JP2020123654A - Wiring board and mounting structure - Google Patents

Abstract

To provide a wiring board that can stably operate an electronic component.SOLUTION: A wiring board comprises: an insulating substrate 2 in a quadrangle shape that includes a plurality of laminated first insulating layers 7; a mounting area 10 that is partitioned on a top face of the insulating substrate 2 and has corner parts; wiring conductors 3 that are located between the first insulating layers 7; a plurality of connection pads 4 that are located on an under surface of the insulating substrate 2; and a via hole conductor 14 that is located in the first insulating layers 7, and electrically connects the wiring conductors 3 between layers different from each other and the connection pads 4 and the wiring conductors 3. On the undermost layer of the insulating substrate 2 corresponding to at least one of an area where the connection pads 4 at the four corners of the insulating substrate 2 are located in a transparent plan view and an area where the connection pads 4 at the corners of the mounting area 10 are located in a transparent plan view, second insulating layers 12 having a Young's modulus smaller than the Young's modulus of the first insulating layers 7 are located.SELECTED DRAWING: Figure 1

Description

The present invention relates to a wiring board and a mounting structure including the wiring board.

2. Description of the Related Art In recent years, electronic devices typified by computers and game machines have become more sophisticated. Corresponding to such an electronic device, a wiring board for mounting a semiconductor chip capable of simultaneously performing many arithmetic processes has been developed (see Patent Document 1).

JP, 2008-251702, A

A semiconductor chip with excellent arithmetic processing capacity generates a large amount of heat during operation. Therefore, when a wiring board to which a semiconductor chip is connected is mounted on an electric board such as a mother board, the electric board thermally expands and contracts due to the heat released from the semiconductor chip. At this time, stress may be generated in the connection portion with the wiring board, and cracks may occur in the connection portion. As a result, the semiconductor chip may not operate stably.

The wiring substrate of the present disclosure includes a rectangular insulating substrate including a plurality of stacked first insulating layers, a mounting region that is partitioned on the upper surface of the insulating substrate and has a corner, and an interlayer between the first insulating layers. The wiring conductor located, the plurality of connection pads located on the lower surface of the insulating substrate, the wiring conductors located in the first insulating layer and different from each other, and the connection pad and the wiring conductor are electrically connected to each other. Corresponding to at least one of the via-hole conductors that are electrically connected to each other, the regions where the connection pads at the four corners of the insulating substrate are located in plan view, and the regions where the connection pads at the corners of the mounting region are located in plan view. The second insulating layer having a Young's modulus smaller than that of the first insulating layer is located at the lowermost layer of the insulating substrate.

The mounting structure according to the present disclosure covers at least a part of the electronic component on the upper surface of the wiring board, the electronic component located in the mounting area, and the wiring board configured as described above, and is connected to the periphery of the mounting area. It is characterized in that it has a metal lid and an electric board connected to the connection pad of the wiring board via a conductive material.

According to the structure of the present disclosure, it is possible to provide a wiring board capable of stably operating an electronic component.

According to the structure of the present disclosure, it is possible to provide a mounting structure capable of stably operating an electronic component.

FIG. 1 is a schematic plan view showing an example of a wiring board according to the present disclosure. FIG. 2 is a schematic cross-sectional view showing an example of a wiring board according to the present disclosure. FIG. 3 is a schematic plan view showing another example of the wiring board according to the present disclosure. FIG. 4 is a schematic cross-sectional view showing an example of the mounting structure according to the present disclosure.

Next, the wiring board 1 which is an example of the present disclosure will be described based on FIGS. 1 to 3. FIG. 1 is a plan view showing the lower surface of the wiring board 1. FIG. 2 is a sectional view taken along line XX in FIG. FIG. 3 is a plan view showing the lower surface of the wiring board 1 in another example.

The wiring board 1 includes an insulating substrate 2, a wiring conductor 3, a connection pad 4, and a solder resist 5.

The insulating substrate 2 has a quadrangular shape in a plan view and has a function of ensuring the rigidity and mechanical strength of the wiring substrate 1. Further, the insulating substrate 2 has a function as a base for electrically arranging the wiring conductor 3 and the plurality of connection pads 4 with each other.

The insulating substrate 2 includes a core substrate 6 and a first insulating layer 7 for lamination. The core substrate 6 includes, for example, an insulating material obtained by impregnating a glass cloth with an epoxy resin, a bismaleimide triazine resin, or the like and curing the glass cloth. The core substrate 6 has a plurality of through holes 8. The diameter of the through hole 8 is set to, for example, 100 to 200 μm.

The first insulating layer 7 contains, for example, an insulating material in which inorganic insulating particles such as silica and alumina are dispersed and cured in epoxy resin or polyimide resin. In this example, two first insulating layers 7 are laminated on each of the upper and lower surfaces of the core substrate 6. The first insulating layer 7 has a plurality of via holes 9. The diameter of the via hole 9 is set to, for example, 10 to 80 μm.

The thickness of the first insulating layer 7 is set to, for example, 5 to 25 μm. The Young's modulus of the first insulating layer 7 is set to, for example, 5 to 15 GPa.

On the upper surface of the insulating substrate 2, a mounting area 10 having a corner is defined. In the mounting area 10, mounting pads 11 for mounting an electronic component 20 such as a semiconductor chip are located in a vertical and horizontal array. In other words, there is a region in which a plurality of mounting pads 11 are arranged vertically and horizontally at the center of the upper surface of the insulating substrate 2, and this region is the mounting region 10.

The mounting pad 11 is connected to the electronic component 20 via, for example, solder. As a result, the electronic component 20 and the wiring board 1 are electrically and mechanically connected. The mounting pad 11 contains a good conductive metal such as copper plating. The surface of the mounting pad 11 may have a thin layer such as gold plating. In this case, the connectivity between the mounting pad 11 and the solder is improved.

On the lower surface of the insulating substrate 2, connection pads 4 for connecting to an electric substrate 40 such as a mother board are located in a vertical and horizontal array. The connection pad 4 is connected to the electric board 40 via, for example, solder. As a result, the electric board 40 and the wiring board 1 are electrically and mechanically connected to each other. As a result, the electronic component 20 and the electric board 40 are electrically connected. The connection pad 4 contains a good conductive metal such as copper plating.

In an example of the wiring board 1 of the present disclosure, the lowermost layer of the insulating substrate 2 has a lower Young's modulus than the Young's modulus of the first insulating layer 7 in a region where the connection pads 4 at the corners of the mounting region 10 are seen in a plan view. The second insulating layer 12 having a small Young's modulus is located. In other words, in the lowermost layer of the insulating substrate 2, the second insulating layer 12 is located in the region where the connection pad 4 is located, overlapping the four corners of the mounting region 10 in plan view.

The second insulating layer 12 contains, for example, silicon resin or polyimide resin. The thickness of the second insulating layer 12 is the same as the thickness of the first insulating layer 7 located in the lowermost layer of the insulating substrate 2.

The Young's modulus of the second insulating layer 12 is smaller than that of the first insulating layer 7, and is set to 0.5 GPa, for example. Therefore, the second insulating layer 12 is richer in elastic force than the first insulating layer 7 and has a function of dispersing stress from the outside. Thereby, for example, even when the stress due to the thermal expansion and contraction of the electric substrate 40 is applied to the connection pad 4 located on the lower surface of the second insulating layer 12, the stress can be dispersed by the second insulating layer 12. .. That is, it becomes possible to avoid the stress from concentrating on the connection pads 4 that are the connection portions with the electric substrate 40. The Young's modulus of the second insulating layer 12 can be measured by a method such as a tensile test method.

As described above, when the second insulating layer 12 having a Young's modulus smaller than the Young's modulus of the first insulating layer 7 is located in the region where the connection pad 4 at the corner of the mounting region 10 is located in a perspective view, Especially, it is advantageous to avoid stress concentration on the connection pad 4 when the difference in thermal expansion and contraction between the electronic component 20 and the wiring board 1 is large.

That is, for example, in the corner portion where the stress is most concentrated, including the boundary between the mounting region 10 in which the electronic component 20 having a small thermal expansion/contraction amount is mounted and the region in which the electronic component 20 is not mounted and the thermal expansion amount is large, By avoiding stress by the insulating layer 12, it is possible to suppress the occurrence of cracks between the connection pads 4 and the electric substrate 40.

As shown in FIG. 3, when the second insulating layer 12 is located in the regions where the connection pads 4 are located at the four corners of the insulating substrate 2, the thermal expansion and contraction of the wiring substrate 1 and the electrical substrate 40 is particularly likely to occur. When the difference is large, it is advantageous to avoid concentration of stress on the connection pad 4.

That is, for example, the stress is avoided by the second insulating layer 12 at the four corners of the insulating substrate 2 where the stress is most concentrated in the connection region between the wiring substrate 1 having a small thermal expansion and contraction amount and the electric substrate 40 having a large thermal expansion and contraction amount. Thus, it is possible to suppress the occurrence of cracks between the connection pads 4 and the electric board 40.

The second insulating layer 12 has no via-hole conductor 14 described later, and the connection pad 4 located on the lower surface of the second insulating layer 12 has the via-hole conductor 14 located on the first insulating layer 7. It may be electrically connected to the upper wiring conductor 3 by 14.

In other words, the connection pad 4 located on the lower surface of the second insulating layer 12 is located above the connection pad 4 by the via hole conductor 14 located on the lowermost first insulating layer 7 of the insulating substrate 2. Is electrically connected to the wiring conductor 3.

When the via-hole conductor 14 located in the second insulating layer 12 having a small Young's modulus and the wiring conductor 3 located in the first insulating layer 7 having a large Young's modulus are connected, for example, the wiring board 1 is heated. Is added, the difference between the amount of thermal deformation of the first insulating layer 7 and the amount of thermal deformation of the second insulating layer 12 becomes large, and a large stress is generated in the connection portion between the via-hole conductor 14 and the wiring conductor 3 to cause cracks. May occur.

As described above, when the via-hole conductor 14 is not provided in the second insulating layer 12, it is possible to avoid the stress generated at the connecting portion between the via-hole conductor 14 and the wiring conductor 3, so that the connection reliability can be improved. It is advantageous for improvement.

The size of the second insulating layer 12 is set such that the length of one side is approximately 3 to 15 mm in plan view. When it is smaller than 3 mm, the stress is insufficiently dispersed, and the effect of suppressing cracks between the connection pads 4 and the electric substrate 40 may be reduced. If it is larger than 15 mm, the area where the via-hole conductor 14 is not formed becomes large and the degree of freedom of wiring may be reduced. The area of the second insulating layer 12 may be made larger than the above, as long as the formation area of the via-hole conductor 14 is not affected.

The wiring conductor 3 contains a good conductive metal such as copper plating or copper foil. The wiring conductors 3 are located on the upper and lower surfaces of the core substrate 6, the inside of the through holes 8, the upper or lower surface of the first insulating layer 7, and the inside of the via holes 9. The wiring conductor 3 inside the through hole 8 functions as a through hole conductor 13. The wiring conductor 3 inside the via hole 9 functions as the via hole conductor 14.

The wiring conductors 3 located on the upper surface and the lower surface of the core substrate 6 are electrically connected via the through hole conductors 13. The wiring conductors 3 located on the upper surface or the lower surface of the first insulating layer 7 and the wiring conductors 3 located on the upper and lower surfaces of the core substrate 6 are electrically connected via the via hole conductors 14.

The mounting pad 11 and the connection pad 4 are electrically connected by the wiring conductor 3 including the through hole conductor 13 and the via hole conductor 14.

The solder resist 5 contains, for example, an electrically insulating material containing a thermosetting resin having photosensitivity such as an acrylic modified epoxy resin. Although the solder resist 5 is not an essential requirement in the present disclosure, when the wiring board 1 and the electronic component 20 are connected via solder, for example, the solder resist 5 protects the wiring conductor 3 from heat when melting the solder. It is advantageous.

The solder resist 5 has an opening 5a that exposes the mounting region 10 collectively. Further, the solder resist 5 located on the lower surface of the insulating substrate 2 has openings 5b for individually exposing the respective connection pads 4.

As described above, according to the example of the wiring substrate 1 of the present disclosure, the insulating substrate 2 including the plurality of stacked first insulating layers 7 and the mounting region that is partitioned into the upper surface of the insulating substrate 2 and has the corners. 10, the wiring conductor 3 located between the first insulating layers 7, the plurality of connection pads 4 located on the lower surface of the insulating substrate 2, and the first insulating layer 7, Areas in which the wiring conductors 3 between different layers, the via-hole conductors 14 that electrically connect the connection pads 4 and the wiring conductors 3, and the connection pads 4 at the four corners of the insulating substrate 2 in plan view are located, The second insulation having a Young's modulus smaller than the Young's modulus of the first insulating layer 7 is formed on the lowermost layer of the insulating substrate 2 corresponding to at least one of the regions where the connection pads 4 are located at the corners of the mounting region 10 as seen through. Layer 12 is located.

Since the Young's modulus of the second insulating layer 12 is smaller than the Young's modulus of the first insulating layer 7, the second insulating layer 12 is more elastic than the first insulating layer 7. Thereby, for example, even when the stress due to the thermal expansion and contraction of the electric substrate 40 is applied to the connection pad 4 located on the lower surface of the second insulating layer 12, the stress can be dispersed by the second insulating layer 12. ..

As a result, according to the structure of the present disclosure, it is possible to prevent the stress from concentrating on the connection pad 4 and to suppress the occurrence of cracks between the connection pad 4 and the electric substrate 40. It is possible to provide the wiring board 1 capable of stably operating.

In addition, such a wiring board 1 is formed as follows, for example.

First, a core substrate 6 having a plurality of through holes 8 is prepared. For the core substrate 6, for example, glass cloth is impregnated with an epoxy resin or a bismaleimidetriazine resin, and a plurality of semi-cured prepregs are laminated, copper foils (not shown) are arranged on the upper and lower surfaces, and a flat plate is hot-pressed. Is formed by. The through hole 8 is formed by, for example, drilling, laser processing, blasting, or the like.

Next, the wiring conductor 3 containing copper-plated metal is formed in the upper and lower surfaces of the core substrate 6 and in the through holes 8 by using, for example, a semi-additive method.

Next, the first insulating layer 7 is formed on the upper and lower surfaces of the core substrate 6. For the first insulating layer 7, a thermosetting resin sheet for an insulating layer containing, for example, an epoxy resin, a bismaleimide triazine resin, a polyimide resin, or the like is adhered to the upper and lower surfaces of the core substrate 6 under vacuum and then thermoset. It is formed by doing.

Next, the via hole 9 is formed in the first insulating layer 7. The via hole 9 is formed by, for example, laser processing or blast processing. The wiring conductor 3 is exposed at the bottom of the via hole 9.

Next, the wiring conductor 3 containing a copper-plated metal is formed on the upper surface or the lower surface of the first insulating layer 7 and the via hole 9 by using, for example, a semi-additive method. By repeating such a method, the required number of layers of the first insulating layer 7 and the wiring conductor 3 can be formed.

Next, the lowermost first insulating layer 7 corresponding to the region where the second insulating layer 12 is formed is removed. The removal of the first insulating layer 7 is performed by, for example, laser processing or plasma processing.

Next, a film for the second insulating layer is applied to the region where the first insulating layer 7 has been removed and cured so that the lower surface of the first insulating layer 7 and the lower surface of the second insulating layer 12 have the same height. Blasting is performed.

Next, the mounting pad 11 is simultaneously formed on the uppermost first insulating layer 7, and the connection pads 4 are simultaneously formed on the lowermost first insulating layer 7 and second insulating layer 12. The mounting pad 11 and the connection pad 4 are formed by using, for example, a semi-additive method.

Finally, a film of a thermosetting resin having photosensitivity is adhered to the upper and lower surfaces of the insulating substrate 2, exposed and developed in a predetermined pattern, and then UV-cured and heat-cured to form the solder resist 5. .. As a result, the wiring board 1 as shown in FIGS. 1 and 2 is formed.

Next, an embodiment example of the mounting structure 50 having the wiring board 1 of the present disclosure will be described based on FIG. 4. The detailed description of the wiring board 1 will be omitted.

The mounting structure 50 includes the wiring board 1, the electronic component 20, the metal lid 30, and the electric board 40.

The electronic component 20 is, for example, an integrated circuit element such as an ASIC (Application Specific Integrated Circuit), and mainly has an arithmetic function. The electronic component 20 contains, for example, silicon or germanium.

The electronic component 20 is mounted via the mounting pad 11 located in the mounting area 10 of the wiring board 1 and the solder 15. As a result, the electronic component 20 and the wiring board 1 are electrically and mechanically connected to each other.

A space between the electronic component 20 and the wiring board 1 is filled with an insulating sealing resin 22. The sealing resin 22 has a function of reinforcing the mechanical connection between the electronic component 20 and the wiring board 1. As the material of the sealing resin 22, for example, epoxy resin or the like is used.

The metal lid 30 covers the electronic component 20 on the upper surface of the wiring board 1 and is connected to a region around the mounting region 10 with an adhesive. The upper portion of the electronic component 20 and the coating portion of the metal lid 30 are in contact with each other via grease for heat dissipation.

The metal lid 30 contains a metal such as copper or aluminum. The metal lid 30 mainly has a function of suppressing the deformation of the wiring board 1.

The electric board 40 may be, for example, a motherboard. The electric board 40 includes an insulating plate 41 and a conductor layer 42.

The insulating plate 41 includes an insulating material obtained by impregnating glass cloth with epoxy resin, bismaleimide triazine resin, or the like and curing the glass cloth. The insulating plate 41 has a plurality of through holes 43.

The conductor layer 42 is located on the upper surface and the lower surface of the insulating plate 41 and inside the through hole 43. The conductor layer 42 contains a highly conductive metal such as copper. A part of the conductor layer 42 located on the upper surface and the lower surface is electrically connected by the conductor layer 42 in the through hole 43.

A part of the conductor layer 42 located on the upper surface of the insulating plate 41 functions as a first electrode 44 connected to the wiring board 1. A part of the conductor layer 42 located on the lower surface of the insulating plate 41 functions as, for example, a second electrode 45 connected to an electronic device.

In such a mounting structure 50, the wiring board 1 having the second insulating layer 12 that can disperse the stress even when the stress accompanying the thermal expansion and contraction of the electric substrate 40 is applied to the connection pad 4 as described above. Since it is mounted, the connection reliability between the wiring board 1 and the electric board 40 is excellent.

As described above, according to the structure of the present disclosure, it is possible to provide the mounting structure 50 capable of stably operating the electronic component 20.

The wiring board 1 according to the present disclosure is not limited to the above-described example of the embodiment, and various modifications can be made without departing from the scope of the present disclosure.

Although FIG. 1 shows an example in which the second insulating layer 12 has a quadrangular shape in a plan view, the second insulating layer 12 may have an L-shape, a rectangular shape, or a polygonal shape in a plan view. I do not care. The degree of freedom in wiring design can be improved by appropriately designing the shape in accordance with the position of the connection pad 4 where external stress concentrates.

Further, in the above example, the four second insulating layers 12 have the same shape and size, but the second insulating layer 12 has different shapes and sizes. I don't mind. By setting the shape and size of the second insulating layer 12 in accordance with the position of the connection pad 4 where the stress from the outside concentrates, it is possible to obtain the wiring board 1 in which the stress is more dispersed.

Further, in the example of the mounting structure 50 described above, the case where one electronic component 20 is mounted on the wiring board 1 is shown, but for example, even if a plurality of electronic components are mounted around the electronic component 20. I do not care. Such electronic components are, for example, HBM (High Bandwidth).
A wide band memory such as Memory) and the like. The mounting structure 50 including the HBM and the ASIC described above can process a large amount of information at high speed.

The metal lid 30 connected to the mounting structure 50 may have an opening that exposes the upper part of the electronic component 20. In other words, when viewed from above, the upper portion of the electronic component 20 is positioned so as to be visible inside the opening. The upper portion of the electronic component 20 may be higher or lower than the upper portion of the metal lid 30. In such a case, for example, a cooling member can be connected to the upper part of the above-mentioned ASIC that generates a large amount of heat, and the influence of heat on the mounting structure 50 can be reduced.

1 Wiring Board 2 Insulating Board 3 Wiring Conductor 4 Connection Pad 7 First Insulating Layer 10 Mounting Area 12 Second Insulating Layer 14 Via Hole Conductor 20 Electronic Component 30 Metal Lid 40 Electric Board 50 Mounting Structure

Claims (4)

A rectangular insulating substrate including a plurality of stacked first insulating layers;
A mounting region having a corner portion which is partitioned on the upper surface of the insulating substrate;
A wiring conductor located between the first insulating layers,
A plurality of connection pads located on the lower surface of the insulating substrate,
A via-hole conductor that is located in the first insulating layer and that electrically connects the wiring conductors between different layers and the connection pad and the wiring conductor;
The insulating substrate corresponding to at least one of a region where the connection pads are located at four corners of the insulating substrate in plan view and a region where the connection pads are located at corners of the mounting region in plan view. The second insulating layer having a Young's modulus smaller than the Young's modulus of the first insulating layer is located as the lowermost layer of the wiring board. The via-hole conductor is absent in the second insulating layer, and the connection pad is electrically connected to the wiring conductor in the upper layer by the via-hole conductor located in the first insulating layer. The wiring board according to claim 1, wherein: The wiring board according to claim 1 or 2,
An electronic component located in the mounting area,
On the upper surface of the wiring board, a metal lid that covers at least a part of the electronic component and is connected to the periphery of the mounting area,
An electric board connected to the connection pad of the wiring board via a conductive material,
A mounting structure characterized by having. The mounting structure according to claim 3, wherein the metal lid has an opening that exposes an upper portion of the electronic component.

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