JP2001274277A - Printed wiring substrate with projection electrode and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring substrate with a projection electrode of high aspect ratio, which can maintain a clearance between a chip and a wiring substrate to enable sealing resin to be poured therein readily, and is excellent in connection reliability even in connection of a chip electrode of narrow pitch. SOLUTION: In this printed wiring substrate with a projection electrode, a side surface of a projection electrode 7, which is formed of conductive paste 6 and is projected to a surface of the wiring substrate 1, is coated with a protection layer 5 consisting of a photosensitive resin layer 2 in a printed wiring substrate, where a via hole and the projection electrode 7 formed of the conductive paste 6 are formed integrally.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board suitably used for CSP (chip size package), BGA (ball grid array) and the like.
We propose a printed wiring board with protruding electrodes with excellent connection reliability and its manufacturing technology.

[0002]

2. Description of the Related Art In recent years, as electronic devices and electronic components have been miniaturized, the connection form of an IC chip used for them to a printed wiring board has been changing from wire bonding to flip chip mounting.

[0003] In this flip chip mounting, a method of joining electrodes using solder balls is widely known. For joining using this solder ball, the solder ball is arranged on one of the electrodes of the wiring board or the IC chip,
The connection is performed by reflowing after the alignment with the other connection electrode, and the sealing resin is poured into the gap between the IC chip and the wiring board and hardened, thereby improving the connection reliability.

According to the above-described joining method using solder balls, the height of the IC chip mounted on the printed wiring board can be increased by adjusting the diameter of the solder balls. As a result, it is possible to reduce the influence of external stress caused by a difference in the coefficient of thermal expansion between the chip and the wiring board due to a change in ambient temperature, and to improve electrical connection reliability by resin sealing.

However, in such a bonding method using solder balls, when the electrode spacing in the IC chip becomes narrow (narrow pitch), minute solder balls are required in accordance with the pitch. The interval becomes smaller. As a result, in the connection of the chip electrodes having a reduced pitch, the effect of reducing the external stress due to a change in ambient temperature cannot be expected. In addition, since it is difficult to pour the sealing resin, it is desired to increase the gap between the IC chip and the electrode of the wiring board in terms of connection reliability.

[0006] On the other hand, various connection techniques have been proposed in place of the above-mentioned joining method using solder balls. For example, a method in which an electrode of a wiring board and a bump (projection electrode) of an IC chip are joined via a conductive adhesive and sealed with a sealing resin,
There is known a method in which an anisotropic conductive film is arranged between an electrode of a wiring board and a bump of an IC chip, aligned, and then bonded by applying pressure and heat.

According to these joining methods, it is easy to cope with a narrow pitch. However, in the bonding method using a conductive adhesive, the bump height to be formed on the chip side is limited because the bump is formed by plating or stud bump.

In addition, in the bonding method using an anisotropic conductive film, the reliability of the electrical connection between the electrodes is ensured through the conductive particles in the film by applying pressure and heat.
In order to maintain the connection reliability, the thickness (mounting height) of the film is restricted.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned restrictions and the like, and its main object is to connect a chip and a wiring board even when connecting chip electrodes having a reduced pitch. An object of the present invention is to provide a printed wiring board having a projection electrode having a high aspect ratio, which is capable of maintaining an interval for facilitating the flow of the sealing resin, and which is excellent in connection reliability. Another object of the present invention is to
An object of the present invention is to propose a technique for manufacturing a wiring board in which protruding electrodes having a high aspect ratio can be stably arranged on the surface of a printed wiring board.

[0010]

Means for Solving the Problems The inventors of the present invention have intensively studied for realizing the above-mentioned object, and as a result, have arrived at an invention having the following content as a gist configuration. That is,. The printed wiring board with a protruding electrode of the present invention is a printed wiring board in which via holes and a protruding electrode made of a conductive paste are integrally formed, wherein the protruding electrode made of a conductive paste protruding on the surface of the wiring board is The side surface of the electrode is covered with a protective layer made of a photosensitive resin layer. Here, as a preferred embodiment, the printed wiring board with a projecting electrode of the present invention preferably has a projecting electrode having an aspect ratio (projection height / projection diameter) in which the projection height is larger than the projection diameter, which is 1 or more, It is also preferable to use it for flip chip mounting.

[0011] The method for manufacturing a printed wiring board with bump electrodes according to the present invention includes at least the following steps, that is, (1) a step of sequentially forming an insulating resin layer and a photosensitive resin layer on a core substrate surface provided with a wiring pattern; 2) a step of piercing a hole reaching the wiring pattern through a thickness direction of the resin layer formed in the above (1) using a laser beam, and (3) a step of using an active energy ray, that is, a negative type. In the case of a photosensitive resin, the photosensitive resin layer is irradiated with an active energy ray, and in the case of a positive photosensitive resin, the resin is thermally decomposed by irradiation with an active energy ray and heating, so that the photosensitive resin layer is subjected to the above (2). A step of forming an exposure pattern that becomes a protective layer having a certain width from the inner wall surface of the perforated hole,
(4) a step of filling the hole with a conductive paste to be a via hole and a protruding electrode and thermosetting, and then removing excess paste protruding from the hole by surface polishing; (5) the step of (3). Developing the photosensitive resin layer that has been subjected to the pattern exposure to form a bump electrode having a structure covered with a protective layer made of the photosensitive resin layer. Here, as another aspect, in the manufacturing method of the present invention, in the step (3), the pattern exposure of the photosensitive resin layer can be performed by a laser beam.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A printed wiring board with a protruding electrode according to the present invention protects a protruding electrode made of a conductive paste protruding from the surface of an insulating resin substrate by protecting a side surface excluding an electrical connection portion from a photosensitive resin. The feature is that the structure is covered with a layer. With such a structure, even when a projection electrode having a projection height larger than the projection diameter and having an aspect ratio (projection height / projection diameter) of 1 or more is formed on the wiring board, it is regarded as a minute projection. A structure resistant to external stress is obtained. As a result, through the protruding electrodes, the electrodes can be connected to each other with high reliability while ensuring a wide space between the chip and the wiring board. In addition, the flow of the sealing resin is facilitated, so that the process can be shortened and the reliability of electrical connection can be improved by reliable resin sealing.

Hereinafter, the present invention will be described in more detail with reference to a manufacturing process diagram of a printed wiring board with bump electrodes shown in FIG. (1) First, an insulating resin layer 2 and a photosensitive resin layer 3 are sequentially formed on a core substrate (a multilayer wiring substrate 1 is illustrated in FIG. 1) having at least one surface provided with a wiring pattern (FIG. 1). FIG. 1A). In particular, in the present invention, the height of the projection electrode 7 to be formed can be arbitrarily adjusted by the thickness of the photosensitive resin layer 3. Here, as the insulating resin layer 2 that can be used in the present invention, an insulating resin composition constituting an interlayer material or the like of a build-up substrate may be mentioned.
The form of use may be liquid or film. Examples of the photosensitive resin layer 3 that can be used in the present invention include a photosensitive resin composition having a negative or positive developing property, and the resin type may be an alkali developing type, a solvent developing type, or a water developing type. The form of use may be liquid or film. However, it is necessary that this photosensitive resin composition does not contain a thermosetting component. These resin layers are
When the resin composition is in a liquid state, it is applied by a method such as screen printing, curtain coating, roll coating, spray coating and the like, and then dried. It is formed as a coating film, and in such a manufacturing stage, the insulating resin layer can be in a state of being cured by heating.

(2) Next, a hole 4 is formed in a predetermined position of the resin layer formed in the above (1) in the thickness direction to reach the wiring pattern by using a laser beam. here,
As the laser light used for perforating the hole 4, any laser light used for a laser abrasion method can be used without particular limitation. For example, an excimer laser,
Examples include a YAG laser, a carbon dioxide laser, and a semiconductor laser. "Laser abrasion method"
The term means a method of irradiating a laser beam to an object to decompose or evaporate and scatter the laser irradiation portion of the object to a desired depth.

(3) Next, when a negative photosensitive resin is used as the photosensitive resin layer 3, it is cured by irradiation with active energy rays through a mask, and a positive photosensitive resin is used as the photosensitive resin layer 3. In this case, the holes 4 formed in (2) above are formed in the photosensitive resin layer 3 by thermal decomposition of the resin by irradiation with active energy rays through a mask and heating.
An exposure pattern to be a protective layer 5 having a constant width is formed from the inner wall surface (see FIG. 1B). Here, the above (2)
And the pattern exposure of the photosensitive resin layer 3 can be continuously processed by laser light. Further, the pattern exposure by irradiation with the active energy ray (ultraviolet light, laser light in the ultraviolet wavelength range, etc.) may be performed before the perforation of the hole 4 described in the above (2), but when a negative photosensitive resin is used. Is advantageous in that the exposure after exposure of the hole 4 allows the resin layer located at the bottom of the hole 4 to be efficiently cured.

(4) Next, the hole 4 is filled with the conductive paste 6 to be the via hole and the protruding electrode 7 and thermally cured, and then the excess paste 6 protruding from the hole 4 is removed by surface polishing. (See FIG. 1 (c)). The hardening of the conductive paste 6 performed before the surface polishing may be either temporary hardening or full hardening. Further, pressure may be applied during curing. Here, examples of the conductive paste 6 include pastes used for filled vias and the like of a build-up substrate, such as Ag powder, Cu powder, gold-plated Ni powder, and the like.
Alternatively, a paste in which a solder powder or the like and a thermosetting resin such as an epoxy resin are mixed can be used. In particular, in the present invention, the paste 6 is embedded in the photosensitive resin layer 3.
Since the surface can be polished to adjust the height of the bump electrodes 7, a bump electrode group having a high aspect ratio can be stably formed at a uniform height even at a narrow pitch.

(5) By developing the photosensitive resin layer 3 which has been subjected to the pattern exposure in the above (3), a projecting electrode 7 having a structure in which the side surface is covered with the protective layer 5 made of the photosensitive resin layer 3 is formed. FIG. 1D). Here, a known developer can be used as the developer used for developing the resin layer. For example, as a weak alkaline aqueous solution, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, amine Aqueous dilute aqueous alkali solutions such as those described above can be used.

The printed wiring board with the protruding electrodes manufactured in this way is a printed wiring board in which the via holes made of the conductive paste 6 and the protruding electrodes 7 are integrally formed, and protrudes from the surface of the wiring board. It is characterized in that the side surface of the bump electrode 7 made of the conductive paste 6 is covered with the protective layer 5 made of the photosensitive resin layer 3.

Such a printed wiring board with protruding electrodes is electrically connected to the electrodes of an IC chip, for example, as follows. That is,. A connection layer 8 made of solder, conductive adhesive, or the like is formed on the surface of the bump electrode 7 of the printed wiring board by plating, screen printing, transfer, or the like (see FIG. 2A). . The electrodes 10 of the IC chip 9 are aligned with the protruding electrodes 7 of the wiring board, and the electrodes are connected by heating or heating / pressing. . Further, after an operation test of the IC chip 9 is performed, a sealing resin 11 is poured between the IC chip 9 and the wiring board in order to maintain the connection reliability, and is sealed by heating and curing (FIG. 2).
(B)).

[0020]

EXAMPLES The present invention will be described in detail with reference to the following examples, but it goes without saying that the present invention is not limited to the following examples. (Example 1) (1) First, a thermosetting insulating resin composition containing an epoxy resin as a main component is applied on the entire surface of a glass epoxy substrate on which a conductive circuit is formed by screen printing, and then,
The composition was cured at 150 ° C. for 30 minutes to form an insulating resin layer having a thickness of 20 μm. Further, a negative photosensitive resin composition is applied on the entire surface of the insulating resin layer by screen printing, and then dried at 80 ° C. × 20 minutes to obtain a thickness of 100 μm.
A μm negative photosensitive resin layer was formed. (2) Next, using a carbon dioxide laser, a via hole having an inner diameter of 100 μm and a hole for forming a protruding electrode that penetrates the two resin layers formed in the above (1) in the thickness direction and reaches the inner layer circuit conductor is formed. Perforated. (3) In the hole with an inner diameter of 100 μm drilled in (2),
A mask having an opening having a diameter of 50 μm is aligned so that the center of the hole and the opening of the mask coincide with each other, and is irradiated with ultraviolet light.
The negative photosensitive resin layer was cured to a thickness of about 25 μm from the inner wall surface of the hole. (4) Next, a thermosetting silver paste was buried in the via hole and the hole for forming the protruding electrode, and temporarily cured at 100 ° C. for 30 minutes. Then, excess paste protruding from the holes was removed by polishing until the surface of the photosensitive resin layer was exposed. (5) Developing with a 1.0% aqueous solution of sodium carbonate for 90 seconds, followed by washing with water for 30 seconds and drying to remove the unexposed portion of the photosensitive resin layer. (6) Thereafter, the silver paste was fully cured at 150 ° C. for 60 minutes.

The printed wiring board with the protruding electrodes manufactured as described above has an outer diameter of 100 μm and a height of about 100 μm.
A projection electrode was formed in a state where a side surface of a cylindrical projection made of a silver paste (aspect ratio = 1) was covered with a protective layer made of a negative photosensitive resin having a thickness of about 25 μm.

(Embodiment 2) In (3) of Embodiment 1, instead of irradiating ultraviolet rays through a mask, 364
Approximately 25 mm from the inner wall of the hole using an excimer laser
A printed wiring board with protruding electrodes was manufactured in the same manner as in Example 1 except that the negative photosensitive resin layer was cured to a thickness of μm.

The printed wiring board with the protruding electrodes according to the above embodiment manufactured as described above has a structure resistant to external stress, and has a group of cylindrical projections having a large aspect ratio and a uniform height. Met. Further, even in connection of the chip electrodes having a reduced pitch, the structure is such that the sealing resin can be easily poured, and flip-chip mounting with excellent reliability of the connection portion can be easily realized.

[0024]

As described above, according to the present invention, even in the connection of the chip electrodes having a reduced pitch, the distance between the chip and the wiring board can be maintained at such a distance that the sealing resin can be easily poured. A printed wiring board having a protruding electrode having a high aspect ratio can be provided. Further, in the printed wiring board with the protruding electrodes of the present invention, the protruding electrodes are covered with the protective layer made of the photosensitive resin, so that the protruding electrodes resistant to external stress are formed. Moreover, the height of the protruding electrodes can be arbitrarily adjusted depending on the thickness of the photosensitive resin layer, and a protruding electrode group having a uniform height can be obtained. as a result,
If the electrodes of the wiring board and the electrodes of the IC chip are connected via such protruding electrodes, flip-chip mounting with excellent reliability of the connection portion can be easily realized.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a printed wiring board with a protruding electrode according to the present invention.

FIG. 2 is a printed wiring board with a protruding electrode and an IC according to the present invention.
It is a figure showing the example of connection with a chip.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wiring board 2 Insulating resin layer 3 Photosensitive resin layer 4 Via hole and hole for projection electrode 5 Protective layer 6 Conductive paste 7 Projection electrode 8 Connection layer 9 IC chip 10 IC chip electrode 11 Sealing resin

Claims (5)

[Claims] In a printed wiring board in which a via hole made of a conductive paste and a projecting electrode are integrally formed, a side surface of the projecting electrode made of a conductive paste projecting on the surface of the wiring board is photosensitive. A printed wiring board with protruding electrodes, which is covered with a protective layer made of a resin layer. 2. The printed wiring board with projection electrodes according to claim 1, further comprising projection electrodes having an aspect ratio (projection height / projection diameter) in which the projection height is larger than the projection diameter and is 1 or more. 3. The printed wiring board according to claim 1, wherein the printed wiring board is used for flip-chip mounting. 4. At least the following steps: (1) a step of sequentially forming an insulating resin layer and a photosensitive resin layer on the surface of the core substrate on which the wiring pattern is provided; and (2) the step (1) using a laser beam. A) forming a hole through the resin layer formed in the thickness direction to reach the wiring pattern; and (3) forming a hole in the photosensitive resin layer using the active energy ray in the step (2). A step of forming an exposure pattern to be a protective layer having a certain width from the inner wall surface of the hole, (4) filling the hole with a conductive paste to be a via hole and a protruding electrode, thermosetting, and then projecting from the hole (5) removing the excess paste by surface polishing, and (5) developing the photosensitive resin layer subjected to the pattern exposure in (3) to develop a structure in which the side surface is covered with a protective layer made of the photosensitive resin layer. Forming a protruding electrode. A method for manufacturing a printed wiring board with a protruding electrode, the method comprising: 5. The method according to claim 4, wherein in the step (3), the pattern exposure of the photosensitive resin layer is performed by a laser beam.