JP2003209141A - Flexible wiring board and packaging method of semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable flexible wiring board by uniformly applying pressure to conductive particles in an ACF and adhering them to a connecting terminal and an electrode terminal when a semiconductor element is bonded by thermal compression to the flexible wiring board of a multilayer construction using the ACF. <P>SOLUTION: The flexible wiring board FC includes wiring layers 2A, 2B and a protective layer 6 on both front and rear faces of a film substrate 1 and has the semiconductor element 4 fitted by thermocompression bonding on a packaging region 3 formed on the front face, wherein an opening 9 is formed on the rear face of the packaging region 3 in which the wiring layers 2A, 2B and the protective layer 6 are not arranged of which each area is the same as or larger than the base area of the semiconductor element 4. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible wiring board having a multilayer structure and a method for mounting a semiconductor element.

[0002]

2. Description of the Related Art A flexible wiring board has a multi-layered structure in which a wiring pattern made of metal is formed on the front surface or front and back surfaces of a flexible film substrate and is appropriately protected by a resin or the like. It is often arranged between and used as a connection circuit board. In addition, there are also those in which semiconductor elements such as ICs and LSIs, electronic parts, etc. are mounted. Due to the flexibility of the flexible wiring board, it is possible to absorb minute positional deviations and vibrations between electronic components and devices,
Further, since it can be bent and used, it is effective for downsizing of products and has been widely used in recent years.

The structure of a conventional flexible wiring board is shown in FIG.
Shown in. The flexible wiring board FC is formed on the front and back surfaces of the film substrate 1 formed of a resin film such as polyimide,
Metal wirings 2A and 2B made of copper or the like are formed in a predetermined shape, and the wirings 2A and 2B on the front and back surfaces are appropriately conducted by the through hole 5 and the through hole plating 5a. In the mounting area 3 on the film substrate 1, the wiring 2A
The electrode terminal P is formed by the semiconductor element 4 such as an LSI.
Has been implemented. Further, in order to protect the wirings 2A and 2B, a protective agent (cover film made of urethane solder resist, polyimide or the like) 6 is provided. As shown in FIG. 3, the cross-sectional shape of the flexible wiring board FC is such that the film substrate 1, the wirings 2A and 2B, and the protective agent 6 are layered on top of each other. The flexible wiring board FC having such a shape has a multilayered flexible wiring. Also called a substrate.

The semiconductor element 4 is an anisotropic conductive resin film (Anisotropic) which is a paste or film adhesive.
A conductive film (hereinafter referred to as ACF) 7 is used for mounting by thermocompression bonding. ACF7 is a thermoplastic or thermosetting resin film in which conductive particles are dispersed. As for the mounting method, as shown in FIG. 4, the flexible wiring board FC is fixed to the carrier stage S, and the A
CF7 is applied, the semiconductor element 4 is aligned, and heating and pressurization are performed by a heating tool 8 which moves up and down from above. As a result, the conductive particles of the ACF 7 are brought into close contact with each other between the connection terminal 4a of the semiconductor element 4 and the electrode terminal P, and the connection terminal 4a and the electrode terminal P are electrically connected.

[0005]

When the wirings 2A and 2B and the protective agent 6 are formed on both surfaces of the flexible wiring board FC, the wiring 2B and the wiring 2B are also formed on the back surface side of the mounting area 3 where the semiconductor element 4 is mounted. Since the protective agent 6 was formed, the pressure at the time of thermocompression bonding was absorbed in each layer. That is, when the semiconductor element 4 is mounted, an AC voltage is applied between the semiconductor element 4 to be heated and pressed and the transfer stage S.
In addition to F7, the electrode terminal P by the wiring 2A, the film substrate 1, the wiring 2B, and the protective agent 6 are arranged in this order in four layers. When the semiconductor element 4 is mounted on the flexible wiring board FC having a multilayer structure via the ACF7, heating There is a problem that the pressure from the tool 8 is lost in each layer, the adhesiveness of the conductive particles of the ACF 7 is lowered, and stable conduction cannot be obtained. Further, when the pattern shape of the wiring 2B on the back surface side is not uniform in the mounting region 3, the pressure by the heating tool 8 is not constant, which causes a problem in that the adhesion of the conductive particles of the ACF 7 becomes uneven. . After the mounting, a continuity test is conducted by energizing. However, depending on the degree of unevenness of adhesion, even if the continuity is confirmed during the continuity test, the continuity may not be established due to vibration or deterioration over time. In addition, the continuity test requires a power supply, a measuring instrument, etc.
In particular, in the case of mass-produced products, when performing 100% testing, the labor and cost were problems.

Therefore, an object of the present invention is to apply a paste or film adhesive to a flexible wiring board having a multi-layer structure by thermocompression bonding a semiconductor element using the paste or film adhesive. It is an object of the present invention to provide a highly reliable flexible wiring board and a method for mounting a semiconductor element on this board by making them adhere uniformly.

[0007]

In order to solve the above-mentioned problems, the flexible wiring board according to claim 1 of the present invention comprises:
At least wiring layers having electrode terminals are provided on both front and back surfaces of the film substrate, and the semiconductor element is heat-pressed using a paste-like or film-like adhesive in a mounting area on the film substrate, thereby In a flexible wiring board having a multi-layer structure in which the connection terminals are electrically connected to the wiring layer, whether the bottom surface area of the semiconductor element is the same as the bottom surface side of the semiconductor element mounted in the mounting area of the film substrate. Alternatively, a region where a wiring layer is not arranged is formed in a large area.

According to the present invention, a region where the wiring layer is not arranged is formed on the back surface side of the mounting region where the semiconductor element is mounted, the area being equal to or larger than the bottom area of the semiconductor element. When mounting a semiconductor element by thermocompression bonding,
The pressure is not absorbed by the wiring layer on the back surface side, so that the connection reliability in mounting the semiconductor element can be improved.

According to a second aspect of the present invention, in the flexible wiring board according to the first aspect of the present invention, the film substrate has a position of a semiconductor element to be mounted or a connection of semiconductor elements to be mounted. The position of the terminal is transparent so that it can be seen from the region where the wiring layer is not arranged. Here, when the paste-like or film-like adhesive is an anisotropic conductive film (ACF), the film substrate is so transparent that the conductive particles in the adhesive can be confirmed from a region where the wiring layer is not arranged. Also good.

According to the present invention, after mounting the semiconductor element, the position of the semiconductor element, the position of the connection terminal of the semiconductor element, or the anisotropic conductive film (ACF) is measured from the rear surface side of the film substrate.
In this case, the conductive particles of the adhesive can be confirmed. Therefore, the connection portion can be confirmed by a simple visual inspection before conducting the continuity test by energizing.

According to a third aspect of the present invention, there is provided a method for mounting a semiconductor element on a flexible wiring board, wherein the semiconductor element is mounted on the flexible wiring board according to the first or second aspect by thermocompression bonding. It is characterized in that a fixing plate having the same area and the same or a large thickness as that of the region is fitted in a region where the wiring layer is not arranged, and after applying heat and pressure, the fixing plate is removed.

According to the present invention, since the fixing plate is fitted in the region where the wiring layer is not arranged and heat and pressure are applied, the pressure applied to the semiconductor element can be reliably received by the fixing plate without passing through the gap. . Therefore, when mounting the flexible wiring board according to claim 1 or 2, when the flexible wiring board is mounted on a carrying stage having the same shape as the conventional one and heat and pressure are applied, the thickness of the wiring layer on the back side is reduced. According to the method of the present invention, it is possible to more effectively apply pressure to the semiconductor element, as compared with the case where a gap is generated between the semiconductor element and the transfer stage.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional structure diagram of a flexible wiring board according to this embodiment, and FIG. 2 is a diagram showing a structure for mounting a semiconductor element on the flexible wiring board according to this embodiment. Flexible wiring board F of the present embodiment
In C, metal wirings 2A and 2B made of copper or the like are formed in a predetermined shape on the front and back surfaces of the film substrate 1 formed of a resin film such as polyimide, and the through hole 5 is formed.
And the wiring 2 on the front and back by the through hole plating 5a
A and 2B are properly conducted. The film substrate 1 is semitransparent, and the wiring 2A on the front surface side can be confirmed from the back surface side. The film substrate 1 does not have to be completely colorless and transparent, and may be transparent so that desired items can be confirmed from the back side with the naked eye or a microscope. The desired matter is the position of the semiconductor element to be mounted, the position of the connection terminal of the semiconductor element to be mounted, or when the paste-like or film-like adhesive is an anisotropic conductive film (ACF), Conductive particles and the like in the adhesive, and in the case of a semiconductor element 4 with a bump electrode (bump), which will be described later,
That is the protruding electrode. In addition, in order to make it easy to confirm these desired items, it is possible to color the object. The film substrate 1 can be made close to transparent by reducing the thickness of the film substrate 1 (for example, 25
μm). In the mounting area 3 on the film substrate 1, the electrode terminal P is formed by the wiring 2A, and the semiconductor element 4 such as IC or LSI is mounted. Furthermore, the wiring 2A, 2B
A protective agent (a urethane solder resist, a cover film made of polyimide, etc.) 6 is provided to protect the.

Then, on the back surface side of the mounting region 3 where the semiconductor element 4 is mounted, the window 9 in which the wiring 2B and the protective agent 6 on the back surface side are removed so as to form a rectangle having a slightly larger area than the semiconductor element 4. Are formed. The window 9 is a region on the back surface of the film substrate 1 where the wiring layer, the protective layer, and the like are not arranged, and is formed in a rectangular shape. In the present embodiment, the length of one side of the rectangular window 9 is approximately 1.5 to 2 times the length of one side of the semiconductor element 4 mounted on the back surface side of the window 9. 4 is formed so that there is a gap between the side of the window 9 and the side of the semiconductor element 4 when mounted, but on the back surface of the window 9, the inside of the window 9 (enclosed by the side of the window 9 The same size may be used as long as the semiconductor element 4 can be fitted in the (part), and its shape does not matter. In addition, the semiconductor element 4 with the bump electrode (bump)
In this case, it is possible to form the window 9 only in the bump portion to be connected.

The semiconductor element 4 is mounted by thermocompression bonding using an anisotropic conductive film (ACF) 7 which is a paste or film adhesive. ACF7 is a thermoplastic or thermosetting resin film in which conductive particles are dispersed. Specifically, conductive particles are dispersed in an insulating adhesive, have conductivity in the thickness direction (connection direction), and have insulating properties in the plane direction (lateral direction), and are composed of conductive particles and an adhesive. To be done. The connection is basically thermocompression bonding, the conductive particles are responsible for the function of electrical connection, and the adhesive is responsible for the function of maintaining the pressed state. An insulating coating is applied to the surface of the conductive particles, and when the pressure is applied in a specific direction, the insulating coating is partially destroyed. Resin is often used as the material of the insulating film. There is also one in which the conductive particles are heated and pressed so as to be crushed.
In the case of ACF7, the paste-like or film-like adhesive used in the present invention does not limit the constitution of the conductive particles or the adhesive, etc. ACF is sufficient, and in the case other than ACF, a conductive adhesive (conductive paste) or cream solder may be used.

When mounting the semiconductor element 4, as shown in FIG. 2, the flexible wiring substrate FC is moved to the carrying stage S.
Fixed to. A fixed plate 10 having the same shape as the window 9 and having a size that can be fitted into the window 9 is attached to the transport stage S in advance, and the flexible wiring board FC is fixed so that the fixed plate 10 is fitted into the window 9. Next, ACF 7 is applied to the mounting region 3, the semiconductor element 4 is aligned, and heated and pressed by a heating tool 8 from above (on the back surface side of the mounting surface of the semiconductor element 4). As a result, the conductive particles of the ACF 7 are brought into close contact between the connection terminal 4a of the semiconductor element 4 and the electrode terminal P, and the connection terminal 4a and the electrode terminal P are electrically connected.
Specifically, when the semiconductor element 4 is mounted, only the electrode terminal P by the wiring 2A and the film substrate 1 are interposed between the fixing plate 10 and the semiconductor element 4 in addition to the ACF 7. Therefore, the pressure applied by the heating tool 8 is applied to the semiconductor element 4 without being absorbed by the wiring 2B on the back surface side and the protective agent 6 and without being biased. As a result, pressure is applied to the conductive particles without unevenness, the insulating coating of the conductive particles is evenly broken, or the elasticity (restoration) of the conductive particles is effectively exhibited. Therefore, the conductive particles of the ACF 7 are not biased in the semiconductor element 4 and
The connection terminal 4a and the electrode terminal P are in close contact with each other, and stable conduction is obtained.

In order to effectively obtain the pressure from the heating tool 8, the thickness of the fixing plate 10 needs to be at least larger (thicker) than the depth of the window 9. Although the fixing plate 10 of the present embodiment is made of stainless steel, it is sufficiently hard to withstand the heat and pressure of the heating tool 8 and has sufficient hardness so as not to absorb the pressure of the heating tool 8. Any other metal, ceramic, resin or the like may be used. Further, since the fixing plate 10 is manufactured according to the shape of the window 9, it is preferable that the fixing plate 10 can be attached to and detached from the conventional transfer stage S (it is preferable that it can be attached and detached). It should be noted that it is possible to form the fixed plate 10 as the carrying stage S integrated with the carrying stage depending on the implementation.

In the above, the case where the semiconductor element 4 is mounted on the flexible wiring board FC has been described as an example in the present embodiment, but the present invention is also applicable to the case where other electronic elements such as capacitors and electronic parts are mounted. Is.

[0019]

The multilayer flexible wiring board of the present invention is an area in which a wiring layer or the like is not arranged on the back surface side of the mounting area in which the semiconductor element is mounted, in the same area as or larger than the bottom area of the semiconductor element. Therefore, when mounting the semiconductor element by thermocompression bonding via a paste or film adhesive, it is possible to apply sufficient pressure to the wiring layer on the back side without absorbing the pressure. The connection reliability can be improved. Further, by bringing the film substrate close to transparent, the position of the semiconductor element, the position of the connection terminal of the semiconductor element, and the like can be confirmed from the back surface side of the film substrate after mounting the semiconductor element. Therefore,
By conducting a simple visual inspection to check the connection parts before conducting a conduction test by energizing, it is possible to sort out those with a good mounting state to some extent, and only those with a high probability of being in a good conduction state are conducted. You can take the test.

Further, according to the semiconductor element mounting method of the present invention, the fixing plate is fitted into the region where the wiring layer and the protective layer are not provided and the pressure is applied to the semiconductor element, so that the pressure applied to the semiconductor element has a gap. It can be reliably received by the fixing plate without intervention. Therefore, when mounting the flexible wiring board according to claim 1 or 2, when the flexible wiring board is mounted on a carrying stage having the same shape as the conventional one and heat and pressure are applied, the thickness of the wiring layer on the back side is reduced. However, according to the method for mounting a semiconductor element of the present invention, a pressure can be applied to the semiconductor element more effectively, and a flexible wiring board with high reliability can be obtained, compared with the case where a gap is generated between the semiconductor element and the transfer stage. .

[0021]

[Brief description of drawings]

FIG. 1 is a sectional structural view of a flexible wiring board according to an embodiment of the present invention.

FIG. 2 is a diagram showing a mounting structure of a semiconductor element according to an embodiment of the present invention.

FIG. 3 is a diagram showing a structure of a conventional flexible wiring board.

FIG. 4 is a view showing a mounting structure of a semiconductor element in a conventional form.

[Explanation of symbols]

1 film substrate 2A, 2B wiring 3 mounting area 4 Semiconductor element 4a connection terminal 5 through holes 5a through hole plating 6 protectant 7 ACF 8 heating tools 9 windows (area where wiring layer and protective layer are not placed) 10 Fixed plate FC flexible wiring board P electrode terminal S transfer stage

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Daijuro Takano             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5E319 AA03 AA06 AB05 AC03 AC20                       BB01 BB16 CC12 GG20                 5F044 KK03 LL11

Claims (3)

[Claims] 1. A film substrate having at least wiring layers having electrode terminals on both front and back surfaces, and a semiconductor element is thermocompression-bonded to a mounting region on the film substrate by using a paste-like or film-like adhesive. Thus, in the flexible wiring board having a multi-layer structure in which the connection terminals of the semiconductor element are electrically connected to the wiring layer, the semiconductor element is provided on the back surface side of the semiconductor element mounted in the mounting area on the film substrate. A flexible wiring board having a region in which a wiring layer is not arranged is formed in an area equal to or larger than the bottom area of the flexible wiring board. 2. The film substrate is so transparent that a position of a semiconductor element to be mounted or a position of a connection terminal of the semiconductor element to be mounted can be confirmed from a region where the wiring layer is not arranged. The flexible wiring board according to claim 1. 3. When mounting the semiconductor element on the flexible wiring board according to claim 1 or 2 by thermocompression bonding, the area where the wiring layer is not arranged has the same area and the same or large thickness as the area. Fit the fixing plate of
A method for mounting a semiconductor element, comprising: removing a fixing plate after applying heat and pressure.