KR20030091393A - Printed circuit board having permanent solder mask - Google Patents

Abstract

A printed circuit board with a kind of fixed soldering mask reinforces a substrate made of epoxy resin with glass fibers on the printed circuit board, and a conductive pattern is placed on the upper and lower surfaces of the substrate, respectively, and one epoxy resin soldered. A mask is placed on the surface of the substrate and the upper conductive pattern is covered again. The epoxy resin soldering mask has a thickness of between 2 µm and 200 µm, and the difference between the largest and the smallest thickness is equal to or smaller than 10 µm when the thickness is measured every 500 mm. The roughness degree of the surface is between 0.5 µm and 10 µm in the value of Rz.

Description

Printed Circuit Board with Fixed Solder Mask {PRINTED CIRCUIT BOARD HAVING PERMANENT SOLDER MASK}

TECHNICAL FIELD The present invention relates to the structure of a printed circuit board, and more particularly, to a printed circuit board having a kind of fixed solder mask.

Regarding the technique of installing a fixed solder mask on a printed circuit board, there is currently a relatively advanced one known as US Patent No. 5,626,774. The above patent is mainly a technique of using a resin that is four times as large as the resin contained in a kind of use and printed circuit board as a material of a soldering mask, and how to install the material on a printed circuit board to make a fixed soldering mask. Soldering masks manufactured according to the patented technology described above had a non-uniform thickness of a conventional soldering mask, low glass transition temperature (Tg), and could not accurately represent a portion of a circuit to be soldered onto a printed circuit board. The defect which the prior art had was able to be solved. However, it does not mention how uniform the thickness of the soldering mask and the total thickness of the soldering mask must be.

If the thickness of the solder mask is not uniform, the surface of the solder mask may be encapsulated in the encapsulation process subsequent to the printed circuit board, resulting in a gap between the space under pressure or a material overflow. In addition, if the surface of the solder mask of the conventional printed circuit board described above does not match the degree of roughness, the sealing material may not be firmly coupled to the surface of the solder mask and pressurized material during the subsequent encapsulation process. The phenomenon easily occurs.

In addition, since the conventional printed circuit board does not cover the circuit with a solder mask, if the circuit arrangement is densely packed to a degree or more, ion migration frequently occurs. In other words, this can reduce the density of the circuit layout. In addition, although the purpose of the opening was originally intended to be electrically conducted, it is not good to increase the heat, especially during the subsequent encapsulation of the enclosed entire structure, because the air is filled in the hollow plated opening of the upper and lower electric circuits. Not affected.

The main object of the present invention is to provide a printed circuit board with a kind of fixed solder mask. The thickness of the solder mask can be achieved according to a method of encapsulating various semiconductor chips.

It is still another object of the present invention to provide a kind of fixing in which a soldering mask can be tightly combined with a molding material for encapsulating the entire chip when making a base material for encapsulating a semiconductor chip, and does not cause a problem of overflowing material during the molding process. It is to provide a printed circuit board with a solder mask.

It is still another object of the present invention to provide a printed circuit board having a kind of fixed solder mask capable of increasing the placement density of the conductive pattern.

In order to achieve the above object, the printed circuit board of the kind of fixed solder mask provided by the present invention has one substrate. The substrate is composed of a material including the material of the first resin, and has one upper surface and a lower surface. The upper surface has a first conductive pattern, and the pattern has a shielded portion and an exposed portion. The first soldering mask is configured as a second resin, and the thermal expansion coefficient of the second resin is substantially the same as that of the first resin. The solder mask is again placed on the trademark surface of the substrate in such a way as to cover the shielded portion of the first conductive pattern and form a smooth outer surface. The uniformity of the thickness of the solder mask is equal to or smaller than 10 µm when the thickness is the largest and the smallest when the unit is measured every 500 mm.

Another feature of a printed circuit board with a kind of fixed solder mask provided by the present invention is a shielded portion and an exposed portion of the first conductive pattern, wherein the pattern of the exposed portion has a root portion and a head portion. The first solder mask has a first zone and a second zone, the first zone being installed on the branded surface of the substrate in such a way as to cover the shielded portion of the first conductive pattern and form a smooth outer surface. The second zone surrounds the root portion of the pattern of the exposed portion of the conductive pattern.

In order to more precisely understand the detailed structure and effects of the present invention, the following examples are added and the following description of the drawings is added.

1 is a cross-sectional view according to an embodiment of the present invention.

2 is a view for explaining a manufacturing process of installing a soldering mask on a substrate according to an embodiment of the present invention.

3 is an enlarged view of a portion A of FIG. 1;

4 is a cross-sectional view of a chip encapsulation method in a stacking manner in accordance with an embodiment of the present invention.

Fig. 5 is a cross-sectional view of a chip encapsulation method in a line laying manner according to another embodiment of the present invention.

6 is a cross-sectional view showing a relationship between an exposed portion of a conductive pattern and a solder mask in accordance with another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

10; Printed circuit board

20; Board

22; Upper surface 24; if

26; Conductive pattern 261; Shielded part

263; Exposed part 265; Root

28; Plated openings 281; Molding material

40; Soldering mask 401; Aluminum foil

402; Epoxy resin layer 403; Photo-resist layer

60; Chip 66; Exposed part

661; Root portion 70; glue

1 and 2, the printed circuit board 10 according to the embodiment of the present invention has one substrate 20 and two solder masks 40.

Substrate 20 is composed of a resin material containing a fiber material, the fiber material may be a glass fiber, the resin material is epoxy resin, polyamide resin, kaiite resin ( cyanoester resin). The substrate 20 has an upper surface 22 and a lower surface 24. The conductive pattern 26 is formed on the upper surface and the lower surface, respectively, and a shielded portion is formed on the conductive pattern 26 made of copper. 261 and exposed portion 263. Each of the conductive patterns communicates with a plated opening 28 passing through the plurality of substrates 20.

Each of the solder masks 40 is made of a resin material that has a thermal expansion coefficient similar to or the same as that of the resin contained in the substrate 20. The second solder mask 40 is attached to the upper surface 22 and the lower surface 24 of the substrate, and completely covers the shielded portions 261 of the conductive patterns 26 and plated openings 28 Fill in the empty middle of the). The molding material 281 at the center of the plated opening 28 is formed of the same material as the second solder mask 40 to form a single body.

When attaching the solder mask 40 to the outer surface of the substrate, an aluminum foil is first covered and a partially cured (B-staged) epoxy resin layer 402 is applied on the surface. Then, the aluminum foil is pasted on the surface of the substrate, and the epoxy resin layer 402 is sandwiched between the copper foil (aluminum foil) 401 and the surface of the substrate 20. The above combination is pressed for 1.5 to 3 hours with a pressure of 10 to 40 kgw / cm 2 and a temperature between 140 ° C and 180 ° C. In this way, the epoxy resin layer 420 is cured, fills each of the plated openings 28, and adheres to the outer surface of the substrate as shown in FIG.

In the following description, as shown in FIG. 2 (B), after the photo-resist layer 403 is applied to the aluminum foil surface, the lower surface thereof is exposed to the photo-resist layer 403. Photo-resist layer 403 creates significant shadows at locations on the shielded portions of conductive pattern 26. Again remove the photoresist layer 403 and the aluminum foil of the portion that has not yet been shadowed with a suitable solvent so as to be exposed out in correspondence with the solder mask of the exposed portion of the conductive pattern as shown in FIG. . Then, the remaining photo-resist layer 403 as a suitable chemical solvent is removed as shown in Fig. 2D.

Then, the solder mask on the exposed portion of the conductive pattern 26 is removed by using an electrolytic etching method and a laser, and as shown in FIG. 2E, the conductive pattern 26 on the substrate 20 is removed. Exposed portion 263 is exposed outward.

Finally, the remaining aluminum foil is removed as an equally suitable solvent to complete the manufacturing work of the soldering mask 40, as shown in Fig. 2F.

The thickness of the completed solder mask 40 is between 2 μm and 200 μm, and the smoothness is also quite good. Furthermore, as shown in Fig. 3, when the completed solder mask 40 is measured every 500 mm, the difference between the largest (tmax) and the smallest (tmin) is 10. It is equal to or smaller than the micrometer, and the micro-roughness of the soldering mask is generally between the Rz values of 0.5 mu m to 10 mu m.

In addition, the thickness of a soldering mask can be made relatively thick, when trying to mix | blend a stacking method of chip encapsulation with the said printed circuit board. This allows the chip 60 to adhere closely to the solder mask 40 surface. As shown in Figure 4, there is no need to fill any other material between the two. When the method of enclosing the wire encapsulation method is incorporated into the printed circuit board, as shown in FIG. 5, the thickness of the solder layer can be made relatively thin, and the chip is firmly attached to the printed circuit board with a very small amount of adhesive 70. Can be. This can significantly reduce the thickness of the entire encapsulation.

In addition, referring to FIG. 6, it is possible to have two zones when installing the soldering mask 40 of the present invention. The first zone 401 is used to completely cover the shielded portion 261 of the conductive pattern, and the second zone 402 is used to cover the root portion 265 of the exposed portion 263 of the conductive pattern. . As a result, the bonding force between the exposed portion of the conductive pattern and the substrate 20 may be increased. In addition, since the edge of the root portion 661 of the exposed portion 66 is surrounded by the insulating solder mask 402, the ion separation phenomenon does not easily occur between the adjacent patterns of the exposed portion. Therefore, the pitch of each pattern can be further reduced. In other words, the wiring density of the printed circuit board can be increased.

Claims (18)

In a printed circuit board with a fixed solder mask, A substrate made of a material comprising a first resin, having a top surface and a bottom surface, the substrate having a first conductive pattern on at least one of the top surface and the bottom surface; A first solder mask made of a second resin having a coefficient of thermal expansion substantially the same as the coefficient of thermal expansion of the first resin, the first soldering mask disposed on the top surface of the substrate to cover the shielded portion of the first conductive pattern or to form a smooth outer surface Including, The first soldering mask is a printed circuit board having a difference between the largest thickness tmax and the smallest thickness tmin when the unit is measured every 500 mm. The method of claim 1, The lower surface of the substrate also has a second conductive pattern, the second conductive pattern also has a shielded portion and an exposed portion, A printed circuit board having a second soldering mask made of said second resin and installed on said bottom surface of said substrate in such a way that said soldering mask covers the shielded portion of said second conductive pattern or forms a smooth outer surface in the same manner. The method of claim 2, A plurality of plated openings penetrating both the trademark surface and the bottom surface of the substrate, electrically communicating with the first conductive pattern and the second conductive pattern, each having a molding material separately in the plated openings; A printed circuit board having the same material as each material and the solder mask. The method of claim 1, Printed circuit board having a thickness of the solder mask is between 2㎛ 200㎛ The method of claim 1, Printed circuit board whose roughness of the outer surface of the solder mask layer is between 0.5 µm and 10 µm in terms of Rz value The method of claim 1, Printed Circuit Board Using First Resin And Second Resin As Epoxy Resin The method of claim 1 Printed circuit board using first resin and second resin as polyamide resin The method of claim 1 Printed circuit board using the first resin and the second resin as the chianeite resin In a printed circuit board with a fixed solder mask, It is made of a material including the first resin, and has one upper and one lower surface, and the first conductive pattern is installed on the outer surface of the upper surface, the pattern has a shielded portion and exposed portions, the exposed portion roots Substrate with parts and heads, Made of a second resin having a coefficient of thermal expansion substantially the same as the coefficient of thermal expansion of the first resin, having a first zone and a second zone, wherein the first zone covers or covers the shielded portion of the first conductive pattern or has a smooth outer surface. And a first soldering mask disposed on the trademark side of the substrate, the second zone including a first solder mask used to cover the root portion 265 of the exposed portion 263 of the conductive pattern. The method of claim 9, When the first zone of the first solder mask is measured every 500 mm, the difference between the thickness t max at the largest thickness and the thickness t min at the smallest thickness is equal to 10 µm, or Printed circuit board smaller than that. The method of claim 9, A second conductive pattern is provided on the lower surface of the substrate, and the pattern has a shielded portion and an exposed portion, and the exposed portion has a root portion and a head portion. It is made of a second resin, has a first zone and a second zone, the first zone is installed on the bottom surface of the substrate by covering the shielded portion of the second conductive pattern or to form a smooth outer surface, the second zone The printed circuit board includes a second solder mask in the region that covers the root portion 265 of the exposed portion 263 of the conductive pattern. The method of claim 11, It comprises a plurality of plated openings penetrating both the trademark surface and the lower surface of the substrate, electrically conductive with the first conductive pattern and the second conductive pattern, each having a molding material separately in the plated opening, A printed circuit board having the same material as each of the molding materials and each of the solder masks. The method of claim 9, Printed circuit board having a thickness of the solder mask is between 2㎛ 200㎛ The method of claim 9, Printed circuit board having a roughness degree of the first zone and the outer surface of the solder mask layer between 0.5 µm and 10 µm in terms of Rz value The method of claim 9, Printed Circuit Board Using First Resin And Second Resin As Epoxy Resin The method of claim 9 Printed circuit board using first resin and second resin as polyamide resin The method of claim 9 Printed circuit board using the first resin and the second resin as the chianeite resin In a printed circuit board with a fixed solder mask, It is made of a material containing a first resin, and has a top surface and a bottom surface, the first conductive pattern is provided on the top surface, the pattern has a shielded portion and an exposed portion, the lower surface of the second conductive A substrate having a pattern, the pattern having a shielded portion and an exposed portion, A first resin made of a second resin having a coefficient of thermal expansion substantially the same as the coefficient of thermal expansion of the first resin, the first resin being installed on the trademark surface of the substrate by covering the shielded portion of the first conductive pattern or forming a smooth outer surface; Soldering masks, and It is made of a second resin, and has a first zone and a second zone, the first zone to be installed on the lower surface of the substrate by covering the shielded portion of the second conductive pattern or to form a smooth outer surface 2 soldering mask Including; A plurality of plated openings penetrating both the upper and lower surfaces of the substrate, electrically communicating with the first conductive pattern and the second conductive pattern, each having a molding material separately in the openings; Printed circuit board with a kind of fixed soldering mask of the same material as each soldering mask.