JP2013187359A - Method for producing substrate having built-in components and substrate having built-in components - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing a substrate having built-in components with high reliability.SOLUTION: The method for producing a substrate having built-in components comprises: (i)preparing a core layer having a component-mount surface with a land formed thereon; (ii)putting, on the land, a bonding material including a thermosetting resin, solder particles and a granular material having a melting point higher than that of the solder particles; (iii) mounting an electronic component on the core layer with the bonding material interposed therebetween; (iv) heating the core layer with the electronic component mounted thereon at a temperature higher than the melting point of solder and lower than the melting point of the granular material to form a solder-connecting part for connecting a terminal and the land, and to form a resin-coating part for covering the solder-connecting part; (v)laminating a prepreg on the core layer so that the electronic component is enclosed by the prepreg; and (vi) applying pressure to the resultant laminate of the core layer and the prepreg in a laminating direction and heating the laminate, thereby encapsulating the electronic component by the hardened prepreg.

Description

  The present invention relates to a component-embedded substrate comprising a core layer having a component mounting surface on which a metal foil wiring pattern is formed, an electronic component mounted on the component mounting surface, and a resin layer for sealing the electronic component. In particular, it relates to a manufacturing method thereof.

  Many electronic components such as semiconductor elements are incorporated in electronic devices in the form of electronic component modules. An electronic component module is generally formed by mounting an electronic component on a substrate on which a metal foil wiring pattern is formed, and then sealing the electronic component with a resin layer. While a higher mounting density of electronic component modules is required, a component-embedded substrate in which a plurality of wiring patterns are stacked and an electronic component is mounted on an inner layer wiring pattern has been used (for example, Patent Document 1).

  In the component-embedded substrate of Patent Document 1, first, thermosetting cream solder is supplied to the land (electrode) of the wiring pattern of the core layer. The thermosetting cream solder contains a thermosetting resin and solder particles dispersed in the thermosetting resin, and the thermosetting resin has a flux action to remove the oxide film on the solder surface. It is. Then, after mounting an electronic component on a core layer via a thermosetting cream solder, the core layer is heated to form a solder joint that connects the terminal and the land of the electronic component.

  Next, a roughening process (blackening process) of the wiring pattern is performed, and a prepreg is arranged on the roughened surface so as to surround the electronic component. And another wiring layer or metal foil is arrange | positioned so that a core layer may be opposed via a prepreg, and a component built-in board | substrate is formed by pressing and heating the obtained laminated body in the lamination direction.

  In the manufacturing method as described above, since the thermosetting resin having the action of flux is cured, unlike the case of using a general cream solder, there is no need to clean the flux residue. It is advantageous. Moreover, it is excellent also in the point which can protect a solder joint part from the chemical agent used by a roughening process with the hardened | cured material of a thermosetting resin.

  On the other hand, in an electronic component mounting method in which an electronic component having a terminal on a side surface is mounted on an electrode of a substrate via a thermosetting cream solder, the thermosetting resin contained in the thermosetting cream solder is used as the lower surface of the electronic component. It has been proposed to improve bonding reliability by entering a gap with the substrate (Patent Document 2).

JP 2009-110992 A JP 2006-114542 A

  However, in the manufacturing method disclosed in Patent Document 1, when the core layer on which the electronic component is mounted is heated, the thermosetting resin contained in the thermosetting cream solder causes the lower surface of the electronic component and the core layer to be entrained while enclosing the void. As a result, the reliability of the solder joint may be impaired. The reason will be described below. Note that the penetration of the thermosetting resin including the voids into the gap between the lower surface of the electronic component and the substrate also occurs in the electronic component mounting method as disclosed in Patent Document 2.

  6A, the terminals 7a of the electronic component 7 are connected to the land of the wiring pattern 3 of the core layer 1 via the thermosetting cream solder 6 including the thermosetting resin 6a and the solder particles 6b dispersed therein. The state landed on 3a is shown. At this stage, the thickness of the thermosetting cream solder 6 is relatively large, and a gap 8 corresponding to the thickness of the thermosetting cream solder 6 is formed between the lower surface of the electronic component 7 and the core layer 1. .

  However, when the core layer 1 is heated, the viscosity of the thermosetting resin 6a contained in the thermosetting cream solder 6 decreases and the solder particles 6b melt and crawl up to the surface of the terminal 7a. Move in the direction. Therefore, as shown in FIG. 7B, the thickness of the solder joint portion 6x is reduced, and the gap between the lower surface of the electronic component 7 and the core layer 1 is reduced. Most of the thermosetting resin is cured to form a resin coat portion 6y that covers the solder joint portion 6x. However, a part of the thermosetting resin having a reduced viscosity is voided in a narrow gap due to a capillary phenomenon. It penetrates while involving 8b. That is, the narrowing of the gap between the lower surface of the electronic component 7 and the core layer 1 promotes the penetration of the thermosetting resin including the void into the gap.

  When the gap between the electronic component 7 and the core layer 1 is sealed halfway by the cured product of the thermosetting resin including the void 8b, the solder joint portion 6x is used during re-flow for heating the component-embedded substrate. Therefore, the molten solder enters the void 8b, and the reliability of the joint is impaired. In particular, when a void path is formed to communicate between the terminals 7a of the electronic component 7, a short circuit between the terminals may occur due to solder flash.

  On the other hand, the gap 8 between the lower surface of the electronic component 7 and the core layer 1 is essentially desirably completely sealed with a resin material. Therefore, it is conceivable to seal the gap between the lower surface of the electronic component 7 and the core layer 1 with a prepreg in the second half of the manufacturing process of the component-embedded substrate. However, in addition to the narrowing of the gap as described above, it is difficult to seal the gap with the prepreg because the thermosetting resin that has entered the gap at the middle halfway becomes an obstacle.

  When the core layer 1 is mainly composed of a resin substrate, the volatile component contained in the resin substrate is gasified by heating, so that the problem of void entrainment due to the thermosetting resin becomes more obvious. In order to suppress gas generation from the resin substrate, it is necessary to heat-treat the core layer at an appropriate temperature before use.

As described above, there is still room for improvement in the manufacturing method for efficiently producing the component-embedded substrate.
Accordingly, one aspect of the present invention is: (i) a step of preparing a core layer having a component mounting surface on which a first wiring pattern including a land for connecting electronic components is formed; and (ii) the first wiring pattern A step of disposing a bonding material including a thermosetting resin, solder particles dispersed in the thermosetting resin, and granular materials having a melting point higher than the melting point of the solder particles at least in a portion covering the land. And (iii) preparing an electronic component having a terminal, landing the terminal on the land via the bonding material, and mounting the electronic component on the component mounting surface; and (iv) the electronic The core layer on which the component is mounted is first heated at a temperature higher than the melting point of the solder and lower than the melting point of the granular material to melt the solder and adhere to the land and the terminal, and then solidify. By letting Forming a solder joint portion for joining the terminal to the land, and forming a resin coat portion for curing the thermosetting resin to cover the solder joint portion; and (v) mounted on the component mounting surface. A step of laminating the prepreg on the core layer so that the electronic component is surrounded by the prepreg, and (vi) pressurizing the laminated body of the core layer and the prepreg in the laminating direction and performing second heating. And a step of sealing the electronic component with a cured product of the prepreg.

  Another aspect of the present invention includes a core layer having a component mounting surface on which a first wiring pattern including a land is formed, an electronic component having a terminal facing the land, the land, and the terminal of the electronic component. A solder joint that connects the solder joint, a resin coat that covers the solder joint, and a sealing resin that seals the component mounting surface together with the electronic component and the resin coat, and the solder joint includes A first region containing particulate matter and a second region covering the first region, wherein at least the second region is a metal region electrically connecting the land and the terminal, and the core layer The present invention relates to a component-embedded substrate in which a gap between the electronic component and a surface facing the core layer is sealed with the sealing resin.

  According to the present invention, since the bonding material for bonding the land of the core layer and the terminal of the electronic component includes a granular material that does not melt at the melting point of the solder particles, when heating the core layer on which the electronic component is mounted, The granular material serves as a spacer, and the narrowing of the gap between the lower surface of the electronic component and the core layer is suppressed. As a result, penetration of the thermosetting resin including voids due to capillary action into the gap is suppressed, and a fixed space is maintained between the lower surface of the electronic component and the core layer even after the electronic component is mounted. The Therefore, when the electronic component is sealed with the prepreg, the prepreg easily enters between the lower surface of the electronic component and the core layer, and a highly reliable sealing is achieved.

Explanatory drawing which shows the process ((A)-(C)) until it mounts an electronic component in the component mounting surface of a core layer through a bonding material among the manufacturing processes of the component built-in board which concerns on one Embodiment of this invention. It is. It is explanatory drawing which shows the process ((D)-(F)) until it arrange | positions a prepreg after forming a solder joint part by a reflow process among the manufacturing processes of the component built-in board which concerns on one Embodiment of this invention. . Among the manufacturing steps of the component built-in substrate according to the embodiment of the present invention, the steps ((G) to (I) until the component built-in substrate in which a plurality of wiring patterns are laminated from the laminated body of the core layer and the prepreg are completed. It is explanatory drawing which shows)). It is an enlarged view which shows notionally the principal part structure of the component built-in board which concerns on one Embodiment of this invention. It is an enlarged view which shows notionally the principal part structure of the component built-in board | substrate which concerns on another embodiment of this invention. Among conventional manufacturing processes of component-embedded substrates, steps from mounting an electronic component on a component mounting surface of a core layer via a bonding material to forming a solder joint by a reflow process ((A) to (B) FIG.

First, the basic structure of the component built-in substrate will be described.
The component-embedded substrate has a structure in which a plurality of wiring layers or wiring patterns (metal foils) are stacked around a base layer. The base layer includes a core layer having a component mounting surface on which a wiring pattern is formed, and an electronic component mounted on the component mounting surface by a solder joint.

  Electronic components mounted on the component mounting surface of the core layer include chip-type small electronic components with connection terminals formed at both ends, such as chip capacitors and chip resistors, and metal bumps that serve as connection terminals on the bottom surface Examples thereof include, but are not particularly limited to, an electronic component including the prepared semiconductor.

  A sealing resin (resin layer) made of a cured prepreg is disposed between adjacent wiring patterns. The sealing resin has a function of bonding the wiring patterns adjacent to each other. Since an electronic component such as a chip component is mounted on the wiring pattern of the core layer, the sealing resin has a function of protecting the component mounting surface together with the electronic component.

  Cream solder is generally used to connect the terminals of the electronic component and the land of the wiring pattern. Therefore, when manufacturing the component-embedded substrate, heating for mounting the electronic component on the wiring pattern, and heating for bonding the wiring patterns together are repeated.

  The core layer has a thin resin substrate having a thickness of about 30 to 100 μm, for example, and a wiring pattern (first wiring pattern) is formed on one or both surfaces thereof. Many resin substrates contain volatile components, and thus generate gas when heated. Therefore, from the viewpoint of suppressing generation of voids inside the component-embedded substrate, the resin substrate may be used after being heat-treated at 125 ° C. to 150 ° C. The shape of the wiring pattern varies, and the portion connected to the terminal of the electronic component is called a land. Such a core layer is formed by attaching a metal foil such as a copper foil to a resin substrate and then patterning the metal foil.

Next, the manufacturing method of the component built-in substrate of this invention is demonstrated.
The component-embedded substrate manufacturing method includes: (i) preparing a core layer having a component mounting surface on which a first wiring pattern including lands for connecting electronic components is formed; and (ii) at least one of the first wiring patterns. A step of disposing a bonding material including a thermosetting resin, solder particles dispersed in the thermosetting resin, and a granular material having a melting point higher than the melting point of the solder particles on a portion covering the land; (Iii) preparing an electronic component having a terminal, landing the terminal on the land via the bonding material, and mounting the electronic component on the component mounting surface; and (iv) the electronic component The core layer on which is mounted is first heated at a temperature higher than the melting point of the solder and lower than the melting point of the granular material to melt the solder and adhere to the land and the terminal, and then solidify. By before Forming a solder joint portion for joining the terminal to the land, and forming a resin coat portion for curing the thermosetting resin to cover the solder joint portion; and (v) mounted on the component mounting surface. A step of laminating the prepreg on the core layer so that the electronic component is surrounded by the prepreg, and (vi) pressurizing the laminated body of the core layer and the prepreg in the laminating direction and performing second heating. And a step of sealing the electronic component with a cured product of the prepreg.

  In addition, before pressurizing the said laminated body and carrying out 2nd heating, you may arrange | position metal foil, such as copper foil, so that a core layer may be opposed via a prepreg. In this case, after the second heating, via conductors connecting the plurality of wiring patterns are formed, or the metal foil is patterned to form second and third wiring patterns derived from the metal foil. can do. By repeating the same operation, it is possible to obtain a component-embedded substrate having a high mounting density in which a plurality of wiring patterns are stacked.

Hereinafter, each process will be described with reference to the drawings.
1-3 is explanatory drawing which shows each process of the manufacturing method of the component built-in board | substrate which concerns on one Embodiment of this invention.

First, a core layer having a component mounting surface on which a first wiring pattern including lands for connecting electronic components is formed is prepared (step (i)).
In FIG. 1A, the core layer 1 includes an insulating resin substrate 2, a first wiring pattern 3 disposed on the upper surface of the resin substrate 2, and a first wiring pattern 4 disposed on the lower surface of the resin substrate 2. It consists of and. Each wiring pattern is formed of a metal thin film (for example, a metal foil such as a copper foil). The upper surface of the core layer 1 is a component mounting surface, and a part of the first wiring pattern 3 functions as an electrode for connecting with a terminal of an electronic component, that is, a land 3a. For example, electronic components such as a chip resistor and a chip capacitor are mounted on the land 3a.

  The size of the electronic component is not particularly limited, but from the viewpoint of enabling high-density mounting, the height from the land is 0.5 mm or less, and further 0.05 mm to It is preferable to use a 0.2 mm electronic component. Such a small electronic component has a small gap formed between the core layer 1 and the demand for suppressing the narrowing of the gap is high.

  Note that the wiring patterns 3 and 4 include not only a part that actually functions as a wiring circuit but also a part that remains on the surface of the core layer 1 after patterning and does not have a function as a wiring circuit. Such a portion has a function of ensuring the strength of the core layer 1, for example.

Next, as shown in FIG. 1 (B), thermosetting cream solder is disposed as a bonding material 6 in a portion covering at least the land 3a of the wiring pattern 3 (step (ii)).
Examples of the method for disposing the bonding material 6 on the surface of the core layer 1 include a screen printing method, a coating method using a dispenser, and a method of bonding a bonding material previously formed into a film shape onto a component mounting surface. Various methods can be selected according to the shape and range of the part where the bonding material 6 is disposed.

  The bonding material 6 is disposed at least in a portion covering the land 3a. However, the bonding material 6 may be disposed so that not only the surface of the land 3a but also the first wiring pattern 3 is entirely covered. For example, the bonding material 6 may be disposed over the entire area where the first wiring pattern 3 is formed on the upper surface of the resin substrate 2. In this case, a method of sticking the bonding material 6 formed in a film shape to the component mounting surface is convenient.

  A general thermosetting cream solder used as the bonding material 6 is a paste including a thermosetting resin (thermosetting flux) 6a and solder particles 6b dispersed in the thermosetting resin 6a. The thermosetting cream solder used in the invention further includes a granular material 6A that does not melt at the melting point of the solder particles 6b. Since the granular material 6A does not melt even when the solder particles 6b are melted by the reflow process, the granular material 6A serves as a spacer for securing a certain distance between the land 3a of the core layer 1 and the terminal 7a of the electronic component 7. Function.

  From the viewpoint of securing the function of the spacer as described above, the particle size of the granular material 6A is determined according to the size of the gap between the desired electronic component and the core layer. Although it depends on the amount of the granular material 6A contained in the bonding material 6, the particle diameter in the particle size distribution d90 of the granular material 6A is preferably selected from the range of 5 μm to 50 μm. By using a granular material having a particle diameter in such a range, it becomes easy to control the distance between the electronic component mounted on the component mounting surface and the land to a range of 20 μm to 50 μm. The “particle size in the particle size distribution d90” is a particle size in which the cumulative number from the smallest particle size in the cumulative particle size distribution becomes 90%.

  The melting point of the granular material 6A may be higher than the reflow temperature at which the solder particles 6b are melted. However, from the viewpoint of suppressing melting of the granular material 6A when the solder particles 6b are melted, the difference between the melting point of the solder particles 6b and the melting point of the granular material 6A is preferably 30 ° C. or higher.

  The thermosetting resin 6a included in the bonding material 6 desirably includes a component having an active action of removing the oxide film on the surface of the solder particles. Examples of the component having such an active action include components used in fluxes such as organic acids, amines, and halides (for example, hydrohalides). As the main component of the thermosetting resin, epoxy resin, acrylate resin, polyimide, polyurethane, phenol resin, unsaturated polyester resin, or the like is used. The thermosetting resin may contain a curing agent, a curing accelerator, and the like. As the curing agent, an acid anhydride, an aliphatic or aromatic amine, imidazole or a derivative thereof is preferably used, and examples of the curing accelerator include dicyandiamide.

  Although it does not specifically limit as solder particle 6b, It is preferable to have a composition which does not melt | dissolve in the heating process for bonding the prepreg performed later to the core layer 1. FIG. For example, a solder such as a Sn—Cu alloy, a Sn—Ag alloy, a Sn—Ag—Cu alloy, a Sn—Bi alloy, or a Sn—Zn alloy can be used. Each alloy may further include at least one of In, Zn, Bi and the like as the third or fourth element. The particle diameter of the solder particles 6b may be appropriately selected according to the size of the electronic component or the land. For example, solder particles having a particle diameter of 15 to 20 μm in the particle size distribution d50 can be used. The “particle size in the particle size distribution d50” is a particle size in which the cumulative number from the smallest particle size in the cumulative particle size distribution becomes 50%.

  Next, an electronic component 7 having a terminal 7a is prepared. As shown in FIG. 1C, the terminal 7a is landed on the land 3a through the bonding material 6, and the electronic component 7 is mounted on the component mounting surface. (Step (iii)). In FIG. 1C, a chip component having terminals 7a at both ends is mounted as the electronic component 7. However, the present invention is not limited to this.

  Various electronic component mounting apparatuses can be used for mounting the electronic component 7. Generally, an electronic component mounting apparatus has a mounting head provided with a suction nozzle, and the mounting head can freely move in a three-dimensional direction. The electronic component 7 is supplied to the component supply unit of the electronic component mounting apparatus by a tape feeder or the like. In the component supply unit, the mounting head picks up the electronic component 7 and moves it above the component mounting surface of the core layer 1. Then, the alignment between the terminal 7a of the electronic component 7 and the land 3a of the first wiring pattern 3 is automatically performed. Subsequently, the electronic component 7 is mounted so that the terminal 7 a is landed on the land 3 a via the bonding material 6.

  Thereby, the electronic component 7 is held by the core layer 1 through the adhesive bonding material 6. At this time, as shown in FIG. 1C, a gap 8 corresponding to the coating height of the bonding material 6 is formed between the upper surface of the core layer 1 and the lower surface of the electronic component 7. The distance L of the gap 8 at this time depends on the coating thickness of the bonding material 6 (thermosetting cream solder).

  Next, as shown in FIG. 2D, the core layer 1 on which the electronic component 7 is mounted is heated (first heating), and the terminals 7 a of the electronic component 7 are connected by solder contained in the bonding material 6. Bonded to the land 3a. By heating, the solder particles 6b are melted and move and agglomerate in the thermosetting resin having a reduced viscosity, and wet and spread on the lands 3a and the terminals 7a. Thereafter, when the temperature of the solder is lowered, the solder is solidified to form a solder joint 6x that joins the terminal 7a and the land 3a. On the other hand, the thermosetting resin 6a is separated from the metal component and cured to form a resin coat portion 6y that covers at least a part of the solder joint portion 6x. The resin coating portion 6y covering the solder joint portion 6x serves to protect the solder joint portion 6x and reinforce the joining of the electronic component 7 to the core layer 1 by the solder joint portion 6x.

  As described above, in the first heating, since it is necessary to melt the solder particles 6b included in the bonding material 6, it is necessary to heat the core layer 1 at a temperature higher than the melting point of the solder. At that time, a volatile component may be volatilized as a gas from the resin substrate 2 forming the core layer 1. Moreover, the solder particles 6b are melted by the first heating, and the viscosity of the thermosetting resin 6a is reduced.

  In such a situation, when there is no granular material 6A that does not melt at the melting point of the solder, the bonding material 6 cannot support the electronic component 7, and the electronic component 7 moves in the direction of gravity. Further, the terminal 7a of the electronic component 7 is attracted to the land 3a by the surface tension of the molten solder when the land 3a and the terminal 7a are spread. As a result, the gap between the lower surface of the electronic component 7 and the upper surface of the core layer 1 is narrowed to a considerable extent. The thermosetting resin 6a having a reduced viscosity enters the narrowed gap due to the capillary phenomenon. At that time, the thermosetting resin 6a enters the gap in a state where the gas generated from the resin substrate 2 is entrained.

  On the other hand, when the bonding material 6 includes a granular material 6A that does not melt at the melting point of the solder, the granular material 6A serves as a spacer and the electronic component 7 moves in the direction of gravity as shown in FIG. (Subduction) is suppressed. Therefore, although the gap 8a between the lower surface of the electronic component 7 and the upper surface of the core layer 1 is narrowed to some extent, the degree thereof is reduced, and the distance S is set so that the penetration of the thermosetting resin due to the capillary phenomenon is suppressed. Can be held. Therefore, a constant space is maintained between the lower surface of the electronic component 7 and the core layer 1 even after the first heating. At this time, the distance between the land 3a and the terminal 7a of the electronic component 7 is at least the maximum diameter of the granular material 6A. However, when functioning as a spacer in a state where a plurality of particles of the granular material 6A are aggregated, the maximum diameter of the granular material 6A may be sufficiently smaller than the distance S of the gap to be secured.

  While suppressing the intrusion of the thermosetting resin having a reduced viscosity into the gap 8a, in the subsequent process, from the viewpoint of facilitating the intrusion of the prepreg into the gap 8a, the land 3a and the electronic component 7 after the first heating are prevented. For example, the distance to the terminal 7a is preferably controlled to 20 μm to 50 μm, and more preferably 30 μm to 50 μm. The distance between the land 3a and the terminal 7a of the electronic component 7 means a distance along a direction perpendicular to the component mounting surface of the core layer 1.

  Even when the above distance is ensured, the molten solder flows in the thermosetting resin having a reduced viscosity and moves between the terminal 7a of the electronic component 7 and the land 3a. It can easily spread on the surface of 3a. When the solder is solidified, a fillet-like solder joint 6x is formed between the terminal 7a of the electronic component 7 and the land 3a.

  Here, the solder joint portion 6x includes at least two regions. One is a first region including the granular material 6A, and the other is a second region that covers at least a part of the first region. Among these, the second region is a region formed by solidifying the constituent components of the solder particles 6b after melting, and is a metal region that electrically connects the land 3a and the terminal 7a of the electronic component 7. When the granular material 6A is a metal, the first region also forms a metal region that electrically connects the land 3a and the terminal 7a of the electronic component 7.

Although it does not specifically limit as granular material 6A which has melting | fusing point higher than melting | fusing point of solder particle 6b, Metal powder, ceramic powder, resin powder, etc. can be used. Among these, metal powder is particularly preferable because of its high affinity with the second region, which is a metal region, and easy distribution in the solder joints 6x. For example, Cu, Ag, Ni, or the like can be used as the metal powder. As the ceramic powder, Al ₂ O ₃ , SiO ₂ or the like can be used. Moreover, as resin powder, a fluororesin, a divinylbenzene crosslinked polymer, PEK (polyetherketone), etc. can be used.

  Even if a part of the granular material 6A is distributed in the resin coating portion 6y, as long as the granular material 6A is distributed in the solder joint portion 6x, the function as a spacer is expressed. The distance with the terminal 7a of the electronic component 7 is ensured.

  The metal powder preferably contains a component that forms an alloy with the solder. Such a surface layer portion of the metal powder forms an alloy with the components contained in the solder particles during solder joining by heating. In this case, the solder joint portion 6x includes a first region including the particulate matter 6A, a second region covering at least a part of the first region, and a third region interposed between the first region and the second region. Three areas are included. The third region includes an alloy of a component contained in the first region derived from the metal powder and a component contained in the second region derived from the solder. For example, when the metal powder is Cu and the solder is a Sn—Bi alloy, a Cu—Sn intermetallic compound is formed as the third region. By forming such a third region, it becomes difficult to generate a gap between the metal powder (first region) and the solder (second region), and the strength and reliability of the solder joint 6x are further improved. .

Next, the surface of the wiring patterns 3 and 4 is roughened as necessary.
The roughening treatment is performed in a later step in order to improve the adhesion between the prepreg and each wiring pattern. By the roughening treatment, fine irregularities are formed on the surface of each wiring pattern, and the adhesion between the thermosetting resin contained in the prepreg and the wiring pattern is improved. The method of the roughening treatment is not particularly limited, but can be performed by immersing the core layer in a treatment solution (strongly acidic solution or strongly alkaline solution) having an action of chemically eroding the metal surface. The surfaces 3b and 4b of the wiring pattern roughened by the treatment liquid change color as conceptually shown in FIG. 2E and become black or a color close thereto. Called.
Note that as a roughening treatment method, plasma treatment or the like may be performed in addition to the wet blackening treatment using a treatment liquid.

  When the wet blackening treatment is performed as the roughening treatment, it is desirable to cure the thermosetting resin to a nearly complete state in the first heating, or to perform after-curing separately before the roughening treatment. By sufficiently curing the thermosetting resin, erosion of the resin coat portion 6y by the treatment liquid can be suppressed.

  Alternatively, the roughening treatment is not necessarily performed after the first heating. For example, the surface of the first wiring pattern before the bonding material is disposed may be roughened before the step (ii).

  Next, as shown in FIG. 2F, the prepreg 9 is laminated on the core layer 1 so as to surround the electronic component 7 mounted on the component mounting surface (step (v)).

  When the prepregs 9 are stacked and arranged, it is desirable that the prepregs 9 be arranged so that no gap is generated between the electronic component 7 and the prepreg 9 as much as possible. The prepreg 9 is arranged so that not only the electronic component 7 but also the first wiring pattern 3 is entirely sealed. By doing in this way, the component mounting surface of the core layer 1 with the electronic component 7 and the resin coating part 6y can be sealed with the cured | curing material of a prepreg entirely.

  In FIG. 2F, a prepreg 9 having an opening corresponding to the electronic component 7 is disposed so as to be in close contact with the upper surface of the core layer 1 and the electronic component 7 and to surround the electronic component 7. Further, a pair of prepregs 10a and 10b are arranged so as to sandwich the core layer 1 from both sides, and metal foils 11a and 11b are respectively attached to the surfaces of the prepregs 10a and 10b opposite to the core layer 1 side. It has been. By setting it as such a structure, both surfaces of the core layer 1 can be completely protected by sealing resin derived from a prepreg. In a later step, desired wiring patterns can be formed on the metal foils 11a and 11b, respectively.

  However, when a plurality of electronic components 7 are densely mounted on the core layer 1 at a narrow pitch, it is not necessary to enclose each electronic component 7 one by one or a small number. In such a case, a prepreg having an opening corresponding to the dense region may be prepared, and the prepreg may be arranged in the core layer so that the opening is fitted into the dense region.

  Next, as shown in FIG. 3G, the laminated body of the core layer 1 and the prepregs 9, 10a, and 10b is pressurized in the laminating direction and heated (second heating). Thereby, the electronic component 7 is sealed with the sealing resin 12 which is a cured product of the prepregs 9 and 10a (step (vi)). At this time, since a certain space is held in the gap 8a between the lower surface of the electronic component 7 and the upper surface of the core layer 1, a part of the prepreg can easily enter the gap. Accordingly, a gap filling portion 12a made of a cured product of the prepreg is also formed in the gap, and highly reliable sealing is achieved.

  From the viewpoint of efficiently allowing the prepreg to penetrate into the gap between the lower surface of the electronic component 7 and the upper surface of the core layer 1, it is preferable that the pressurization in the stacking direction of the stacked body is performed in a reduced pressure atmosphere. The pressure of the reduced pressure atmosphere may be, for example, 13.3 kPa (100 Torr) or less.

The laminated body may be heated with a general press device at a pressure of about 30 kgf / cm ² , for example. At this time, the temperature of the second heating may be a temperature at which the curing reaction of the thermosetting resin contained in the prepreg proceeds.

  However, it is preferable that the composition of the solder joint has a melting temperature equal to or higher than the second heating temperature (for example, a temperature higher by 20 ° C. than the second heating temperature) so that the solder joint 6x is not displaced. desirable. For example, when the second heating temperature is about 150 to 175 ° C., the composition of the solder joint may be set to Sn: Bi = 92: 8 (melting temperature about 195 ° C.).

  By the second heating, as shown in FIG. 3 (G), the contact interface between the sealing resin 12 derived from the prepregs 9 and 10a and the resin coating portion 6y is fused and integrated with each other, and the highly reliable component. A built-in substrate 14 is formed. At this time, the first wiring pattern 3 and the electronic component 7 are in close contact with the adjacent prepreg. Similarly, the prepreg 10 b adjacent to the wiring pattern 4 on the lower surface of the core layer 1 forms a resin layer 13 in close contact with the wiring pattern 4. Since fine irregularities are formed on the surfaces of the wiring patterns 3 and 4 by the roughening treatment, good adhesion between the wiring patterns 3 and 4 and the sealing resin or resin layer is achieved.

  Here, it is desirable that the resin coat portion 6y has more flexibility than the sealing resin 12 derived from the prepreg. This is because the resin coat portion 6y directly covers the solder joint portion 6x, and thus is desired to have an action of relieving the stress generated in the solder joint portion 6x. On the other hand, the sealing resin 12 needs to have a certain elastic modulus or more from the viewpoint of securing the strength of the component built-in substrate. From the above, the elastic modulus of the resin coat portion 6y is desirably 50% or less, and more desirably 20% or less of the elastic modulus of the sealing resin 12. A component-embedded substrate that satisfies such conditions can sufficiently relieve stress due to expansion and contraction of the solder joint 6x during a heat cycle or the like, and can achieve high reliability.

  Next, as shown in FIG. 3H, via holes are formed in the obtained component-embedded substrate 14 in the thickness direction, and a plated layer 15 is formed on the inner surface of the holes. As a result, via conductors (interlayer wiring) connecting the first wiring pattern 3 of the core layer 1 and the metal foils 11a and 11b respectively disposed on both surfaces of the component-embedded substrate 14 are formed.

  For example, a conformal method can be used for forming the via hole. First, only the metal foil present on the surface of the via hole forming portion is removed by etching by photolithography or the like. Next, when the portion where the metal foil is removed is irradiated with a laser, the remaining surrounding metal foil becomes a conformal mask, and a via hole can be formed in the portion where the metal foil is removed. For the laser processing, a carbon dioxide laser, a YAG laser, or the like can be used.

  Next, since smear (resin residue) is generated in laser processing, desmear processing in the via hole is performed. As the chemical for desmear treatment, for example, an oxidizing agent aqueous solution or the like can be used. Specifically, an alkaline aqueous solution of potassium permanganate or sodium permanganate, an aqueous sulfuric acid solution of chromic acid or sodium dichromate, or the like can be used. Prior to treatment with these chemicals, pretreatment in the via hole may be performed using an alkali swelling liquid.

After the desmear process, after neutralizing with a predetermined neutralizing solution, a plating layer 15 is formed on the inner surface of the desmeared via hole, and a conduction process is performed. At this time, treatment by a dry method such as vapor deposition, sputtering, or ion plating may be performed, but treatment by a wet method such as electroless plating or electrolytic plating is preferable in consideration of mass productivity.
The method for forming the via conductor is not limited to the above.

  Thereafter, as shown in FIG. 3I, the second wiring pattern 16 is formed by patterning the one metal foil 11a. Of course, the other metal foil 11b may be patterned, and in this case, the third wiring pattern 17 is formed. The second and third wiring patterns formed in this way are further targets for mounting electronic components. By repeating the same operation, it is possible to obtain a component-embedded substrate with a higher mounting density in which more wiring patterns are stacked.

FIG. 4 conceptually shows an essential part structure of the completed component-embedded substrate.
Between the land 3a formed on the component mounting surface of the core layer 1 and the terminal 7a of the electronic component 7, a solder joint portion 6x for electrically connecting them is formed, and the periphery thereof is a resin coating portion. 6y is covering. The component mounting surface including the electronic component 7 and the resin coat portion 6y is sealed with a sealing resin (not shown), and the gap between the core layer 1 and the surface facing the core layer 1 of the electronic component 7 is also It is sealed by a gap filling portion 12a derived from the prepreg. With such a structure, a solder flash does not occur during reflow for heating the component-embedded substrate 14, and a short circuit between the terminals 7a of the electronic component 7 does not occur.

The solder joint portion 6x has a first region containing particulate matter (for example, Cu particles) 6A and a second region derived from solder (for example, Sn—Bi alloy), and the first region is formed by the second region. Covered. In such a combination of solder and granular material 6A, a third region made of an alloy or an intermetallic compound (for example, Cu ₆ Sn ₅ ) is usually interposed between the first region and the second region. Yes. In FIG. 4, the range of the third region 6z is conceptually indicated by a broken line.

  In FIG. 4, the maximum diameter of the granular material 6A matches the distance between the land 3a and the terminal 7a of the electronic component 7, but the maximum diameter of the granular material 6A does not need to match the distance. For example, as shown in FIG. 5, when the particles 6B function as a spacer in a state where a plurality of particles are aggregated, the distance between the land 3a and the terminal 7a of the electronic component 7 is the aggregate of the particles 6B. Depends on size.

  However, the smaller the amount of particulate matter contained in the bonding material 6, the more the number of particulate matter interposed between the land 3a and the terminal 7a of the electronic component 7 is reduced probabilistically. Therefore, it is desirable that the smaller the amount of the granular material contained in the bonding material 6, the larger the diameter of the granular material.

Hereinafter, the preferable composition of the bonding material 6 will be exemplified.
The total amount of solder particles contained in the bonding material 6 and the particulate matter having a melting point higher than the melting point of the solder is preferably 35 to 65% by volume. In this case, the amount of components other than the solder particles and the particulates contained in the bonding material 6, that is, the thermosetting resin (including the activator and the curing agent) is 65 to 35% by volume.

As described above, the preferable range of the amount (volume ratio) of the particulate matter in the total amount of the solder particles and the particulate matter varies depending on the particle diameter of the particulate matter.
Specifically, when the particle size in the particle size distribution d90 is 5 to 15 μm, the volume ratio of the granular material to the total amount of the solder particles and the granular material is 15 to 40 vol% (the solder particles are 60 to 85 vol. (Condition A), and when the particle size in the particle size distribution d90 is 10 to 30 μm, the volume ratio of the granular material to the total amount of the solder particles and the granular material is 5 to 20% by volume ( It is preferable that the solder particles are 80 to 95% by volume) (Condition B). When the particle size in the particle size distribution d90 is 20 to 40 μm, the volume ratio of the particles to the total amount of the solder particles and the particles Is preferably 3 to 10% by volume (the solder particles are 90 to 97% by volume) (Condition C). When the particle size in the particle size distribution d90 is 30 to 50 μm, 1-5% by volume is the volume fraction of the particulate matter to the total amount is preferably (solder particles 95 to 99 vol%) is (condition D).

Preferred compositions that satisfy the above conditions A to D are summarized in Table 1.
Table 2 shows preferable combinations of solder particles and granular materials.

  The present invention comprises a core layer having a component mounting surface on which a metal foil wiring pattern is formed, an electronic component mounted on the component mounting surface, a resin layer for sealing the electronic component, and a plurality of wirings This is useful in the field of component-embedded substrates in which patterns are laminated.

  1: Core layer, 2: Resin substrate, 3, 4: Wiring pattern, 3a: Land, 6: Bonding material, 6a: Thermosetting resin, 6b: Solder particles, 6A, 6B: Granular material, 6x: Solder joint 6y: Resin coated portion, 7: Electronic component, 7a: Terminal, 8, 8a: Gap, 8b: Void, 9, 10a, 10b: Pre-preg, 11a, 11b: Metal foil, 12: Sealing resin, 12a: Gap Filling part, 13: resin layer, 14: component built-in substrate, 15: plating layer, 16: second wiring pattern, 17: third wiring pattern

Claims (13)

(I) preparing a core layer having a component mounting surface on which a first wiring pattern including lands for connecting electronic components is formed;
(Ii) In a portion covering at least the land of the first wiring pattern,
A thermosetting resin;
Solder particles dispersed in the thermosetting resin;
A step of arranging a bonding material including a granular material having a melting point higher than the melting point of the solder particles;
(Iii) preparing an electronic component having a terminal, landing the terminal on the land via the bonding material, and mounting the electronic component on the component mounting surface;
(Iv) The core layer on which the electronic component is mounted is first heated at a temperature higher than the melting point of the solder and lower than the melting point of the granular material to melt the solder and adhere to the land and the terminal. And then solidifying to form a solder joint part for joining the terminal and the land, and curing the thermosetting resin to form a resin coat part covering the solder joint part;
(V) laminating the prepreg on the core layer so that the electronic component mounted on the component mounting surface is surrounded by the prepreg;
(Vi) A step of sealing the electronic component with a cured product of the prepreg by pressurizing the laminated body of the core layer and the prepreg in the laminating direction and secondly heating the laminated body. A method for manufacturing a substrate.   The method for manufacturing a component-embedded board according to claim 1, wherein after the first heating, the distance between the land and the terminal is controlled to 20 μm to 50 μm by the granular material. In the bonding material, the volume ratio of the granular material to the total amount of the solder particles and the granular material, and the particle diameter in the particle size distribution d90 of the granular material are:
Condition A: the volume ratio is 15 to 40% by volume and the particle size in the particle size distribution d90 is 5 to 15 μm,
Condition B: the volume ratio is 5 to 20% by volume and the particle size in the particle size distribution d90 is 10 to 30 μm,
Condition C: the volume ratio is 3 to 10% by volume and the particle size in the particle size distribution d90 is 20 to 40 μm,
Condition D: The method for manufacturing a component-embedded substrate according to claim 1, wherein the volume ratio satisfies 1 to 5% by volume and the particle size in the particle size distribution d90 satisfies 30 to 50 μm.   The manufacturing method of the component built-in board according to any one of claims 1 to 3, wherein a difference between a melting point of the solder and a melting point of the granular material is 30 ° C or higher.   5. The method for manufacturing a component-embedded substrate according to claim 1, wherein the granular material is a metal powder, and the metal powder includes a component capable of forming an alloy with a component contained in the solder. .   The component built-in according to claim 1, further comprising a step of roughening a surface of the first wiring pattern after the first heating and before laminating the prepreg on the core layer. A method for manufacturing a substrate.   The manufacturing method of the component built-in substrate according to claim 1, wherein the temperature of the second heating is lower than the melting point of the solder.   The metal foil is disposed so as to face the core layer via the prepreg, and then the laminated body is pressurized in the laminating direction and second-heated. A manufacturing method of the component-embedded substrate as described.   The method for manufacturing a component-embedded board according to claim 8, wherein after the second heating, the metal foil is patterned to form a second wiring pattern derived from the metal foil. A core layer having a component mounting surface on which a first wiring pattern including lands is formed;
An electronic component having a terminal facing the land;
A solder joint for connecting the land and the terminal;
A resin coat covering the solder joint;
A sealing resin that seals the component mounting surface together with the electronic component and the resin coat portion;
The solder joint includes a first region including a particulate matter and a second region covering the first region, and at least the second region is a metal region that electrically connects the land and the terminal. ,
A component-embedded substrate in which a gap between the core layer and a surface of the electronic component facing the core layer is sealed with the sealing resin.   The first region is a metal region, a third region is interposed between the first region and the second region, and the third region includes a component contained in the first region and the first region. The component built-in board according to claim 10, comprising an alloy with a component contained in two regions.   The component built-in substrate according to claim 10 or 11, wherein an elastic modulus of the sealing resin is larger than an elastic modulus of the resin coat portion.   The component built-in board according to claim 10, wherein a distance between the land and the terminal is 20 μm to 50 μm.

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