JP2003347711A - Printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed circuit board provided with a fixed solder mask having a thickness adaptable to packing semiconductor chips of various types. <P>SOLUTION: A substrate 20 and a solder mask 40 are provided. The substrate 20 is made from a fabric material or an impregnated resin, and comprises a top surface 22 and a bottom surface 24. The top surface 22 is provided with a conductive circuit 26 which includes a shielded part 261 and an exposed part 263. The solder mask 40 is made from a resin material whose thermal expansion factor is substantially identical with that of a resin contained in the substrate 20. The solder mask 40 covers the shielded part 262 of the conductive circuit 26, and is disposed on the top surface 22 of the substrate 20 by a method for forming a flat exterior surface. The difference between the maximum thickness and the minimum thickness of the solder mask 40 is 10 μm or less, making each 500 mm a unit length for measurement. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a printed circuit board, and more particularly, to a printed circuit board having a fixed solder mask.

[0002]

2. Description of the Related Art As a technique for disposing a fixed solder mask on a printed circuit board, US Pat. No. 5,626,774 discloses a relatively advanced technique. There is a technique in which a resin compatible with the contained resin is used for the material of the solder mask, and how the material is disposed on the printed circuit board to form a fixed solder mask. Solder masks manufactured by the technology have solved the problem that the thickness of the conventional solder mask is not uniform, the glass transition temperature (Tg) is low, and the circuit portion to be welded on the printed circuit board is not accurately represented. It does not mention how to select the thickness of the mask or how much the thickness uniformity of all layers of the solder mask should be.

[0003]

If the thickness of the solder mask is not uniform, the printed circuit board will have a gap between the surface of the solder mask and the package die during the subsequent packing process, and the resin will protrude. In addition, in the conventional printed circuit board, since the surface of the solder mask is insufficient in roughness, the solder mask surface and the die material are not firmly connected in the subsequent packing process, and a phenomenon that the die material is peeled off occurs. I tended to.

Further, in a conventional printed circuit board,
In circuits not covered with a solder mask, ion migration often occurs when the wiring is too dense, in other words, this has reduced the wiring density of the circuit board. In addition, since the hollow plating through holes connecting the upper and lower layer circuits of the printed circuit board are filled with air, the subsequent package process, particularly the heating process, has an unfavorable effect on the overall structure of the package.

SUMMARY OF THE INVENTION It is a primary object of the present invention to provide a printed circuit board having a fixed solder mask having a thickness suitable for packing various types of semiconductor chips. The next object of the present invention is to provide a printed circuit board that is tightly bonded to a die material for covering the entire package when the circuit board is used as a base material of a semiconductor chip package, and that does not cause resin to protrude during the die process. To provide. It is a further object of the present invention to provide a printed circuit board that increases the density of conductive circuits.

[0006]

In order to achieve the above object, a printed circuit board according to the present invention is made of a first resin material, has a ceiling surface and a bottom surface, and has a ceiling portion. A first conductive circuit is provided on the surface, and the circuit is made of a substrate having a shielded portion and an exposed portion, and a second resin, and the thermal expansion coefficient of the second resin is substantially the first. And a first solder mask disposed on the ceiling surface of the substrate in such a manner that the solder mask covers the shielded portion of the first conductive circuit and forms a flat outer surface. The thickness uniformity of the solder mask is 500
When mm is a unit of measurement for one length, the difference between the maximum thickness and the minimum thickness of the solder mask in the unit is 10 μm
It is as follows.

Another feature of the printed circuit board according to the present invention is that the first conductive circuit has a shielded portion and an exposed portion, and the exposed portion circuit has a bottom portion and a ceiling portion. It is that you are. The first solder mask has a first region and a second region, the first region covering the shielded portion of the first conductive circuit and forming a flat outer surface. The second region is disposed on the outer surface, and the second region completely covers the circuit bottom of the exposed portion of the conductive circuit.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In order to clarify the detailed structure and effects of the present invention, a description will be given of an embodiment with reference to the drawings. First, referring to FIGS. 1 and 2, a printed circuit board 10 according to a first embodiment of the present invention includes a substrate 20 and two solder masks 40.

The substrate 20 is made of a fiber material and an impregnated resin, the fiber material may be glass fiber, and the resin material is an epoxy resin, a polyamide resin (pol
Select from resins such as yamide resin) and cyanoester resin. The substrate 20 has a ceiling surface 22 and a bottom surface 24, and a conductive circuit 26 having a predetermined pattern is disposed on each of the ceiling surface and the bottom surface.
6 has a shielded portion 261 and an exposed portion 263. A plated through hole 28 penetrating the plurality of substrates 20 communicates with each conductive circuit.

Each solder mask 40 is made of a resin material whose coefficient of thermal expansion is close to or equal to the coefficient of thermal expansion of the resin contained in the substrate 20, and is attached to the ceiling surface 22 and the bottom surface 24 of the substrate 20. The shielded portion 261 of each conductive circuit 26 is completely covered, and the hollow portion of each plated through hole 28 is filled. That is, the filler 281 at the center of each plated through hole 28 has two solder masks 40. And are integrally formed.

When the solder mask 40 is to be adhered to the surface of the substrate, an aluminum foil 401 is first prepared, and a semi-solidified (B-staged) epoxy resin layer 402 is applied on one surface thereof. the attached on the surface of the substrate, the epoxy resin layer 402 so as to through the surface of the aluminum foil 401 and the substrate 20, the above composition at a temperature of 10~40kgw / cm ² pressure and one hundred and forty to one hundred and eighty-five ° C. 1 .5-
Pressure is applied for 3 hours to solidify the epoxy resin layer 402, close each plating through hole 28, and make close contact with the surface of the substrate 20 (see FIG. 2A).

Next, a photoresist (photo-resist) layer 403 is applied to the surface of the aluminum foil (see FIG. 2B), and a film (not shown in the figure) is disposed to form a photoresist layer 40.
3 is exposed, and the photoresist layer 403 is developed at a position corresponding to the shielded portion of the conductive circuit 26. Subsequently, the undeveloped portion of the photoresist layer and the aluminum foil are respectively removed with an appropriate solvent, and the exposed portion of the conductive circuit Is exposed outside (see FIG. 2C). Further, the remaining photoresist layer is removed with an appropriate chemical solvent (see FIG. 2D).

Subsequently, the corresponding solder mask above the exposed portion of the conductive circuit is removed by a plasma etching method or a laser to expose the exposed portion 263 of the conductive circuit 26 on the substrate 20 (see FIG. 2E). Finally,
The remaining aluminum foil is removed with an appropriate solvent to complete the manufacturing process of the solder mask 40 (see FIG. 2F).

The thickness of the solder mask 40 is 2 to 200 μm.
m, and has a very good flatness. More specifically, when 500 mm is taken as one length measurement unit, the maximum thickness t _max and the minimum thickness t _max of the solder mask 40 are set. The difference in _min is controlled so as to be 10 μm or less (see FIG. 3), and the solder mask has extremely excellent micro-roughness.
Usually, the Rz value is between 0.5 and 10 μm.

Therefore, when a flip-chip package is arranged on a printed circuit board, if a solder mask having a large thickness is used, the chip 60 can be brought into close contact with the surface of the solder mask 40, and somehow can be provided between the two. There is no need to fill material (see FIG. 4). As a second embodiment of the present invention, when arranging a wire bonding type package on a printed circuit board, a thin solder mask is used, and at the same time, a chip is firmly attached to the printed circuit board with a very small amount of adhesive 70. However, this makes it possible to greatly reduce the thickness of the entire package (see FIG. 5).

When the solder mask 40 is provided as in the third embodiment of the present invention shown in FIG. 6, a first region for completely covering the shielded portion 261 of the conductive circuit on the solder mask is provided. 401 and exposed part 2 of conductive circuit
A second region 40 for covering only the bottom 265 of 63
2 to improve the bonding strength between the exposed portion of the conductive circuit and the substrate 20. other than this,
Since the periphery of the bottom portion 661 of the exposed portion 66 is surrounded by the insulating solder mask 402, ion migration hardly occurs between exposed adjacent circuits. Therefore, the pitch of each circuit can be further reduced, in other words, the wiring density of the printed circuit board can be further increased.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a printed circuit board according to a first embodiment of the present invention.

FIGS. 2A to 2F are cross-sectional views illustrating a manufacturing process of disposing a solder mask of a printed circuit board on a substrate according to a first embodiment of the present invention;

FIG. 3 is an enlarged view of a portion A in FIG.

FIG. 4 is a cross-sectional view illustrating a state in which a flip-chip package is used in the printed circuit board according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a printed circuit board according to a second embodiment of the present invention using a wire bonding type chip package.

FIG. 6 is a sectional view showing a relationship between an exposed portion of a conductive circuit and a solder mask in a printed circuit board according to a third embodiment of the present invention.

[Explanation of symbols]

10. Printed circuit board 20 substrates 22 Ceiling surface 24 bottom 26 Conductive circuit 40 Solder mask 261 Shielding part 263 Exposed part

Continuation of front page    F term (reference) 5E314 AA32 AA36 BB06 BB12 CC15                       DD07 FF05 FF17 GG05 GG11                       GG17 GG24                 5E317 AA24 BB02 BB03 CC31 CD23                       CD27 GG14 GG16

Claims (18)

[Claims] 1. A first resin material, having a ceiling surface and a bottom surface, a first conductive circuit disposed on the ceiling surface, and the circuit includes a shielded portion and an exposed portion. A substrate, made of a second resin, having a coefficient of thermal expansion substantially the same as that of the first resin, covering the shielded portion of the first conductive circuit and having a flat outer surface And a first solder mask disposed on the ceiling surface of the substrate in a method of forming a printed circuit board. 10μm difference between thickness and minimum thickness
A printed circuit board characterized by the following. 2. A second conductive circuit is provided on a bottom surface of the substrate,
A printed circuit board having a shielded portion and an exposed portion in a circuit, the printed circuit board being made of the second resin, also covering the shielded portion of the second conductive circuit and providing a flat outer surface. The printed circuit board according to claim 1, further comprising a second solder mask disposed on a bottom surface of the substrate in a forming manner. 3. The substrate has a plurality of plated-through holes, penetrates a ceiling surface and a bottom surface of the substrate, and electrically connects the first conductive circuit and the second conductive circuit. And, each with a filler in each plating through hole,
3. The printed circuit board according to claim 2, wherein the material of each filler is the same as the material of each solder mask. 4. The solder mask has a thickness of 2 to 200.
The printed circuit board according to claim 1, wherein the thickness is μm. 5. The printed circuit board according to claim 1, wherein an Rz value, which is a roughness of an outer surface of the solder mask, is 0.5 to 10 μm. 6. The printed circuit board according to claim 1, wherein said first and second resins are epoxy resins. 7. The printed circuit board according to claim 1, wherein said first and second resins are polyamide resins. 8. The printed circuit board according to claim 1, wherein said first and second resin materials are cyanide resins. 9. A first resin material, having a ceiling surface and a bottom surface, a first conductive circuit disposed on the ceiling surface, and the circuit having a shielded portion and an exposed portion. A substrate having a bottom and a ceiling in the circuit of the exposed portion; and a second resin, wherein the second resin has substantially the same thermal expansion coefficient as the first resin. And a second region, the first region being disposed on the ceiling surface of the substrate in a manner to cover the shielded portion of the first conductive circuit and form a flat outer surface. A first solder mask, wherein the second region completely covers the circuit bottom of the exposed portion of the conductive circuit. 10. When the first region of the first solder mask has a length of 500 mm as a unit of measurement,
10. The printed circuit board according to claim 9, wherein a difference between the maximum thickness and the minimum thickness is 10 μm or less. 11. A printed circuit board having a second conductive circuit disposed on a bottom surface of the substrate, the circuit having a shielded portion and an exposed portion, and the exposed portion of the circuit having a bottom portion and a ceiling portion. There is a first region and a second region made of the second resin, wherein the first region covers a shielded portion of the second conductive circuit and forms a flat outer surface. 10. The printed circuit board according to claim 9, wherein the second region is disposed on a bottom surface of the substrate, and the second region completely covers a circuit bottom of the exposed portion of the conductive circuit. 12. The substrate further includes a plurality of plated through holes, which penetrate through a ceiling surface and a bottom surface of the substrate, wherein the first conductive circuit and the second conductive circuit 2. A material is electrically connected to each of the plated through holes, and a filler is provided in each of the plated through holes, and a material of each of the fillers is the same as a material of the solder mask.
The printed circuit board according to claim 1. 13. The printed circuit board according to claim 9, wherein the thickness of the first region of the solder mask is between 2 and 200 μm. 14. The printed circuit board according to claim 9, wherein an Rz value, which is a roughness of an outer surface of the first region of the solder mask, is between 0.5 and 10 μm. 15. The printed circuit board according to claim 9, wherein the first resin and the second resin are epoxy resins. 16. The printed circuit board according to claim 9, wherein said first resin and said second resin are polyamide resins. 17. The printed circuit board according to claim 9, wherein said first resin material and said second resin material are cyanide resins. 18. A first resin material, having a ceiling surface and a bottom surface, wherein a first conductive circuit is disposed on the ceiling surface, and the first conductive circuit has a shielded portion. A second conductive circuit is disposed on the bottom surface, and the second conductive circuit is formed of a substrate having a shielded portion and an exposed portion; and a second resin. Resin having substantially the same coefficient of thermal expansion as the first resin, and disposed on the ceiling surface of the substrate in such a manner as to cover the shielded portion of the first conductive circuit and form a flat outer surface. A first solder mask, which is made of a second resin, and is disposed on the bottom surface of the substrate in a manner to cover the shielded portion of the second conductive circuit and form the outer surface flat. And a second conductive mask and a second conductive mask and a second conductive mask. A printed circuit board, comprising: a plurality of plated through holes electrically connected to a conductive circuit, each including a filler therein, and a material of each filler being the same as a material of each solder mask.