there is no energy difference between the center of the via bottom and the end of the via bottom, and a processed shape with better linearity can be obtained. In order to perform such processing, uniform energy light having a larger diameter than the hole opening diameter 10 may be irradiated.

In order to irradiate energy light having a diameter larger than the opening diameter of the via hole, the two types shown in FIG. 4 can be considered. FIG. 4 (a) shows a method of increasing the light collection diameter at the processing point by mask transfer. Preferably, if the diameter is larger than the opening diameter by about 10 to 50%, uniform energy light is irradiated. FIG. 4B shows a processing method in which a uniform energy band is obtained by drawing a spiral locus with a spot diameter smaller than the via bottom diameter. In FIG. 4 (a), since the burst processing is used, the number of processing pulses can be formed with an appropriate value with respect to the thickness of the second insulating layer. In FIG. 4 (b), the same number of processing pulses is spirally formed. Processing throughput is significantly reduced because it must be irradiated. Preferably, uniform energy light is obtained by burst processing, and processing that does not cause processing residue is performed in order to improve processing throughput.

Regardless of the processing method shown in FIG. 4 (a) or (b), a dedicated drilling process is required for processing the second insulating layer. That is, at least one of burst processing and trepanning (spiral) processing is performed on the wiring layer and the first insulating layer for all coordinates or hole coordinates within a unit area (galvano scan area) under the restrictions of the optical system. Then, by changing to an appropriate energy density, the process proceeds to the processing of the second insulating layer, and drilling using at least one of burst processing or trepanning processing is performed, so that the hole for a via hole of the present invention can be formed. Furthermore, there is no major obstacle in the construction method in terms of processing control in the ultraviolet laser drilling apparatus.

However, the processing method of the second insulating layer is not limited to the above method.

As described above, for example, materials having different wavelengths in the ultraviolet region are used to bond and laminate the wiring layer and the insulating layer made of the resin insulating film, and then processing of the hole for the via hole is performed on the wiring layer and the insulating layer. Interlayer connection reliability is achieved by filling conductive material such as copper into the hole for via holes that have been wiped off the resin processing residue as much as possible by plating or printing filling method using a squeegee and conducting the upper and lower wiring layers. A highly efficient multilayer wiring board can be obtained.

[0033]

[Example] Flexible tape substrate with double-sided copper foil manufactured by Ube Industries, Ltd. (copper / polyimide / copper → 9/25/9 μm thickness)
1 and a hole-stopping process (blind via process) as shown in FIG. 1 was performed using a UV laser with a wavelength of 355 nm and a processing diameter of φ50 μm from the copper foil surface on one side. The structure is such that copper foil is laminated on the front and back with polyimide (insulating layer 1 in the double-sided copper foil tape substrate) interposed. 20J / when processing copper foil
The energy density of cm ^2, at the time of processing the insulating layer was irradiated at a burst processing laser light having an energy density of 2J / cm ^2. After the drilling, the scattered copper (dross) was removed by acid treatment, and then the residue treatment and electroless copper plating containing permanganate as the main component were performed to form an in-hole cleaning and a conductive copper film. Thereafter, the hole was completely filled with copper by electrolytic copper plating. The composition of the electrolytic copper plating bath is copper sulfate.
200 g / L, 100 g / L of sulfuric acid, 50 g / L of hydrochloric acid, a small amount of additive, bath temperature of 25 ° C., and electroplating for 40 minutes at a current density of 2 A / dm ^2. First wiring layer 16 and second wiring layer A first via hole 22 connecting 17 layers was formed.

After the plating step, etching was performed by acid treatment to a specified film thickness (9 μm) because there was a copper thickness of the plating layer + wiring layer. Next, a resist was applied onto the first and second wiring layers simultaneously, and exposed and developed simultaneously on both sides, thereby patterning the resist. The wiring layer was etched with a ferric chloride solution using the patterned resist as an etching mask. Through the above steps, the first and second wiring layers sandwiching the first insulating layer were formed. 2 above
An alignment mark is formed on the layer substrate, which serves as a processing reference for subsequent wiring layer formation.

Next, an elastomer / epoxy main component adhesive film (15 μm) whose front and back surfaces are protected by polyethylene terephthalate is applied to the first and second wirings at 180 ° C.
Temporary pressure bonding was performed using a 3 kg / cm laminate. The polyethylene terephthalate was peeled off, and a polyimide tape substrate with a single-sided copper foil (made by Ube Industries, copper / polyimide → 9/25 μm film thickness) was thermocompression bonded at 180 ° C. and 3 kg / cm. After this lamination step, the obtained laminated substrate was heat-cured at 150 ° C. for 1 hour. The thickness of the adhesive film on the wiring circuit is 5 μm. This lamination process was a process for each side. This is because the thickness of the adhesive film varies due to variations in the laminating roll top pressure and back pressure during laminating simultaneously on both sides. However, if the problem on the manufacturing apparatus is solved, productivity is improved by performing the laminating process on both sides simultaneously.

Via hole 2 for interlayer connection after the lamination process
In order to form 3 and 24 simultaneously, an ultraviolet laser beam having a wavelength of 355 nm is similarly applied to the wiring layer 18 (or 1).
9) Hole processing was performed in the same order of φ50 μm in the order of 9) → insulating layer 2 → adhesive layer 3. Since it was laminated with an adhesive layer interposed, it was processed with a laser beam having an energy density of 8 J / cm ² as an adhesive processing parameter. The energy density of 5 J / cm ² was adopted as a result of verification from the viewpoint of processing quality and processing speed with the adhesive material alone.
Also, the processing diameter was φ80 μm only during the processing of the adhesive, and the processing was performed so that the uniform energy band of the laser beam was irradiated all over the bottom of the via and there was no processing residue of the adhesive layer. Although the diameter is larger than the hole opening diameter, since the energy density is such that copper is not processed, the quality of the hole opening diameter has no particular problem. The number of processing pulses was 5, 10, and 5 pulses applied to each layer of copper, polyimide, and adhesive.

The same hole processing was performed on the back surface. First
In the same manner as in the formation of the via hole, a residue treatment → formation of a conductive film by electroless copper plating → electrolytic copper plating was performed. Through the above steps, a multilayer wiring board having four wiring layers was completed. Moreover, a 6-layer wiring board can also be manufactured by repeating the lamination | stacking process as needed. FIG. 5 shows a form in which the outermost layer of the six-layer wiring board is covered with the solder resist 27.

In order to evaluate the connection reliability of the multilayer wiring board manufactured by the above method, a thermal shock reliability test (−65 ° C.
× 30 min to 125 ° C. × 30 min). The multilayer wiring board for evaluation is a chain circuit, and its main configuration is shown below.

Number of wiring layers 4 and 6 layers Wiring layer thickness 9μm Insulation layer thickness (including adhesive layer) 30μm Line width 50μm Via / land 50μm / 100μm Number of vias per layer 1000 vias Via connection form Stepped and stacked

The results of the thermal shock reliability test are shown in Table 1. For comparison, a reference substrate was used in which the adhesive layer was processed at the same energy density (3 J / cm ² ) as in polyimide processing. This is for comparison with the result obtained when the adhesive processing is not taken into consideration.

[0041]

[Table 1]

Although both the 4th layer and the 6th layer were disconnected in the reference substrate up to 200 cycles, the multilayer wiring substrate using the manufacturing method of the present invention obtained good results up to the specified 1000 cycles. After the reliability evaluation, the reference board and the multilayer wiring board according to the present invention were subjected to failure / destruction analysis. As a result, a great difference was found in the via hole portion. In the reference substrate, cracks occurred at the interface between the land copper and the bottom of the via hole. However, in the multilayer wiring board of the present invention that passed the reliability test, no crack was observed between the land / via hole bottom. This is because the thermal expansion coefficient of copper and polyimide is about 15 to 20 ppm, whereas that of an elastomer / epoxy adhesive is 100 ppm at around 120 ° C. That is -6
Interfacial delamination between the land / via hole bottoms is caused by the difference in thermal expansion of each material at a temperature difference between 5 ° C. and 125 ° C., and it is considered that the reference substrate failed. Since the multilayer wiring board of the present invention optimized the processing of the adhesive layer and formed the via hole in a state where there was no processing residue, such a failure could be avoided. In other words, it can be said that the via hole connection reliability is high.

[0043]

According to the method for manufacturing a hole for a via hole of the present invention, the energy density of the laser beam is reduced in each of the wiring layer and the insulating layer in the multilayer wiring board in which the wiring layer and the insulating layer are alternately laminated. By optimizing, a shape with high connection reliability of the via hole can be obtained.

[0044]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a hole stop (blind via) processing in a flexible multilayer wiring board.

FIG. 2 is a cross-sectional view of hole stop (blind via) processing in a rigid type multilayer wiring board.

FIG. 3 is a schematic explanatory diagram when a blind via hole is formed by a laser beam having an energy band.

FIG. 4 is an explanatory diagram showing a processing example when processing the bottom of the via-ball hole.

FIG. 5 is an explanatory diagram showing a six-layer wiring layer substrate that is multi-layered using an adhesive layer.

[Explanation of symbols]

1 Insulating layer on double-sided copper foil tape substrate 2 First insulating layer 3 Second insulation layer 4 Land 5 Wiring layer 6 Holes for via holes 7 Core substrate 8 Through hole 9 Uniform energy band of laser light 10 Via hole opening diameter 11 Remaining adhesive layer processing 12 Bottom diameter of via hole 13 Laser beam diameter by burst processing 14 Single spot light diameter by trepanning method 15 Trajectory by trepanning method 16 First wiring layer 17 Second wiring layer 18 Third wiring layer 19 Fourth wiring layer 20 Fifth wiring layer 21 Sixth wiring layer 22 First via hole 23 Second via hole 24 3rd via hole 25 4th via hole 26 Fifth Beer Hall 27 Solder resist

Continued front page    F-term (reference) 4E068 AF00 CA01 CA02 CA04 DA11                       DB14                 5E346 AA02 AA12 AA15 AA32 AA43                       CC04 CC08 CC09 CC10 CC32                       DD12 DD32 EE06 EE07 EE42                       EE43 FF07 FF15 FF18 FF22                       GG06 GG15 GG17 GG22 GG28                       HH07 HH11 HH22 HH25 HH26

Claims (7)

[Claims] 1. A method for manufacturing a multilayer wiring board, comprising: laminating a wiring layer made of a conductor film and an insulating layer made of a resin insulating film; and processing a hole for the via hole in the wiring layer and the insulating layer. The method of manufacturing a multilayer wiring board, wherein the processing of the hole is processing using an ultraviolet laser drill in which the laser beam energy density is different between the wiring layer and the insulating layer. 2. The method of manufacturing a multilayer wiring board according to claim 1, wherein the ultraviolet laser drill for processing the insulating layer has a uniform energy density distribution within ± 10%. 3. The processing using the ultraviolet laser drill is drill processing combining punching processing or trepanning processing which is a spiral locus, or a combination of both processing methods. A method for producing a multilayer wiring board according to 1 or 2. 4. The processing using the ultraviolet laser drill is at least one of burst processing in which drilling of each layer is performed at the same coordinate and cycle processing in which the coordinates of all via hole holes are performed for each wiring layer and insulating layer. The method for producing a multilayer wiring board according to claim 1, wherein: 5. A blind hole (blind via) in which the diameter of a hole for a via hole when processing using the ultraviolet laser drill is 50 μm or less and the ratio of the hole bottom diameter to the hole opening diameter is 0.6 or more. The method for producing a multilayer wiring board according to claim 1, wherein: 6. The insulating layer comprises a first insulating layer and a second insulating layer, the second insulating layer has an adhesive function, and a wiring layer is laminated thereon. The manufacturing method of the multilayer wiring board in any one of -5. 7. A multilayer wiring board characterized in that a conductive material is filled in the via hole hole processed by the method according to claim 1, and the upper and lower wiring layers are electrically connected.