JPS61185446A - Laminated film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to adhesive technology for laminating copper-clad printed circuits for sheet coils for flat motors, for example, and particularly for bonding technology that has high heat resistance and high lamination density. The present invention relates to a laminated film that can be used in thin, high-density laminations to achieve excellent adhesive performance and insulation performance.

<Prior art and its problems> For example, when laminating copper-clad printed circuits for sheet coils for flat motors, one conventional method is to impregnate glass fiber with thermosetting resin or thermoplastic resin. They are bonded using prepared prepreg to ensure lamination of one circuit and insulation.

This method is a common method for laminating ordinary printed circuits, but since the density of the lamination is limited by the thickness of the prepreg, it is not suitable for high-density lamination. In order to achieve high-density lamination, a laminated film is used in which a thermosetting adhesive diluted with a solvent is applied to both sides (one side) of polyimide for insulation, and the solvent is volatilized.

Although this method allows use of a complete set of laminating equipment and uses a solvent, (1) the traces of the solvent become minute irregularities and the thickness becomes non-uniform.

(2) Residual solvent causes foaming during heat curing.

(3) Adhesion failure is likely to occur due to residual solvent.

(Electrocorrosion is likely to occur due to gases sorbed by residual solvent.

There were some drawbacks.

In addition, some attempts have been made to bond adhesives that harden at room temperature by applying adhesives, but these have no storage stability at all and workability is poor, and the adhesive strength under heat is extremely poor. It has some disadvantages, such as being inferior, so it is hard to call it an excellent technology.

OBJECT OF THE INVENTION The present invention aims to provide a volatile-free laminated film to be produced in a completely solvent-free process, thereby eliminating the numerous disadvantages caused by residual solvents, especially for high-density The present invention aims to provide a laminated film that can be used as a heat-resistant laminated film for copper-clad printed circuits.

<Structure of the Invention> The present invention provides a laminated film in which a layer of a thermosetting solvent-free adhesive having a softening point of 30 to 100°C is provided on one or both sides of a polyimide film.

The laminated film of the present invention will be explained in more detail below.

In the loading film of the present invention, a polyimide film is used as the base material. Examples of currently widely available products include Kapton ■ (Outont) and Upilex ■.
(Ube Industries), but other polyimide films with slightly different molecular designs that have imide groups in the molecule are being commercialized. Polyimide is a material with high heat resistance, excellent mechanical and electrical properties, and is also highly moisture resistant, so it is gradually being used in electronic components that are used in harsher environments, where polyester films have traditionally been used. It is being replaced. However, due to its high price, polyester is currently used in cheap products.

The thickness of the base material can range from several microns to several hundred microns, but in consideration of both film strength and lamination density, a base material of 10 to 20 microns is preferably used. Polyimide film is not difficult to adhere to, unlike polyester film, and has high strength, so it is easy to process. However, in cases where the adhesive strength is somewhat weak, effective adhesion can be expected by performing plasma treatment.

Solvent-free adhesives mean, of course, that no solvent is mixed during manufacturing, but they also have zero volatile content.
．． It is also required that the content be 5 wt% or less. Therefore, especially when adding a low molecular weight non-reactive material for any purpose, care must be taken regarding the boiling point of the material.

Thermosetting adhesive refers to a material in which a chemical reaction is promoted by heat, and monomers and prepolymers connect with each other to form a three-dimensional network structure and solidify, firmly bonding adherends. Examples include epoxy adhesives.

It is preferable that the coating method be carried out using a specially prepared device, without using a normal laminating device. It can be implemented if This method is an example of a specific coating method, and it goes without saying that other coating methods may be used.

Table 1: Coating method As mentioned above, there are epoxy adhesives, acrylic adhesives, etc., and these will be explained in detail.

L Hiroto Etara 11 Preferably used is an epoxy resin that is solid at room temperature or a mixture of epoxy resin that is liquid at room temperature, with a scorbability imparting agent, filler, etc. added if necessary, and a latent curing agent. be done. The coating process is carried out at 80 to 100°C, and the viscosity at this time is less than a few thousand voids, even if polyimide surface treatment and adhesion promoters and coupling agents are added to improve sheet formation using a comma coater. good.

Acrylic monomers and acrylic oligomers, mixed with acrylic rubber if necessary, and mixed with peroxide or the like as a catalyst are used. The process is similar to that used for epoxy adhesives, including adding fillers and anti-sagging agents for flow control.

It is best to use adhesives such as those mentioned above that have a softening point of 30 to 100°C as measured by the Ba1l & Ring method.
This is because the adhesive is highly sticky and hinders work, and when the temperature exceeds 100°C, the viscosity immediately before curing is too high and the adhesive layer becomes thick.

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples.

(Example-1) Table-2 Adhesive formulation (softening point: 40°C) Using the coating equipment shown in Figure 1, the adhesive listed in Table-2 was released by heating with 80°C hot water. 401 on the pattern
L, 80%, 120. It was applied to a thickness of . A polyimide film (25JL) was bonded thereon and wound up to create a single-sided coated film.

Further, on the polyimide side of the single-sided coated film rolled up together with the release paper, adhesive was applied to the desired thickness in the same manner as before, and the film was rolled up to create a double-sided coated film.

Using a film coated with 601L adhesive on both sides, two sheets of rolled copper foil with a thickness of 40IL were pasted together for 18 hours.
Pressing was performed at 0°C for 3 minutes.

In this way, a bonded copper foil with a total thickness of 120% was obtained. Note that the excess adhesive is flowing out from the sides. Since the adhesive thickness is 40JL including the polyimide thickness of 25L, it can be regarded as an adhesive layer of 7.5JL on each side.

This bonded copper foil was cut into a 1c layer width and subjected to a T-peel test, and the results shown in Table 3 were obtained.

Table-3 Peeling test (Example-1) Note) Tensile speed 50+m/5in (Comparative example-1) The adhesive shown in Table-2 was solvent-free and was used in Example-1. Melt this adhesive with MEK and add 70% 5ol
Got the id dope. This dope is a condensed milk-like liquid and can be applied to polyimide film at room temperature.

This dope was coated on the same polyimide film as used in Example 1 using a spatula, and dried in an oven at 100° C. for 20 minutes to obtain a double-sided coated copper-clad laminate-like laminate film. This was done again according to the same procedure as in Example-1.
Laminated 0JL thick rolled copper foil, total thickness 120
Table 4 shows the results of the T-peel test of Comparative Example 1, in which a laminated copper foil of L was obtained.

Table 4 Peel Test (Comparative Example-1) The peel strength is about 50% lower on average than in Example-1 over the entire temperature range measured. This is only because a solvent was used.

(Comparative Example-2) The same dope as in Comparative Example-1 was applied to a polyimide film, the drying time was shortened, and the drying temperature was increased instead. After drying in an oven at 100° C. for 10 minutes, the same measurements as in Example-1 and Comparative Example-1 were performed. Regarding drying time, the production of such laminated films is usually done on a line, and the film flows along the line, but the line length required for each process depends on the speed of the line. This means that it is the product of the time required for the process. Temporarily increase the line speed to 2~3m
/min is 40 to 6 for the drying conditions of Comparative Example-1.
A drying zone of 0 m is required. Comparative example-2 is the point 2
It has the advantage that it only takes 0 to 30 m. In Example-1, a drying zone is completely unnecessary.

Table 5 shows the results of the T-peel test for Comparative Example 2. Table-5 Peeling test (Comparative example-2) It can be seen that the strength is even lower than that of Comparative Example-1.

In Comparative Example-2, a foaming phenomenon that was not observed in Example-1 or Comparative Example-1 appears. I think it is clear that this is one of the direct causes of the decrease in adhesive strength (peel strength) and is a result of the use of a solvent.

(Example-2) Table-6 Adhesive formulation An acrylic adhesive composition consisting of the formulation shown in Table-6 with a softening point of 43°C was molded into a laminated film in the same manner as in Example-1, and in the same manner as the others. A T-type peel test was conducted on the laminated copper foil, and the test results are shown in Table 0-7.

In this case, a 40-grade electrolytic copper foil was used as the copper foil.

Table 7 Peeling test (Example 2) (Comparative example 3) A dope with a solid content of 80% was prepared by dissolving the composition shown in Table 6 in Doolol, and the same procedure as in Example 2 was made. A laminated film was made using the method described above, and a T-peel test was conducted on the laminated copper foil in the same manner as the others.Table 8 shows the test results.

Note that the same copper foil as in Example 2 was used.

Table 8 Peel test (Comparative example 3) As can be seen from the results in Table 8, the adhesive strength was significantly lower than that of the same adhesive without solvent (listed in Table 7, Example 2). There is. In particular, the degree of decrease is remarkable at temperatures above 150°C, and when visually observing the condition of the adhesive surface, it was observed that many random air bubbles were generated, suggesting that the residual solvent may have vaporized during the curing process, and this may be the cause. It is inferred.

(Comparative Example 4) The same adhesive dope as in Comparative Example 3 was used, but only the drying conditions were changed to 100°C for 40 minutes to ensure sufficient drying of the solvent. The laminated film obtained in this way is free of solvent, but at the same time, the 7-cryl monomer volatilizes violently and curing has not progressed sufficiently. Peeling at 150°C and 180°C is close to natural peeling, and at lower temperatures 200～
Although the peeling force is 400g/am, it is close to adhesive, and the adhesive layer is also thick
01L or higher) It is impossible to compare the data with each other (it is a well-known fact that the thicker the adhesive layer, the stronger the peeling will be)
.

<Effects of the Invention> As explained above, the laminated film for copper foil printed circuits, etc. according to the present invention can not only be manufactured with a simple device that does not require a solvent drying zone or a solvent recovery device, but also can be manufactured using conventional solvent-based adhesives. It has the advantage of eliminating drawbacks such as foaming and poor adhesion (deterioration) that occur when adhesives are applied.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus for producing the laminated film of the present invention. Explanation of symbols. l・-111 pattern paper, 2...Heat roll%3...
Comma coater, 4... Lamination roll, 5... Heat roll, 6... Winding roll 1.7...φ tension roll, 8... Polyimide film

Claims (1)

[Claims] Softening point 30~ on one or both sides of polyimide film
A laminated film with a layer of thermosetting solvent-free adhesive at 100°C.