JP4801750B2 - Flexible metal laminate with stable dimensional change rate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a flexible metal laminate, and more particularly, a flexible metal laminate that is a main material of a flexible circuit board used in large-sized LCDs such as notebook computers, monitors, and televisions, and small electronic devices such as mobile phones and PDAs. About.

  In general, a printed circuit board (PCB) is a printed circuit board that connects or supports various components according to a circuit design of electrical wiring, and is often compared to a neural circuit of an electronic product. With the remarkable growth of electronic devices such as notebook personal computers, mobile phones, PDAs, small video cameras, and electronic notebooks, the importance of printed circuit boards in high integration and miniaturization of products is increasing.

  The printed circuit board is similar to a rigid printed circuit board, a flexible printed circuit board, a rigid-flexible printed circuit board in which the two are combined, and a rigid-flexible printed circuit board, depending on its physical characteristics. Divided into multi-flexible printed circuit boards.

  Among them, soft metal laminates, which are the raw materials for flexible circuit boards, are used in digital home appliances such as mobile phones, digital camcorders, notebook computers, LCD monitors, etc. In recent years, demand has increased rapidly due to the characteristic of being.

  However, conventional soft metal laminates use a polymer film as a substrate for forming a circuit. However, the difference between the strength of the polymer film, the thermal expansion coefficient, etc., and the strength of the metal layer forming the circuit, the thermal expansion coefficient, etc. As a result, stress is present in the interior, and this leads to a problem that a dimensional change occurs when the metal layer that forcibly restrains the polymer film is removed after the pattern is formed.

  Thus, if the rate of dimensional change after pattern formation increases, when mounting a semiconductor chip on a circuit or connecting an LCD panel and a PCB substrate, as shown in FIG. There may be a case where the metal layer is shifted (S). This may cause a problem that the wiring is disconnected, and if the deviation of the change rate is large other than the center value of the dimensional change rate, there may be a problem that stable wiring and connection may not be possible.

  The present invention was devised to solve the above-mentioned problems, and it has excellent characteristics of low dimensional change even after pattern formation by adjusting the components of the metal layer and the physical properties of the structure and the polymer film. An object is to provide a flexible metal laminate.

  Other objects and advantages of the present invention will be described later and will be understood through embodiments of the present invention. The objects and advantages of the invention may also be realized by means and combinations set forth in the appended claims.

  According to another aspect of the present invention, there is provided a flexible metal laminate including a polymer film, a tie coat layer, a metal seed layer, and a metal conductive layer. The total content of impurities contained in the conductive layer is 0.03% or less, the volume fraction of the main orientation component of the texture of the metal conductive layer is 50% or more, and the macro crystal grains of the metal conductive layer The ratio is 10% or less.

  The modulus of the polymer film is 5.0 to 10.5 GPa, the coefficient of thermal expansion (CTE) is 11 to 18 um / m ° C, and the coefficient of moisture expansion (CHE) is 5.5 to 9.5 ppm. It is desirable.

  The tie coat layer may be made of nickel (Ni), chromium (Cr), or an alloy thereof, the metal seed layer and the metal conductive layer may be made of copper or a copper alloy, and the polymer film may be made of polyimide. desirable.

  Further, the flexible metal laminate preferably has a dimensional change rate of 0.05% or less after pattern formation and a deviation of the dimensional change rate of 0.02% point or less.

  According to another aspect of the present invention, as a method for producing a flexible metal laminate used for a flexible circuit board, (a) preparing a polymer film, (b) forming a tie coat layer on the polymer film (C) forming a metal seed layer on the polymer film on which the tie coat layer is formed; and (d) forming a total impurity content of 0. 0 on the metal seed layer by electroplating. The manufacturing method of a soft metal laminated board including the step of forming a metal conductive layer having a volume fraction of a main orientation component of a texture of 50% or more and a ratio of macro crystal grains of 10% or less. Is provided.

  Preferably, in the step (a), the modulus is 5.0 to 10.5 GPa, the coefficient of thermal expansion (CTE) is 11 to 18 um / m ° C, and the coefficient of moisture expansion (CHE) is 5.5 to 5.5. A polymer film having a property of 9.5 ppm is prepared.

  According to the present invention, the polymer film with controlled physical properties and the impurity content, texture, and crystal grain ratio of the metal layer formed on the polymer film are controlled to stabilize the low rate of dimensional change even after pattern formation. A soft metal laminate can be provided.

The following drawings attached to the specification illustrate preferred embodiments of the present invention, and together with the detailed description, serve to further understand the technical idea of the present invention. It should not be construed as being limited to the matters described in the drawings.
It is the figure which showed the state of the connection failure by the dimensional change which arises in the soft circuit using the conventional soft metal laminated board. It is the schematic which showed the cross section of the soft metal laminated board by one Example of this invention. It is the flowchart which showed schematically the process of manufacturing the soft metal laminated sheet by one Example of this invention.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and claims should not be construed to be limited to ordinary or lexicographic meanings, and the inventor himself should explain the invention in the best possible manner. It must be interpreted with the meaning and concept corresponding to the technical idea of the present invention in accordance with the principle that the term concept can be appropriately defined. Therefore, the configuration described in the embodiments and drawings described in this specification is only the most preferable embodiment of the present invention, and does not represent all of the technical idea of the present invention. It should be understood that there are various equivalents and variations that can be substituted at the time of filing.

  FIG. 2 is a schematic view showing a cross section of a soft metal laminate according to an embodiment of the present invention.

  Referring to FIG. 2, the flexible metal laminate according to the present invention includes a tie coat layer 110 made of a different metal on a polymer film 100, a metal seed layer 120 deposited on the tie coat layer 110, and the metal seed. A metal conductive layer 130 electrodeposited on layer 120 is included.

  The polymer film 100 is made of a polyimide film having flexibility so as to be compatible with a soft metal laminate. Polyimide films are often used as materials for flexible films because they have high heat resistance and flexibility, excellent mechanical strength, and the same thermal expansion coefficient as metal. Here, the polymer film 100 is formed to have excellent physical properties. That is, the polymer film 100 has a modulus characteristic of 5.0 to 10.5 GPa, a thermal expansion coefficient (CTE) of 11 to 18 um / m ° C, and a moisture expansion coefficient (CHE). 5.5 to 9.5 ppm. It will be described later that the polymer film 100 satisfying such conditions has excellent physical properties. In particular, these conditions are due to the physical properties of the dimensional change rate and change rate deviation after forming a pattern on the metal layer to be described later for the production of a flexible circuit board and removing the metal layer along the pattern. This is to reduce the size.

  The tie coat layer 110 is formed on the surface of the polymer film 100 by a vacuum film formation method. The tie coat layer 110 is interposed between the polymer film 100 and the metal seed layer 120 deposited on the tie coat layer 110, and plays a role of strengthening the bonding force between both layers and serving as a barrier. Therefore, it is possible to prevent the metal seed layer 120 from being peeled from the polymer film 100 even when the soft metal laminate is subjected to a high temperature treatment.

  It is desirable to adjust the thickness of the tie coat layer 110 within a range in which the tie coat layer 110 is not peeled off by penetration of the plating solution after the high temperature treatment or at the time of circuit formation. In addition, the tie coat layer 110 is interposed between the polymer film 100 and the metal seed layer 120 and is used for enhancing the bond between the two layers, and therefore need not be so thick. Desirably, the thickness of the tie coat layer 110 is 50 to 300 mm. When the thickness of the tie coat layer 110 is too thin, the tie coat layer 110 is weak at high temperatures and has poor corrosion resistance, and may be peeled off by permeation of the plating solution after the high temperature treatment or circuit formation.

  As a material of the tie coat layer 110, a metal having good binding force and reactivity with other substances, for example, chromium, nickel, or an alloy of chromium and nickel is desirable.

  The metal seed layer 120 may be formed on the tie coat layer 110 by various vacuum deposition methods including sputtering. Preferably, the metal seed layer 120 is copper (Cu) or a copper alloy. And the thickness is adjusted so as to have a certain range or more of adhesive strength with the metal conductive layer 130 described later. Desirably, the thickness of the metal seed layer 120 is 500 mm or more.

  The metal conductive layer 130 is formed on the metal seed layer 120 by electrolytic plating. That is, after forming the metal seed layer 120 by vacuum deposition, the metal seed layer 120 is immersed in a plating solution so that the metal conductive layer 130 can be electrodeposited on the metal seed layer 120 by an electrochemical reaction. Preferably, the metal conductive layer 130 is a copper or copper alloy layer.

  The metal conductive layer having electrical conductivity is formed so as to have a structure and components having excellent physical properties. That is, the total content of carbon (C) and sulfur (S), which are impurities contained in the metal conductive layer, is 0.03% or less, and the volume fraction of the main orientation component of the texture of the metal conductive layer is 50%. As described above, the ratio of the macro crystal grains of the metal conductive layer is set to 10% or less. It will be described later that the metal conductive layer 130 having such conditions has excellent physical properties. Similar to the description in the polymer film 100, such conditions are used to reduce the dimensional change rate and change rate deviation after the metal layer is removed by patterning for the production of a flexible circuit board. It is.

  On the other hand, the texture refers to one aggregate composed of a large number of crystal grains having the same crystal orientation in a polycrystalline material. For example, a texture in a crystal orientation plane refers to a texture in which materials are regularly arranged with a specific direction (perpendicular to the plane) as an axis. A metal sheet having two or more textures exhibits important properties in physical properties.

  Desirably, when the dimensional change rate after the metal layer is removed after pattern formation is 0.05% or less and the deviation of the dimensional change rate is 0.02% point or less, stable wiring and connection are possible. It is.

  Next, the manufacturing method of the soft metal laminated board by this invention is demonstrated concretely.

  FIG. 3 is a flowchart schematically showing a process of manufacturing a soft metal laminate according to an embodiment of the present invention.

  Referring to FIG. 3, first, a polymer film 100 is prepared (step S10), and a tie coat layer 110 made of a dissimilar metal is formed by a vacuum film forming method such as a sputtering method, a vacuum evaporation method, or an ion plating method. (Step S20).

  Specifically, the polymer film 100 has a modulus characteristic of 5.0 to 10.5 GPa, a thermal expansion coefficient (CTE) of 11 to 18 um / m ° C, and a moisture-containing expansion coefficient (CHE) of 5.5 to 9.5. Prepare to form 5 ppm. The polymer film thus prepared is carried into a chamber in which a vacuum is maintained, and a gas such as argon, oxygen, nitrogen, or a mixed gas thereof is injected, and dry pretreatment with plasma is performed, so that the surface of the polymer film is obtained. To reform. Next, the vacuum in the chamber is maintained and a tie coat is applied on the polymer film 100 by various vacuum film forming methods including sputtering from a metal target (a nickel-chromium alloy element metal target) in an inert gas atmosphere such as argon. Layer 110 is formed.

  Next, a metal seed layer 120 made of copper or a copper alloy is formed on the tie coat layer 110 (step S30). The metal seed layer 120 maintains the degree of vacuum in the chamber, and the metal seed layer 120 is formed on the tie coat layer 110 by sputtering from a copper or copper alloy target in an inert gas atmosphere such as argon.

  Next, the metal conductive layer 130 is formed on the metal seed layer 120 (step S40). The metal conductive layer 130 uses an electrolytic plating method using a plating solution. When the metal conductive layer 130 is formed by electrolytic plating, the components, crystal grains, and texture of the metal conductive layer 130 are adjusted according to many variables described below.

  When the tie coat layer 110 and the metal seed layer 120 are laminated on the polymer film 100, the conditions for the pre-modification of the polymer film, that is, the type of gas, the mixing ratio, the power, the pre-treatment method, The pressure, the distance between the polymer film and the metal target, the lamination speed, and the temperature of the polymer film are changed. When the metal conductive layer 130 is plated, the temperature of the plating solution, the composition of the plating solution, and the current density during electrolytic plating are changed. The size of the crystal grains of the tie coat layer 110 and the metal seed layer 120 formed thereby, the surface state, the temperature of the plating solution, the composition of the plating solution, the current density during electrolytic plating, and the like constitute the metal conductive layer 130. Change the organization. As a result, the content of the impurity component in the metal conductive layer, the ratio of the macro crystal grains, and the volume fraction of the main orientation component of the texture are determined.

  Alternatively, a separate magnet may be prepared outside the plating tank containing the plating solution containing metal ions to be plated, and the texture of the metal conductive layer 130 may be changed by applying a magnetic field from the magnet.

  On the other hand, the present invention will be described in more detail by explaining more specific experimental examples of the present invention. However, the present invention is not limited to the following experimental examples, and it is needless to say that various embodiments can be implemented within the scope of the appended claims.

  In this experimental example, a sample is prepared by sequentially forming a tie coat layer, a metal seed layer, and a metal conductive layer on a polymer film. At this time, a large number of samples in which the physical properties of the polymer film, the components of the metal layer, and the structure are changed are prepared. The dimensional change rate after pattern formation of the sample prepared in this way and its deviation are each tested.

  Tables 1 and 2 below show the total impurity content of the metal conductive layer (Cu layer), the volume fraction of the main orientation component, the ratio of macro crystal grains, the modulus of the polymer film, the thermal expansion coefficient, the moisture expansion coefficient, etc. It is the table | surface which showed the Example and comparative example of experiment which measured the dimensional change rate after pattern formation, and its deviation using the sample formed by changing a factor.

  With reference to Table 1 and Table 2, the evaluation result value by the factor of each item is demonstrated with respect to experiment of an Example and a comparative example.

  First, as shown in Table 1, in the examples according to the present invention, the total content of impurities (C and S) of the metal conductive layer (Cu layer) is 0.03% or less, and the main orientation of the texture A sample having a volume fraction of components of 50% or more and a macro crystal grain ratio of 10% or less was used. The modulus property of the polymer film is in the range of 5.0 to 10.5 GPa, the coefficient of thermal expansion (CTE) is in the range of 11 to 18 um / m ° C, and the moisture expansion coefficient (CHE) is 5.5 to 9 Samples in the .5 ppm range were used.

  As a result of measuring a dimensional change rate and a dimensional change rate deviation after pattern formation using a sample of a soft metal laminate formed so as to satisfy such conditions, as shown in Table 1, the dimensional change rate was 0. The value was measured as a value of 05% or less, and the dimensional change rate deviation was also measured as a value of 0.02% point or less.

  Next, as shown in Table 2, in the comparative example, when a sample in which the total impurity content of the metal conductive layer was 0.03% or more was used, the dimensional change rate after pattern formation was measured. Was 0.056% to 0.063%, which was a value exceeding 0.05% which is the reference value of the present invention. Moreover, when the sample whose volume fraction of the main azimuth | direction component of the texture of a metal conductive layer is 50% or less was used, the result of having measured the dimensional change rate is 0.058%-0.071%, The value exceeded the 0.05% which is the reference value of the present invention. Further, when a sample in which the proportion of macro crystal grains in the metal conductive layer is 10% or more is used, the dimensional change rate is 0.056% to 0.074%, which is also the reference value of the present invention. The value exceeded 0.05%.

  Further, when a sample having a modulus characteristic of the polymer film of 5.0 GPa or less was used, the dimensional change rate was 0.059%, which exceeded the reference value of the present invention, and a sample of 10.5 GPa or more was used. In this case, the dimensional change rate was 0.057% to 0.062%, which exceeded the reference value of the present invention. When a sample having a thermal expansion coefficient (CTE) of the polymer film of 18 um / m ° C or more is used, the dimensional change rate is 0.077% to 0.081%, which exceeds the standard value of the present invention. Even when a sample of 11 um / m ° C. or less was used, the dimensional change rate was 0.056% to 0.061%, which exceeded the reference value of the present invention. Further, even when a sample having a moisture expansion coefficient (CHE) of the polymer film of 11 ppm or more is used, the dimensional change rate is 0.061% to 0.065%, which is also the criterion of the present invention. The result is exceeding the value.

  Thus, under the conditions in the comparative example, the dimensional change rate after pattern formation cannot satisfy 0.05% or less, which is the reference value of the present invention, and the dimensional change rate deviation is also the reference value of the present invention. Examples that could not satisfy 0.02 percentage points or less continued.

  Therefore, when the results of the experimental examples described above are combined, the polymer film has a modulus characteristic in the range of 5.0 to 10.5 GPa, and the coefficient of thermal expansion (CTE) is in the range of 11 to 18 um / m ° C. The expansion coefficient (CHE) is preferably formed so as to satisfy the 5.5 to 9.5 ppm range. The metal conductive layer has a total content of impurities (C and S) contained therein of 0.03% or less, a volume fraction of the main orientation component of the texture of the metal conductive layer is 50% or more, It is desirable to form the metal conductive layer so as to satisfy the condition that the ratio of macro crystal grains is 10% or less. Thus, it is possible to realize a flexible metal laminate having excellent characteristics in which the dimensional change rate is 0.05% or less and the dimensional change rate deviation is 0.02% point or less even after pattern formation.

  Although the present invention has been described with reference to the limited embodiments and drawings, the present invention is not limited to this, and the technical idea and the present invention can be determined by those who have ordinary knowledge in the technical field to which the present invention belongs. It goes without saying that various modifications and variations are possible within the equivalent scope of the claims.

100 polymer film 110 tie coat layer 120 metal seed layer 130 metal conductive layer

Claims (7)

In a flexible metal laminate including a polymer film, a tie coat layer, a metal seed layer, and a metal conductive layer,
The total content of impurities contained in the metal conductive layer is 0.03% or less, the volume fraction of the main orientation component of the texture of the metal conductive layer is 50% or more, and the macro of the metal conductive layer The proportion of crystal grains is 10% or less,
The modulus of the polymer film is 5.0 to 10.5 GPa, the coefficient of thermal expansion (CTE) is 11 to 18 um / m ° C, and the coefficient of moisture expansion (CHE) is 5.5 to 9.5 ppm. A soft metal laminate characterized by the above. The soft metal laminate according to claim 1, wherein the tie coat layer is made of nickel (Ni), chromium (Cr), or an alloy thereof. The soft metal laminate according to claim 1, wherein the metal seed layer and the metal conductive layer are made of copper or a copper alloy. The flexible metal laminate according to claim 1, wherein the polymer film is made of polyimide. The soft metal laminate according to claim 1, wherein the flexible metal laminate has a dimensional change rate of 0.05% or less after pattern formation. 2. The soft metal laminate according to claim 1, wherein the soft metal laminate has a dimensional variation rate deviation of 0.02% or less after pattern formation. 3. A method for producing a flexible metal laminate used for a flexible circuit board,
(A) The modulus is 5.0 to 10.5 GPa, the coefficient of thermal expansion (CTE) is 11 to 18 um / m ° C, and the coefficient of moisture expansion (CHE) is 5.5 to 9.5 ppm. A step of preparing a polymer film having,
(B) forming a tie coat layer on top of the prepared polymer film;
(C) forming a metal seed layer on the polymer film on which the tie coat layer is formed;
(D) Above the metal seed layer, the total content of impurities by electroplating is 0.03% or less, the volume fraction of the main orientation component of the texture is 50% or more, and the ratio of macro crystal grains Forming a metal conductive layer having a thickness of 10% or less.

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