JPH09289368A - Two-layer type printed circuit board and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a very fine circuit pattern at a high yield by specifying the number and max. length of through-holes piercing a two-layer type printed circuit board and conductive metal layer to reach the surface of an insulation film. SOLUTION: A conductive metal layer 2 is formed on an insulation film 1 and chemically adsorbed pref. through a water soln. to pin-holes through which the film 1 is exposed, i.e., defects of this metal layer 2 and, if required, to bored throughholes to expose the film 1, and then the electroplating is made to obtain a two-layer type printed board. It is specified that the number and max. length of pin-holes of this board are 10 holes/m<2> or less and 10 microns or less as measured with the transmitted light and steromicroscope. Thus it is possible to produce a fine pattern with through-holes of 80 microns or less pitch at a high yield which was difficult to mass-produce, whereby more highdensity and more high-integration degree electric and electronic apparatus are expectable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-layer type printed circuit board having no adhesive layer and capable of providing an ultrafine circuit pattern having a pitch of 80 μm or less in a high yield.

[0002]

2. Description of the Related Art Conventionally, a so-called "three-layer type" in which a copper foil is laminated on a polyimide film or a PET film via an adhesive has been used as a substrate for a flexible printed circuit. Since the three-layer type printed circuit board uses an epoxy resin or an acrylic resin as an adhesive, it has a drawback that the electrical characteristics are deteriorated by impurity ions contained in the adhesive, and the heat resistance temperature of the adhesive is high. Since the temperature is 100 to 150 ° C at the best, it has a drawback that the high heat resistance (400 ° C or higher) of polyimide cannot be fully utilized, so it is possible to reduce the specifications by wire bonding to IC chips that require high temperature mounting. Is forced. Also, in the case of a three-layer type printed circuit board, the typical film thickness of the copper foil is 18 μm or 35 μm. Therefore, in order to perform patterning at a pitch of 80 μm (copper wiring 40 μm, gap 40 μm) or less. The copper is too thick, the etching rate is significantly reduced, the circuit width on the copper foil surface side is significantly different from the circuit width on the adhesive surface side, or the whole is remarkably thinned by etching and the target circuit pattern cannot be obtained. There is also.

In recent years, in order to solve these drawbacks, electrolytic copper is deposited on an insulating film by various vapor deposition methods such as vacuum vapor deposition method, sputtering method or various ion plating methods without using an adhesive agent. A so-called "two-layer type", which is obtained by plating, has been proposed. This is because the copper film thickness can be freely changed by electrolytic copper plating. For example, if the copper film thickness is 8 μm, a 60 μm pitch circuit pattern can be easily created, and the heat resistant temperature of various insulating films can be kept unchanged. It has characteristics that can be reflected.

Regarding these two-layer types, Japanese Patent Publication No. 2-5
Japanese Patent Publication No. 5943 describes that undercutting from tin or gold plating can be improved by depositing chromium on a polyimide film, depositing copper on it, and then performing electrolytic copper plating.

Further, Japanese Patent Laid-Open No. 63-185091 discloses a high frequency bias sputtering after copper sputtering.
It is described that a two-layer type circuit board having excellent adhesion can be obtained by a high frequency bias sputtering method in which electrolytic copper plating is further performed.

In addition, as a method for producing a two-layer type circuit board by an all wet method, in JP-A-7-216553, a polyimide surface is etched with caustic, a catalyst is applied thereto, and then nickel is added. It is described that the adhesion strength of 1.0 Kgf / cm or more can be obtained by electrolessly depositing a metal such as the above, heat treating it in an inert gas atmosphere, and then performing electrolytic copper plating.

Since these two-layer type are considered to have weaker adhesiveness between the insulating film / copper and chemical resistance than the three-layer type, they are intended to improve it. However, the biggest drawback of the two-layer type is a through hole (commonly called "pinhole", hereinafter sometimes simply referred to as pinhole) penetrating from the copper layer to the surface of the insulating film. Because of pinholes, circuit pattern chipping, wire breakage, or floating may occur.
It is difficult to produce a fine pattern with a pitch of 0 micron or less with high yield. That is, the two-layer type printed circuit board prepared by the vapor deposition method or the wet method is used.
When a printed circuit board with a micron pitch (copper wiring 30 microns, gap 30 microns) is manufactured, the wiring width is 1
If at least one or more chips of / 3 or more are present in the entire circuit pattern, the entire board fails. Therefore, chips having a width of 10 microns or more with respect to the wiring width of 30 microns are rejected. If the pinhole has a size of 10 microns or more, chipping of the pattern or disconnection may occur. The nature is great.

In the case of various vapor deposition methods, the cause of the pinhole is dust that adheres to the surface of the insulating film, or vapor deposition abnormality due to bumping of metal during vapor deposition causes a partial non-vapor deposited portion. Serves as a pinhole penetrating from the surface of the deposited film to the surface of the insulating film. Generally, when the deposited film has a thickness of hundreds to tens of thousands of angstroms, a pinhole having a number of submicrons to hundreds of microns is generated in the hundreds to tens of thousands / m ² . Therefore, it is extremely difficult to reduce the pinhole generation of the vapor deposition film to zero for the entire width and the entire length of the film to be processed.

Even if a plated film having a pinhole is plated with copper having a thickness of 18 to 35 microns, a pinhole having a thickness of several tens of microns or more can be obtained.
However, even if the pinhole of about 30 microns or less is buried and the appearance as a continuous film is exhibited, the adhesive force between the copper plating layer and the insulating film at the pinhole is obtained. However, when the circuit pattern is formed by etching, floating from the insulating film or blistering at the time of heat treatment occurs at that portion, which significantly deteriorates the reliability of the printed circuit board.

Also, when the two-layer type circuit board is manufactured by the all wet method, pinholes are generated although the mechanism of occurrence is different. That is, in the step of electroless plating for depositing a metal after the catalyst is adsorbed on the insulating film, the deposition reaction basically involves generation of hydrogen gas on the surface of the object to be treated. An unprecipitated portion of metal is generated at the hydrogen gas generation portion, and the pinhole is generated. In addition, when the polyimide surface is activated by etching with a caustic soda, the catalyst in the next step is not adsorbed to the defective portion, and copper is not deposited at that portion, so that pinholes are generated. The confirmation test of the present inventors, those from those submicron several hundred microns was confirmed several hundreds to several thousands pieces / m ² after copper plating 18 micron.

The method for manufacturing a three-layer flexible printed circuit board with a sulfol is 18 μm or 3
After sticking a 5 micron copper foil to the insulating film via an adhesive, through holes are processed with a press or a drill, etc., and the catalyst is adsorbed to the places, and electroconductivity plating is used to secure conductivity. Next, electrolytic copper plating is performed. In that case, the copper film thickness inside the through hole is generally about 15 μm, which can ensure the conduction reliability. Therefore, when 15 μm of copper plating is added to 18 μm copper foil, the total film thickness becomes 33 μm, and the above etching rate is extremely poor. Is difficult to make.

[0012]

In recent years, IC and high density / high integration of electric / electronic devices have been rapidly advanced, and the pattern width of the flexible printed circuit board has been increased to 150 with it.
Progressing from ˜200 micron pitch to 80 to 150 micron pitch, and nowadays, it is required to be compatible with 30 to 80 micron pitch. Therefore, the object of the present invention is 80
It is intended to provide a two-layer type printed circuit board and a two-layer type printed circuit board capable of obtaining an ultrafine circuit pattern of a micron pitch or less in a high yield. Another object of the present invention is to provide such a two-layer type printed circuit board and
A method of obtaining a layered printed circuit board is provided.

[0013]

According to the studies made by the present inventors, the objects of the present invention have been industrially conveniently achieved by the following present invention.

[1] In a two-layer type printed circuit board in which a conductive metal layer and a copper plating layer are sequentially formed on an insulating film, an insulating property is obtained by penetrating the copper plating layer and the conductive metal layer. The number of through holes reaching the film surface is 10
A two-layer type printed circuit board, wherein the number of holes / m ² or less and the maximum length of the through holes is 10 μm or less.

[2] The insulating film is a film made of a polymer selected from the group consisting of polyethylene terephthalate, polyphenylene sulfide, polyetherketone, aromatic polyamide, polyarylate, polyimide, polyamideimide, and polyetherimide. The two-layer type printed circuit board according to [1] above.

[3] A conductive metal layer is provided on one or both sides of an insulating film having no adhesive layer by vapor deposition, and then a chemical method using an aqueous solution is applied to a portion where the conductive metal is not deposited and the insulating film is exposed. The method for producing a two-layer type printed circuit board according to the above [1] and [2], characterized in that the conductive metal layer is adsorbed by the above method and an electrolytic copper plating layer is further formed.

[4] The two-layer type printed circuit board according to the above [1] and [2], which has a through hole penetrating the conductive metal layer, the copper plating layer and the insulating film.

[5] After providing a conductive metal layer by vapor deposition on one or both sides of an insulating film having no adhesive layer, or after sequentially providing a conductive metal layer and a copper plating layer,
A hole is drilled through the conductive metal layer, the copper plating layer and the insulating film, and a chemical method is applied to a portion where the insulating film is exposed by the hole drilling and a portion where the conductive metal is not deposited on the insulating film. The method for producing a two-layer type printed circuit board according to the above [4], which comprises adsorbing a conductive metal layer and further forming an electrolytic copper plating layer.

[6] After the through hole is formed in the insulating film, a conductive metal layer is provided on both sides and the through hole by vapor deposition, and then the conductive metal is not deposited on the exposed portion of the insulating film. The method for producing a two-layer type printed circuit board according to the above [4], wherein a conductive metal layer is adsorbed by a chemical method using an aqueous solution, and an electrolytic copper plating layer is further formed.

[7] The above-mentioned [1], [2] and [4] characterized in that a vapor deposition layer made of metal and ceramics is provided between the insulating film and the conductive metal layer.
2-layer printed circuit board.

[8] A circuit pattern is formed on the two-layer type printed circuit board of the above [1], [2] and [4], and further nickel, palladium, gold, silver, tin, solder, rhodium, platinum. And a two-layer type printed circuit board characterized in that a plating selected from the group of these compounds is formed.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The most important feature of the present invention is to provide a conductive metal layer on an insulating film, a pinhole portion where the insulating film is exposed due to a defect of the conductive metal layer, and if necessary. That is, a conductive metal layer is adsorbed by a chemical method to a place where the insulating film is exposed by the through hole processing, preferably with an aqueous solution, and then electrolytic copper plating is performed.

That is, the insulating film is subjected to corona treatment or plasma treatment, which is a known pretreatment, to improve the hydrophilicity of the film surface, and dust is removed with an ultrasonic cleaner, and then nickel is deposited by a vapor deposition method. , Iron, cobalt, copper, tin,
A conductive metal layer made of palladium, chromium, and a compound thereof is usually formed in a thickness of 500 to 10000 angstrom. Vapor deposition methods include vacuum vapor deposition, sputtering, and ion plating methods. Among them, the sputtering method and ion plating method, which can form a film with high energy, have dense film quality, and relatively few pinholes, are preferable. The film thickness of the conductive metal layer is required to be resistant to it because it is chemically treated in the next step. That is, the film thickness is 2
If it is 000 angstroms or less, the adhesion strength is lowered, and if it is 7,000 angstroms or more, the manufacturing cost is high.
A range of m is preferred.

In the pinhole, the thickness of the conductive metal layer decreases to about 3000 angstroms, and the thickness tends to reach a saturation state when the thickness is more than 3000 angstroms. The conductive metal layer has a thickness of 3000 to 5000 angstroms. -The optimum range is

Next, a conductive metal layer is adsorbed by a chemical method, preferably by an aqueous solution, on the place where the conductive film is not vapor-deposited and the insulating film is exposed. The method is, for example, as follows. That is, the conductive metal layer is treated with a pretreatment degreasing liquid containing a surfactant, and then the exposed film surface at the pinhole location is activated in a chemical solution such as an aqueous solution of caustic soda so as to have a thickness of 72 dyne or more. Make sure that you can get wet. Then, a conductive metal layer such as a palladium or a compound of palladium and tin is adsorbed. The thickness of the conductive metal layer is preferably 0.01 to 0.1 Ω / □ in terms of surface resistance after drying in consideration of electrolytic copper plating.

The copper plating layer is usually formed by electrolytic plating. In the present invention, the electrolytic plating method is preferably copper sulfate plating having a current efficiency of 100%, which does not generate hydrogen gas which causes pinholes from the surface of the object to be treated during copper plating deposition. The copper sulfate plating solution is a low-concentration sulfuric acid type having a high copper concentration and a sulfuric acid concentration of about 50 g / l as the first treatment, and after performing copper plating of 0.1 to 0.7 micron,
As the secondary treatment, it is preferable to perform copper plating to a predetermined film thickness with a high sulfuric acid type having a sulfuric acid concentration of about 180 g / l that can obtain a dense copper layer with a uniform film thickness.

The pinholes of the two-layer type printed circuit board obtained in the above step were measured with transmitted light and an actual microscope. As a result, 0 to 1 / pinhole having a major axis of 2 to 3 microns was obtained. It was m ² .

Regarding the influence of the diameter and number of the pinholes on chipping and disconnection of the wiring, the wiring pattern (6
Table 1 shows the results of observing cracks and wire breakages of 5,000 of them prepared. Regarding chips, those of 10 microns or more were rejected.

[0029]

[Table 1] From Table 1, the yield rate of 60 micron pitch wiring is 10
In order to achieve 0%, it is necessary to satisfy the maximum pinhole diameter of 30 microns or less and 50 pieces / m ² or less. Also,
Considering the case where the wiring width is 20 or 10 μm, the maximum diameter of the pinhole is required to be 10 μm or less and 10 pieces / m ² or less.

In addition, after forming a conductive metal layer by vapor deposition, a sulcer hole drilling through the conductive metal layer and the insulating film layer is performed, and the conductive metal layer is adsorbed by the above-mentioned chemical method, and further, electric By plating with copper, it is possible to obtain a substrate having a through hole and a conductive metal layer having a copper film thickness of approximately the same and having little or no pinhole. Depending on the diameter of the hole, for example, φ0.
If it is about 5 mm, machining by a drill or press is preferable, and if it is several tens of microns or more, excimer
The etc. are preferred. In addition, the conductive metal layer at the location where the sulfol is processed can be dissolved with an etching solution, and then the insulating film can be chemically drilled with a known etching solution. These processing methods are preferably selected according to the purpose. Further, the drilling can be performed after electrolytic copper plating is performed on the conductive metal layer. In that case, the film thickness of the electrolytic copper plating is preferably about several microns in order to suppress the decrease in the etching rate as much as possible and to prevent heat-resistant blisters.

A 10-micron copper-thickness product produced by the above method and a conventional two-layered copper-thickness product having a 18-micron thickness were subjected to a sulfol processing, and then 10-micron copper plating was performed, and a total was obtained. A film having a film thickness of 28 μm was patterned with a circuit width of 30 μm, and the etching rate was measured. The etching rate was calculated from the values of A, B and h in FIG. 1 by the following formula.

Etching rate = 2 h / BA As a result, the etching rate of the 10-micron copper film thickness product (the product of the present invention) is 6.6, while the etching rate of the conventional 2-layer product of 28 microns. Was 3.6.

The etching rate of the conventional three-layer product is 2.5 to
Since it is about 3.0, it can be seen that 6.6 is a dramatic improvement.

Further, the sulfol processing is carried out before forming the conductive metal layer by vapor deposition, and the same steps as described above are carried out to obtain a two-layer with a sulfur having a high etching rate and little or no pinhole. A printed circuit board for a mold can be achieved.

In addition, when the printed circuit board is used in a high temperature heat resistant atmosphere or in a high temperature and high humidity environment, it can be achieved by providing a layer made of metal and ceramics between the insulating film and the conductive metal layer. You can The metals and ceramics are preferably titanium, chromium and zirconium, and can be obtained by sputtering or ion plating in an oxygen or nitrogen atmosphere. Since the oxides and nitrides cannot be etched with ferric chloride and cupric chloride, which are etching solutions, the oxidation and nitridation rates of titanium, chromium and zirconium must be adjusted to ensure the stability of the line insulation resistance over time. It is preferably 99% or more. If it is less than 99%, the insulation resistance between lines changes by about one digit after the initial value. The film thickness is preferably a discontinuous film having an island structure of 70 Å or less. In the case of a continuous film, poor adhesion may occur between the continuous film and the conductive metal film, resulting in poor reliability.

The insulating film is suitable for printed circuit boards and suitable for vapor deposition, chemical treatment or plating, polyethylene terephthalate, polyphenylene sulfide,
Polyetherketone, aromatic polyamide, polyaryle
, Polyimide, polyamideimide, and polyetherimide can be used, and among them, polyimide having high temperature heat resistance is most suitable.

Further, in the above-mentioned two-layer type printed circuit board, an etching resist is applied or laminated on the copper plating layer, and after UV exposure and development, a circuit pattern is formed by an etching solution, and a component mounting portion and a component mounting portion are formed. A masking agent such as solder resist is coated on the parts other than the terminals, and the exposed part is plated with nickel, palladium, gold, silver, tin, solder, rhodium, platinum or a compound thereof. The two-layer type printed circuit board of the present invention is obtained by forming the.

Thus, according to the present invention, a fine pattern with a pitch of 80 μm or less on a two-layer type printed circuit board is used.
It can be produced in high yield with sulfone attached.

[0039]

EXAMPLES Next, the present invention will be specifically described by way of examples, but the present invention is not limited to these.

Example 1 A roll-shaped polyimide film "Kapton V" (manufactured by DuPont Toray Co., Ltd.) having a thickness of 25 μm was treated by corona discharge treatment up to 72 dyne or more at which water was sufficiently wet, and then ultrasonic waves were applied. Dust and foreign substances were removed with a washing machine. The nuclear film was set in a sputtering device and evacuated to 5 × 10 ⁻⁵ torr, then 2 × with argon gas.
Adjusted to 10 ^-3 torr and used nickel for sputtering voltage 500V.
Was evaporated to a film thickness of 100 angstroms, and copper was evaporated on the nuclear nickel film in the same manner as 3000 angstroms. The above-mentioned sputtering operation was repeated twice to form a copper layer on both surfaces. For pinhole observation, one side was etched out and the number of pinholes was counted with transmitted light and a real microscope. The results are shown in Table 2. Degreasing agent AZ-700 for evaporated copper surface
(Made by Canning Japan) to activate the exposed polyimide surface with pinholes in a mixed solution of hydrazine added to caustic soda, and then tin / palladium in a mixed solution of tin and palladium. Adsorbed on the surface.
Immediately thereafter, 0.5 μm electrolytic copper plating was performed at 1 A / dm ² in a low concentration copper sulfate plating solution having a sulfuric acid concentration of 50 g / l, and then 3 A in a high concentration copper sulfate plating solution having a sulfuric acid concentration of 150 g / l. 8 micron electrolytic copper plating at / dm ² . Table 2 shows the results of counting the pinholes after electrolytic copper plating by the same method as described above. As a result, the number of pinholes of 10 μm or less was reduced to 1 / m ² .
After that, a photosensitive liquid resist was coated, and UV exposure and development were performed using 1024 masks of a circuit pattern of 60 micro pitch (30 μm of copper conductor-30 μm of gap), and the circuit was formed with an etching solution of ferric chloride. Pattern
Formed. Fifty circuit patterns are observed under a 150 × microscope, and chips (10% or more chips are rejected. If one or more of the 1024 lines are rejected, the circuit pattern is rejected. ) And the result of judging the quality of the pattern due to the disconnection are shown in Table 3. By this, 100%
A yielded circuit pattern was obtained.

Next, after coating a polyimide-based resist except for the IC mounting portion and the terminal portion, electroless nickel of 5 μm and gold plating for electroless bonding were applied to the exposed copper circuit pattern portion. After performing 5 micron, a fine pitch two-layer type printed circuit board shown in FIG. 2 was obtained.

(Comparative Example 1) For comparison, after nickel and copper were sputtered in the same process as in Example 1, the pinholes were counted and the high-concentration copper sulfate plating solution was used under the same conditions.
Table 2 shows the results of measuring the pinhole by the same method after performing electrolytic copper plating of 5 microns and adjusting the copper film thickness.
Then, the results of observing a circuit pattern patterned by the same method with an actual microscope are shown in Table 3. As a result, although the pinholes were reduced by about 60% by electrolytic copper plating, the yield after patterning was 18%, which is far from a practical level.

[0043]

[Table 2]

[0044]

[Table 3] (Example 2) Upilex 50S having a thickness of 50 microns
(Manufactured by Ube Industries, Ltd.) was pretreated in the same process as in the example, and it was confirmed that wetting of 75 dyne or more was secured. Set the film in the sputtering device and
After evacuating to × 10 ⁵ torr, 2 × 10 ³ torr was adjusted with nitrogen gas to deposit zirconium to a thickness of 20 Å, and then copper was deposited to a thickness of 3000 Å in the same manner as in Example 1. . Next, after making through holes of φ50 μm with an excimer laser, a conductive metal layer was formed by a wet method as in Example 1, and then a copper layer was formed to 8 μm by electrolytic copper plating. After performing a 60 micron pitch pattern on it, the etching rate was measured.
6.8 and a sharp pattern with a small difference between "A" and "B" in FIG. 1 was obtained.

[0045]

As described above, according to the present invention,
Fine patterns with sulphate of 80 micron pitch or less, which had been considered to be difficult to mass-produce in the past, can be produced with high yield, and dramatic progress in high density and high integration of electrical and electronic equipment is expected. it can.

[Brief description of drawings]

FIG. 1 is a sectional view showing an etching rate measurement pattern.

FIG. 2 is a cross-sectional view of the two-layer printed circuit board according to the first embodiment.

[Explanation of Codes] 1 ... Insulating film 2 ... Copper layer 3 ... Etching resist 4 ... Two-layer type printed circuit board 5 ... Insulating film (Kapton V) 6 ... Nickel Deposition layer / copper deposition layer 7 ... Low concentration copper sulfate layer 8 ... High concentration copper sulfate layer 9 ... Electroless nickel / Electroless gold for bonding 10 ... 30 micron copper circuit pattern 11. ..30 micron gap

Claims (8)

[Claims] 1. A two-layer type printed circuit board in which a conductive metal layer and a copper plating layer are sequentially formed on an insulating film, the insulating film penetrating the copper plating layer and the conductive metal layer. The number of through holes reaching the surface is 10 / m
² or less, and two-layered printed circuit board, wherein the maximum length of the through hole is less than 10 microns. 2. An insulating film made of a polymer selected from the group consisting of polyethylene terephthalate, polyphenylene sulfide, polyetherketone, aromatic polyamide, polyarylate, polyimide, polyamideimide, and polyetherimide. The two-layer type printed circuit board according to claim 1, wherein 3. A conductive metal layer is provided on one or both sides of an insulating film having no adhesive layer by vapor deposition, and then a conductive metal is chemically deposited on the exposed portion of the insulating film without depositing conductive metal. 3. The method for manufacturing a two-layer type printed circuit board according to claim 1, wherein the metal layer is adsorbed and an electrolytic copper plating layer is further formed. 4. The two-layer type printed circuit board according to claim 1, further comprising a through hole penetrating the conductive metal layer, the copper plating layer and the insulating film. 5. A conductive metal layer, which is obtained by depositing a conductive metal layer on one or both surfaces of an insulating film having no adhesive layer by vapor deposition, or by sequentially depositing a conductive metal layer and a copper plating layer. A hole is drilled through the copper plating layer and the insulating film, and the conductive metal layer is adsorbed by a chemical method at the location where the insulating film is exposed by the hole drilling and the location where the conductive metal is not deposited on the insulating film. And further forming an electrolytic copper plating layer.
2. A method for manufacturing a two-layer type printed circuit board. 6. After the through hole is formed in the insulating film, a conductive metal layer is provided on both sides and the through hole by vapor deposition, and then the conductive metal is not deposited and the insulating film is exposed at the exposed area. 5. The method for manufacturing a two-layer type printed circuit board according to claim 4, wherein the conductive metal layer is adsorbed by a static method, and an electrolytic copper plating layer is further formed. 7. The two-layer type printed circuit board according to claim 1, wherein a vapor deposition layer made of metal and ceramics is provided between the insulating film and the conductive metal layer. 8. A circuit pattern is formed on the two-layer type printed circuit board according to any one of claims 1, 2 and 4, and is further selected from the group consisting of nickel, palladium, gold, silver, tin, solder, rhodium, platinum and compounds thereof. A two-layer type printed circuit board, which is characterized in that the formed plating is formed.