JP4735274B2 - Flexible wiring board and manufacturing method thereof. - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a semiconductor package wiring board used for various electrical devices and a method for manufacturing the same, and more particularly, to a TAB (Tape Automated Bonding) tape in which a wiring circuit on an insulating film is formed by plating, a flexible wiring board, and It relates to the manufacturing method.

In general, TAB tape, flexible wiring boards, etc. form a wiring circuit by forming a photoresist on copper foil formed on an insulating resin film such as polyimide film, and etching unnecessary copper foil. A semi-additive method, which is advantageous for forming fine wiring, has been proposed because of the demand for higher circuit density.
In the semi-additive method, a photoresist pattern is formed on a metal seed layer formed on an insulating film, a wiring circuit is formed by plating the surface of the metal seed layer exposed to the photoresist pattern, and then the resist is applied. Peeling and removing are performed, and the remaining metal seed layer is removed by etching (see, for example, Patent Document 1).

The conventional semi-additive method will be described below with reference to FIG.
First, as shown in FIG. 4A, a nickel / chromium alloy layer as a first metal seed layer 2 and a copper sputter layer as a second metal seed layer 3 were formed on an insulating film 1 made of a polyimide film. A photoresist layer 4 is formed on the surface of a two-layer CCL (Cupper Claded Laminate) substrate using a dry film resist or the like.
Next, as shown in FIG. 4B, a desired circuit pattern is exposed on the resist layer 4 and developed to form a photoresist pattern 4 ′. The circuit pattern mask 18 at this time is corrected so that the circuit wiring width is widened in advance because the circuit wiring width is reduced by etching in a later process. That is, the width of the photoresist pattern 4 ′ is slightly narrowed.
Next, as shown in FIG. 4C, the opening from which the photoresist pattern 4 'has been removed is subjected to copper plating using a copper sulfate plating bath or the like to form a metal wiring layer 5'. Thereafter, the photoresist pattern 4 ′ is peeled and removed. The width of the metal wiring layer 5 ′ obtained at this time is slightly wider than the final target value W.

Next, as shown in FIG. 4D, the second metal seed layer 3 made of a copper sputter layer exposed between the metal wiring layers 5 ′ is removed by etching. For etching the copper sputter layer, a soft etching solution composed of sulfuric acid and hydrogen peroxide is often used. At this time, the side surface of the metal wiring layer 5 ′ is also etched, so that the etching is performed in excess of the conventional etching using only copper sputtering. In addition, it is preferable to use spray etching in order to provide selectivity of the etching rate between the upper surface of the metal wiring layer and the side surface of the metal wiring layer and to facilitate the etching of the side surface of the metal wiring layer.
Further, at this time, the metal wiring layer is thinned by etching the side surface of the metal wiring layer, but a desired metal wiring layer width W is obtained here.
Next, as shown in FIG. 4E, the first metal seed layer 2 made of a nickel / chromium alloy layer is removed by etching with a commercially available dedicated solution.
Thereafter, as shown in FIG. 4 (f), an anticorrosive metal plating layer 7 such as nickel, gold, tin plating or the like is formed on the metal wiring circuit pattern as required, and then the entire substrate surface is insulative sealing material. Cover with resin 8. At this time, if the interval between the metal wiring layers is narrowed, a gap 9 may be generated between the metal wiring layers.
Recently, a full additive method in which a metal catalyst layer is formed on an insulating film without forming a metal seed layer, and then a resist is formed and plated to form a circuit has been studied (for example, Patent Documents). 2).
JP-A-5-90737 JP-A-8-181402

In recent years, the fine pitch trend has increased in flexible wiring boards, and the area ratio of circuit wiring within the product area has been increasing. After manufacturing the flexible wiring board, it is joined to the IC chip and then sealed with the encapsulant resin, but due to the high area ratio of the wiring, the interval between the circuit wirings becomes narrower, and the encapsulant resin and the wiring board In this bonding, the ratio of direct bonding to the wiring board decreases, and the bonding ratio on the upper surface of the circuit wiring increases. As for the Pi surface, since the bonding area is reduced, poor adhesion between the substrate and the sealing material resin occurred when the heat cycle test was performed.
The problem to be solved by the present invention is to solve the above-mentioned problems and increase the bonding area with the encapsulant resin while ensuring the top-bottom ratio that is indispensable for making fine pitches. The present invention provides a flexible wiring board having high bonding strength and high reliability and a method for manufacturing the same.

In order to solve the above-mentioned problems, the present invention is a metal wiring board in which a metal wiring layer is formed on at least one surface of an insulating film, and a flexible wiring board having a depression on a side surface of the metal wiring layer.
By using a flexible wiring board having such a structure, it is possible to increase the contact area of the encapsulant resin and to have a high adhesion strength and a highly reliable flexible wiring board.

In the flexible wiring board of the present invention, the metal wiring layer has a laminated structure, the metal forming the intermediate layer exhibits microcrystals, and the recesses are formed on the side surfaces of the intermediate layer made of the metal microcrystals. It can be.
This is because the presence of the microcrystalline metal layer in the metal wiring layer portion makes it possible to easily form a depression by an etching process.

In the flexible wiring board of the present invention, the metal wiring layer is preferably formed of a copper plating layer on the surface of the insulating film via at least one metal seed layer.
This is because a wiring circuit firmly bonded to the substrate can be easily obtained.
Moreover, in the flexible wiring board of the present invention, the intermediate layer exhibiting microcrystals is 0.1 μm or more from the interface with the insulating film or the metal seed layer on the surface of the insulating film and 0.1 μm or less from the surface of the metal wiring layer. It is preferable to be formed between. The depth of the depression on the side surface of the metal wiring layer is preferably 0.1 μm or more and 25% (one side) or less of the metal wiring layer width from the side surface of the metal wiring layer.
This is because the contact area of the sealing material resin is ensured and a highly reliable flexible wiring board including the sealing material resin having high adhesion strength is provided.

One of the methods for producing a flexible wiring board of the present invention is to form a photoresist layer on at least one surface of an insulating film, and after exposing and developing, copper plating is applied to the substrate patterned with the photoresist. In the method of manufacturing a circuit wiring board for forming a metal wiring layer, a copper plating is performed by setting the current density in the middle of the copper plating step to be lower than the current density in the preceding and succeeding steps, and then etching is performed. The manufacturing method is to form a depression on the side surface of the wiring layer.
Another method for producing a flexible wiring board according to the present invention is to form at least one metal seed layer on at least one surface of an insulating film, then form a photoresist layer, and after exposure, development, In a method for manufacturing a circuit wiring board in which a metal wiring layer is formed by performing copper plating on a substrate patterned with a resist, the current density in the middle of the copper plating process is made lower than the current density in the preceding and following processes. This is a manufacturing method in which a depression is formed on the side surface of the metal wiring layer by performing an etching process after copper plating.
In addition, it is possible to employ a manufacturing method in which the current density in the copper plating step is increased immediately after the start of plating, the current density is once lowered, and then the current density is increased again.
By adopting such a method, the metal crystal in the middle of the metal wiring layer becomes a fine crystal, and a recess can be easily formed on the end face by etching.

Further, in the method for manufacturing a flexible wiring board of the present invention, following the manufacturing method, a metal plating layer is formed at a desired location on the surface of the metal wiring layer, and the entire surface of the substrate excluding the metal plating layer is encapsulated with resin. It is preferable to seal with.
With such a manufacturing method, the contact area of the encapsulant resin can be ensured, and a highly reliable flexible wiring board equipped with the encapsulant resin having high adhesion strength can be reliably formed by a simple method. it can.

  As described above, the wiring board according to the present invention can provide a highly reliable wiring board since the number of sealing resin peeling defects is reduced as compared with a conventional wiring board.

The flexible wiring board of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional structure diagram showing an example of the flexible wiring board of the present invention.
A flexible wiring board 10 of the present invention shown in FIG. 1 includes a first metal seed layer 2 made of a Ni / Cr alloy and a second metal seed made of a sputtered copper layer on one surface of an insulating film 1 made of polyimide resin or the like. A metal wiring layer 5 made of a copper plating layer is formed through the layer 3.
The metal wiring layer 5 has a three-layered structure, the intermediate portion 5b of the metal wiring layer 5 is made of copper microcrystals, and the vicinity 5a of the interface with the second metal seed layer 3 and the outermost surface 5c are plated. It exhibits the usual crystal size of precipitated copper. And it has the hollow 6 in the side surface of the metal wiring layer of the intermediate part 5b. The depression 6 on the side surface of the metal wiring layer 5 is for encroaching a sealing material resin to be firmly joined as will be described later.

FIG. 2 is a sectional structural view showing another example of the flexible wiring board of the present invention.
The flexible wiring board 11 of the present invention shown in FIG. 2 has a first metal seed layer 2 made of Ni / Cr alloy and a second metal seed made of a sputtered copper layer on one surface of an insulating film 1 made of polyimide resin or the like. A metal wiring layer 5 made of a copper plating layer is formed through the layer 3.
The metal wiring layer 5 has a three-layered structure, the intermediate portion 5b of the metal wiring layer 5 is made of copper microcrystals, and the vicinity 5a of the interface with the second metal seed layer 3 and the outermost surface 5c are plated. It exhibits the usual crystal size of precipitated copper. And it has the hollow 6 in the side surface of the metal wiring layer 5 of the intermediate part 5b.

On the surface of the metal wiring layer 5, a metal plating layer 7 is formed on a terminal portion for preventing corrosion and making contact with an external lead if necessary, and the entire surface of the flexible wiring board excluding the metal plating layer 7. Is covered with a sealing material resin 8 and sealed.
If the flexible wiring board having such a structure is used, the sealing material resin 8 bites into the depression 6 on the side surface of the metal wiring layer 5, so that the sealing material resin 8 and the metal wiring layer 5 bite in and firmly bond. Therefore, the possibility that the sealing material resin is peeled off is extremely reduced. A metal plating layer 7 of a corrosion-resistant metal is formed on the terminal portion for the external contact, and the entire surface of the flexible wiring board excluding the metal plating layer 7 is covered with a sealing material resin 8, so that even if the metal wiring layer is sealed Even when the cavity 9 is generated in the stopper resin 8, the sealing resin 8 is not peeled off, and the performance of the wiring board is not deteriorated by being corroded by moisture in the atmosphere.

Hereinafter, an example of a method for producing a flexible wiring board in the present invention will be described with reference to FIG.
FIG. 3 is a cross-sectional process diagram illustrating an example of a method for manufacturing a flexible wiring board according to the present invention.
First, as shown in FIG. 3A, for example, a substrate material in which two metal seed layers 2 and 3 made of a nickel / chromium alloy layer and a copper sputter layer are formed on one surface of an insulating resin film 1 such as polyimide resin. , A photoresist layer 4 made of a dry film is formed on the surface of the copper sputter layer forming the second metal seed layer 3 by a laminating method.
Next, as shown in FIG. 3B, the photoresist layer 4 is exposed and developed to form a resist pattern 4 '. The circuit pattern mask 18 at this time is corrected so that the circuit wiring width is widened in advance because the circuit wiring width is reduced by etching in a later process. That is, the width of the photoresist pattern 4 ′ is slightly narrowed.

Next, as shown in FIG. 3C, the surface of the copper sputter layer, which is the second metal seed layer 3 exposed at the opening of the resist pattern 4 ', is plated with copper to form a metal wiring layer 5'. Do. The width of the metal wiring layer 5 ′ is slightly larger than the target width of the metal wiring layer. A commercially available copper sulfate plating bath can be used for copper plating.
At this time, the current density of the copper plating is deposited on the surface of the second metal seed layer 3 in the initial stage of plating, so that the resistance value is high and a high current cannot be set. Therefore, it starts at a low current density at the initial stage of plating, and gradually increases to a higher current density as the latter half is reached. However, the current density is lower than the current density setting value before and after the intermediate stage of copper plating. Thus, a plating layer is formed.
The copper plating layer in the vicinity 5a of the interface with the second metal seed layer 3 deposited at a high current density and the outermost surface 5c has a normal crystal size of plated copper. On the other hand, the intermediate portion 5b deposited at a low current density exhibits copper microcrystals, and a brittle plating layer is formed.

Next, as shown in FIG. 3D, the second metal seed layer 3 made of a copper sputter layer exposed between the metal wiring layers 5 ′ is removed by etching. For etching the copper sputter layer, a soft etching solution composed of sulfuric acid and hydrogen peroxide is often used. At this time, since the side surface of the metal wiring layer 5 ′ is also etched, the etching is performed in excess of the conventional etching using only copper sputtering. In addition, it is preferable to use spray etching in order to provide selectivity of the etching rate between the upper surface of the metal wiring layer and the side surface of the metal wiring layer and to facilitate the etching of the side surface of the metal wiring layer.
At this time, the width of the metal wiring layer is reduced by etching the side surface of the metal wiring layer, but a desired metal wiring layer width W is obtained here.

Next, as shown in FIG. 3E, the first metal seed layer 2 made of a nickel / chromium alloy layer is removed by etching with a commercially available nickel / chromium etchant to expose the insulating film 1.
Thereafter, as shown in FIG. 3 (f), the side surface of the metal wiring layer made of the copper plating layer is spray-etched using an acidic etching solution mainly composed of hydrogen chloride and ferric chloride. At this time, since the intermediate portion 5b presenting the microcrystals deposited at a low current density of the metal wiring layer 5 is fragile, the interface vicinity 5a and the outermost surface 5c with the second metal seed layer 3 exhibiting a normal crystal size. Since the etching speed is faster than that, a recess 6 is formed in the intermediate portion 5b.
In this way, the flexible wiring board 10 having excellent durability and high reliability shown in FIG. 1 is obtained.

  Further, in the flexible wiring board of the present invention, a terminal portion for making contact with external wiring is provided on the pattern of the metal wiring circuit as necessary, as in the prior art, following the above, and the metal wiring of the terminal portion is provided. The surface of the circuit pattern can be plated with a desired metal, such as nickel, gold, or tin plating, which has good electrical conductivity and is resistant to rust. If the front surface of the substrate excluding the terminal part is sealed with an insulating sealing resin after the terminal part is plated with metal, the flexible wiring board 11 having excellent durability and high reliability as shown in FIG. Become.

The present invention will be further described with reference to the following examples.
In this example, a flexible wiring board having the structure shown in FIG. 2 was prepared according to the process diagram shown in FIG.
In this example, a material in which a nickel / chromium layer having a thickness of 170 mm and a copper sputter layer having a thickness of 0.3 μm formed by a sputtering method on a polyimide film having a thickness of 38 μm was used.
First, as shown in FIG. 3A, a dry film resist (product name RY-3215: Hitachi Chemical Co., Ltd.) was laminated on the surface of the copper sputter layer.
Next, as shown in FIG. 3B, the dry film resist was exposed at an illuminance of 40 mJ, developed by bringing the dry film resist into contact with a 1% sodium carbonate aqueous solution at a temperature of 30 ° C., and a resist pattern was formed. .

Next, as shown in FIG.3 (c), the copper plating was performed using the commercially available copper sulfate plating bath. With regard to copper plating, single layer lamination has high electrical resistance and slow plating speed, resulting in a reduction in production efficiency. Therefore, for the plating tank, the distance between the tanks was shortened to such an extent that the resistance value did not increase, and efforts were made to improve production efficiency. Therefore, the plating tank was separated into 12 tanks. In the initial stage of plating, since it is deposited on the seed layer surface, the electric resistance is high and an overcurrent cannot flow. Therefore, the initial current density was started from 0.5 A / dm ² , and the current density was stepped up in three stages to obtain a laminated structure of a total of 12 plating layers. The maximum current density after the sixth layer is 4.0 A / dm ^{2. In} this example, the current density of the eighth layer was set at 0.5 A / dm ² .
As a result, as shown in FIG. 3C, a copper plating layer in which fine crystal grain layers were laminated in the vicinity of the intermediate layer of the metal wiring layer was formed. Thereafter, the dry film resist was peeled and removed using an aqueous sodium hydroxide solution having a concentration of 5%.

Next, as shown in FIG. 3 (d), using a soft etching solution (product name: CPE800: manufactured by Hishie Chemical Co., Ltd.) whose main components are sulfuric acid and hydrogen peroxide, a temperature of 30 ° C. and a pressure of 0.1 MPa. Then, a spray etching process was performed for about 30 seconds to remove the copper sputtered layer by etching.
Next, as shown in FIG. 3 (e), the exposed nickel / chromium alloy layer was immersed for 2 minutes at a temperature of 40 ° C. using a commercially available nickel / chromium selective etching solution (product name CH1920: MEC), The nickel / chromium alloy layer was removed.
Next, as shown in FIG.3 (f), the exposed part of the obtained copper plating layer is made into the commercially available acidic etching liquid (Product name C-800: Asahi Denka Kogyo (product name C-800) whose main components consist of hydrogen chloride and ferric chloride. Was used, and the spray etching treatment was performed at 40 ° C. for 10 seconds. As a result, the fine crystal grain layer in the intermediate layer of the metal circuit wiring made of the copper plating layer had a depression shape on the side surface because the etching rate at that portion was faster than the others.

  After that, as in the conventional technology, if necessary, tin plating is applied to the metal wiring pattern, and a protective film made of a sealing material resin is formed on the entire surface of the substrate including the exposed surface of the metal circuit wiring pattern. A substrate was obtained.

  After performing ACF bonding with an IC chip on the flexible wiring board formed as described above, a sample subjected to hermetic insulation treatment with a sealing material resin was used as a JESD22-A104-A temperature cycle test, -65 + 0 / When 500 cycles were carried out at −10 * 200 + 10 / −0 ° C., peeling between the encapsulant resin and the substrate wiring occurred at 8/1000 pcs for those manufactured by the conventional manufacturing method. For the flexible wiring board, the number of peeling defects decreased to 0/1000 pcs. Due to the depression shape of the side surface of the metal wiring, the adhesive force with the sealing material resin was increased, and the number of defective peeling was reduced, so that a highly reliable wiring board could be provided.

It is sectional drawing which shows an example of the flexible wiring board of this invention. It is sectional drawing which shows the other example of the flexible wiring board of this invention. It is sectional process drawing explaining the manufacturing method of the flexible wiring board of this invention, (a) is the figure which formed the photoresist layer, (b) is the figure which formed the photoresist pattern, (c) is metal by plating. The figure which formed the wiring layer, (d) is the figure which removed the 2nd metal seed layer, (e) is the figure which removed the 1st metal seed layer, (f) is the completion figure of the flexible wiring board of this invention It is. It is sectional process drawing explaining the manufacturing method of the conventional flexible wiring board, (a) is the figure which formed the photoresist layer, (b) is the figure which formed the photoresist pattern, (c) is metal wiring by plating. The figure which formed the layer, (d) the figure which removed the 2nd metal seed layer, (e) the figure which removed the 1st metal seed layer, (f) formed the metal plating layer and the sealing material resin It is the completion drawing of the flexible wiring board which was made.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulating film 2 1st metal seed layer 3 2nd metal seed layer 4 Photoresist layer 5 Metal wiring layer 6 Depression 7 Metal plating layer 8 Sealing material resin 9 Space | gap 10, 11 Flexible wiring board

Claims (8)

A metal wiring board having a metal wiring layer formed on at least one surface of an insulating film,
The metal wiring layer is composed of a copper plating layer deposited at a high current density, wherein the interface between the intermediate copper plating layer deposited at a low current density and the intermediate portion is higher than the current density at the middle portion. A flexible wiring board having a structure and having a depression on a side surface of the intermediate portion . The intermediate portion, the insulating film or the interface from 0.1μm above the metal seed layer of the insulating film surface, to claim 1, characterized by being formed during the following 0.1μm from the metal wiring layer surface The flexible wiring board as described. Depression depth of the side surface of the metal wiring layer, or 0.1μm from the side surface of the metal wiring layer, 25% of the metal wiring layer width (one side) of claim 1 or 2, wherein the less is Flexible wiring board.   In a method of manufacturing a circuit wiring board, a photoresist layer is formed on at least one surface of an insulating film, and after exposure and development, a metal wiring layer is formed by performing copper plating on a substrate patterned with a photoresist. A recess is formed on the side surface of the metal wiring layer by performing an etching process after performing copper plating by making the current density in the middle of the copper plating process lower than the current density of the preceding and succeeding processes. Manufacturing method of flexible wiring board.   After forming at least one metal seed layer on at least one side of the insulating film, a photoresist layer is formed, and after exposure and development, the substrate patterned with photoresist is plated with copper to form a metal. In the method of manufacturing a circuit wiring board for forming a wiring layer, a metal wiring is obtained by performing an etching process after performing copper plating by lowering the current density in the middle of the copper plating process to be lower than the current density in the preceding and succeeding processes. A method for producing a flexible wiring board, comprising: forming a depression on a side surface of a layer. The method for manufacturing a flexible wiring board according to claim 4, wherein the current density in the copper plating step is increased immediately after the start of plating, the current density is once decreased, and then the current density is increased again. A method for manufacturing a flexible wiring board, comprising forming a metal plating layer at a desired location on the surface of the metal wiring layer following the manufacturing method according to any one of claims 4 to 6 . The manufacturing method of the flexible wiring board characterized by sealing the board | substrate whole surface except the said metal plating layer with sealing material resin further following the manufacturing method of Claim 7 .

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