JPH07176565A - Wiring board and its manufacture - Google Patents

Abstract

PURPOSE:To form a protective film which has fine apertures whose diameters are smaller than the diameters of connection pads with a high accuracy and at a low cost in order to prevent solder from penetrating onto wiring patterns from the connection pads on a wiring board when the connection electrodes of an electronic component such as a semiconductor chip are connected to the connection pads on the wiring boards with solder bumps which are formed on the connection electrodes of the electronic components beforehand. CONSTITUTION:A wiring board 41 has wiring patterns having connection pads to which the connection electrodes of an electronic component are connected. A protective film composed of an insulating film 51 such as polyimide film, PET film or PES film is applied to the approximately whole surface of a wiring board 41 which includes the wiring patterns and connection pads which are composed of metal films 43. Then the parts of the protective film composed of the insulating film 51 which are on the connection pads are removed by a laser beam 54 such as an excimer laser to form apertures 55.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board, and more particularly, to a structure of a connection portion of the wiring pattern with an electronic component,
The present invention relates to a method for manufacturing the connecting portion.

[0002]

2. Description of the Related Art Generally, a semiconductor chip such as an LSI (Large Scale Integrator) is mounted on a wiring board.
(ion: large-scale integrated circuit) is one of the methods for mounting flip-chip bonding. In this flip-chip bonding, when the connection electrodes of the LSI are connected to the connection pads of the wiring pattern of the wiring board by thermocompression bonding via solder bumps, the solder once melted during the thermocompression bonding flows out onto the wiring pattern from the connection pads, Furthermore, it may flow out from above the wiring pattern toward the adjacent wiring pattern, and a short circuit may occur between the adjacent wiring patterns. Therefore, it is necessary to form a solder flow prevention dam on the wiring board.

FIG. 6 shows an example of a conventional wiring board on which a solder flow prevention dam is formed by printing.
2, 62, 62, ... And their connection pads 63, 63,
On the wiring substrate 61 on which 63, ... Are formed, for example, by using a solder resist by printing such as screen printing,
The protective film 66 for preventing the solder flow having the opening 67 corresponding to the arrangement portion of the connection pads 63, 63, 63, ... Is formed. Reference numeral 65 indicates the chip size of the LSI 71 (see FIG. 7) mounted.

[0004]

In the protective film 66 formed by such printing, since the printing precision is not so high in the printing technique, as shown in FIG. 6, an opening having a size slightly larger than the chip size 65 to be mounted is formed. Only the portion 67 can be printed, and it is impossible to form an ideal solder flow prevention dam by corresponding to each individual connection pad 63, 63, 63 ,.

Therefore, as shown in FIGS. 7A and 7B, the connection electrodes 72 of the LSI 71 are connected to the connection pads 63 of the wiring pattern 62 of the wiring substrate 61 via the solder bumps 75 provided in advance. Melted solder 7 when thermocompression bonded
6 has a drawback that it flows out along the wiring pattern 62. The ideal solder shape is indicated by reference numeral 75, and the current solder shape is indicated by reference numeral 76. According to the current solder shape 76, the position of the LSI 71 is lowered as indicated by the dotted line shape.

By the way, when a metal film is adhered on a wiring board via an adhesive and a wiring pattern is formed by photoresist formation and wet etching, for example, even if the line width of the photoresist is 50 μm or less, the adhesive Since the cross section becomes almost trapezoidal due to the existence and the hem portion cannot be removed, the line width of the wiring pattern cannot be set to 50 μm or less, and the limit is about 50 to 60 μm. In this case, assuming that the diameter of the connection pad is about 100 to 140 μm, if the connection electrode of the LSI is connected to this connection pad by thermocompression bonding via the solder bump, the line width of the wiring pattern is relatively large, about 50 to 60 μm. During the thermocompression bonding, the solder once melted flows out from the connection pad onto the wiring pattern.

Therefore, in order to prevent the solder from flowing out from the connection pad to the wiring pattern, the diameter of the opening of the protective film is made slightly smaller than the diameter of the connection pad.
There is also a method of setting the thickness to about 100 μm and blocking the solder by the opening. However, if the diameter of the opening of the protective film is a fine pattern of about 60 to 100 μm, the protective film having such an opening cannot be formed by screen printing, and the protective film should be formed by the photolithography method. become. The reason is that in the case of screen printing, the minimum diameter of the opening is about 200 μm and the positional accuracy is within ± 300 μm, whereas in the case of the photolithography method, the minimum diameter of the opening is 10 μm.
This is because the position accuracy is within ± 20 μm at about μm.

However, when a protective film having a fine pattern of openings is formed by a photolithography method, the number of steps is considerably large and productivity is poor as compared with the case where it is formed by screen printing. However, there was a problem that the cost increased.

Therefore, an object of the present invention is to dampen solder from a connection pad on a wiring board to a wiring pattern when connecting by thermocompression bonding to a connection electrode of an electronic component such as a semiconductor chip via a solder bump provided in advance. In order to stop the problem, it is an object of the present invention to provide a wiring board in which a protective film having a fine opening smaller than the diameter of the connection pad is formed accurately and at low cost, and a manufacturing method thereof.

[0010]

In order to solve the above problems, the invention according to claim 1 is, for example, a wiring board having a wiring pattern having a connection pad connected to a connection electrode of an electronic component such as a semiconductor chip. A protective film made of, for example, an insulating film of polyimide, PET, PES, or the like is formed on almost the entire surface of the wiring board including the wiring pattern and the connection pad. The structure is characterized in that an opening removed by a laser beam such as an excimer laser is formed on the upper surface.

The invention according to claim 2 is, for example,
In a method of manufacturing a wiring board having a wiring pattern having a connection pad connected to a connection electrode of an electronic component such as a semiconductor chip, almost the entire surface including the wiring pattern and the connection pad of the wiring board, for example, A manufacturing method is characterized in that after bonding a protective film made of an insulating film such as polyimide, PET or PES, the upper surface of the connection pad of the protective film is removed by laser light such as excimer laser to form an opening. I am trying.

[0012]

According to the present invention, the upper surface of the connection pad of the protective film formed by the insulating film bonded to almost the entire surface of the wiring board including the wiring pattern and the connection pad is removed by laser light such as an excimer laser to form an opening. Since the portion is formed, it is possible to accurately form a fine opening portion smaller than the diameter of the connection pad in the protective film at low cost.

[0013]

EXAMPLE An example of a wiring board and a method for manufacturing the same according to the present invention will be described below with reference to FIGS.

First, FIGS. 1 and 2 partially show a wiring board 1 as an example to which the present invention is applied, in which 2 is a wiring pattern, 3 is a connection pad, 4 is a protective film, and 5 is an opening. is there. The wiring substrate 1 may be either a hard substrate made of ceramic or glass epoxy, or a flexible substrate made of polyimide or another resin.

As shown in FIGS. 1 and 2, the wiring board 1
On the upper surface of the wiring pattern 2, a wiring pattern 2 made of a metal film such as copper and a substantially circular connection pad 3 at its end are formed via an adhesive (not shown). Further, polyimide, PET (polyethylene terephthalate), or PES is formed on the upper surface of the wiring board 1 via an adhesive (not shown).
A protective film 4 made of an insulating film such as (polyether sulfone) is bonded.

The protective film 4 made of this insulating film
A small circular opening 5 having a substantially circular shape is formed by removing the upper surface of the connection pad 3 by irradiation with laser light such as an excimer laser described later. Here, the line width of the wiring pattern 2 is about 50 to 60 μm, and the connection pad 3
Has a diameter of about 100 to 140 μm, and the diameter of the opening 5 is about 60 to 100 μm.

A method of mounting the LSI 11 on the wiring board 1 will be described with reference to FIG. As shown in the figure, the LSI 11 has a predetermined number of connection electrodes 12 on its lower surface.
5 is provided. The LSI 11 is attracted and moved by a thermocompression bonding head (not shown), and the solder bumps 15 provided in advance on the connection electrodes 12 are aligned with the openings 5 on the wiring board 1 placed on the pressure bonding machine head (not shown). .

As described above, the solder bumps 15 are interposed between the solder bumps 15 on the wiring board 1 and the LSI 11 is pressed and heated by the thermocompression bonding head.
To melt and solidify. As a result, the connection electrodes 12 on the lower surface of the LSI 11 are connected to the connection pads 3 of the wiring board 1 via the solder bumps 15, and moreover, the solder melts and flows by the inner walls of the minute openings 5 of the protective film 4. Then, the LSI 11 is fixed on the wiring board 1 by blocking.

Next, in the case of manufacturing the wiring board 1 as described above, FIGS. 4 (a) to 4 (f) and 5 (g) to
This will be described with reference to (j).

First, FIG. 4A shows a step of adhering a metal film, in which a metal film 43 of copper or the like is adhered onto a hard or flexible substrate 41 using an adhesive 42.
Here, the substrate 41, the adhesive 42, and the metal film 43
Although the metal film 43 has a layered structure, the metal film 43 may have a two-layered structure formed by a method such as sputtering or vapor deposition instead of bonding. When the metal film 43 is directly formed on the substrate 41 without using an adhesive, the line width of the wiring pattern 2 obtained as described later can be about 10 to 30 μm.

FIG. 4B shows the next resist coating step. A resist 44 is coated on the upper surface of the metal film 43 for circuit patterning. FIG. 4C shows the next exposure step, in which the resist 44 is exposed with light energy 46 such as UV light using a glass mask 45 having a predetermined pattern.

FIG. 4D shows the next development step.
As a result, resist openings 47, 47, 47, ... Are formed. FIG. 4E shows the next etching step.
As a result, the openings 48 between the patterns are formed in the metal film 43. FIG. 4 (f) shows the next resist stripping step. In this way, the resists 44, 44, 44, ... Are stripped to form a circuit pattern by the metal films 43, 43, 43 ,.

Then, FIG. 5 (g) shows the next laminating step, in which an adhesive 52 such as an epoxy resin is provided on the entire upper surface of the substrate 41 on which the circuit pattern is formed by the metal films 43, 43, 43, .... An insulating film 51 such as polyimide or PET or PES laminated on one surface is laminated by upper and lower rollers 53, 53. Figure 5
(H) shows the next curing step, in which the adhesive 52 is cured by heating and the insulating film 51 is fixed.

Further, FIG. 5 (i) shows the next patterning step, in which the insulating film is locally irradiated with a laser beam 54 such as an excimer laser capable of easily performing high-precision spot processing at low cost. Only the upper surface portion of the connection pad 3 in the wiring pattern 2 by the metal film 43 of 51 is locally heated to be carbonized and removed, thereby forming the opening 55, and the patterned metal film 4 is formed.
The surface of 3 is exposed.

Here, the laser beam 54 is scanned in the X and Y directions to carbonize and remove the insulating film 51 on the connection pad 3 one after another. The specific removal is a vacuum. It is carried out by any means such as pulling, washing, blowing air.

FIG. 5 (j) shows the final ashing step. In order to remove scum (organic residue) remaining on the surface of the metal film 43 exposed in the opening 55, ashing is performed by oxygen plasma. To do.

In this way, the wiring pattern 2 having a line width of about 50 to 60 μm (or about 10 to 30 μm) and the connection pad 3 having a diameter of about 100 to 140 μm are formed by the metal film 43, and the insulating film 51 is used. An opening 55 opened by the laser beam 54 in the protective film 5
To form an opening 5 having a diameter of about 60 to 100 μm.

As described above, the insulating film 51 is laminated on the entire upper surface of the substrate 41 on which the circuit pattern is formed by the metal film 43, and the upper surface portion of the connection pad is removed by using the laser beam 54 by the excimer laser. The formation of the opening 55 as an ideal solder flow prevention dam is possible at low temperature and at low cost even in a flexible substrate or ultrafine. Further, since the entire circuit pattern is completely coated with the insulating film 51, the inter-pattern insulating property can be improved and the mechanical strength of the pattern can be dramatically improved.

Although the LSI is mounted on the wiring board in the above embodiments, the present invention is not limited to this, and electronic components such as other semiconductor chips can be mounted on the wiring board. It may be. Further, the shape of the wiring pattern, the application of the present invention, and the like are arbitrary, and it is needless to say that the specific detailed structure and the like can be appropriately changed.

[0030]

As described above, according to the wiring board and the method of manufacturing the same of the present invention, the upper surface of the connection pad of the protective film formed of the insulating film bonded to almost the entire surface including the wiring pattern and the connection pad is formed. By removing with a laser beam such as an excimer laser, a fine opening smaller than the diameter of the connection pad can be formed accurately and at low cost. Therefore, when connecting by thermocompression bonding to a connection electrode of an electronic component such as a semiconductor chip through a solder bump provided in advance, the solder is blocked by the fine opening in the connection pad on the wiring board to ensure a reliable connection. It can be carried out.

[Brief description of drawings]

FIG. 1 is a plan view partially showing a wiring board as an example to which the present invention is applied.

2 is a cross-sectional view of each part of the wiring board of FIG.
1A is a sectional view taken along the line AA of FIG. 1, and FIG. 1B is a sectional view taken along the line BB of FIG.

FIG. 3 is a cutaway side view showing an example of mounting an LSI on the wiring board of FIG. 1 according to the present invention.

4A and 4B show a manufacturing process of a wiring board to which the present invention is applied, wherein FIG. 4A is a sectional view showing a bonding process of a metal film;
Is a sectional view showing a resist coating step, (c) is a sectional view showing an exposure step, (d) is a sectional view showing a developing step, (e) is a sectional view showing an etching step, and (f) is a resist stripping step. It is sectional drawing shown.

5A to 5C show a manufacturing process of a wiring board according to the present invention subsequent to the manufacturing process of FIG. 4, in which (g) is a sectional view showing a laminating process, (h) is a sectional view showing a curing process, and (i) is a sectional view. FIG. 3J is a sectional view showing a patterning step, and FIG. 3J is a sectional view showing an ashing step.

FIG. 6 is a schematic plan view illustrating a wiring board having a conventional solder flow prevention dam formed by printing.

7A and 7B show an example of mounting the LSI on the wiring board of FIG. 6, where FIG. 7A is a cutaway side view and FIG. 7B is a plan view showing the LSI in a see-through state.

[Explanation of symbols]

 1 Wiring Board 2 Wiring Pattern 3 Connection Pad 4 Protective Film 5 Opening 11 LSI 12 Connection Electrode 15 Solder Bump 41 Substrate 42 Adhesive 43 Metal Film 44 Resist 45 Glass Mask 46 Light Energy 47, 48 Opening 51 Insulating Film 52 Adhesive 53 roller 54 laser light 55 opening

Claims (2)

[Claims] 1. A wiring board having a wiring pattern having a connection pad connected to a connection electrode of an electronic component, wherein an insulating film is formed on substantially the entire surface of the wiring board including the wiring pattern and the connection pad. A wiring board, wherein a protective film is formed, and an opening removed by laser light is formed on an upper surface of the connection pad of the protective film. 2. A method for manufacturing a wiring board having a wiring pattern having a connection pad connected to a connection electrode of an electronic component, wherein an insulating film is formed on substantially the entire surface of the wiring board including the wiring pattern and the connection pad. The method for manufacturing a wiring board according to claim 1, wherein after the protective film is bonded, the upper surface of the connection pad of the protective film is removed by laser light to form an opening.