JP6706942B2 - Circuit board with built-in components - Google Patents

Description

The present invention relates to a component built-in circuit board which board built chip resistor is embedded in the insulating resin layer.

In recent years, with the miniaturization and higher functionality of electronic devices, a device for increasing the circuit density per unit area of the circuit board has been made by incorporating a chip resistor in the circuit board. In such a circuit board, after embedding a chip resistor in a base substrate made of an insulating resin layer, the surface of this resin layer is irradiated with a laser to perform a drilling process, and the inside of the hole is plated. The vias are formed by connecting the external electrodes of the chip resistor to the vias.

Here, at the time of drilling, it is necessary to irradiate a laser toward the external electrode of the chip resistor embedded in the resin layer to expose the external electrode. Generally, the opaque material is used as the resin layer. However, the external electrodes of the chip resistor embedded in the resin layer cannot be visually inspected. Therefore, there is a problem that the hole forming position is displaced during the drilling process, and the connection reliability between the external electrode and the via is deteriorated.

In order to solve such a problem, in the chip resistor described in Patent Document 1, the external electrode is enlarged to ensure the connection with the via. That is, as shown in FIG. 7, a chip resistor 101 described in Patent Document 1 includes a rectangular parallelepiped insulating substrate 102 and a pair of first and second opposing faces arranged at a predetermined interval on the surface of the insulating substrate 102. 1 internal electrode 103, a resistor 104 provided on the surface of the insulating substrate 102 so as to be connected to the pair of first internal electrodes 103, a first protective layer 105 and a first protective layer 105 formed so as to cover the resistor 104, and 2 protective layer 106, a pair of second internal electrodes 107 formed so as to cover the exposed portion of the first internal electrode 103 and the end portion of the second protective layer 106, and formed so as to cover the second internal electrode 107. And an external electrode 108.

The first internal electrode 103 is made of a conductive material containing silver as a main component, and is formed as a thick film on the surface of the insulating substrate 102 by screen printing. Specifically, by setting a screen mask on the surface of the insulating substrate 102, supplying Ag-Pd paste for printing on the screen mask and performing squeezing, the Ag-Pd paste passes through the pattern holes of the screen mask. By coating the surface of the insulating substrate 102, drying it, and then firing it, the first internal electrode 103 made of a thick-film fired body is obtained. Similarly, the resistor 104, the protective layers 105 and 106, and the second internal electrode 107 are also formed into a thick film by screen printing.

In the chip resistor 101 described in Patent Document 1, since the facing distance between the pair of second internal electrodes 107 is smaller than the facing distance between the pair of first internal electrodes 103, the second internal electrode 107 is A wide surface area of the external electrode 108 to be covered can be secured. As a result, it becomes possible to connect the external electrode of the chip resistor and the via even if the formation position of the hole is slightly displaced.

JP, 2011-91140, A

By the way, in thick film formation by screen printing, there is a possibility that variations in the intervals between internal electrodes and dimensions of resistors may occur due to screen mask displacement, paste sag, etc., which may affect the accuracy of resistance values. It is conceivable to form the thin film by photolithography or the like instead of forming the thick film by screen printing for the internal electrodes and the resistor. In this way, it becomes possible to keep the intervals of the internal electrodes and the like at constant intervals, and it is possible to manufacture a chip resistor having high electrode dimension accuracy and resistance value accuracy. In addition, since the resistance value of silver used for thick internal electrodes generally fluctuates greatly depending on the temperature, the resistance value fluctuates due to the temperature change of the internal electrodes themselves, and silver does not resist when the resistor is formed. Diffusion into the body increases the risk of fluctuations in the resistance value of the resistor. Therefore, by forming a thin film of a material such as Cu on the internal electrodes, it is possible to reduce the variation in the resistance value of the internal electrodes due to temperature changes, and manufacture a chip resistor in which the variation in resistance values due to temperature changes is small. can do.

Therefore, as shown in FIG. 8, by forming a thin film of the first and second internal electrodes and the resistor and a thick film of the protective layer, a large surface area of the external electrode is ensured and the external electrode and the via are secured. A chip resistor that can be easily connected to is considered. That is, the chip resistor 111 shown in FIG. 8 has a rectangular parallelepiped insulating substrate 112, a pair of first internal electrodes 113 formed in thin films on both ends in the longitudinal direction of the insulating substrate 112, and these first internal electrodes 113. A resistor 114 formed in a thin film so as to be connected to a resistor, a protective layer 115 formed in a thick film so as to continuously cover the end portion of the first internal electrode 113 and the resistor 114, and a pair of first internal electrodes. A pair of second internal electrodes 116 formed in a thin film so as to have an opposing interval narrower than the opposing interval of 113, and an external electrode 117 formed by plating so as to cover the second internal electrode 116.

In the chip resistor 111 configured as described above, the thick protective layer 115 is formed on the thin first internal electrode 113, and the first internal electrode 113 and the protective layer 115 are continuously connected to the second internal electrode 116. Since it is formed so as to cover the surface of the first internal electrode 113 from the end surface of the protective layer 115, a step portion is formed, and as a result, the external electrode 117 covering the surface of the second internal electrode 116 is formed. A large step portion 118 is generated.

When forming a via in the base substrate having the chip resistor 111 built therein, the surface of the external electrode 117 in the vicinity of the step portion 118 is formed in a step-like shape, and therefore, it is directly above the step portion 118. When a hole is formed by irradiating a resin layer in the vicinity with a laser, there is a fear that the connection between the via formed inside the hole and the external electrode 117 may be poor. In this way, even if the technique described in Patent Document 1 is applied to form the external electrode in a large size, the region outside the step portion 118 on the surface of the external electrode 117 becomes a region in which connection with the via is difficult, Substantially, the area where the external electrode 117 and the via can be connected is limited to the narrow area F shown in the figure inside the step portion 118 on the surface of the external electrode 117.

The present invention has such has been made in view of the circumstances of prior art, and it is desirable drilling for vias to provide easy component built-in circuit board.

To achieve the above Symbol purpose of the built-in component type circuit board of the present invention is the component built-in circuit board has the chip resistor is embedded in the inner layer of the base substrate made of an insulating resin layer, said chip resistor And a resistor having a thin film formed so as to be connected to the pair of first internal electrodes, the pair of first internal electrodes having a thin film formed on both ends in the longitudinal direction of the insulating substrate. A body, a protective layer formed in a thick film so as to cover at least the resistor, and a pair of second internal electrodes formed in a thin film so as to have an opposing interval narrower than the opposing interval of the pair of first internal electrodes. An external electrode plated to cover the second internal electrode, wherein the protective layer is formed to cover the resistor and the first internal electrode, and An exposed portion that is not covered by the protective layer is formed at positions inwardly separated from both ends in the longitudinal direction of the insulating substrate, and the second internal electrode covers the protective layer including the exposed portion. by being formed, the recess is formed at a position corresponding to the exposed portion, Ri formable der vias to be connected to the external electrode across the recess on the base substrate, the width of the concave portion the via It is characterized in that it is formed to be narrower than the inner diameter of .

According to the present invention, the height of the surface of the external electrode is almost the same except for the recess, so that the surface of the external electrode except at least the recess can be used as a region connectable to the via. Further, according to the present invention, since the via can be formed in the base substrate so as to extend over the recess formed in the position corresponding to the exposed portion of the first internal electrode, the entire surface of the external electrode including the recess is connected to the via. This is a possible area, which facilitates drilling for vias.

According to the present invention, it is possible to drilling for vias that provide easy component built-in circuit board.

1 is a plan view of a chip resistor for a substrate inner layer according to a first embodiment example of the present invention. It is sectional drawing which follows the AA line of FIG. It is explanatory drawing which shows the manufacturing process of the said chip resistor. It is sectional drawing of the component built-in type circuit board in which the said chip resistor was internal-layered. It is a top view of the chip resistor for substrate inner layers which concerns on the example of 2nd Embodiment of this invention. It is a top view of the chip resistor for substrate inner layers which concerns on the example of 3rd Embodiment of this invention. It is sectional drawing of the chip resistor for substrate inner layers which concerns on a prior art example. It is sectional drawing of the component built-in type circuit board based on a conventional proposal.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, a chip resistor for a substrate inner layer (hereinafter referred to as a chip resistor) 1 according to a first embodiment of the present invention includes a rectangular parallelepiped insulating substrate 2 and an insulating substrate 2. A pair of first internal electrodes 3, 4 formed in thin films at both ends in the longitudinal direction, a resistor 5 formed in a thin film so as to be connected to the pair of first internal electrodes 3, 4, and at least the resistor 5 is covered. The protective layer 6 thus formed in a thick film, the pair of second internal electrodes 7, 8 formed in a thin film so as to have an opposing interval narrower than the opposing interval of the pair of first internal electrodes 3, 4; It is mainly configured by external electrodes 9 and 10 formed by plating so as to cover the internal electrodes 7 and 8.

The insulative substrate 2 is made of a ceramic substrate, and the insulative substrate 2 is obtained by dividing a large-sized substrate, which will be described later, along division grooves extending vertically and horizontally to obtain a large number.

The resistor 5 is made of a resistive material such as Ni—Cr based on which a thin film is formed on the surface of the insulating substrate 2. The resistor 5 has a meandering (serpentine) meandering resistance pattern at its central portion. The resistor 5 is formed by vapor-depositing or sputtering a Ni—Cr-based material or the like on the entire surface of the insulating substrate 2 and then photolithographically/etching the same to pattern it in a meandering shape.

The pair of first internal electrodes 3 and 4 is made of an electrode material such as Cu formed in a thin film on both ends of the resistor 5, and these first internal electrodes 3 and 4 are the resistive film (resistor 5) before patterning. After Cu or the like is vapor-deposited or sputtered on the entire surface of the above, it is photolithographically/etched and patterned into a rectangular shape. The pair of first internal electrodes 3, 4 have exposed portions that are not covered by the protective layer 6.

The protective layer 6 is made of an insulating material such as an epoxy resin formed as a thick film so as to cover the first internal electrodes 3 and 4 and the resistor 5, and the protective layer 6 has an insulating property in the first internal electrodes 3 and 4. The exposed portions 3a and 4a located at positions inwardly separated from both ends in the longitudinal direction of the substrate 2 and the insulating substrate 2 extending from the exposed portion 3a on the left side in the figure to both long sides of the insulating substrate 2 and continuing to the exposed portion 3a. Except for the region 2a and the region 2b of the insulating substrate 2 which extends from the exposed portion 4a on the right side of the figure to both long sides of the insulating substrate 2 and is continuous with the exposed portion 4a, the surfaces of the first internal electrodes 3, 4 are Screen-printing a paste-like insulating material such as epoxy resin on the surface of the resistor 5 exposed from the first internal electrodes 3 and 4, and on the surface of the insulating substrate 2 exposed from the first internal electrodes 3 and 4 and the resistor 5, respectively. It was then cured by heating.

The pair of second internal electrodes 7 and 8 is made of an electrode material such as Cu that is formed in a thin film so as to cover the protective layer 6 including the exposed portions 3a and 4a of the first internal electrodes 3 and 4. The electrodes 7 and 8 are deposited on the regions 2a and 2b of the insulating substrate 2 and the exposed portions 3a and 4a of the first internal electrodes 3 and 4 and the entire surface of the protective layer 6 by depositing or sputtering Cu or the like, and then performing photolithography/ It has been etched and patterned.

The pair of external electrodes 9 and 10 is made of an electrode material such as Ni or Cu formed so as to cover the second internal electrodes 7 and 8, and these external electrodes 9 and 10 are the surfaces of the second internal electrodes 7 and 8. It is formed by applying Ni plating, Cu plating or the like to the whole.

The second internal electrodes 7 and 8 are formed into a thin film so as to cover the protective layer 6 including the exposed portions 3a and 4a of the first internal electrodes 3 and 4, so that the region 2a of the insulating substrate 2 and the first internal electrodes are formed. The concave portion 11 is formed at a position corresponding to the exposed portion 3a of the insulating substrate 3, and the concave portion 12 is formed at a position corresponding to the region 2b of the insulating substrate 2 and the exposed portion 4a of the first internal electrode 4. These recesses 11 and 12 have a rectangular shape in a plan view, and are longer than both ends in the longitudinal direction of the insulating substrate 2 so as to extend parallel to the short side of the insulating substrate 2 from the upper side to the lower side of the insulating substrate 2. It is formed inside.

Next, a method of manufacturing the chip resistor 1 configured as described above will be described with reference to FIG. 3(b1), (b2), (b3), (b4), (b5), and (b6) are shown in FIGS. 3(a1), (a2), (a3), (a4), and (a5), respectively. ), (a6) are sectional views taken along the line AA.

First, as shown in FIGS. 3A1 and 3B1, a large-sized substrate 2A from which a large number of insulating substrates 2 are taken is prepared. Dividing grooves (not shown) are previously provided in a grid pattern on the large-sized substrate 2A, and each of the cells divided by the dividing groove serves as a chip forming area. Although one chip forming area is representatively shown in FIG. 3, each step described below is collectively performed on a large-sized substrate 2A described later which actually corresponds to a large number of chip forming areas. Is done.

Next, although not shown, after forming a thin resistance film by sputtering Ni—Cr or the like on the entire upper surface of the large-sized substrate 2A on which a large number of insulating substrates 2 are taken, the upper surface of this resistance film is formed. An electrode film is thinly formed on the whole by sputtering Cu or the like.

Next, as shown in FIGS. 3A2 and 3B2, the electrode film formed as a thin film on the entire upper surface of the resistance film is photolithographically/etched to form a pair of first internal electrodes 3 on both ends of the resistance film. , 4 are respectively formed, the central portions of the resistance films exposed from the first internal electrodes 3, 4 are photolithographically/etched to form meander-shaped resistors 5.

Although not shown, the order of forming the resistance film and the electrode film can be reversed, and after the pair of first internal electrodes are thinly formed on both ends of the insulating substrate in the longitudinal direction, the pair of first internal electrodes is formed. It may be a manufacturing method in which a resistor is formed into a thin film so as to be connected to the first internal electrode.

Next, as shown in FIGS. 3(a3) and 3(b3), an insulating material such as an epoxy resin is screen-printed so as to cover the first internal electrodes 3 and 4 and the resistor 5, and photolithography is performed using a photosensitive resin. By forming the insulating substrate 2, the regions 2a and 2b of the insulating substrate 2 and the exposed portions 3a and 4a of the first internal electrodes 3 and 4 of the insulating substrate 2, the first internal electrodes 3 and 4 and the resistor 5 are removed. By forming the insulating material on each surface, the protective layer 6 made of a thick film is obtained. By this protective layer forming step, exposed portions 3a, 4a where the first internal electrodes 3, 4 are exposed are formed at positions spaced inward from both ends in the longitudinal direction of the insulating substrate 2.

Next, as shown in FIGS. 3(a4), (b4), (a5), and (b5), regions 2a and 2b of the insulating substrate 2, exposed portions 3a and 4a of the first internal electrodes 3 and 4 and protection. After Cu or the like is sputtered so as to cover the layer 6 to form a thin electrode film, photolithography/etching is performed to form a pair of second internal electrodes 7 and 8. By this second internal electrode forming step, the second internal electrodes 7 and 8 of the thin film cover the thick protective layer 6 including the exposed portions 3a and 4a of the first internal electrodes 3 and 4 of the thin film. The recess 11 is formed at a position corresponding to the exposed portion 3a of the electrode 3, and the recess 12 is formed at a position corresponding to the exposed portion 4a of the first internal electrode 4.

Next, after the second internal electrode forming step, the large-sized substrate 2A is diced along the dividing grooves (not shown) to form the second internal electrodes 7 and 8 as shown in FIGS. 3(a6) and 3(b6). A pair of external electrodes 9 and 10 are formed by covering with Ni plating or Cu plating. This completes the chip resistor 1 shown in FIGS.

FIG. 4 is a cross-sectional view of a component built-in type circuit board in which the chip resistor 1 configured as described above is internally layered, and the portions corresponding to FIG. 1 are denoted by the same reference numerals.

As shown in FIG. 4, the chip resistor 1 is embedded in a resin layer 20 of a base substrate such as a laminated circuit substrate, and a wiring pattern (not shown) is provided on the upper surface of the resin layer 20. Two holes 21 and 22 are formed in the resin layer 20, the hole 21 on the left side in the figure reaches the upper surface of the external electrode 9 which covers the second internal electrode 7, and the hole 22 on the right side in the figure is the hole 22 in the second side. Has reached the upper surface of the external electrode 10 covering the.

These holes 21 and 22 are formed by irradiating the surface of the resin layer 20 with a laser, and a conductive material such as Cu is plated inside the holes to form vias (not shown). It becomes possible to connect the side wiring pattern and the external electrodes 9 and 10 of the chip resistor 1 through the vias in the holes 21 and 22.

As described above, in the chip resistor 1 for a substrate inner layer of the first embodiment, the pair of first internal electrodes 3, 4, the resistor 5 and the second internal electrodes 7, 8 are formed into a thin film, and the resistor 5 is formed. Since the covering protective layer 6 is formed as a thick film, it is possible to manufacture a chip resistor having a high resistance value accuracy and a small resistance value variation due to a temperature change. Further, in the chip resistor 1, the facing interval between the pair of second internal electrodes 7 and 8 is formed to be narrower than the facing interval between the pair of first internal electrodes 3 and 4, and the second internal electrodes 7 and 8 are located inside the first internal electrode. Since it is formed so as to cover the protective layer 6 including the exposed portions 3a and 4a of the electrodes 3 and 4, it is possible to widen the surface area of the external electrodes 9 and 10 that cover the second internal electrodes 7 and 8.

In the first embodiment, the exposed portions 3a and 4a of the first internal electrodes 3 and 4 which are not covered by the protective layer 6 are formed at positions inwardly separated from both longitudinal ends of the insulating substrate 2. Therefore, when the second internal electrodes 7 and 8 are formed into a thin film so as to cover the protective layer 6 including the exposed portions 3a and 4a of the first internal electrodes 3 and 4, the exposed portions 3a and 4a of the first internal electrodes are Recesses 11 and 12 are formed at corresponding positions. At this time, the surfaces of the external electrodes 9 and 10 covering the second internal electrodes 7 and 8 have almost the same height except for the recesses 11 and 12, so that at least the surfaces of the external electrodes 9 and 10 except the recesses 11 and 12 are via-formed. It can be used as a connectable area with. As described above, in the chip resistor 1 for the substrate inner layer of the first embodiment, even if the first and second internal electrodes and the resistor are formed into a thin film in order to obtain a highly accurate chip resistor, connection with the via is performed. A wide area of possible external electrodes can be secured.

Further, according to the method for manufacturing the chip resistor 1 for a substrate inner layer according to the first embodiment, the protective layer forming step is performed in the first inner electrodes 3 and 4 at positions separated inward from both longitudinal ends of the insulating substrate 2. Since it is a step of forming the thin-film resistor 5 and the first internal electrodes 3, 4 so as to be covered with the thick-film protective layer 6 except for the exposed portions 3a, 4a in FIG. The exposed portions 3a and 4a which are not covered with the protective layer 6 are formed. Then, by the second internal electrode forming step in which the exposed portions 3a and 4a and the protective layer 6 are covered with the second internal electrodes 7 and 8, a concave portion 11 is formed at a position corresponding to the exposed portions 3a and 4a of the first internal electrode. 12 is formed. Then, the heights of the surfaces of the external electrodes 9 and 10 are almost the same except for the recesses 11 and 12, so that at least the surfaces of the external electrodes 9 and 10 excluding the recesses 11 and 12 can be connected to the vias. Can be used as. As described above, in the method for manufacturing the chip inner-layer chip resistor 1 of the first embodiment, even if the first and second internal electrodes and the resistor are formed into thin films in order to obtain a highly accurate chip resistor, It is possible to secure a wide area of the external electrode that can be connected to the via.

Particularly, in the first embodiment, the widths 11a and 12a of the recesses 11 and 12 are narrower than the inner diameters 21a and 22a of the holes 21 and 22 so that the holes 21 and 22 can be formed across the recesses 11 and 12, respectively. Is formed. Therefore, even if the chip resistor 1 is embedded in the inner layer of the base substrate and the resin layer 20 located immediately above the recesses 11 and 12 of the chip resistor 1 is irradiated with a laser to form the holes 21 and 22, the holes are formed. Since the parts 21 and 22 are formed so as to straddle the recesses 11 and 12, respectively, the external electrode and the via can be reliably connected. Therefore, the area where the via hole can be formed (the area where the external electrode and the via can be connected) is the wide area E shown in FIG. 4, that is, the entire surface of the external electrodes 9 and 10 including the recesses 11 and 12. Become. As described above, in the circuit board with a built-in component of the first embodiment, even if the first and second internal electrodes and the resistor are formed into a thin film in order to obtain a highly accurate chip resistor, the external part including the concave portion is formed. Since the entire surface of the electrode can be a region that can be connected to the via, it is possible to easily perform drilling processing for the via.

In the first embodiment, the recesses 11 and 12 formed at the positions corresponding to the exposed portions 3a and 4a of the first internal electrodes 3 and 4 are insulated along the short sides of the insulating substrate 2 substantially in parallel. Although it is formed so as to extend to both long sides of the flexible substrate 2 (see FIG. 1), the configuration is not limited to this. The second and third embodiments of the present invention will be described below with reference to FIGS.

As shown in FIG. 5, the recess of the chip resistor 31 according to the second embodiment is formed so as to extend toward one of the upper side and the lower side of the insulating substrate 2 as compared with the recess of the first embodiment. It is different in that it is done. That is, the recesses 32 and 34 of the second embodiment are formed so as to extend toward the upper side of the insulating substrate 2 and the recesses 33 and 35 extend toward the lower side of the insulating substrate 2 toward the lower side. Is formed in.

Further, as shown in FIG. 6, the recess of the chip resistor 41 according to the third embodiment is formed so as to extend to the front of both long sides of the insulating substrate 2 as compared with the recess of the first embodiment. It is different in that it is done. In addition, in the third embodiment, the recesses 42, 43 are formed only at the positions corresponding to the exposed portions of the first internal electrodes 3, 4, but the invention is not limited to this, and the recesses 42, 43 may be formed. The structure may be formed up to the positions corresponding to the exposed portions of the first internal electrodes 3 and 4 and the region of the insulating substrate 2.

In this way, even when the recess is formed as in the second and third embodiments, the effect of the first embodiment, that is, even if the electrodes and resistors are formed into thin films, the external electrodes and the vias are formed. It is possible to provide a chip resistor that can be easily connected to, a method of manufacturing such a chip resistor, and a component-embedded circuit board that can be easily drilled for vias.

Although not shown, the recesses of the first to third embodiments are formed in a rectangular shape in plan view, but the configuration is not limited to this, and may be formed in a circular shape or an elliptical shape in plan view. It may be.

1,31,41 Chip resistor for substrate inner layer 2 Insulating substrate 2A Large-sized substrate 3,4 First internal electrode 5 Resistor 6 Protective layer 7,8 Second internal electrode 9,10 External electrode 11,12,32-35 , 42, 43 recesses 20 resin layers 21, 22 holes

Claims (1)

In a component built-in type circuit board in which a chip resistor is embedded in the inner layer of a base board made of an insulating resin layer,
The chip resistor is formed into a rectangular parallelepiped insulating substrate, a pair of first internal electrodes formed into thin films at both ends in the longitudinal direction of the insulating substrate, and a thin film formed to be connected to the pair of first internal electrodes. Resistor, a protective layer formed as a thick film so as to cover at least the resistor, and a pair of second thin films formed so as to have an opposing interval narrower than the opposing interval between the pair of first internal electrodes. An internal electrode and an external electrode formed by plating so as to cover the second internal electrode,
The protective layer is formed so as to cover the resistor and the first internal electrode, and the protective layer covers the first internal electrode at positions separated from both ends in the longitudinal direction of the insulating substrate. An exposed part that is not exposed is formed,
Since the second internal electrode is formed so as to cover the protective layer including the exposed portion, a recess is formed at a position corresponding to the exposed portion,
Vias connecting to the external electrodes can be formed in the base substrate across the recesses,
A circuit board with a built-in component, wherein the width of the recess is formed to be narrower than the inner diameter of the via.