KR20220062712A - Base film for felxible printed circuit substrate - Google Patents

Abstract

A substrate for a flexible printed circuit board according to an embodiment comprises: a first material of an acid anhydride having an ester group of TAHQ or BP-TME; and at least one second material of m-tolidine and flexible diamine.

Description

Substrate for flexible printed circuit boards {BASE FILM FOR FELXIBLE PRINTED CIRCUIT SUBSTRATE}

The embodiment relates to a substrate for a flexible printed circuit board.

With the development of society, miniaturization of home appliances is progressing. The existence of flexible printed circuit boards (FPCBs) is essential for miniaturization of home appliances. A rigid printed circuit board (PCB) is used for the main board of home appliances, and it is necessary to connect many parts and the main board to give various functions.

In this case, it is the flexible printed circuit board that contributes to the miniaturization. Recently, it is possible to connect to the Internet using wireless even outdoors, and a radio wave reception function is equipped as a standard in notebook computers and smartphones. In addition, the speed of Internet access has increased due to the development of communication technology. Currently, it is the transition period from 4G to 5G, and an era of new high-speed communication using the GHz band is opening in the future.

Conventionally, polyimide (PI) has been used as a base material for flexible printed circuit boards.

Polyimide Flexible Copper Clad Laminate (FCCL) has good size stability, heat resistance, coefficient of thermal expansion, mechanical strength and resistance insulation, and is widely applied in the electronics industry. , polyimide has characteristics such as high dielectric constant and high loss factor, so it is not suitable as an insulating layer for high-frequency substrates.

Accordingly, in the prior art, as a flexible printed circuit board for a high-frequency signal, a copper foil was pressed onto a liquid crystal polymer (LCP) and manufactured.

However, due to the unique molecular structure characteristics of LCP, excessive forward alignment occurs, which tends to cause defects in mechanical properties in the transverse direction, and there are problems in that LCP thin film processing and product application are severely restricted.

In addition, due to the unique molecular structure characteristics of LCP, the glass transition temperature (Tg) and melting point (Tm) of the polymer are close, so it is difficult to control the size stability in the thermocompression bonding process of the flexible printed circuit board to which the LCP is applied.

Accordingly, there is a need for a substrate for a flexible printed circuit board that can solve the above problems.

The embodiment relates to a substrate for a flexible printed circuit board, and by optimizing the ratio of the imide group and ester group of polyimide, it is intended to provide a substrate for a flexible printed circuit board that can satisfy the physical properties required for the flexible printed circuit board. .

A substrate for a flexible printed circuit board according to an embodiment includes a first material of an acid anhydride having an ester group of TAHQ or BP-TME; and a second material of at least one of m-tolidine and flexible diamine.

The polyimide substrate according to the embodiment may plasticize the coefficient of thermal expansion of the polyimide substrate by controlling the mole % ratio of materials including imide groups.

That is, the coefficient of thermal expansion of the polyimide substrate can be controlled similarly to that of a circuit pattern, for example, copper.

Accordingly, the flexible printed circuit board including the polyimide substrate according to the embodiment may have improved size (dimensional) stability and adhesion with the circuit pattern.

In addition, since the polyimide substrate according to the embodiment has a low dielectric constant and a low dielectric loss tangent, it is possible to reduce signal loss due to a high frequency signal even when applied to an electronic device that transmits a high frequency signal.

1 is a view showing a cross-sectional view of a flexible printed circuit board according to an embodiment.
2 is a diagram illustrating a cross-sectional view of a flexible printed circuit board according to an embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical spirit of the present invention is not limited to some of the described embodiments, but may be implemented in various different forms, and within the scope of the technical spirit of the present invention, one or more of the components may be selected between embodiments. It can be used by combining or substituted with .

In addition, terms (including technical and scientific terms) used in the embodiments of the present invention may be generally understood by those of ordinary skill in the art to which the present invention belongs, unless specifically defined and described explicitly. It may be interpreted as a meaning, and generally used terms such as terms defined in advance may be interpreted in consideration of the contextual meaning of the related art.

In addition, the terminology used in the embodiments of the present invention is for describing the embodiments and is not intended to limit the present invention. In this specification, the singular form may also include the plural form unless otherwise specified in the phrase, and when it is described as "at least one (or one or more) of A and (and) B, C", it can be combined with A, B, and C. It may include one or more of all possible combinations.

In addition, in describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the component from other components, and are not limited to the essence, order, or order of the component by the term.

And, when it is described that a component is 'connected', 'coupled' or 'connected' to another component, the component is not only directly connected, coupled or connected to the other component, but also with the component It may also include a case of 'connected', 'coupled' or 'connected' due to another element between the other elements.

In addition, when it is described as being formed or disposed on "above (above) or below (below)" of each component, the top (above) or bottom (below) is one as well as when two components are in direct contact with each other. Also includes a case in which another component as described above is formed or disposed between two components.

In addition, when expressed as “up (up) or down (down)”, it may include not only the upward direction but also the meaning of the downward direction based on one component.

A flexible printed circuit board according to an embodiment will be described with reference to FIG. 1 . The flexible printed circuit board according to the embodiment may be applied to an antenna and a cable that transmits a high frequency signal of 24 GHz to 100 GHz.

Referring to FIG. 1 , the flexible printed circuit board according to the embodiment may include a substrate 100 , a circuit pattern 200 , and a protective layer 300 .

The substrate 100 may be rigid or flexible.

The substrate 100 may include a transparent, translucent, or opaque substrate. For example, the substrate 100 may include a resin material. Also, the substrate 100 may include an insulating material. Preferably, the substrate 100 may include polyimide (PI).

The thickness of the substrate 100 may be 125 μm or less. In detail, the thickness of the substrate 100 may be 25 μm to 125 μm. In more detail, the thickness of the substrate 100 may be 50 μm to 100 μm.

When the thickness of the substrate 100 is less than 25 μm, the strength of the substrate 100 may be lowered, so that the supporting power of the circuit pattern 200 and the protective layer 300 supported by the substrate 100 may be reduced. .

In addition, when the thickness of the substrate 100 exceeds 125 μm, the overall bendability and flexibility of the flexible printed circuit board may be reduced due to an increase in the thickness of the substrate 100 .

In addition, the substrate 100 may include at least one functional group. For example, the substrate 100 may include at least one functional group selected from an ester group and an imide group. That is, the substrate 100 may be a substrate composition including at least one of a first material including an ester group and a second material including an imide group.

The substrate 100 may have a low dielectric constant, a low coefficient of thermal expansion and a glass transition temperature by controlling the mole % of the first material including the ester group and the second material including the imide group.

The first material and the second material included in the substrate 100 will be described in detail below.

The circuit pattern 200 may be disposed on the substrate 100 . The circuit pattern 200 may be disposed on the substrate 100 and serve as a wiring through which a current or a signal moves in the flexible printed circuit board. For example, a high-frequency signal of 24 GHz to 100 GHz may move in the circuit pattern 200 .

Accordingly, the circuit pattern 200 may be formed of a metal material having high electrical conductivity. For example, the circuit pattern 200 may include at least one selected from gold (Au), silver (Ag), platinum (Pt), titanium (Ti), tin (Sn), copper (Cu), and zinc (Zn). It may be formed of a metal material of

Alternatively, the circuit pattern 200 is selected from among gold (Au), silver (Ag), platinum (Pt), titanium (Ti), tin (Sn), copper (Cu), and zinc (Zn) having excellent bonding strength. It may be formed of a paste including at least one metal material or a solder paste. Preferably, the circuit pattern 200 may be formed of copper (Cu), which has high electrical conductivity and is relatively inexpensive.

The circuit pattern 200 is a conventional manufacturing process of a printed circuit board, such as additive process (Additive process), subtractive process (Subtractive Process), MSAP (Modified Semi Additive Process), SAP (Semi Additive Process) method, etc. possible, and a detailed description thereof will be omitted herein.

The circuit pattern 200 may be formed in multiple layers. For example, the circuit pattern 200 may include a first metal layer 201 and a second metal layer 202 . In detail, the circuit pattern 200 may include a first metal layer 201 disposed on the substrate 100 and a second metal layer 202 disposed on the first metal layer 201 .

The first plating layer 201 may be formed through electroless plating, that is, the first metal layer 201 may be a seed layer for electrolytic plating of the circuit pattern 200 . Accordingly, the thickness of the first metal layer 201 may be smaller than the thickness of the second metal layer 202 .

For example, the thickness of the first metal layer 201 may be 300 nm or less. In detail, the thickness of the first metal layer 201 may be 10 nm to 300 nm. When the thickness of the first metal layer 201 is less than 10 nm, it may be difficult to form the second metal layer 202 through a subsequent plating process through electrolytic plating. In addition, when the thickness of the first metal layer 201 is greater than 300 nm, a process time for forming the first metal layer 201 may increase, and thus process efficiency may decrease.

The first metal layer 201 may include copper (Cu) or silver (Ag). Accordingly, since the first metal layer 201 does not include a material that causes magnetic loss, such as nickel (Ni) or chromium (Cr), signal loss of the circuit pattern 200 can be reduced.

The second metal layer 202 may be disposed on the first metal layer 201 . The second metal layer 202 may include the same or similar material to the first metal layer 201 . For example, the second metal layer 202 may include copper (Cu).

The second metal layer 202 may be formed through electroplating. A thickness of the second metal layer 202 may be greater than a thickness of the first metal layer 201 .

The thickness of the circuit pattern 200 formed by the first metal layer 201 and the second metal layer 202 may be 3 μm or less. In detail, the thickness of the circuit pattern 200 may be 0.3 μm to 3 μm.

The protective layer 300 may be disposed on the circuit pattern 200 . The protective layer 300 may be disposed on the circuit pattern 200 to protect the circuit pattern 200 from external impact. That is, the protective layer 300 may be a cover disposed on the outermost side of the flexible printed circuit board.

The protective layer 300 may include the same or similar material to the substrate 100 described above.

For example, the protective layer 300 may be transparent, translucent, or opaque. For example, the protective layer 300 may include a resin, and the protective layer 300 may include an insulating material. For example, the protective layer 300 may include polyimide (PI), polyethylene terephthalate (PET), propylene glycol (PPG), polycarbonate (PC), or the like.

The thickness of the protective layer 300 may be 200 μm or less. In detail, the thickness of the protective layer 300 may be 5 μm to 200 μm. In more detail, the thickness of the protective layer 300 may be 50 μm to 100 μm.

When the thickness of the protective layer 300 is less than 5 μm, it is difficult to maintain the shape of the protective layer 300 , so process efficiency may be reduced, and the circuit pattern 200 is effectively protected by the protective layer 300 . Can not.

In addition, when the thickness of the protective layer 300 exceeds 200 μm, the overall bendability and flexibility of the flexible printed circuit board may be reduced due to an increase in the thickness of the protective layer 300 .

As described above, the substrate 100 may include polyimide (PI). In detail, the substrate 100 may include polyimide formed of a polyimide resin composition.

The polyimide resin composition may include a first material and a second material. That is, the substrate 100 may be formed of a polyimide resin composition including at least one of the first material and the second material. That is, the substrate 100 may be formed of a polyimide resin composition including the first material and the second material.

The first material may include an ester group. Specifically, the first material is 4,4'-biphenylbis(trimellitic acid monoesteric anhydride) (TAHQ) and BP-TME (4,4'-bis(1,3-dioxo-1,3-dihydroisobenzofuran) -5-ylcarbonyloxy)biphenyl) may include at least one material.

In addition, the second material may include an imide. In detail, the second material may include at least one of m-tolidine and flexible diamine. In this case, the diamine is 4,4'-oxydianiline (4,4 ODA), 3,4'-oxydianiline (3,4 ODA), 1,3-bis(4-aminophenoxy)benzene ( TPE-R), 1,4-bis (4-aminophenoxy) benzene (TPE-Q), 3,3 APB (1,3'-Bis (3-aminophenoxy) benzene) and 4,4 BAPP (2, At least one material of 2-Bis [4-(4-aminophenoxy)phenyl] propane) may be included.

The polyimide resin composition may include the first material in an amount of 100 mol% and the second material in an amount of 100 mol%.

In addition, the second material may include at least one of m-tolidine and flexible diamine. In detail, the second material may include only m-tolidine. Alternatively, the second material may include m-tolidine and flexible diamine.

The m-tolidine and the flexible diamine may be included in different mole %. In detail, in the second material, a mole % of the m-tolidine may be greater than a mole % of the flexible diamine.

In detail, the m-tolidine may be included in an amount of 70 mol% to 100 mol% based on the total amount (100 mol%) of the second material. That is, when the second material includes only m-tolidine, the m-tolidine may be included in an amount of 100 mol%. In addition, when the second material includes the m-tolidine and the flexible diamine, the m-tolidine is 70 mol based on the total amount of the second material. % to less than 100 mol%.

In addition, the flexible diamine may be included in an amount of 0 mol% to 30 mol% based on the total amount (100 mol%) of the second material. That is, when the second material includes only m-tolidine, the flexible diamine may be included in an amount of 0 mol%. In addition, when the second material includes the m-tolidine and the flexible diamine, the flexible diamine is more than 0 mol% based on the total amount of the second material. 30 mol% may be included.

When the mole % of the m-tolidine and the flexible diamine is out of the above range, the coefficient of thermal expansion of the polyimide substrate formed by the polyimide resin composition is increased, thereby The difference in thermal brim coefficient between the substrate and the copper foil, that is, the circuit pattern may increase, so that size stability of the substrate may be reduced.

Meanwhile, an adhesive layer 400 may be disposed between the substrate 100 and the protective layer 300 . In detail, the adhesive layer 400 may be disposed on at least one of one surface of the substrate 100 and the other surface opposite to the one surface.

That is, when the circuit pattern 200 is disposed on only one surface of the substrate 100 , the adhesive layer 400 is disposed on only one surface of the substrate 100 , and the circuit pattern 200 is disposed on the substrate ( 100 ), the adhesive layer 400 may be disposed on both the one surface and the other surface of the substrate 100 .

The adhesive layer 400 may include a polyimide resin composition. In detail, the adhesive layer 400 may include a resin composition having a composition different from that of the base material 100 . In detail, the adhesive layer 400 may include an acid anhydride including PMDA, sBPDA, and diamine including 4,4BAPP.

Hereinafter, the present invention will be described in more detail through a method for manufacturing a substrate according to Examples and Comparative Examples. These manufacturing examples are merely presented as examples in order to explain the present invention in more detail. Therefore, the present invention is not limited to these preparation examples.

Example 1

Nitrogen was introduced into a 1 L glass reaction vessel. Thereafter, dimethylacetamide (DMAc) was added to a glass reaction vessel and stirred.

Then, m-tolidine was added and stirred until completely dissolved. Then, BP-TME was added and the temperature was raised to 50°C. Subsequently, stirring was continued at a solid content concentration of 16 wt% at a molar ratio of BP-TME/m-Tolidine = 1 to obtain a polyamic acid solution having a final viscosity of 2000 poise.

Then, the polyamic acid solution is applied to a glass substrate, dried at 160° C. for 5 minutes, removed from the glass substrate, fixed to a tenter fixed substrate, and maintained at 160° C. for 5 minutes, 180° C. for 5 minutes, and 220° C. for 5 minutes. , was put into an electric furnace set at 220 ℃, the temperature was raised to 450 ℃, and dried at 450 ℃ for 3 minutes to prepare a polyimide substrate.

Example 2

Example 1 and Example 1, except that 100 mol% of m-tolidine was not added, and 90 mol% of m-tolidine and 10 mol% of 4,4 ODA were added. Similarly, a polyimide substrate was prepared.

Example 3

Example 1 and Example 1, except that 100 mol% of m-tolidine was not added, and 80 mol% of m-tolidine and 20 mol% of 4,4 ODA were added. Similarly, a polyimide substrate was prepared.

Example 4

Example 1 and Example 1, except that 100 mol% of m-tolidine was not added, and 70 mol% of m-tolidine and 30 mol% of 4,4 ODA were added. Similarly, a polyimide substrate was prepared.

Example 5

Example 1 and Example 1, except that 100 mol% of m-tolidine was not added, and 90 mol% of m-tolidine and 10 mol% of 3,4 ODA were added. Similarly, a polyimide substrate was prepared.

Example 6

Same as Example 1, except that 100 mol% of m-tolidine was not added, and 90 mol% of m-tolidine and 10 mol% of TPE-R were added. A polyimide substrate was prepared.

Example 7

In the same manner as in Example 1, except that 100 mol% of m-tolidine was not added, and 90 mol% of m-tolidine and 10 mol% of APB were added. A mid substrate was prepared.

Example 8

Example 1, except that 100 mol% of m-tolidine was not added, and 90 mol% of m-tolidine and 10 mol% of 4, 4 BAPP were added. Similarly, a polyimide substrate was prepared.

Example 9

A polyimide substrate was prepared in the same manner as in Example 1, except that TAHQ was added without BP-TME.

Example 10

TAHQ rule was added without BP-TME, m-Tolidine was not added 100 mol%, m-Tolidine 90 mol% and 4,4 ODA was added 10 mol% A polyimide substrate was prepared in the same manner as in Example 1, except that it was added.

Example 11

TAHQ rule was added without BP-TME, m-Tolidine was not added 100 mol%, m-Tolidine 97 mol% and 3,4 ODA was added 3 mol% A polyimide substrate was prepared in the same manner as in Example 1, except that it was added.

Example 12

TAHQ rule was added without BP-TME, m-Tolidine was not added 100 mol%, m-Tolidine 97 mol% and TPE-R was added 3 mol% A polyimide substrate was prepared in the same manner as in Example 1, except that

Example 13

TAHQ rule was added without BP-TME, 100 mol% m-tolidine was not added, m-Tolidine 97 mol% and APB were added 3 mol%. Except for the point, a polyimide substrate was prepared in the same manner as in Example 1.

Example 14

TAHQ rule was added without BP-TME, m-Tolidine was not added 100 mol%, m-Tolidine 97 mol% and 4,4 BAPP was 3 mol% A polyimide substrate was prepared in the same manner as in Example 1, except that it was added.

Comparative Example 1

Example 1 and Example 1, except that 100 mol% of m-tolidine was not added, and 60 mol% of m-tolidine and 40 mol% of 4,4 ODA were added. Similarly, a polyimide substrate was prepared.

Comparative Example 2

Example 1, except that 100 mol% of m-tolidine was not added, and 20 mol% of m-tolidine and 80 mol% of 4,4 ODA were added. Similarly, a polyimide substrate was prepared.

Comparative Example 3

A polyimide substrate was prepared in the same manner as in Example 1, except that 100 mol% of m-tolidine was not added and 100 mol% of 4,4 ODA was added.

Comparative Example 4

TAHQ rule was added without BP-TME, m-Tolidine was not added 100 mol%, m-Tolidine 60 mol% and 4,4 ODA was 40 mol% A polyimide substrate was prepared in the same manner as in Example 1, except that it was added.

Comparative Example 5

TAHQ rule was added without BP-TME, m-Tolidine was not added 100 mol%, m-Tolidine 20 mol% and 4,4 ODA was 80 mol% A polyimide substrate was prepared in the same manner as in Example 1, except that it was added.

Comparative Example 6

Same as Example 1, except that TAHQ rule was added without BP-TME, 100 mol% of m-tolidine was not added, and 100 mol% of 4,4 ODA was added A polyimide substrate was prepared.

Comparative Example 7

Same as Example 1, except that PMDA was added without BP-TME, 100 mol% of m-tolidine was not added, and 4,4 ODA was added 100 mol% A polyimide substrate was prepared.

Dk Df coefficient of thermal expansion
(ppm/℃) glass transition temperature
(℃) Example 1 3.2 0.0027 10 350 Example 2 3.2 0.0027 13 350 Example 3 3.2 0.0027 16 350 Example 4 3.2 0.0027 19 350 Example 5 3.2 0.0027 19 350 Example 6 3.2 0.0027 19 350 Example 7 3.2 0.0027 19 350 Example 8 3.2 0.0027 19 350 Example 9 3.1 0.0035 16 350 Example 10 3.1 0.0035 19 350 Example 11 3.1 0.0035 19 350 Example 12 3.1 0.0035 19 350 Example 13 3.1 0.0035 19 350 Example 14 3.1 0.0035 19 350 Comparative Example 1 3.2 0.0027 40 350 2 in comparison 3.2 0.0027 55 350 Comparative Example 3 3.2 0.0027 70 350 Comparative Example 4 3.1 0.0035 60 350 Comparative Example 5 3.1 0.0035 80 350 Comparative Example 6 3.1 0.0035 100 350 Comparative Example 7 3.3 0.01 40 340

Referring to Table 1, it can be seen that the polyimide substrates according to Examples 1 to 14 have a lower coefficient of thermal expansion than the polyimide substrates according to Comparative Examples 1 to 7.

That is, it can be seen that the polyimide substrates according to Examples 1 to 14 have a coefficient of thermal expansion similar to that of copper (18 ppm/° C.) used as a circuit pattern.

That is, it can be seen that the difference in the coefficient of thermal expansion between the polyimide substrate and the circuit pattern according to Examples 1 to 14 is smaller than the difference in the coefficient of thermal expansion between the polyimide substrate and the circuit pattern according to Comparative Examples 1 to 7.

Accordingly, the flexible printed circuit board including the polyimide substrate according to Examples 1 to 14 may have improved size (dimensional) stability and adhesion with the circuit pattern.

In addition, since the polyimide substrates according to Examples 1 to 14 have a low dielectric constant and a low dielectric loss tangent, signal loss due to a high frequency signal can be reduced even when applied to an electronic device transmitting a high frequency signal.

Features, structures, effects, etc. described in the above-described embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to one embodiment. Furthermore, the features, structures, effects, etc. illustrated in each embodiment can be combined or modified for other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

In addition, although the embodiments have been described above, these are merely examples and do not limit the present invention, and those of ordinary skill in the art to which the present invention pertains are exemplified above in a range that does not depart from the essential characteristics of the present embodiment. It can be seen that various modifications and applications that have not been made are possible. For example, each component specifically shown in the embodiments may be implemented by modification. And differences related to these modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

Claims (5)

a first substance of an acid anhydride having an ester group of TAHQ or BP-TME; and
A substrate for a flexible printed circuit board comprising a second material of at least one of m-tolidine and flexible diamine. The method of claim 1,
The m-tolidine (m-Tolidine) is included in an amount of 70 mol% to 100 mol% with respect to the total (100 mol%) of the second material,
The flexible diamine is included in an amount of 0 mol% to 30 mol% based on the total amount of the second material (100 mol%). The method of claim 1,
The flexible diamine is a substrate for a flexible printed circuit board comprising at least one of 4,4 ODA, 3,4 ODA, TPE-R, TPE-Q, 3,3 APB, and 4,4 BAPP. A flexible printed circuit board comprising the substrate for the flexible printed circuit board of any one of claims 1 to 3. a first substance of an acid anhydride having an ester group of TAHQ or BP-TME; and a substrate for a flexible printed circuit board comprising a second material of at least one of m-tolidine and flexible diamine;
an acid anhydride including PMDA and sBPDA, disposed on at least one of one surface and the other surface of the flexible printed circuit board substrate; And a flexible printed circuit board comprising an adhesive layer comprising a diamine containing 4,4BAPP.

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