PCB Stack With Embedded Component Package And Sintered Via

Abstract

The invention discloses a method. The method is performed by attaching a component to a first PCB; positioning a prepreg proximate the first PCB, the prepreg having a via hole and a component cavity in which the component is in the component cavity; placing a conductive material in the via hole of the prepreg; positioning a second PCB near the first PCB, wherein the component and the prepreg are between the first PCB and the second PCB; and curing the conductive material to form a sintered via connecting the first PCB with the second PCB. An apparatus has: a first PCB; a component attached to the first PCB; a second PCB positioned proximate to the first PCB with the component between the first PCB and the second PCB; and a sintered metal via of conductive material, the sintered metal via of conductive material connecting the first PCB with the second PCB.

Description

[0001] Related patent applications

[0002] This application claims priority to commonly owned U.S. Application No. 63 / 444,444, filed on February 9, 2023, the entire contents of which are hereby incorporated by reference for all purposes. Technical Field

[0003] The present disclosure relates to a printed circuit board (PCB) with embedded component packages, in particular to a PCB with embedded component packages and printed conductive material vias electrically connecting the PCB and a method for manufacturing such a PCB stack. Background Art

[0004] The conventional process for embedding components into a printed circuit board (PCB) stack involves interrupting the PCB manufacturing process so that additional copper foil and / or core can be laminated with the prepreg and later drilled, etched and plated to allow the component package to be embedded into the PCB stack.

[0005] Specifically, conventional embedded component PCB processes add component packages to the inner layers of the PCB by soldering, conductive epoxy, sintering, or direct vias to the terminals. In order to create electrical connections between the layers bonded during lamination, holes are drilled and plated with copper. These vias can be through-holes, blind vias, microvias (μvia), or other vias. Vias for connecting across embedded prepreg layers are made by drilling holes and plating holes with copper. After lamination, the outer copper foil / core and vias of the PCB stack can be processed.

[0006] According to conventional processes, the component package can also be attached to the core PCB, which has a copper layer. In the PCB stack, the core can be a layer of woven glass reinforced epoxy laminate with a copper layer on either side. The layer of woven glass reinforced epoxy laminate can be formed between two smooth copper foils to a specified thickness. The prepreg can be a layer of uncured woven glass reinforced epoxy laminate, which glues the etched core together, or glues the copper foil to the etched core. The thickness of the prepreg can vary with the height of the etched board on either side. Holes can be drilled through the core to connect buried vias, but the holes can limit which layers can be connected to other layers. The planed, stamped or cut prepreg is placed on the component package, and the planed, stamped or cut prepreg has an additional copper layer to form a prepreg stack. The stack is laminated to encapsulate the component package. The laminate can be a laminated prepreg. The stack is then processed by drilling and copper-plating through-holes, blind vias, microvias or other vias to connect the copper layer in the core PCB to another PCB in the PCB stack. This conventional process produces a PCB stack with an embedded component package attached to the core PCB by a component interconnect. The prepreg above the PCB allows the component package to be embedded above the core PCB. The prepreg positioned below the core PCB allows the component package to be embedded below the core PCB and can provide an additional copper layer. Drill and copper-plated through-holes / blind vias are used to connect the copper layer of the PCB above and below the embedded component package attached to the core PCB.

[0007] Conventional processes rely on plated through-hole, blind via or microvia processes to connect the copper layers of the PCB together after the component packages in prepreg are embedded into the PCB. Embedded component packages are conventionally processed on existing large PCB panel formats of 12″×18″, which significantly increases cost and risk of failure as more circuits (and component packages) are added to the PCB panel to make the process cost effective. However, the disadvantage of large PCB panel formats is the increased risk of catastrophic yield loss (if the entire PCB panel is scrapped).

[0008] The cost and lead time to manufacture a PCB stack with a component package embedded inside is higher and longer than the cost and lead time to manufacture a PCB stack without the embedded component package.

[0009] A cheaper and less time consuming manufacturing process is needed to manufacture a PCB package having embedded components and the PCB electrically connected through vias. Summary of the invention

[0010] According to one aspect, a method is provided, the method comprising: attaching a component to a first printed circuit board; positioning a prepreg near the first printed circuit board, the prepreg having a via and a component cavity, wherein the component is in the component cavity; placing a conductive material in the via of the prepreg; positioning a second printed circuit board near the first printed circuit board, wherein the component and the prepreg are between the first printed circuit board and the second printed circuit board; and curing the conductive material to form a sintered via connecting the first printed circuit board to the second printed circuit board, thereby forming a PCB stack.

[0011] On the one hand, a device is provided, which includes: a printed circuit board stack, the printed circuit board stack including: a first printed circuit board; a component, the component is attached to the first printed circuit board; a second printed circuit board, the second printed circuit board is adjacent to the first printed circuit board, wherein the component is between the first printed circuit board and the second printed circuit board; and a sintered via, the sintered via including a conductive material connecting the first printed circuit board to the second printed circuit board.

[0012] In one aspect, a method is provided, comprising: stacking a plurality of laminates into a laminate stack to form a prepreg body; forming a component cavity in the prepreg body; masking the component cavity with a mask; and forming a via through the mask and the body. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings illustrate an example PCB package with an embedded component and printed conductive material vias connecting the PCB, and also illustrate methods of manufacturing an embedded component package with printed conductive material vias connecting completed top and bottom printed circuit boards and manufacturing a prepreg with printed conductive material vias.

[0014] Figures 1A to 1E Illustrated are cross-sectional side views of a PCB stack with embedded component packages at various times in a process for manufacturing a PCB stack with printed vias connecting completed top and bottom printed circuit boards.

[0015] Figure 2 A cross-sectional side view of a PCB stack with embedded component packages is illustrated, with sintered vias connecting the completed top and bottom printed circuit boards.

[0016] FIG. 3A to FIG. 3F Illustrated are cross-sectional side views of a PCB stack with an embedded component package at various moments in a manufacturing process for manufacturing the PCB stack with an embedded component package.

[0017] 4A to 4D Cross-sectional side views of a prepreg at various times during its manufacture are illustrated.

[0018] Figure 5 A top view of a printed circuit board with attached components is shown, wherein a prepreg is placed on the printed circuit board so that the components are received in the component cavities of the prepreg.

[0019] FIG. 6A to FIG. 6D A cross-sectional side view of a PCB with component packages and prepreg is shown at various times as conductive material is printed into the vias of the prepreg.

[0020] Figure 7 A flow chart of a method for manufacturing an embedded component package with printed vias connecting completed top and bottom printed circuit boards is shown.

[0021] Figure 8 A flow chart of a method for manufacturing a prepreg having holes for vias is shown.

[0022] Fig. 9 A flow chart of a method for manufacturing a prepreg having printed conductive material vias is shown.

[0023] Reference numerals for any illustrated element that appear in multiple different figures have the same meaning in the multiple figures, and reference or discussion herein to any illustrated element in the context of any particular figure also applies to every other figure (if any) in which the same illustrated element is shown. DETAILED DESCRIPTION

[0024] Various aspects provide an embedded component package with sintered vias connecting finished top and bottom printed circuit boards and methods for making prepregs and embedded component packages.

[0025] The component can be attached to the first printed circuit board. Multiple epoxy resin laminates can be stacked into a laminate stack to make a prepreg body. The epoxy resin laminate can be planed, punched or cut to form a component cavity in the prepreg body. The component cavity can be masked by placing a film above the component cavity. The hole can be made through the film and the body by drilling through the prepreg. The prepreg can be positioned close to the first printed circuit board, where the component is positioned in the component cavity of the prepreg. The via can be printed by processing a flowable conductive material into the hole of the prepreg, while the mask prevents the conductive material from entering the component cavity. The flowable conductive material can be placed in the hole by printing, flowing or injecting, but is not limited to this. Alternatively, a solid or semi-solid conductive material can be pushed, squeezed or injected into the hole (but not limited to this), which can cancel the use of a mask. The prepreg can be exposed by removing the film from the component cavity. Encapsulation material can be added to the component cavity. The second printed circuit board can be positioned adjacent to the first printed circuit board with the components and prepreg between the first and second printed circuit boards to form a PCB stack. The flowable conductive material can be sintered to form sintered vias to connect the first printed circuit board to the second printed circuit board.

[0026] Prepreg is a pre-impregnated insulating layer, such as a dielectric material, which is sandwiched between two cores or between a core and a copper foil in a PCB to provide insulation and can bond the two cores or the core and the copper foil. Prepreg can be a fiberglass fabric / cloth impregnated with a resin binder. More broadly, prepreg can be a stack of epoxy resin laminates.

[0027] Prepregs may include a thermosetting epoxy resin that starts out as a liquid and completely impregnates the fiber reinforcement. The epoxy resin may undergo partial curing, which changes the state of the resin from liquid to solid, which is the "B-stage." In the B-stage, the resin is partially laminated and may be tacky. As the resin reaches elevated temperatures, it returns to a liquid state before fully hardening. Once laminated, the thermosetting resin is fully cross-linked.

[0028] The components can be attached to the first PCB (see Figure 1A ) and encapsulated with prepreg between two additional PCBs. Figure 1E . Vias between two additional PCBs may be added where conductive material is printed, flowed, or injected into pre-drilled holes in the prepreg. The conductive material printed, flowed, or injected into the pre-drilled holes in the prepreg may be sintered to form sintered vias to connect copper features on the two PCBs, thereby completing the electrical connection between them. Once the embedded component process is complete, the completed PCB stack is ready for other PCBA processes, such as surface mount technology (SMT) on the outer layers of the completed PCB stack.

[0029] According to some aspects, after embedding components between two PCBs, plating equipment or lines may not be required to connect copper layers. It may not be necessary to interrupt the PCB manufacturing process to embed components. The cost of PCBs with embedded components can be reduced, and the manufacturing process can produce lower yield losses, lower premium costs, and allow less complex facilities to manufacture PCB stacks. Various aspects manufacture completed PCB stacks with embedded components at a lower cost and shorten manufacturing lead time. Depending on tolerances, various aspects can provide relatively small PCB stack sizes.

[0030] Various aspects use sintered vias to form electrical connections between copper layers above and below the embedded component. The prepreg can be planed, stamped or cut with cutouts to allow the component package to be placed within it, and the prepreg can be placed above the component package. Sufficient prepreg layers are added or stacked to achieve the prepreg height required for the embedded component. Copper foil or core can be added above the prepreg. The material stack can then be laminated in a press, which causes the prepreg epoxy to flow and cure, whereby the component package is encapsulated and the PCBs are attached together as a PCB stack. This lamination step embeds the component package within the PCB stack.

[0031] Sintered vias can electrically connect the copper layers above and below the component. After routing, stamping or cutting the prepreg for the component cavity, a plastic film can be added to the top of the prepreg and the stack can be adhered to the first PCB, and then the vias can be laser drilled down to the first PCB. The stack can be adhered to the first PCB by partial curing, which changes the state of the resin from liquid to solid ("B stage"). In the B stage, the resin is partially laminated and can be viscous. Once the via is drilled, a conductive material (transient liquid phase sintering material, conductive adhesive, silver sintering, copper sintering, mixed epoxy resin / sintering paste or sintering paste, but not limited to this) can be printed, flowed or injected into the opening until the opening is filled with conductive material. The plastic film can be removed to expose the prepreg. Then a second PCB can be added to the top of the prepreg stack, and the entire PCB stack can be laminated. Lamination embeds the component package and also cures / sinters the conductive material in place, which therefore forms a sintered via between the first PCB and the second PCB. Lamination is the process of causing the resin in the prepreg to flow and solidify in the structure at high temperature and pressure. Sintering is the process of curing the sintered material at high temperature and pressure. The temperature and pressure conditions sufficient for lamination can be the same as those sufficient for sintering. After lamination, the PCB stack is ready for further PCBA processing and does not need to continue with any PCB manufacturing process (such as drilling, etching or plating) to form vias.

[0032] The conductive material may be a transient liquid phase sinter, a conductive adhesive, or a sinter paste, but is not limited thereto. The sinter paste may be a combination of small particles of solder material in a fluxing polymer binder and small particles of a solderable metal. During lamination of the PCB stack, the conductive material may be solidified. Solidifying the sinter paste may include heating until the solder particles melt, the molten solder wets the solderable particles, and forming an interconnected metal network when the molten solder cools and solidifies around the solderable particles.

[0033] In another aspect, vias may be mechanically drilled in the prepreg prior to adhering the prepreg to the first PCB.

[0034] Figures 1A to 1E A cross-sectional side view of a PCB stack at various moments in a process for manufacturing an embedded component in a PCB stack is illustrated. Component 112 is attached to a completed first PCB 114 having a copper layer 124 and vias 118 via component interconnects 116. See Figure 1A In one example, the via 118 may include a μtvia. The PCB 114 may have a μtvia 118 or any form of via to complete any electrical connection to additional layers, which may be design-dependent. Sintered vias may provide an electrical connection between two copper layers adjacent to an embedded part. A prepreg 122 that has been routered, punched, or cut and drilled is placed on the PCB 114. Vias 126 are pre-drilled in the prepreg 122, and component cavities 128 are pre-routed, punched, or cut. See Figure 1B . The prepreg 122 is placed on the PCB 114 so that the component 112 is in the component cavity 128. A conductive material 134 (such as a sintering material) is printed, flowed, or injected into the via 126 of the prepreg 122. Specifically, the conductive material 134 can be transitional liquid phase sintering (TLP S), conductive adhesive, silver sintering, copper sintering, hybrid epoxy resin / sintering paste, or sintering paste, but is not limited thereto, and can be printed, flowed, or injected into the drilled via 126. See Figure 1C The completed second PCB 142 is placed over the prepreg 122 to form a PCB stack 144 with the components 112 and vias between the first PCB 114 and the second PCB 142. Figure 1D The PCB stack 144 is pressed and heated to laminate the stack, thereby encapsulating the components 112 with the molten fluid material (which may be a material similar to the prepreg 122), and curing the conductive material 134 to form sintered vias 132 connecting the first PCB 114 to the second PCB 142. Figure 1E One way to cure the conductive material 134 is by sintering.

[0035] Microvias are small, miniature holes through which the layers of a multi-layer PCB remain connected. Microvias are sometimes referred to as uVia. Microvias have a conical frustum shape that slopes inward as they make a layer transition and terminates at a pad in the next layer. Microvias can span a single layer, or multiple microvias can be stacked to form connections that span multiple layers in a PCB.

[0036] Figure 2 A cross-sectional side view of a PCB stack 144 with an embedded component package 112 having a sintered via 132 is shown. The PCB stack 144 has a component package 112 embedded between a first PCB 114 and a second PCB 142. The component package 112 is attached to the first PCB 114 by a component interconnect 116. The prepreg 122 between the first PCB 114 and the second PCB 142 embeds the component package 112. The sintered via 132 connects the microvia 118 of the first PCB 114 with the microvia 118 of the second PCB 142.

[0037] FIG. 3A to FIG. 3F 1 illustrates cross-sectional side views of a PCB stack at various moments in a process for manufacturing a PCB stack with embedded component packaging. Figure 3A As shown, component package 112 is attached to the completed first PCB 114 via component interconnect 116. The completed first PCB 114 has copper plated layer 124 and μvia 118. The prepreg 122 that has been planed, punched or cut and drilled is placed over the component 112 on the PCB 114. Figure 3B . Reference Figure 3C , the conductive material 134 is printed, flowed or injected into the via 126 of the prepreg 122. Specifically, the conductive material 134 (e.g., transition liquid phase sintering (TLPS), conductive adhesive, silver sintering, copper sintering, hybrid epoxy resin / sintering paste, or sintering paste, but not limited thereto) can be applied to the film 129 and wiped across the film 129 to process the conductive material 134 into the via 126 until the via 126 is completely filled with the conductive material 134. Figure 3D As shown, the film 129 is then removed from the top of the prepreg 122, thereby leaving the conductive material 143 in the via 126. Figure 3E, the completed second PCB 142 is placed over the prepreg 122 to form a PCB stack 144, wherein the component package 112 and the conductive material 134 are between the first PCB 114 and the second PCB 142. A liquid encapsulating material may flow into the component cavity 128 until the component package 112 is completely covered, wherein the encapsulating material may be similar to the epoxy resin of the prepreg 122. The PCB stack 144 is pressed and heated to laminate the stack, thereby encapsulating the component 112 by the cured encapsulating material of the material similar to the prepreg 122, and sintering or curing the conductive material 134 in the via 126 to form a sintered via 132 connecting the first PCB 114 and the second PCB 142. See FIG. Figure 3F .

[0038] 4A to 4D Illustrated for preparing FIG. 3B to FIG. 3C The process of the prepreg 122 shown in FIG. Figure 4A As shown, multiple laminate sheets or layers 122A, 122B, ... 122i of woven glass reinforced epoxy laminate may be stacked on top of each other to achieve an overall height high enough to embed the component package 112 (see Figure 3B ) of the prepreg 122. Figure 4B , a component cavity 128 is formed in the prepreg 122 that is large enough to receive the component package 112. The component cavity 128 can be routered using a router or punched / cut using a press. Figure 4C As shown, the laminates 122A, 122B, ... 122i are adhered together at a lower temperature / pressure than that used for lamination to avoid curing of the epoxy resin of the laminates, wherein the temperature / pressure is high enough to achieve the viscous properties of the epoxy resin to bond the laminates together, but not high enough to bond the laminates together. A film 129 is adhered to the top of the prepreg 122 to act as a template / mask during the upcoming via printing process. The film 129 can be adhered by a hot roller press under reduced heat and pressure compared to the heat and pressure sufficient for full curing. As shown in FIG. Figure 4D As shown, vias 126 are drilled (mechanically or laser) through the film 129 and the adhered laminates 122A, 122B, ... 122i, after which the prepreg 122 is ready for placement over the component 112 on the PCB 114. Figure 3B .

[0039] Figure 5 A top view of a prepreg 122 having eight component cavities 128 positioned on a PCB 114 having eight component packages 112 is shown, with the film 129 having been removed. Figure 3DSeveral vias 126 filled with conductive material 134 are shown around each component cavity 128. The vias 126 filled with conductive material 134 have a circular area cross-section parallel to the first printed circuit board 114. Tooling holes 136 are provided to position the PCB 114 in a tooling machine for production.

[0040] FIG. 6A to FIG. 6D 1 shows a cross-sectional side view of a first PCB 114 with a component package 112 and prepreg 122 at various times during the process of printing a conductive material 134 to form a sintered via. Fig. 6A As shown, a prepreg 122 having a component cavity 128 is positioned on a first PCB 114 such that a component package 112 is in the component cavity 128. The prepreg 122 has a film 129 that masks the component cavity 128. A scraper 152 prints the conductive material 134 into the via 126 in the prepreg 122 by wiping the conductive material 134 across the film 129. Fig. 6A As shown, the first via hole 126 is completely filled with the conductive material 134. Figure 6B As shown, when the wiper blade 152 is wiped across the membrane 129, the first via 126 is completely filled with the conductive material 134 and the second via 126 is partially filled with the conductive material 134. Figure 6C As shown, both vias 126 are completely filled with conductive material 134 . Fig.6D It is shown in the film 129 (see Figure 6C ) has been removed leaving the conductive material 134 in the via 126.

[0041] In an alternative, the conductive material may be placed in the vias in the prepreg by printing, flowing, injecting, pushing or hammering, but not limited to this. A flowable conductive material may be placed in the holes of the prepreg by printing, flowing or injecting, but not limited to this. Where the conductive material is flowable, a mask may facilitate the placement of the conductive material in the vias. A solid or semi-solid conductive material may be pushed, squeezed, injected, inserted or hammered into the hole, but not limited to this. Where the conductive material is solid or semi-solid, the conductive material may be placed in the vias without a mask on the prepreg.

[0042] Figure 7A flow chart of a method for manufacturing an embedded component package having sintered vias connecting completed top and bottom printed circuit boards is shown. A component is attached 702 to a first printed circuit board. A prepreg having a via and a component cavity is positioned 704 near the first printed circuit board, wherein the component is positioned in the component cavity. The method is described with respect to a single component mounted on a bottom printed circuit board having a single component cavity, however this is not meant to be limiting in any way, and multiple components having associated corresponding cavities may be utilized without exceeding the scope. A conductive material is placed 706 into the via of the prepreg. A second printed circuit board is positioned 708 near the first printed circuit board, wherein the component and the prepreg are between the first printed circuit board and the second printed circuit board. The conductive material is cured 710 to form a sintered via connecting the first printed circuit board and the second printed circuit board.

[0043] Figure 8 A flow chart of a method for making a prepreg having holes for vias is shown. Multiple epoxy resin laminates are stacked 802 into a laminate stack to make a prepreg body. A component cavity is formed 804 in the prepreg body of the stacked epoxy resin laminates. The component cavity can be formed by router or by stamping or cutting. Alternatively, each of the laminates can have a component cavity before stacking. Vias are made 806 through the prepreg body.

[0044] Fig. 9 A flow chart of a method for manufacturing a prepreg having printed conductive material vias is shown. Multiple epoxy resin laminates are stacked 902 into a laminate stack to form a prepreg body. A component cavity is formed in the prepreg body. The component cavity can be formed by routing, stamping or cutting 904. Alternatively, each of the laminates can be formed with a component cavity before stacking 902. The component cavity is masked 906. Masking can be performed by placing a film over the component cavity. Vias are manufactured 908 through the film and the prepreg body. The vias are filled 910 with conductive material to form filled vias. The component cavity is exposed 912. The exposure can be performed by removing the film from the component cavity. The conductive material filled in the via is at least partially cured 914 to at least partially cure the conductive material so as to form a partially sintered via. The partially cured conductive material is sufficiently cured to allow the prepreg to be produced as a stand-alone product, wherein the prepreg can be handled without the conductive material falling out of the via. When the standalone prepreg is added to the PCB stack, the conductive material can be fully cured to electrically connect the two PCBs.

[0045] Although examples have been described above, other modifications and examples may be made in accordance with this disclosure without departing from the spirit and scope of these disclosed examples.

Claims

1. A method, comprising: attaching a component to a first printed circuit board; positioning a prepreg proximate to the first printed circuit board, the prepreg having a via and a component cavity in a prepreg body, wherein the component is in the component cavity; placing a conductive material in the via of the prepreg; positioning a second printed circuit board adjacent to the first printed circuit board, wherein the component and the prepreg are between the first printed circuit board and the second printed circuit board; as well as The conductive material is cured to form sintered vias connecting the first printed circuit board with the second printed circuit board, thereby forming a PCB stack.

2. The method of claim 1, comprising preparing the prepreg by stacking a plurality of laminates into a laminate stack to make the prepreg body.

3. The method according to one of the preceding claims 1 to 2, comprising flowing an encapsulation material over the component in the cavity of the body, and heating the material of the plurality of laminates and the encapsulation material to laminate the prepregs and encapsulate the component.

4. The method according to one of the preceding claims 1 to 3, comprising preparing the prepreg by masking the component cavity with a film, making the via through the film and the body, and wherein placing a conductive material in the via of the prepreg comprises filling the via with the conductive material.

5. The method of claim 4, wherein the conductive material is selected from the group consisting of transient liquid phase sintering materials, sintering pastes, silver sintering, copper sintering, and hybrid epoxy / sintering pastes.

6. A device, comprising: a first printed circuit board; a component attached to the first printed circuit board; a second printed circuit board, the second printed circuit board being adjacent to the first printed circuit board, wherein the component is between the first printed circuit board and the second printed circuit board; and A sintered via including a conductive material connecting the first printed circuit board to the second printed circuit board. 7 . The apparatus of claim 6 , wherein the sintered via comprises a circular area cross-section parallel to the first printed circuit board.

8. The device according to one of the preceding claims 6 to 7, comprising a prepreg between the first printed circuit board and the second printed circuit board.

9. The device according to one of the preceding claims 6 to 8, comprising an encapsulation material between the first printed circuit board and the second printed circuit board.

10. The device according to one of the preceding claims 6 to 9, wherein the conductive material is selected from the group consisting of transient liquid phase sintering materials, sintering pastes, silver sintering, copper sintering and hybrid epoxy / sintering pastes.

11. The device according to one of the preceding claims 6 to 10, wherein the first printed circuit board has a first microvia and the second printed circuit board has a second microvia, wherein the sintered via connects the first microvia with the second microvia.

12. A method comprising: stacking a plurality of laminates into a laminate stack to form a prepreg body; forming a component cavity in the prepreg body; as well as A via is formed through the body.

13. The method of claim 12, wherein forming a component cavity comprises routering the component cavity in the prepreg body.

14. The method according to one of the preceding claims 12 to 13, comprising: masking the component cavity; filling the hole with a flowable conductive material; exposing the component cavity; as well as The conductive material is at least partially cured.

15. The method according to one of the preceding claims 12 to 14, comprising placing a solid or semi-solid conductive material in the via.

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