JP2000178793A - Manufacturing method of metal polyimide substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal polyimide substrate composed of a thin polyimide layer having a sufficient insulation reliability and a metal layer when obtaining a metal polyimide substrate by depositing an electrodepositable polyimide on a metal foil. To provide SOLUTION: An electrodeposition polyimide is electrodeposited on a metal surface so as to have a desired film thickness, and then a polyimide resin film is formed on the metal surface.
Heat treatment at 0 to 400 ° C. to make an insulator, then
A set of steps of electrodepositing an electrodepositable polyimide on the polyimide resin film obtained by the insulating treatment is performed, and at least one set of the steps is performed to obtain a polyimide resin film having a desired film thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for obtaining a metal polyimide substrate by forming a polyimide resin film on a metal plate by an electrodeposition method, and more particularly to a method for manufacturing a metal polyimide substrate having a polyimide resin film without pinholes. .

[0002]

2. Description of the Related Art Polyimide resins have high heat resistance, chemical stability, and electrical insulation properties, and are therefore widely used as insulating materials for electronic components. For example, tape automatic bonding (TAB), flexible printed circuit (FP)
C) Electronic components such as a substrate and a chip size package (CSP) are usually obtained by processing a copper foil and a polyimide film by a photolithography technique or the like using a copper polyimide substrate composed of a polyimide film and a copper foil.

[0003] As a method of forming such a metal polyimide substrate, which is a composite of a metal layer and a polyimide, a method of laminating a metal foil and a polyimide film with an adhesive layer, a method of applying a polyimide precursor to the surface of the metal foil, and the like. In general, a method of imidization by thermal polymerization and a method of forming a metal layer on the surface of a polyimide film by dry or wet plating are generally known.

On the other hand, in response to recent demands for lighter and thinner electronic devices, the density of electronic components has rapidly increased,
For each material, further reduction in weight, thickness, and high reliability are required, and naturally, reduction in manufacturing cost is also required. In response to this requirement, as a method for forming the above-mentioned metal polyimide substrate, a polyimide resin having a charged functional group on the surface of a metal foil (hereinafter, referred to as “electrodepositable polyimide”) is electrodeposited. A method of forming a polyimide layer in such a manner is being studied. This method can be said to be excellent in economy and suitable for weight reduction since the polyimide layer can be made thinner and the polyimide layer can be formed only at a desired portion of the metal foil.

[0005]

However, when a circuit board is prepared by using the metal polyimide substrate obtained by the above-mentioned electrodeposition method, and a circuit board of a thin polyimide film which is the original object is obtained, the thickness of the polyimide film is reduced. The thinner the film, the lower the insulation reliability of the polyimide film.
It was found that this defect became remarkable when it was less than m.

[0006] The present invention has been made to improve this point, and an object of the present invention is to provide a metal polyimide substrate comprising a thin polyimide layer and a metal layer having sufficient insulation reliability. I do.

[0007]

The present inventors have scrutinized the reason why sufficient insulation reliability cannot be obtained in the polyimide resin of the above thin film, and as a result, a fine pinhole is present in the polyimide film. The present inventors have found that pinholes are related to insulation reliability, and have reached the present invention.

That is, according to the first invention for solving the above-mentioned problem, when a metal polyimide substrate is formed by electrodepositing an electrodepositable polyimide on a metal surface, the metal film has a desired thickness on the metal surface. The process of electrodepositing an electrodepositable polyimide, then treating the polyimide resin film as an insulator, and then depositing the electrodepositable polyimide on the polyimide resin film obtained by the insulator treatment is regarded as one set. By performing at least one set of the steps, a polyimide resin film having a desired film thickness is obtained. The insulating treatment is performed by heat-treating the polyimide resin film formed by electrodeposition at a temperature of 50 to 400 ° C. For example, it is convenient.

Further, the second invention is a metal polyimide substrate having a polyimide resin film having a thickness of 10 μm or less and having substantially no pinhole formed by the method of the first invention.

A third aspect of the present invention is an electronic component for mounting a semiconductor manufactured using the substrate of the second aspect of the present invention.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Metals that can be used in the substrate of the present invention are metals such as copper, nickel, cobalt and iron alone or alloys containing these metals as main components. Further, copper, a copper alloy, and an iron alloy are preferable in terms of price, versatility as an electronic material, and the like.

[0012] The cause of pinholes generated in the polyimide film formed by electrodeposition is that bubbles generated on the metal surface or the polyimide surface during electrodeposition are directly adsorbed on the electrodeposition surface, and new electrodeposition occurs on that portion. This is probably because the conductive polyimide did not deposit and became a pinhole.

In the first invention, after a polyimide film is once formed by an electrodeposition method, the formed polyimide film is subjected to an insulating process. The mechanism of electrodeposition of polyimide is such that a polymer aggregate having a charged functional group on its surface adheres to the electrode.Insulating treatment involves removing the solvent by heat treatment and dehydrating the electrode. It enhances the connectivity between the kimonos and renders them passive. The range of the heat treatment temperature cannot be unconditionally limited because it depends on the molecular structure of the polyimide, the concentration and structure of the charged functional group, the boiling point of the solvent used, and the like. Therefore, it is necessary to determine the optimum conditions in advance, but usually the range of 50 to 400 ° C. is preferable. When the temperature is lower than the appropriate temperature range, a sufficient insulating treatment is not performed and the conductivity is maintained. When re-electrodeposition for filling the pinhole is performed in such a state, the conductive polyimide is electrodeposited in portions other than the pinhole portion, and it is difficult to adjust the thickness of the polyimide film. If the temperature exceeds the appropriate temperature, deterioration of the polyimide due to heat and deformation of the substrate are likely to occur.

The heat treatment time depends on the heat treatment temperature and is not specifically limited, but is preferably 10 to 60 minutes in consideration of economy, productivity, reliability and the like. In addition,
In this heat treatment, in consideration of the removal of the solvent, for example, the temperature is increased stepwise, or treated at a relatively low temperature for a desired time,
Then, it may be divided into a plurality of heat treatment steps so as to perform treatment at a high temperature for a desired time.

In the present invention, after performing the above-mentioned insulating treatment,
The electrodeposition of polyimide is performed again. The purpose of this is to improve the insulation reliability of the polyimide film by selectively electrodepositing polyimide on a pinhole portion generated during the first film formation and burying the pinhole. That is,
Since the electrodepositable polyimide is electrodeposited again after the above-mentioned insulating treatment, the electrodepositable polyimide is selectively applied to the conductor surface portion exposed by the pinhole or the bottom of the concave portion of the relatively non-conductive surface. Electrodeposit.

In the present invention, in order to obtain a polyimide film having a predetermined thickness in a plurality of times, the condition of the insulating treatment is adjusted and the conductivity of the polyimide film is adjusted. Also in this case, since there is a difference in conductivity between the pinhole portion and the polyimide film surface, the preferential electrodeposition on the peahole portion is not hindered.

According to the method of the present invention described above, the second
It is possible to easily obtain a metal polyimide substrate having a polyimide resin film having a thickness of 10 μm or less and having substantially no pinholes. The use of the metal polyimide substrate of the present invention is most suitable for manufacturing a laminated wiring board and the like.

In the present invention, the term "substantially having no pinhole" means that the substrate has a line gap of 0.15 mm.
Means that the electrical insulation is 10 ¹² ohms or more when the wiring board is prepared and held at 120 ° C. and 98% RH for 1000 hours while applying a voltage of 24 VDC between the wires. If this condition is satisfied, it can be proved that no migration of metal occurs in addition to the pinhole.

The third aspect of the present invention relates to a semiconductor mounting electronic component manufactured using the substrate of the second aspect of the present invention.
Electronic components such as TAB tape, FPC board, BGA, CSP, etc. These electronic components can be easily manufactured by using a generally used known photolithography method or the like.

[0020]

Next, the present invention will be further described with reference to examples. (Example 1) Average molecular weight of 830 as electrodepositable polyimide
00, a block copolymerized polyimide containing a carboxyl group as an electrodeposition component (trade name, manufactured by P.I.
A copper foil having a thickness of 8 μm was immersed in a solution containing N-methyl-2-pyrrolidone containing 3% by weight of (cupilone) and water as main components, and a clad material of titanium and platinum was immersed as a cathode.

A voltage of 80 volts was applied between the two electrodes for 30 seconds to deposit a polyimide film on the copper foil surface. Thereafter, the anode was immersed in an aqueous solution containing 50% by volume of N-methyl-2-pyrrolidone at 25 ° C. for 1 minute, and then further placed in an aqueous solution containing 30% by volume of N-methyl-2-pyrrolidone at 25 ° C. for 1 minute. It was immersed and then washed with water to perform a fixing process.

The fixed anode is heated at 90 ° C. for 30 minutes to form an insulator, and then heated at 200 ° C. for 30 minutes to remove the solvent remaining on the polyimide film. The coating, fixing and heat treatment were performed to obtain a copper polyimide substrate having a polyimide film having a thickness of 5 μm.

Using the obtained copper-polyimide substrate, a wiring board having a line spacing of 0.15 mm was prepared by photolithography, and 120 V DC was applied between the lines while applying a voltage of 24 VDC.
The change in interline resistance was determined while maintaining the temperature at 98 ° C. and 98% RH for 1000 hours. As a result, the initial value was 6 × 10 ¹³ ohms, and was approximately 5 × 10 ¹² ohms after 100 hours.

(Embodiment 2) Using the wiring board obtained in Embodiment 1 as an anode, electrodepositable polyimide is electrodeposited on copper wiring in the same manner as in Embodiment 1, fixed, heat-treated, and treated with a polyimide resin. Covered the wiring section. In this way, the thickness of 5μm
A wiring board having a polyimide film was prepared. After keeping the obtained circuit wiring board in a chamber set at 120 ° C., 98% RH and 2 atm for 100 hours, an appearance inspection and an insulation test were performed. As a result, abnormalities such as discoloration were confirmed. It was found that the insulation reliability was sufficient.

Example 3 Passivation treatment was carried out at 50 ° C. for 60 hours.
A copper polyimide substrate was obtained in the same procedure as in Example 1 except that the heat treatment was performed for 5 minutes. Using the obtained copper polyimide substrate, a wiring board having a line width of 0.15 mm is prepared by a photolithographic method, and is kept at 120 ° C. and 98% RH for 1000 hours while applying a DC voltage of 24 volts between the lines. And the change in line resistance was determined. As a result, the initial value is 6 × 10 ¹³
Ohms, and was approximately 5 × 10 ¹² ohms after 100 hours.

Example 4 A wiring board having a 5 μm-thick polyimide film on the circuit surface was prepared in the same manner as in Examples 1 and 2, except that the copper polyimide substrate obtained in Example 3 was used. After keeping the obtained circuit wiring board in a chamber set at 120 ° C., 98% RH and 2 atm for 100 hours,
An appearance inspection and an insulation test were performed. As a result, no abnormality such as discoloration was confirmed, and it was found that the insulation had sufficient insulation reliability.

Example 5 Passivation treatment was carried out at 400 ° C. for 5 days.
A copper polyimide substrate was obtained in the same procedure as in Example 1 except that the heat treatment was performed for 5 minutes. Using the obtained copper polyimide substrate, a wiring board having a line width of 0.15 mm is prepared by a photolithographic method, and is kept at 120 ° C. and 98% RH for 1000 hours while applying a DC voltage of 24 volts between the lines. And the change in line resistance was determined. As a result, the initial value is 6 × 10 ¹³
Ohms, and was approximately 5 × 10 ¹² ohms after 100 hours.

Example 6 A wiring board having a 5 μm-thick polyimide film on the circuit surface was prepared in the same manner as in Examples 1 and 2, except that the copper polyimide substrate obtained in Example 5 was used. After keeping the obtained circuit wiring board in a chamber set at 120 ° C., 98% RH and 2 atm for 100 hours,
An appearance inspection and an insulation test were performed. As a result, no abnormality such as discoloration was confirmed, and it was found that the insulation had sufficient insulation reliability.

Example 7 A copper polyimide substrate was produced in the same manner as in Example 1 except that a voltage of 80 volts was applied between both electrodes for 90 seconds to deposit a polyimide film on the copper foil surface. When the thickness of the obtained polyimide film was measured, it was 10 μm on average, and it was a uniform film. Using the obtained copper polyimide substrate, a wiring board having a line interval of 0.15 mm is formed by photolithography, and a voltage of 24 VDC is applied between the lines at 1000C under a temperature of 120 ° C and 98% RH.
While maintaining the time, the change in line resistance was determined. as a result,
Good results were obtained as in Example 1.

Example 8 A copper polyimide substrate was manufactured in the same manner as in Example 1 except that a voltage of 80 volts was applied between both electrodes for 10 seconds to deposit a polyimide film on the copper foil surface. When the thickness of the obtained polyimide film was measured, it was 3 μm on average and was uniform. Using the obtained copper polyimide substrate, a wiring board having a line interval of 0.15 mm is formed by photolithography, and a voltage of 24 VDC is applied between the lines at 1000C under a temperature of 120 ° C and 98% RH.
While maintaining the time, the change in line resistance was determined. as a result,
Good results were obtained as in Example 1.

Comparative Example 1 A copper polyimide substrate was obtained in the same manner as in Example 1 except that the electrodeposition was not performed again after the first polyimide electrodeposition. Using the obtained copper polyimide substrate, a wiring board having a line width of 0.15 mm was prepared by photolithography, and a voltage of 24 VDC was applied between the lines at 120 ° C. and 98% RH.
After holding for 00 hours, a spot-like discolored portion was confirmed on a part of the circuit surface, and the resistance value after 100 hours was 10 minutes.
^It was much less than ¹² ohms and sufficient insulation reliability was not obtained.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the passivation treatment was carried out at 40 ° C. for 120 minutes and the electrodeposition was carried out again without any other heat treatment. A copper polyimide substrate was obtained by the procedure. When the copper polyimide substrate was inspected, the average thickness of the polyimide resin film was 7 μm on average, but there was a portion of 20 μm, which did not satisfy the dimensional accuracy. Therefore, this copper polyimide substrate was used as a substrate for electronic components. It turned out to be unusable.

Comparative Example 3 A copper polyimide substrate was obtained in the same manner as in Example 1, except that the passivation treatment was performed by heat treatment at 420 ° C. for 2 minutes. Since the obtained copper polyimide substrate was deformed by the heat treatment and did not satisfy the dimensional accuracy, it was found that it could not be used as an electronic component.

[0034]

As described above, according to the present invention, a polyimide film having sufficient insulation reliability can be formed by electrodeposition using a thin film which has been difficult in the past. It is possible to supply copper polyimide substrates for electronic components such as FPC, TAB, and CSP, which are high-density, excellent in quality, and inexpensive.

Claims (3)

[Claims] When a metal polyimide substrate is formed by electrodepositing an electrodepositable polyimide on a metal surface, the electrodepositable polyimide is electrodeposited on the metal surface so as to have a desired thickness. Insulation treatment, and then, a step of electrodepositing an electrodepositable polyimide on the polyimide resin film obtained by the insulation treatment is considered as one set, and at least one set of the steps is performed. A method for producing a metal polyimide substrate, wherein a film is obtained, wherein the insulating treatment is performed by heat-treating the polyimide resin film formed by electrodeposition at a temperature in the range of 50 to 400C. 2. A metal polyimide substrate having a polyimide resin film having a thickness of 10 μm or less and having substantially no pinholes produced by the method according to claim 1. 3. An electronic component for mounting a semiconductor, wherein the electronic component is manufactured using the metal polyimide substrate according to claim 2.