JPH03268384A - Manufacture of wiring board provided with through hole - Google Patents

Abstract

PURPOSE:To form an etching resist layer surely by a method wherein an insulating substrate is immersed in a specific photosensitive resist liquid, it is pulled up and a photosensitive resist layer is formed on the whole surface of the insulating substrate including the inside of a hole for through-hole use. CONSTITUTION:An insulating substrate 1 is immersed wholly in a photosensitive resist liquid 3 whose viscosity is 30 to 1500cPs and whose thixotropic value is 1.2 to 9; and it is pulled up. Thereby, the whole surface of the insulating substrate 1 including the inner wall surface of a hole 10 for through-hole use is covered with a photosensitive resist liquid layer; an etching resist layer of a prescribed pattern is formed of the photosensitive resist liquid layer. When the viscosity and the thixotropic value of the photosensitive resist liquid 3 are set properly, the photosensitive resist liquid 3 adheres satisfactorily to the hole 10 for throughhole use and the like. Thereby, the etching resist layer of a sufficient thickness can be formed surely on the inside and edge parts of the hole 10 for through-hole use.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a wiring board with through holes,
In detail, wiring boards are used for mounting electronic components, are used as insertion holes for lead wires, are used for electrical connections of surface-mounted components, and are used for electrical connections between the eyebrows of double-sided or multilayer wiring boards. The present invention relates to a method of manufacturing a wiring board having a through hole passing through the wiring board.

[Conventional technology]

To manufacture a wiring board with through-holes, first, through-holes are made in a commercially available insulating substrate or copper-clad laminate, etc., and then electroless plating or a combination of this and electrolytic plating is performed. When used in combination, a conductive metal layer that becomes a wiring circuit is formed on the inner wall of the through hole and the entire surface of the substrate.

This conductive metal layer is formed into a predetermined wiring circuit pattern, and the following method has conventionally been adopted as a method for forming this circuit.

(1) As shown in FIG. 7, the through-hole holes 10 are formed on an insulating substrate l on which the conductive metal layer 2 is formed on the entire surface including the inner wall of the through-hole holes 10 by printing or other means. After protecting the hole walls by filling the hole with a hole-filling ink 90 made of etching ink, the conductive metal layer 2 on the surface of the insulating substrate 1 is etched from above the hole-filling ink 90 with an etching resist N.
91, patterning the etching resist layer 91 by a printing method or a photographic method, and then etching the conductive metal layer 2 to form a circuit, a so-called "hole-filling method".

(2) As shown in FIG. 8, after closing the opening surface of the through hole hole 10 and laminating a film resist 92 such as a photosensitive dry film on the surface of the conductive metal layer 2 of the insulating substrate 1, as appropriate. After forming an etching pattern using a so-called "tenting method" in which the film resist 92 is formed into a predetermined pattern by exposing and developing ultraviolet rays through a mask, the circuit is etched using an etching solution such as cupric chloride or ferric chloride. A circuit is formed by melting and removing unnecessary conductive metal layer 2 other than the pattern. Next, the etching resist 92 is removed using a resist stripping solution made of an organic solvent or an inorganic alkaline solution.

The above two methods are common methods, but another method is (3) the so-called "pattern plating method" in which only the circuit pattern portion of the conductive metal layer is plated with a different metal and a circuit is formed by selective etching. , or (4)
There is a so-called "additive method" in which a conductive metal is deposited on an insulating substrate only in the parts necessary for the circuit by electroless plating. These methods are described, for example, in Japanese Unexamined Patent Publication No. 5
This method is disclosed in JP-A No. 4-50872, Japanese Unexamined Patent Publication No. 187095-1980, and the like. In addition, (5) forming a circuit by uniformly electrodepositing a photoresist on the inner wall surface of the through hole and the surface of the conductive metal layer, patterning it by a photographic method, and then etching the conductive metal layer; There is also a so-called "electrodeposition coating method."

Among the conventional methods mentioned above, (3) "Pattern plating method" is successful in finishing high-density circuit patterns with high precision, but requires overlay plating, which makes the manufacturing equipment very expensive. There are drawbacks. In addition, the "additive method" (4) has recently been attracting attention in the field of industrial use, etc., but it requires the use of a laminated plate containing a catalyst with a special adhesive, which increases the labor and cost of manufacturing. It has the disadvantage that it takes a long time. And (5) “electrodeposition coating method”
However, since the resin composition must be capable of imparting charge mobility to the resin particles in the electrodeposition liquid, it is difficult to form a good film, and the electrodeposition liquid is difficult to control. Therefore, conventionally, the above-mentioned "hole filling method" (1) and "tenting method" (2), which can be manufactured relatively easily and at low cost, have been adopted for boat fishing. However, the "hole filling method" (No. 11) has the disadvantage of poor through-hole reliability. This is because, as shown in FIG. Due to dimensional shrinkage during drying and hardening, etching resist layer 91 being melted by the solvent contained in hole-filling ink 90, etc., etching resist layer 91 covering open hole C of through-hole hole 10 may be damaged. This is because it becomes thinner and more likely to cause disconnection or poor continuity.Also,
There is also the problem that a two-step process of filling and curing the hole-filling ink 90 and forming the etching resist layer 91 is required, which takes a long time.

The "tenting method" in (2) uses a film resist 92 called a photosensitive dry film, but this film resist 92 must be quite thick from the viewpoint of productivity and handling. However, when forming a circuit pattern, it is difficult to form a fine circuit pattern of 100 nm or less. Improvements have been made to the quality of the film resist 92, but when attempting to form fine patterns of 100 μm or less, not only various processes and working conditions but also the surface properties of the conductive metal layer 2 to which the film resist 92 is attached must be affected. However, it required detailed management and was difficult to implement.

Further, since the film-like resist 92 is formed to cover the opening surface of the hollow through-hole hole 10 in a tent-like manner, the through-hole hole 10 is covered by a so-called tenting effect. When forming a pattern, a wide area from the opening surface of the through-hole hole 10 to a considerable outside area is covered with a film resist 92, and the film resist 92 is sufficiently attached and supported on the surface of the conductive metal layer 2. If not, the tenting effect cannot be achieved, and the film-like resist 92 covering the through-hole holes 10 may peel off or the through-hole holes 10 may
A problem arises in that the conductive metal layer 2 inside is etched.

If a circuit is formed using the conductive metal N2 while covering a wide area around the through-hole hole 10 with a film-like resist 92, for example, in a wiring circuit pattern as shown in FIG. 20.20 (The conductor circuit on the back side is represented by a dotted line) Through hole part 2 that connects
1, a land portion 22 having a much larger line width than the conductor circuit 20 is formed around the through-hole portion 21. If there is such a large land portion 22, the conductor circuit 20 passing on that side must be patterned to bypass the land portion 22, which greatly impedes miniaturization and higher density of wiring circuits. was.

Therefore, it is an object of the present invention to solve the problems of each of the above-mentioned prior art technologies, and to easily and inexpensively manufacture a wiring board with through-holes that allows the formation of fine patterns and has high through-hole reliability. The purpose is to provide a method.

[Means to solve the problem]

In order to solve the above problems, the method for manufacturing a wiring board with through holes according to the present invention includes the steps of forming an etching resist layer in a predetermined pattern for patterning a conductive metal layer including through holes in an insulating substrate. By immersing the entire insulating substrate in a photosensitive resist solution with a viscosity of 30 to 1500 cps and a thixotropy value of 1.2 to 9 and pulling it up, the entire surface of the insulating substrate, including the inner wall surface of the through-hole hole, is coated with the photosensitive resist. After that, an etching resist layer having a predetermined pattern is formed from this photosensitive resist liquid layer.

In addition, in the method for manufacturing a wiring board with through holes according to the second aspect, the photosensitive resist liquid has a solid content concentration of 60-1% or less and a thixotropic control agent is added.

The material and structure of the insulating substrate, the material of the conductive metal constituting the conductive metal layer, the method of forming the conductive metal layer, the shape and dimensions of the through-hole hole, and the processing method are the same as those for ordinary wiring boards with through-holes. can.

The method of covering the insulating substrate with an etching resist liquid layer by immersing the insulating substrate in a photosensitive resist solution and pulling it up is similar to the so-called "dip method" used in ordinary synthetic resin formation. The specific equipment and steps used can be the same as those for the conventional "dip method". For example, as a pretreatment for an insulating substrate to be immersed in a photosensitive resist solution, the surface of the insulating substrate may be polished or immersed in a chemical that improves wettability. Further, after the insulating substrate is immersed in the photosensitive resist solution, degassing treatment may be performed to prevent air bubbles from remaining inside the through-hole holes.

The components of the photosensitive resist liquid include UV-curable and thermosetting resin components, such as acrylic monomers, epoxy-based or novolac-based reactants, and various conventional photopolymerization initiators and photopolymerization accelerators. , a diluent such as an organic solvent, a thermosetting agent, and a thixotropic modifier described below. The specific compounds of each compounded component other than the regulator are the same as those used in the production of ordinary wiring boards.

The photosensitive resist liquid used in this invention has a solid content concentration of 60
-t% or less (preferably 15 to 50-t%), and the viscosity and thixotropy values are usually within the above numerical ranges. Note that the above solid content concentration refers to the photosensitive resist layer consisting of a resin film that is dried after forming the photosensitive resist liquid layer and removes the solvent, etc., but the proportion that remains as a resin film is
This indicates what -t% of the photosensitive resist liquid 10100i%.

When the solid content concentration exceeds 60 wt%, it tends to become difficult to maintain the viscosity and thixotropy within appropriate ranges.

The viscosity of the photosensitive resist liquid is 30 to 1500 cps, preferably 40 to 400 cps. Viscosity is 3
If the viscosity is less than 0 cps, the thickness of the etching resist layer formed will become thinner, and when etching the conductive metal layer, disconnection or circuit defects will easily occur at the circuit pattern portion or through hole edge portion. Air bubbles remain in the resist layer inside the hole, pinholes occur in the resist layer in the circuit pattern area, or the resist layer is not uniform over the entire surface of the insulating substrate and is too thick or too thin. This has the disadvantage that it can occur locally.

The above viscosity values are based on the B-type viscometer (Tokyo Keiki layer).
Using N081 to N0030-N, the rotation speed is 6° rpm.
The thixotropic value of the photosensitive resist solution, which is based on the value measured in
．． Use a range of 0. The above thixotropy value is determined by measuring the viscosity described above with high speed rotation of 6 Orpm and 5 rpm.
The test was performed at a low speed rotation of 100 pm, and expressed as the viscosity ratio of both. That is, the thixotropic value in this invention is a value defined by the following formula.

If the above-mentioned thixotropy value is less than 1.2, it will not be possible to ensure a sufficient thickness of the etching resist layer at the edge portion of the through hole. It becomes difficult to secure at least 1μ. Thixotropy value is 9.
If it exceeds 0, the variation in the thickness of the etching resist layer in the circuit pattern forming area becomes too large.

It is easy to adjust the thixotropy value to the above numerical range by using a thixotropy regulator as in claim 2.

Examples of thixotropic modifiers (hereinafter referred to as "modifiers") include finely powdered silica, calcium stearate,
Examples include zinc stearate, aluminum stearate, aluminum oxide, zinc oxide, magnesium oxide, silicon dioxide, glass, diatomaceous earth, titanium oxide, zirconium oxide, and organic substances such as fatty acid amide wax and polyethylene oxide. The regulator is preferably a powder with a fine particle size, especially a particle size of 0.001
It is preferable that it is about ˜number n (for example, 0.001˜In). In fine powder silica, primary particles aggregate to form secondary particles, and the particle size of the primary particles is 0.005 to 0.
It is about 5n.

Since the modifier does not normally dissolve in the photosensitive resist solution, it must be sufficiently stirred to be uniformly dispersed, or a suitable dispersant may be used in combination with the modifier. The thixotropic value may also be adjusted without using a regulator.

The solvent for the photosensitive resist solution is a main solvent with a boiling point of 100°C or higher, and a solvent that is compatible with the main solvent and has a boiling point of 75 to 150°C.
It is preferable that the solvent be made of a solvent having a boiling point of . for example,
Preferably, the main component is a compound such as ethylene glycol monoethyl ether acetate, xylene, methyl isobutyl ketone, toluene, methyl ethyl ketone, ethyl acetate, ethanol, or isopropanol. There are positive type and negative type photosensitive resist liquids, and either type can be used, but the positive type is preferable for through holes with a large aspect ratio. This is because when the aspect ratio of the through hole increases, it is difficult to use a negative type, which requires irradiation of ultraviolet rays deep into the through hole to harden the photosensitive resist liquid.

As mentioned above, the insulating substrate is immersed in a photosensitive resist solution and pulled up using the "dip method" to cover the entire surface of the insulating substrate and the inner wall of the through-hole hole with a layer of photosensitive resist solution, followed by a drying process and ultraviolet rays. An etching resist layer with a predetermined pattern is formed by a method similar to a pattern forming method for ordinary photosensitive resists, such as a curing process. The subsequent etching process of the conductive metal layer and other steps are carried out in the same manner as in the ordinary manufacturing method of wiring boards with through holes.

[For production]

By immersing the insulating substrate in the photosensitive resist solution and pulling it up, the photosensitive resist solution penetrates into the inside of the through-hole hole and adheres to the entire surface of the insulating substrate, including the through-hole hole. The etching resist layer can be simultaneously formed on the inner wall of the through-hole and the surface other than the through-hole in one step.

By appropriately setting the viscosity and thixotropy value of the photosensitive resist liquid, the adhesion of the photosensitive resist liquid to the through-hole holes, etc. is improved, and the inside of the through-hole hole and the edge portion of the through-hole hole are improved. In addition, it is possible to reliably form an etching resist layer with a sufficient thickness, and it is also possible to form an etching resist layer with a uniform thickness on the surface of the insulating substrate other than the through hole. In other words, as the viscosity and thixotropy of the photosensitive resist liquid increases, the fluidity of the photosensitive resist liquid becomes suppressed, and the photosensitive resist liquid flows to the surrounding areas such as the edges of through holes and escapes. This results in a sufficient thickness of photosensitive resist solution adhering even to easily exposed areas. However, if the fluidity of the photosensitive resist solution becomes too low, air bubbles may remain inside the through-hole holes, or the resist solution may not adhere uniformly to the surface of the insulating substrate, resulting in variations in thickness. It is necessary to limit the value to a range of sexual values.

The etching resist layer formed by the method of this invention is
Since the etching resist layer is formed in close contact with the surface of the insulating substrate along the entire inner wall of the through-hole hole, even if an etching pattern is formed just outside the edge of the through-hole hole, the etching resist layer will not peel off. The etching pattern will not be damaged. Therefore, unlike the conventional "tenting method", there is no need to form an etching pattern at a position far outside the edge of the through hole.

Furthermore, when using a thixotropy modifier, the thixotropy value can be adjusted very easily.

〔Example〕

Next, the present invention will be explained in detail below with reference to the drawings showing examples.

FIG. 1 is a process flowchart showing an embodiment of the method for manufacturing a wiring board with through holes according to the present invention, and the process will be sequentially explained according to this process flowchart. Further, the structure of the wiring board in the middle of the process is shown in FIGS. 2 to 5, and in the drawings, the same reference numerals are given to the same structural parts as in the above-described conventional example.

Among the materials of the wiring board, the insulating substrate 1 is made of paper-based phenol resin, paper-based epoxy resin, paper-based polyester resin,
Synthetic resin substrates such as glass-based epoxy resin, glass-based Teflon resin, glass-based polyimide resin, and composite resin; metal-based insulating substrates made by covering metals such as aluminum and iron with epoxy resin and performing insulation treatment; or,
Materials used for ordinary wiring boards, such as ceramic substrates, are used. It is also possible to use a copper-clad laminate in which a conductive metal layer 2 made of copper is laminated in advance on the surface of the insulating substrate 1 as described above.

A hole 10 for a through hole is made in an insulating substrate 1.

The through-hole holes 10 are formed by the same means as in the case of ordinary wiring boards, such as drilling or laser processing. When a ceramic substrate is used as the insulating substrate 1, a method may also be adopted in which holes are formed in a ceramic green sheet before firing by means such as punching, and then fired. The diameter of the through-hole hole 10 is usually 0.1 nm or less, but depending on the application, the diameter can be larger than that. Cutting debris and smear may be generated during this drilling process, and to remove these cutting debris, physical treatment methods such as high-pressure water washing and sandblasting, or chemical treatment methods such as sulfuric acid method and chromic acid method are required. The through-hole holes 10 are cleaned using a standard treatment method.

A conductive gold M layer 2 is formed on both the front and back surfaces of the insulating substrate (or copper-clad laminate) 1 in which through-hole holes 10 are formed and on the inner wall surface of the through-hole holes 10 by an appropriate plating method or the like. Before plating the insulating substrate 1, if necessary, the surface of the insulating substrate 1 and the inner wall surface of the through-hole hole 10 are etched and soft etched, and then metallic palladium is deposited. Activate the surface. The insulating substrate 1 that has been pretreated as described above is immersed in, for example, a chemical plating bath or the like to form a conductive metal N2 made of copper, nickel, gold, or the like.

The conductive metal layer 2 obtained by the chemical plating method as described above is
-For boat fishing, it is a thin layer of about 0.1 to several microns, so if a thicker conductive metal layer 2 is required, continue to use chemical plating to form an even thicker conductive metal layer 2. Alternatively, a thick conductive metal layer 2 can be further formed by electrolytic plating on the conductive metal layer 2 formed by the chemical plating method. When using the copper-clad laminate 2 instead of the insulating substrate 1, part of the process of forming the conductive metal layer 2 can be omitted. In addition to the method described above, the method for forming the conductive metal layer 2 can be changed to various methods for forming the conductive metal layer, which are employed in ordinary methods for manufacturing wiring boards with through holes.

Next, an etching resist layer is formed by a dip method, but before that, the substrate is pretreated if necessary. Pretreatment of the substrate is broadly classified into the following two treatments. First, the first process is to physically and chemically polish the surface of the insulating substrate 1. The specific polishing method is the same as in the case of ordinary wiring boards. The amount of polishing is preferably about 0.1 to 10 microns, more preferably about 0.2 to 2 microns. The second process is to immerse the insulating substrate 1 in a chemical to keep the inside of the through-hole hole 10 in a wet state. This treatment improves the wettability to the photosensitive resist solution, and in the step of soaking in the photosensitive resist solution, the holes 10 for through-holes are
This can prevent air bubbles from entering inside. As the chemical for dipping the insulating substrate 1 in this process, for example, a photosensitive resist solution used in the subsequent process can be diluted to lower its viscosity, but if it can achieve the same effect,
Other suitable chemicals may also be used. Each of the pretreatments described above is performed as necessary, and may not be performed if unnecessary.

Next, as shown in FIG. 2, the entire insulating substrate 1 is immersed in the photosensitive resist liquid 3 adjusted to the above-described viscosity and thixotropy values and appropriately stored in the liquid storage tank 4.
The insulating substrate 1 is pulled up with the photosensitive resist liquid 3 still attached, and the photosensitive resist liquid 3 is dried.
A photosensitive resist layer 30 is formed on the entire surface. The resist liquid 3 is reacted and formed into a film by the heat treatment in this drying process. At this time, if necessary, degassing inside the through-hole hole 10 is performed while the insulating substrate 1 is immersed in the photosensitive resist solution 3. The photosensitive resist liquid 3 is
It is made to adhere uniformly to the inside of the through-hole hole 10 of the insulating substrate 1 and to the entire other surfaces with a sufficient thickness. The specific working equipment and working conditions in this process are the same as in the normal "dip method".

When applying the photosensitive resist liquid 3 to the entire surface of the insulating substrate 1 using such a method, the viscosity and thixotropy of the photosensitive resist liquid 3, the pulling speed of the insulating substrate 1, etc. The thickness of the attached photosensitive resist liquid 3, that is, the formed photosensitive resist) J
The thickness of ii30 can be adjusted. For example, the thickness of the photosensitive resist layer 30 can be freely controlled by adjusting the viscosity and thixotropy within the above-mentioned ranges.

FIG. 3 shows the insulating substrate 1 on which the photosensitive resist N30 is formed, and the photosensitive resist (Jii30) made of the photosensitive resist liquid 3 is applied through the conductive metal N2 surface on both sides of the insulating substrate 1. The inner wall surface of the hole 10 is covered with a thickness similar to -, and the edge portion 11 of the through hole 10 is also covered with a thick photosensitive resist layer 30 in the same way as other parts. . Note that at the center of the interior of the through-hole hole 10, the photosensitive resist layers 30 on both sides are connected to form a connecting portion 31. This is due to the low fluidity of the photosensitive resist solution 3.
The photosensitive resist liquid 3 that entered the layer remains connected and does not affect its function as an etching resist layer.

Furthermore, depending on the implementation conditions, there is no problem even if such a connecting portion 31 is not formed.

In this invention, by using the photosensitive resist liquid 3 having the above-described viscosity and thixotropy values, it is possible to easily form a resist layer 30 having a sufficient thickness over the entire surface including the edge portion 11 of the through-hole hole 10. However, if the viscosity and thixotropy value of the photosensitive resist liquid 3 are out of the scope of the present invention and the fluidity of the photosensitive resist liquid 3 is too high, the photosensitive resist liquid 3 will have a state as shown in FIG. A resist layer 30'' is formed. That is, even if an attempt is made to attach the photosensitive resist liquid 3 to the edge portion 11 of the through-hole hole 10, the photosensitive resist liquid 3 will not adhere to the surrounding area due to the action of surface tension, etc. The etching resist layer is attracted and escapes from the edge portion 11, and as a result, the etching resist layer in this portion becomes thinner.In such a state, during the etching process of the conductive metal layer 2, the photosensitive resist layer In the thin edge portion 11 of N30'', the etching resist layer becomes such that even the conductive metal layer 2 below the photosensitive resist layer 30# is etched away, resulting in disconnection or poor conduction.

After the photosensitive resist layer 30 is formed on the entire surface of the insulating substrate 1 as described above, as shown in FIG. A predetermined pattern of the eratin resin l-[30' is formed by removing the resist layer at certain locations. A specific pattern forming process for the etching resist layer 30' is carried out by a so-called photographic method, which is similar to the pattern forming method for ordinary photosensitive resists. If a resist pattern is formed by such a photographic method, it becomes possible to form a fine pattern with a line spacing and a line width of 30 mm, which is impossible with other methods such as printing. Since the etching resist layer 30' formed into a predetermined pattern is sufficiently cured by ultraviolet irradiation or a heat drying process, the conductive metal layer 2 can be well protected against etching treatment described later.

In FIG. 4, the etching resist layer 30' is patterned in the periphery of the through-hole hole 10 so that the end portion of the etching resist layer 30' is immediately outside the edge portion 11 of the through-hole hole 10. In the case of this invention, the etching resist layer 30' extends from the inner wall of the through-hole hole 10 to the edge portion 1.
Since it fits tightly along 1 and covers it securely,
In this way, even if a pattern is formed just outside the edge portion 11, the etching resist layer 30' will not peel off or the pattern will be damaged.

Next, the insulating substrate 1, on which the conductive metal layer 2 is covered with the etching resist layer 30' having a predetermined pattern, is immersed or sprayed in an appropriate etching solution to remove unnecessary portions of the conductive metal layer 2. A conductive metal layer 2 having a predetermined circuit pattern is formed. This etching process for the conductive metal layer 2 can be carried out in exactly the same manner as in a normal wiring board manufacturing method. After etching, the resist layer 30' is usually
Try to remove it.

FIG. 5 shows an example of the wiring circuit pattern of the wiring board with through-holes manufactured as described above. (shown by dotted lines) are connected by through holes 21. As explained in FIG. 4, the etching resist layer 30' for forming the through hole 21 is
Since the pattern is formed just outside the edge portion 11 of the through-hole hole 10, this etching resist layer 3
The wiring circuit pattern formed by patterning the conductive metal N2 in accordance with 0' is a so-called land in which the width of the through hole 21 portion is almost the same as that of the other portion of the conductor circuit 20, and there is no land portion at all. It has a response structure.

If we compare the wiring circuit pattern shown in FIG. 5 with the wiring circuit pattern shown in FIG.
It is clear that the densification or miniaturization of wiring circuits can be greatly advanced.

The method for manufacturing a wiring board with through-holes according to the present invention is carried out according to the steps described above, but in the step of forming the etching resist F130', a photosensitive resist liquid having the above-described viscosity and thixotropy values is used. Except for covering the entire surface of the insulating substrate 1 with the so-called "dip method", ordinary wiring board manufacturing methods such as the circuit forming method using the photographic method described above can be used, and the specific implementation method in each step is as described above. In addition to the example explained,
It can be carried out by combining the means and methods of ordinary wiring board manufacturing methods.

Next, a specific example of manufacturing a wiring board with through holes by actually applying the manufacturing method according to the present invention will be described.

Example 1 A 96% alumina substrate was used as the insulating substrate 1, and a through-hole hole 10 having a hole diameter of 0.3 fi was formed by laser processing. The surface of this alumina sintered insulating substrate 1 and the inner wall surface of the through-hole hole 10 were uniformly roughened with phosphoric acid. After thoroughly cleaning and drying the roughened insulating substrate 1, a conductive metal layer 2 made of a copper layer having a thickness of Ion was formed on the surface of the insulating substrate 10 and the inner wall surface of the through-hole hole 10 by chemical plating.

Next, as a pretreatment for forming an etching resist layer, the surface of the conductive metal layer 2 of the insulating substrate 1 was polished by about 0.4 to 0.6 microns using oscillation polishing. Thereafter, an etching resist liquid layer was formed on the entire surface of the conductive metal layer 2 including the through-hole holes 10 by a dip method in which the insulating substrate 1 was immersed in the photosensitive resist liquid 3. When the viscosity and thixotropy value of the photosensitive resist liquid 3 used at this time were measured using the above-mentioned measuring method, the viscosity was 50.
cps, thixotropic value was 3.0.

The photosensitive resist liquid layer consisting of photosensitive resist liquid 3 is
After drying at .degree. C., an etching resist layer 30' having a predetermined pattern was formed by exposing to ultraviolet light using a positive mask pattern and developing.

When a cross section of the insulating substrate 1 on which such an etching resist layer 30' was formed was observed with a scanning electron microscope, it was found that
The thickness of the etching resist layer 30' at the edge portion 11 of the through-hole hole 10 is 2.0 to 2.3 μm, which is a sufficient thickness, and the thickness of the etching resist layer 30' at the circuit pattern portion is also 9.7 to 10 μm. .0. It was found that the film was formed to have a sufficient and uniform thickness of n.

Next, the conductive metal layer 2 was etched using a normal etching method to form a wiring circuit with a line spacing and a line width of 80n. After the etching process is completed, the etching resist layer 30
' was peeled off with a 3% pJaOH solution to obtain a wiring board with through holes.

Example 2 - A copper-clad laminate consisting of a metal-based insulating substrate in which a metal base material such as iron is coated with an epoxy resin or the like and subjected to insulation treatment was used. After forming through-hole holes 10 with a hole diameter of 0.4 fi in this copper-clad laminate by drilling, the through-hole holes 10 were cleaned by sandblasting or the like. Next, after soft etching the surface and inner wall surface of the copper-clad laminate with phosphoric acid, a copper layer is formed using a chemical plating method, and a thick layer of metallic copper is applied using an electrolytic plating method to form a conductive metal with a thickness of 35 nm. Layer 2 was formed.

As a pretreatment for forming the etching resist layer, the surface of the conductive metal layer 2 of the copper-clad laminate is polished to 0.8
After polishing to about 1.2 μm, soft etching was performed with sulfuric acid.

Thereafter, the positive photosensitive resist solution 3 was applied to the entire surface of the conductive metal layer 2 of the copper-clad laminate using the dip method described above.

At this time, the viscosity of the photosensitive resist liquid 3 was 80 cps, and the thixotropy value was 4.0.

After drying the photosensitive resist solution 3 at 80° C., the finished resist layer 3 having a predetermined pattern is formed by exposing it to ultraviolet light using a positive mask pattern and developing it.
0' was formed. In this state, the thickness of the etching resist layer 30' at the edge portion 11 of the through-hole hole 10 was measured using a scanning electron microscope in the same manner as described above, and the thickness was 3.0 to 4. It was on and had a sufficient thickness. The thickness of the etching resist layer 30' in the circuit pattern part is also 1
The score was good, ranging from 4.0 to 15.0.

Next, the conductive metal layer 2 was etched using a normal etching method to form a wiring circuit with a line width of 80 IIN. After the etching process, the etching resist layer 30
' was peeled off with a 2 to 3% NaOH solution to obtain a wiring board with through holes.

Example 3 A ceramic substrate was used as the insulating substrate 1. First, A1
．． 96 parts by weight of O, powder and 4 parts by weight of a sintering aid such as SiO, Cao, MgO, etc. were mixed, and 12 parts by weight of organic substances (binder, plasticizer, etc.) were added to this mixture. Then, the whole was further mixed. This mixture was formed into a sheet by a doctor blade method to obtain a ceramic green sheet. This green sheet was heated to a semi-hardened state, and then pressed using a mold to form a through-hole hole 10 with a hole diameter of 0°4. The green sheet was dried at 150° C. and then fired at 1600° C. to obtain an insulating substrate 1 made of a ceramic substrate having through holes 10.

After roughening the surface of the insulating substrate 1 with phosphoric acid, a conductive metal layer 2 made of a copper layer with a thickness of 8p is formed using a chemical copper plating method.
It was formed on the substrate surface and the inner wall surface of the through-hole hole 10. Thereafter, through the same steps as in Example 1, a wiring board with through holes made of a ceramic substrate was manufactured.

Example 4 - A wiring board with through holes was manufactured in the same steps as in Example 2 except that a glass-based epoxy resin substrate was used as the insulating substrate 1.

Example 5 A wiring board with through holes was manufactured in the same steps as in Example 1 except that a sintered aluminum nitride substrate was used as the insulating substrate 1.

Example 6 In Example 1, the through hole hole 10 was formed with a hole diameter of 0.5 fl by laser processing, the roughening treatment with phosphoric acid was not performed, and the copper layer with a thickness of 10 I# was formed by sputtering. A wiring board with through holes was manufactured in the same process as in Example 1 except that .

Example 7 - A 96% alumina substrate was used as the insulating substrate 1, and a through-hole hole 10 with a hole diameter of 0.3 fl was formed by laser processing. The surface of this alumina sintered insulating substrate 1 and the inner wall surface of the through-hole hole 10 were uniformly roughened with phosphoric acid. After thoroughly cleaning and drying the roughened insulating substrate 1, a conductive metal layer 2 made of a copper layer having a thickness of 10 μm was formed on the surface of the insulating substrate 1 and the inner wall surface of the through-hole hole 10 by chemical plating.

Next, as a pretreatment for forming a resist layer, the surface of the conductive metal layer 2 of the insulating substrate 1 was polished by about 0.4 to 0.6 nm using oscillation polishing. Thereafter, an etching resist liquid layer is formed on the entire surface of the conductive metal layer 2 including the through-hole holes 10 by a dip method in which the insulating substrate 1 is immersed in a photosensitive resist liquid 3 containing calcium stearate, which is a thixotropic modifier. did.

The composition of the photosensitive resist solution is as follows: novolac resin composition, photosensitizer...approximately 40 wt% melt ■ - ethylene glycol 7-noethyl ether acetate
... Approximately 48 wt% Solvent - Ethyl acetate, toluene, etc... Approximately 10-t% Thixotropic modifier - Calcium stearate
...Approx. 1.5wt% Others (colorants, etc.)
...The viscosity and thixotropy value of the photosensitive resist liquid 3 containing about 0.5 wt% of this thixotropic modifier were measured using the above-mentioned measuring method, and the viscosity was 18.
0 cps, thixotropic value 3.0. Also,
The solid content concentration of the photosensitive resist liquid 3 was about 38-t%.

The photosensitive resist liquid layer consisting of photosensitive resist liquid 3 is
After drying at .degree. C., exposure to ultraviolet light using a positive mask pattern and development were performed to form a notching resist layer 30' having a predetermined pattern.

When the cross section of the insulating substrate I on which such etching resist N30' was formed was observed with a scanning electron microscope, it was found that
The thickness of the etching resist layer 30' at the hole 10 for the through hole 10 is a sufficient thickness of 2.0 to 2.3 μm, and the thickness of the etching resist layer 30' at the circuit pattern portion is also 9.7 μm. ~10. It was found that the film was formed to have a sufficient and uniform thickness.

Next, the conductive metal layer 2 was etched using a normal etching method to form a wiring circuit with a line width of 80 cm. After the etching process is completed, the etching resist layer 30
' was peeled off with a 3% NaOH solution to obtain a wiring board with through holes.

Example 8 - A copper-clad laminate consisting of a metal-based insulating substrate in which a metal base material such as iron was coated with an epoxy resin or the like and subjected to insulation treatment was used. After forming through-hole holes 10 with a hole diameter of 0.4 N in this copper-clad laminate by drilling, the through-hole holes 10 were cleaned by sandblasting or the like. Next, after soft etching the surface and inner wall surface of the copper-clad laminate with phosphoric acid, a copper layer is formed using a chemical plating method, and a thick layer of metallic copper is applied using an electrolytic plating method to form a conductive metal with a thickness of 35 nm. Layer 2 was formed.

As a pretreatment for forming the etching resist layer, the surface of the conductive metal layer 2 of the copper-clad laminate is polished to 0.8
After polishing approximately 1.2 cm, soft etching was performed with sulfuric acid.

Thereafter, the positive photosensitive resist solution 3 was applied to the entire surface of the conductive metal N2 of the copper-clad laminate using the dip method described above.

The composition of the photosensitive resist solution is as follows: Novolak resin composition, photosensitizer...approximately 40-t% solvent - ethylene glycol monoethyl ether acetate
...Approx. 48tst% Solvent - Ethyl acetate, toluene, etc. - Approx. 10wt% Thixotropic modifier - Finely powdered silica... Approx. 1.5iyt% Others (colorants, etc.) - Approx. 0.5wt%
This photosensitive resist liquid 3 to which a small amount of finely powdered silica was added as a thixotropic modifier had a viscosity of 200 CpS and a thixotropic value of 4.0. Further, the solid content concentration of the photosensitive resist liquid 3 was about 40 wt%.

After drying the photosensitive resist solution 3 at 80° C., the etching resist layer 3 having a predetermined pattern is formed by exposing and developing the photosensitive resist solution 3 to ultraviolet light using a positive mask pattern.
0' was formed. In this state, the thickness of the etching resist layer 30' at the edge part 11 of the through-hole hole 10 was measured using a scanning electron microscope in the same manner as described above. Met. The thickness of the etching resist M30' in the circuit pattern part is also 1
4.0-15. It was good as on.

Next, the conductive metal Fii2 is etched using a normal etching method.
A wiring circuit with a line spacing and a line width of 80I# was formed by etching. After the etching process, the etching resist layer 3
0' was peeled off using a 2 to 3% NaOH solution to obtain a wiring board with through holes.

Example 9 - A ceramic substrate was used as the insulating substrate 1. After roughening the surface of this insulating substrate 10 with phosphoric acid, a conductive metal Jii2 consisting of a copper layer having a thickness of 8 μm was formed on the substrate surface and the inner wall surface of the through-hole hole 10 by chemical copper plating. Thereafter, through the same steps as in Example 7, a wiring board with through holes made of a ceramic substrate was manufactured.

Example 1〇--A wiring board with through holes was manufactured in the same process as in Example 8 except that a glass-based epoxy resin substrate was used as the insulating substrate 1.

Example 11 A wiring board with through holes was manufactured in the same steps as in Example 7 except that a sintered aluminum nitride substrate was used as the insulating substrate 1.

Example 12 In Example 7, the through-hole hole 10 was formed with a hole diameter of 0.5 mm by laser processing, the roughening treatment with phosphoric acid was not performed, and the copper with a thickness of 10 μm was formed by sputtering. A wiring board with through holes was manufactured in the same steps as in Example 7 except that the layers were formed.

Example 13 - A wiring board with through holes was manufactured in the same manner as in Example 7 except that the following photosensitive resist solution was used.

The composition of the photosensitive resist solution is as follows: Novolak resin composition, photosensitizer...approximately 24-t% solvent - ethylene glycol monoethyl ether acetate
...Approx. 44.5 wt% Solvent - Ethyl acetate, toluene ... Approx. 28-t% (including toluene...
(approx. 19 wt%) Thixotropic modifier - fine powder silica...approx. 3.5
sjt% The viscosity is 8Qcps, and the thixotropy value is 4.0.
It is.

Further, the thickness of the etching resist layer 30' at the edge portion 11 of the through-hole hole 10 is 3.0 to 4.0 mm. It had a sufficient thickness.

Example 14 - A wiring board with through holes was manufactured in the same manner as in Example 8 except that the following photosensitive resist solution was used.

The composition of the photosensitive resist solution is as follows: Novolak resin composition, photosensitizer...approximately 25-t% solvent - ethylene glycol monoethyl ether acetate
...Approx. 43-t% Solvent - Ethyl acetate, toluene...Approx. 28-t% (Toluene...approx. 19-t%) Thixotropic modifier - Finely powdered silica... Approx. 4ev
t% The viscosity is 120 cps and the thixotropic value is 4.
It is 5.

Further, the thickness of the etching resist layer 30' at the edge portion 11 of the through-hole hole 10 is 4.0~! i′, 0
It had a sufficient thickness of μ.

Example 15 - A wiring board with through holes was manufactured in the same manner as in Example 9, except that the photosensitive resist solution used in Example 13 was used.

Example 16 - A wiring board with through holes was manufactured in the same manner as in Example 10, except that the photosensitive resist solution used in Example 14 was used.

Example 17 - A wiring board with through holes was manufactured in the same manner as in Example 11, except that the photosensitive resist solution used in Example 13 was used.

Example 18 - A wiring board with through holes was manufactured in the same manner as in Example 12, except that the photosensitive resist solution used in Example 13 was used.

Example 19 - A wiring board with through holes was manufactured in the same manner as in Example 7 except that the following photosensitive resist solution was used.

The composition of the photosensitive resist solution is as follows: Novolac resin composition, photosensitizer: approx. 52-t% melt - ethylene glycol monoethyl ether acetate
... Approximately 38-t% Solvent - Ethyl acetate, toluene ... Approximately 81t% Thixotropic modifier - Finely powdered silica... Approximately 1.5-t% The viscosity is 1200 cps, and the thixotropic value is 3.
．． 0, and the solid content concentration is about 49-t%. In addition, the thickness of the etching resist layer 30' in the edge part 1 of the through-hole hole 10 is 4.0 to 5.5 mm. It was found that the etching resist layer 30' in the circuit pattern portion had a sufficient thickness of 14.0 to 15.0x, which was sufficiently uniform.

In addition, in Example 19, since the viscosity was relatively high,
A vacuum degassing process was also used, and the pulling speed of the insulating substrate 1 was slowed down to prevent the photosensitive resist solution from becoming too thick.

A through-hole continuity test was conducted on the wiring boards with through-holes manufactured in Examples 1 to 19, and no defects such as disconnection were observed, indicating that the through-hole reliability was higher than that of the conventional subtract method. proved to be extremely high.

Comparative Example 1 A wiring board with through holes was manufactured in the same manner as in Example 7, except that a photosensitive resist solution containing no calcium stearate was used. The thixotropic value of the photosensitive resist was 1.1. There were places where the thickness of the etching resist layer did not reach 1 μm, and disconnection defects were found on the wiring board.

〔Effect of the invention〕

According to the method for manufacturing a wiring board with through-holes according to the present invention as described above, the inside of the through-hole hole is Since the photosensitive resist layer is formed on the entire surface of the insulating substrate including the insulating substrate, the etching/notching resist layer can be reliably formed with an extremely simple operation. Furthermore, by appropriately controlling the speed at which the insulating substrate is pulled up from the photosensitive resist solution, the thickness of the photosensitive resist solution layer adhering to the insulating substrate, that is, the etching resist layer, can be freely adjusted.

In particular, by using a photosensitive resist liquid whose resist viscosity and chicken tropism value fall within a specific range, the fluidity of the photosensitive resist liquid can be adjusted to an appropriate range, and the insulating substrate can be photosensitive. When the resist liquid is applied, the photosensitive resist liquid can be reliably and sufficiently thickly applied to the inside of the through-hole and the groove portion. That is, the thickness of the etching resist layer formed from the photosensitive resist liquid layer can be made to be 21 or more and at least 1, H or more, even at the edge portion of the through-hole, for example. Therefore, when etching the conductive metal layer, the edge portion is also well protected by a sufficiently thick etching resist layer, and the conductive metal at the edge portion is reliably prevented from being etched. It will be possible.

Therefore, the etching/notching resist layer becomes thinner at the edge of the through hole, which has been a problem with the conventional "hole filling method," and the conductive metal layer in that area is etched, resulting in circuit defects such as disconnections. Through-hole reliability can be improved by solving the problem of causing.

The etching resist layer made of photosensitive resist liquid can be formed much thinner than the photosensitive dry film used in the conventional "tenting method", so it is possible to form fine patterns of 1001 or less, which was difficult with the above conventional method. It is also possible to form. In particular, since the etching resist layer is formed in tight contact along the inner wall surface from the edge of the through-hole hole, there is no need to set a large land at the through-hole location as in the conventional method. It is also possible to form minute through holes and landless through holes that form a circuit pattern right next to the edge of the through hole hole, making it possible to further miniaturize and increase the density of wiring circuits.

Furthermore, the thixotropy value of the photosensitive resist solution can be easily adjusted by using a thixotropy regulator.

[Brief explanation of drawings]

FIG. 1 is a process flowchart showing the manufacturing process of an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the process of applying a photosensitive resist liquid in the manufacturing process, and FIG. FIG. 4 is an enlarged cross-sectional view of the main part of the insulating substrate, and FIG. 4 is a cross-sectional view of the etching resist layer patterned.
The figure is a schematic plan view showing one example of a circuit pattern, FIG. 6 is a sectional view showing a comparative example, FIGS. 7 and 8 are sectional views showing conventional examples, and FIG. 9 is a wiring circuit pattern according to a conventional method. FIG.

Claims (1)

[Scope of Claims] 1. For an insulating substrate in which a conductive metal layer is formed on the inner wall surface of a through-hole hole and on both sides of the substrate, the conductive metal layer is covered with an etching resist layer of a predetermined pattern, and then an etching treatment is performed. In the manufacturing method of a wiring board with through holes in which a circuit is formed using a method, the step of forming an etching resist layer of a predetermined pattern covers the entire insulating substrate with a viscosity of 30 to 1500.
The entire surface of the insulating substrate, including the inner wall surface of the through-hole hole, is covered with a photosensitive resist liquid layer by dipping it in a photosensitive resist liquid having a thixotropy value of 1.2 to 9.0 and then pulling it up. A method for manufacturing a wiring board with through holes, which comprises forming an etching resist layer with a predetermined pattern from this photosensitive resist liquid layer. 2. The method for manufacturing a wiring board with through holes according to claim 1, wherein the photosensitive resist liquid has a solid content concentration of 60 wt% or less and a thixotropic control agent is added.