JP2932397B2 - Printed circuit board manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a printed circuit board, and more particularly to a method for manufacturing a flexible printed circuit board mainly used for a printed wiring board of an electric / electronic device or the like.

(Prior Art) Conventionally, in order to reduce the size and weight of electric and electronic devices and improve the reliability at high temperatures, a printed circuit board in which a copper foil is adhered on a substrate made of a polyimide film inside a control device of the device. Is used.

As a method for manufacturing such a printed board, a method has been used in which an epoxy-based adhesive or an acrylic-based adhesive is applied to a substrate made of a polyimide film, and then a copper foil is bonded to the substrate via the adhesive.

The printed circuit board thus prepared is subjected to a mounting step of connecting electric and electronic components to the printed circuit board by soldering or the like, and then used.

(Problems to be Solved by the Invention) However, the printed circuit board obtained by the above method has a temperature of 250 ° C. during a mounting step by connecting electric and electronic components.
Although the heat resistance required to withstand the above high temperature is required, the adhesive does not provide sufficient heat resistance, and as a result, there is a problem that the peel strength between the substrate and the copper foil is extremely low.

Therefore, an attempt was made to form a copper film by directly depositing a copper material on a substrate by an evaporation method without using an adhesive, but the peeling strength between the substrate and the copper film at a high temperature was determined by using the adhesive. It is as small as 60 to 70% as compared with the case where it is used, and there is a problem that it cannot withstand high temperatures in a mounting process for connecting electric and electronic components.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing a printed circuit board that can withstand high temperatures during a mounting process and that has excellent peeling strength.

(Means for Solving the Problems) In a method for manufacturing a printed board according to the present invention, a polyamic acid thin film is formed by depositing and polymerizing a raw material monomer of polyimide on a substrate made of a polyimide film, and then a vapor deposition method is performed on the thin film. Alternatively, after forming a copper film by a sputtering method, the polyamic acid thin film is subjected to an imidization treatment by heating.

Thickness of polyamic acid deposited and polymerized on the substrate is 1000
Å It is preferable to set the following. When the film thickness is over 1000Å deposited and polymerized on the substrate, when it is heated to imidize the polyamic acid, the generated water causes blistering and the peel strength between the substrate and the copper film is reduced. This is because

(Operation) The raw material monomer of the polyimide evaporates, and the evaporated monomer is vapor-deposited and polymerized on the substrate to form a precursor polyamic acid thin film. The copper material forms a copper film on the substrate via the polyamic acid thin film by a vapor deposition method or a sputtering method. Further, the polyamic acid thin film between the substrate and the copper film is heated to be imidized to form a polyimide adhesive layer. When this polyamic acid thin film is imidized, a chemical bond is formed at the interface with copper.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an example of an apparatus for carrying out the method of the present invention, in which a copper film is formed by an evaporation method.

In the drawing, reference numeral 1 denotes a vacuum processing chamber. The inside of the vacuum processing chamber 1 is connected to an external vacuum pump or other vacuum evacuation system 2, and a delivery roller 3 and a take-up roller 4 are arranged above the vacuum processing chamber 1. A long substrate 5 on which a polyamic acid thin film and a copper film were to be formed was stretched, and the substrate 5 could be moved from the delivery roller 3 side to the winding roller 4 side (in the direction of arrow X).

Further, steel evaporation sources 6, 6 having nickel plating on the inner wall thereof for evaporating the raw materials A and B of polyamic acid at a position in the vacuum processing chamber 1 where the substrate 5 passes, A raw material monomer evaporator 8 having heaters 7 and 7 for heating the raw material monomer therein;
A copper evaporator 11 having an evaporation source 10 for evaporating with the electron beam EB was disposed.

Further, a pattern forming apparatus 15 having a copper film pattern mask 14 movable by a pair of rollers 12 and 13 is disposed above the copper evaporator 11 and close to the front surface of the substrate 5.

Further, in the vacuum processing chamber 1, a heating device 17 including a heater 16 which is a polyimide obtained by imidizing and polymerizing a polyamic acid deposited on the substrate 5 and disposed at a position where the substrate 5 passes is disposed.

In the figure, 18 is a drum for forming a polyamic acid thin film on the substrate 5, 19 is a drum for forming a copper film on the polyamic acid thin film, 20 is a shutter disposed above both evaporation sources 6, 6, 21
Denotes a partition plate provided between the evaporation sources 6, 6, 22 denotes a shutter disposed above the evaporation source 10, and 23 denotes a roller for stabilizing the movement of the substrate 5.

Next, a specific embodiment of a method of manufacturing a printed circuit board using the above-described apparatus will be described.

First, a polyimide film (manufactured by DuPont, trade name: KAPTON) having a thickness of 25 μm, a width of 250 mm, and a length of 600 m was vacuumed for 10 minutes.
A long substrate 5 was prepared by performing a heat treatment at 0 ° C. and degassing.

Next, the long substrate 5 is attached to the delivery roller 3 and the take-up roller 4 in the vacuum processing chamber 1, respectively.
4 and the substrate 5 is driven by a motor (not shown) from the delivery roller 3 side to each of the drums 18, 19 and each roller 23.
And then to the take-up roller 4 side.

Subsequently, pyromellitic dianhydride as the raw material monomer A, diaminopropyltetramethyldisiloxane as the raw material monomer B on one of the evaporation sources 6, 6 of the raw material monomer evaporator 8, and the evaporation source of the copper evaporator 11 10 is filled with copper material having a purity of 99.9% as a raw material C for a copper film, and then the shutters 20 and 22 of the evaporators 8 and 11 are closed. To 1 × 10 ^-5 Torr.

Next, pyromellitic dianhydride was heated to 180 ± 1 ° C. by heaters 7 and 7 while measuring both evaporation of the raw material monomers A and B from the evaporation sources 6 and 6 with an evaporation monitor (not shown). Diaminopropyltetramethyldisiloxane at a temperature of 45
The material C was heated to ± 1 ° C. and the electron beam EB generated by the electron gun 9, respectively.

Next, when the raw material monomers A and B reach a predetermined temperature and a required amount of evaporation is obtained, the shutter 20 is opened, and the raw material is placed on the substrate 5 moving from the feed roller 3 to the winding roller 4 at a moving speed of 10 / min. Monomers A and B were vapor-deposited and polymerized at a deposition rate of 100 ° / min to continuously form a 300 ° -thick polyamic acid thin film P as a precursor. The degree of vacuum during the vapor deposition and polymerization was 5 × 10 ⁻⁵ Torr.

Subsequently, the substrate 5 is moved from the polyamic acid evaporator 8 at the above-mentioned speed, and when reaching the copper evaporator 11, the shutter 22 is opened, and the substrate 5 is continuously moved on the moving substrate 5 through the mask 14 of the pattern forming device 15. By vapor deposition, a copper film F having a pattern of a desired shape having a thickness of 0.5 μm was formed via the polyamic acid thin film P. The degree of vacuum during the deposition was 1 × 10 ⁻⁶ Torr.

Next, the substrate 5 on which the polyamic acid thin film P and the copper film F are formed
Moves from the copper evaporator 11 at the above speed, and the heating device 17
While passing through the inside, the temperature of the polyamic acid thin film P is
The adhesive layer S made of polyimide was continuously formed by imidization sequentially while performing heat treatment at 0 ± 10 ° C. The degree of vacuum during the heating was 1 × 10 ⁻⁵ rr.

Then, as shown in FIG. 2, a printed circuit board 24 integrally formed with a copper film F on a substrate 5 via an adhesive layer S made of polyimide was wound around the winding roller 4 in a long continuous manner.

The room temperature of the printed circuit board 24 (25
° C), the peel strength between the substrate 5 and the copper film F at the respective temperatures of 150 ° C and 250 ° C was examined, and the results shown in the table were obtained.

The peel strength at each temperature was determined by a tensile test.

For comparison with the above embodiment, the thickness of the comparative example 1 was 25 mm.
After applying an acrylic adhesive on a μm polyimide film, a 10 μm-thick copper foil is adhered to form a printed circuit board. The printed circuit board has a room temperature (25 ° C.), a temperature of 150 ° C.,
The peel strength between the substrate and the copper foil at each temperature of 250 ° C. was examined by the same method as in the above-mentioned example, and the results are shown in the table.

Further, as Comparative Example 2, a 0.5 μm-thick copper film was directly deposited on a 25 μm-thick polyimide film by an evaporation method to prepare a printed circuit board, and the room temperature (25 ° C.)
° C), the peel strength of the substrate and the copper film at each of the temperatures of 150 ° C and 250 ° C were examined by the same method as in the above-mentioned Example, and the results are shown.

As is clear from the table, the printed circuit board prepared by the method of the present invention has a temperature of 150 ° C.
It was observed that the peel strength was significantly improved at a high temperature of ° C.

Further, when the polyimide adhesive layer after peeling the copper film from the substrate of the example of the present invention was examined, no blister was observed.

The formation of the copper film in the present invention is not limited to the vapor deposition, and the copper film may be formed on the polyamic acid thin film by an ion plating method or a sputtering method.

If a pattern forming apparatus 15 having a mask 14 having a copper film pattern shape is disposed above the copper evaporating apparatus 11 and immediately before the substrate as in the illustrated apparatus, the copper film F is formed on the substrate 5. Since a desired pattern shape can be deposited, a subsequent etching step (circuit forming step) is not required, and not only productivity is improved, but also a printed circuit board having the same or different pattern shape can be continuously and easily formed. Can be manufactured.

In the illustrated apparatus, the raw material monomer evaporator 8, the copper evaporator 11, and the heating device 17 are arranged in one vacuum processing chamber, but the raw material monomer evaporator 8, the copper evaporator 11, the heating device 17 may be provided separately, and a vacuum exhaust system may be provided for each apparatus. Alternatively, for example, the raw material monomer evaporator 8 and the copper evaporator 11 may be disposed in one vacuum processing chamber, and the remaining heating apparatus may be provided. 17 may be arranged in a separate vacuum processing chamber. In this way, the degree of vacuum in each device can be set arbitrarily, and it is not necessary to adjust the degree of vacuum in each process. The heat imidization into an acid thin film can be continuously and rapidly performed.

(Effect of the Invention) As described above, according to the present invention, when the polyamic acid thin film formed between the substrate and the copper film is imidized, a chemical bond occurs at the interface with copper, and the substrate and the copper film are formed. Since a polyimide adhesive layer with excellent heat resistance and adhesiveness is formed between
This has the effect that a printed circuit board with improved peel strength at high temperatures can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a sectional view of an essential part of an example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a sectional view of a printed circuit board produced by the method of the present invention. 5 ... substrate 24 ... printed circuit board A, B ... polyimide raw material monomer C ... copper material F ... copper film P ... polyamide acid thin film S ... polyimide adhesive layer

Claims (1)

(57) [Claims] 1. A polyamic acid thin film is formed by depositing and polymerizing a raw material monomer of polyimide on a substrate made of a polyimide film, and then a copper film is formed on the thin film by an evaporation method or a sputtering method, and then heated. A method for producing a printed circuit board, comprising imidizing a polyamic acid thin film.