Power module with a molded metal interconnect substrate and method of manufacturing the same

Abstract

An interconnection substrate includes a metal layer, a plurality of metal pads, and a molded package. The molded composite layer encapsulates most of the plurality of metal pads 240. The top surface of each of the plurality of metal pads is exposed to the top surface of the molded package. The top surface of each of the first plurality of metal pads is coplanar with the top surface of the molded composite layer. A power module includes an interconnection substrate, a plurality of chips, a plurality of bonding leads, a plurality of terminals, a plastic housing, and a module-level molded package. A method for preparing an interconnection substrate includes the steps of: preparing a plurality of metal pads; loading a metal layer; preparing a molded package; and using a dicing process.

Description

Technical Field

[0001] The present invention mainly relates to an interconnect substrate having a molded metal and a manufacturing method thereof. More precisely, the present invention relates to a power module having a molded metal interconnect substrate. Background Art

[0002] Figure 1A A top view showing a conventional power module 100 containing a plurality of insulated metal substrates 120, Figure 1B showing a cross-sectional view taken along line AA'. The plurality of insulated metal substrates 120 include a first plate 120A, a second plate 120B, and a third plate 120C. The first plate 120A, the second plate 120B, and the third plate 120C are all rectangular in shape and thus do not extend onto the surrounding boundary regions 160, 162, 164, and 166. The first plate 120A is separated from the second plate 120B by a first gap 140A. The second plate 120B is separated from the third plate 120C by a second gap 140B. A plurality of chips 133 are mounted on the bottom metal layer 137. Figure 1C Showing a cross-sectional view of another conventional power module 101. The bottom metal layer 172 is separated from the top metal layer 174 by an insulating layer 190. The top metal layer 174 is rectangular in shape and does not extend onto the surrounding boundary regions 161 and 165.

[0003] One application of the present invention is a power inverter module, including an interconnect substrate, with a current range of 25 amperes to 200 amperes; a voltage of 600 volts or 1200 volts; dimensions of 107 mm × 45 mm × 17 mm or 122 mm × 62 mm × 17 mm. The electrical paths and electrical pads are embedded in the molded package. According to a predetermined filler percentage and filler type, the coefficient of thermal expansion (CTE) of the molding compound layer is adjusted to be close to that of copper material. Thus, the thermal stress generated in the interconnect substrate is reduced. The power conversion module has high power capacity and high thermal cycling ability (thousands of cycles from -40 degrees Celsius to 125 degrees Celsius). The chip mounting area is increased by 23%. The path inductance is reduced. The manufacturing cost is lowered. Summary of the Invention

[0004] The present invention proposes an interconnect substrate, including a metal layer, a plurality of metal pads, and a molded package. The molded composite layer surrounds most of the plurality of metal pads. The respective top surfaces of each of the plurality of metal pads are exposed on the top surface of the molded package. The respective top surfaces of each of the first plurality of metal pads are coplanar with the top surface of the molded composite layer. The power module includes the interconnect substrate, a plurality of chips, a plurality of bonding leads, a plurality of terminals, a plastic housing, and a module-level molded package.

[0005] The present invention also provides a method for manufacturing an interconnect substrate. The method includes the following steps: preparing a plurality of metal pads; loading a metal layer; preparing a molded package; and using a dicing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1A Fig. shows a top view of a conventional power module, Figure 1B showing a cross-sectional view thereof. Figure 1C Fig. shows a cross-sectional view of another conventional power module.

[0007] Figure 2A Fig. shows a top view of a power module in an example of the present invention, Figure 2B showing a perspective view thereof.

[0008] Figure 3 Fig. shows, in an example of the present invention, Figure 2A a cross-sectional view of the power module shown along line BB'.

[0009] Figure 4 Fig. shows a cross-sectional view of another power module in an example of the present invention.

[0010] Figure 5 Fig. shows a process flow diagram for preparing an interconnect substrate in an example of the present invention.

[0011] Figure 6A 、 6B 6C, 6D, 6E, 6F, 6G, 6H, 6I and 6J show process steps for preparing an interconnect substrate in an example of the present invention.

[0012] Figure 7 Fig. shows a process flow diagram for preparing an interconnect substrate in an example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Figure 2A Fig. shows a top view of a power module 200 in an example of the present invention, Figure 2B showing a perspective view thereof. The power module 200 includes an interconnect substrate 220. The interconnect substrate 220 is not limited to a rectangular shape like the plurality of insulated metal substrates 120 of the conventional power module 100 as shown. The interconnect substrate 220 does not require to be separated by a first gap 140A and a second gap 140B as shown. As shown, the interconnect substrate 220 can extend onto the boundary regions 160, 162, 164 and 166. Figure 1A Fig. shows, in an example of the present invention, Figure 1A as shown, Figure 1A Fig. shows that the interconnect substrate 220 can extend onto the boundary regions 160, 162, 164 and 166.

[0014] Figure 3 Fig. shows, in an example of the present invention, Figure 2ACross-sectional view of the power module 200 along the line BB'. The power module 200 includes an interconnect substrate 220, a plurality of chips 280, a first plurality of bonding leads 290, a second plurality of bonding leads 291, a plurality of terminals 292, a plastic housing 294, and a module-level molding package 296. In an example of the present invention, the module-level molding package 296 is formed in different molding processes from the molding process of preparing the molding composite layer 260. As shown in the figure, the plastic housing 294 includes a plurality of sidewalls arranged around the periphery of the interconnect substrate.

[0015] The interconnect substrate 220 includes a bottom metal plate 230, a plurality of metal paths 241 passing through the entire interconnect substrate 220, a first plurality of metal pads 240 in the central region, and a second plurality of metal pads 250 in the edge region. The edge region is embedded in the molding composite layer 260, covering the metal layer 230. In an example of the present invention, the bottom metal plate 230 is a rectangular prism. The molding composite layer 260 is a rectangular prism. The second plurality of metal pads 250 are conductively connected to the plurality of terminals 292. The molding composite layer 260 encapsulates most of the first plurality of metal pads 240 and most of the plurality of metal paths 241. The molding composite layer 260 encapsulates most of the second plurality of metal pads 250. The entire bottom surface 262 of the molding composite layer 260 is directly connected to the top surface 232 of the metal layer 230. The molding composite layer covers the entire central region of the bottom metal plate and extends to touch the sidewalls of the plastic housing 294. The edge of the molding composite layer 260 is substantially aligned with the inner sidewalls of the plastic housing 294 to provide the self-adaptation advantage when assembling the plastic housing 294 to the interconnect substrate 220. The upper surface 242 of each metal pad in the first plurality of metal pads 240 is exposed from the top surface 264 of the molding composite layer 260. The upper surface 242 of each metal pad in the first plurality of metal pads 240 and the top surface 264 of the molding composite layer 260 are coplanar. The metal paths 241, the first plurality of metal pads 240, and the second plurality of metal pads 250 preferably have the same thickness between 100 and 800 microns, and the minimum spacing between adjacent metal pads or paths filed with the molding composite layer 260 is 400 microns. Preferably, the thickness of the molding composite layer 260 below the metal paths 241, the first plurality of gate pads 240, and the second plurality of metal pads 250 is between 100 and 250 microns to insulate from the bottom metal plate 230. The length (along the X direction) of the molding composite layer 260 is shorter than the length (along the X direction) of the metal layer 230. The width (along the Y direction) of the molding composite layer 260 is shorter than the width (along the Y direction) of the metal layer 230.

[0016] Each of the multiple chips 280 is connected to a corresponding metal pad of the first multiple metal pads 240 through a corresponding one of the multiple conductive materials 282. In one example, the multiple conductive materials 282 are solder paste. In another example, the multiple conductive materials 282 are conductive adhesives. The module-level molded package 296 encapsulates the multiple chips 280, the first multiple bonding leads 290, the second multiple bonding leads 291, a portion of the multiple terminals 292, and an internal portion of the plastic housing 294. The bottom surface 293 of each of the multiple terminals 292 is directly connected to the plastic housing 294. The top surface 264 of the molded composite layer 260 is directly connected to the plastic housing 294.

[0017] In an example of the present invention, the bottom metal plate 230 is made of a first copper material. The first multiple metal pads 240 and the second multiple metal pads 250 are made of a second copper material. In one example, the first copper material and the second copper material are the same copper material. In another example, the first copper material and the second copper material are different copper alloys.

[0018] In an example of the present invention, the molded composite layer 260 is a separate integral structure formed in a separate molding process as shown in Figure 6I In an example of the present invention, the molded composite layer 260 is made of resin or gel.

[0019] In an example of the present invention, the molded composite layer 260 is made of a resin that includes one or more filler materials selected from the group consisting of silicon oxide (SiO 2 ), aluminum oxide (Al 2 O 3 ), and aluminum nitride (AlN) components. In an example of the present invention, the filling rate of the one or more filler materials ranges between 80% and 90%. In a first example, the molded composite layer 260 contains 80% silicon oxide filler. In a second example, the molded composite layer 260 contains 85% aluminum oxide filler. In a third example, the molded composite layer 260 contains 90% aluminum nitride filler. In a fourth example, the molded composite layer 260 contains 20% silicon oxide filler, 30% aluminum oxide filler, and 40% aluminum nitride filler. In an example of the present invention, the percentage and type of the filler are determined to adjust the coefficient of thermal expansion (CTE) of the molded composite layer 260. In one example, the CTE of the molded composite layer 260 with filler is in the range of 99% to 101% of the CTE of the metal layer 230. In another example, the CTE of the molded composite layer 260 with filler is in the range of 95% to 105% of the CTE of the metal layer 230.

[0020] In an example of the present invention, the thickness of each metal pad in the first plurality of metal pads 240 is less than the thickness of the molded composite layer 260. The thickness of each metal pad in the second plurality of metal pads 250 is less than the thickness of the molded composite layer 260.

[0021] In an example of the present invention, the thickness of the bottom metal plate 230 ranges from 500 micrometers (0.5 millimeters) to 800 micrometers (0.8 millimeters).

[0022] In an example of the present invention, the thermal conductivity of the molded composite layer 260 ranges from 5 watts per meter kelvin to 10 watts per meter kelvin.

[0023] In an example of the present invention, each of the second plurality of metal pads 250 is conductively connected to the plurality of terminals 292 through the second plurality of bonding leads 291.

[0024] Figure 4 Shows a cross-sectional view of the power module 400 in an example of the present invention. The power module 400 includes an interconnect substrate 220, a plurality of chips 280, a first plurality of bonding leads 290, a plurality of conductive plates 491, a plurality of terminals 292, a plastic housing 294, and a module-level molding package 296.

[0025] The interconnect substrate 220 includes a metal layer 230, a first plurality of metal pads 240, a second plurality of metal pads 250, and a molded composite layer 260. In an example of the present invention, the bottom metal plate 230 is a rectangular prism. The molded composite layer 260 is a rectangular prism. The second plurality of metal pads 250 are conductively connected to the plurality of terminals 292. The molded composite layer 260 encapsulates most of the first plurality of metal pads 240. The bottom surface 262 of the molded composite layer 260 is parallel to the top surface 232 of the metal layer 230 and is directly connected to the top surface 232. The top surface 242 of each metal pad in the first plurality of metal pads 240 is exposed on the top surface 264 of the molded composite layer 260. The top surface 242 of each metal pad in the first plurality of metal pads 240 and the top surface 264 of the molded composite layer 260 are coplanar. The length (along the X direction) of the molded composite layer 260 is shorter than the length (along the X direction) of the metal layer 230. The width (along the Y direction) of the molded composite layer 260 is shorter than the width (along the Y direction) of the metal layer 230.

[0026] In an example of the present invention, a second plurality of metal pads 250 are conductively connected to a plurality of terminals 292 through a plurality of conductive plates 491. In one example, a corresponding one of the second plurality of metal pads 250, a corresponding one of the plurality of conductive plates 491, and a corresponding one of the plurality of terminals 292 are an integrally formed structure (formed in the same metal preparation process). In another example, a corresponding one of the second plurality of metal pads 250, a corresponding one of the plurality of conductive plates 491, and a corresponding one of the plurality of terminals 292 are a three-piece formed structure (manufactured in three separate metal forming processes and then connected to each other).

[0027] Figure 5 FIG. 500 is a flow chart showing a process 500 for fabricating an interconnect substrate in an example of the present invention. In one example, the fabrication of the interconnect substrate starts with a panel. The panel is rectangular in shape. Hundreds or thousands of interconnected base plates are made from a single panel. Process 500 may start at block 502. Figures 6A - 6J FIG. shows a cross-sectional view of the corresponding step. For simplicity, Figures 6A - 6I only one interconnect substrate is shown in the panel of FIG. Figure 6J The right side in the dashed line (same as the corresponding left side structure in the solid line) is not shown in Figures 6A - 6I FIG.

[0028] At block 502, referring to Figure 6A FIG., a detachable carrier 610 is provided. In one example, the detachable carrier 610 is a rectangular prism. Block 502 may be followed by block 504.

[0029] At block 504, referring to Figure 6B FIG., a tape layer 620 is attached to the detachable carrier 610. In an example of the present invention, the tape layer 620 is a double-sided tape. The tape layer 620 is pressed onto the detachable carrier. Block 504 may be followed by block 506.

[0030] At block 506, referring to Figure 6C FIG., a metal sheet 630 is attached to the tape layer 620. In an example of the present invention, the metal sheet 630 is made of copper material. Block 506 may be followed by block 508.

[0031] At block 508, referring to Figure 6D FIG., a dry film 640 is attached to the metal sheet 630. Block 508 may be followed by block 510.

[0032] At block 510, referring to Figure 6E FIG., etching Figure 6DThe dry film shown to form multiple etched dry films 640P. After block 510 may be block 512.

[0033] In block 512, refer to Figure 6F , etch Figure 6E the metal sheet 630 shown to form multiple metal pads 630P protected by the etched dry films 640P. After block 512 may be block 514.

[0034] In block 514, refer to Figure 6G , remove multiple etched dry films 640P to expose multiple metal pads 630P, forming a preformed intermediate element 651. After block 514 may be block 516.

[0035] In block 516, refer to Figure 6H , load the metal plate 660 and the preformed intermediate element 651 onto the molding groove 669. The metal pads 630P face the metal plate 660 with a preset space of 100 to 800 microns separating the metal pads 630P and the metal plate 660. After block 516 may be block 518.

[0036] In block 518, refer to Figure 6I , fill the space between the metal plate 660, the metal pads 630P, and the tape layer 620 by injecting the molded composite layer 680 to form a molded interconnect substrate assembly. The molded composite layer 680 encapsulates most of the multiple metal pads 630P. The molded composite layer 680 is directly connected to the metal layer 660. After block 518 may be block 520.

[0037] In block 520, refer to Figure 6J , after removing the molded interconnect substrate from the molding groove 669, remove the tape layer 620 and the detachable carrier 610. Reverse the viewing direction in the Z direction (the molded composite layer 680 is Figure 6I below the metal layer 660 shown, the molded composite layer 680 is Figure 6J above the metal layer 660 shown). After block 520 may be block 522.

[0038] In block 522, a dicing process 691 separates Figure 6J the interconnect substrate 699 shown from the surrounding interconnect substrates 697 shown by the dashed line. Optionally, the dicing process may be performed after the semiconductor chips are mounted on the entire panel of the interconnect substrate and / or the plastic housing is mounted on the panel of the interconnect substrate.

[0039] Figure 7Illustrates a flowchart of a process 700 for fabricating a power module in an example of the present invention. In one example, the process 700 is performed before the splitting process step shown in block 522. The process 700 begins at block 702. Figure 5 Before the splitting process step shown in block 522, the process 700 is performed. The process 700 starts at block 702.

[0040] At block 702, Figure 3 the plurality of chips 280 shown are connected to Figure 6J the plurality of metal pads 630P shown. Block 702 may be followed by block 704.

[0041] At block 704, Figure 3 the plastic housing 294 shown is connected to Figure 6J the metal plate 660 shown. Block 704 may be followed by block 706.

[0042] At block 706, Figure 3 the plurality of terminals 292 shown are connected to Figure 3 the plastic housing 294 shown. Block 706 may be followed by block 708.

[0043] At block 708, Figure 3 the first plurality of bonding leads 290 shown are bonded to Figure 3 the plurality of chips 280 shown. Block 708 may be followed by block 710.

[0044] At block 710, a Figure 3 module-level molded package 296 shown is fabricated. Figure 3 The module-level molded package 296 shown encapsulates Figure 3 the plurality of chips 280 shown, Figure 3 the first plurality of bonding leads 290 shown, Figure 3 a portion of the plurality of terminals 292 shown, and Figure 3 a portion of the plastic housing 492 shown.

[0045] Those of ordinary skill in the art will understand that modifications to the disclosed embodiments of the present invention may exist. For example, the number of the plurality of terminals 292 may be changed. Those of ordinary skill in the art may also conceive of other modifications, and all such modifications are considered to be within the scope of the present invention as defined by the claims.

Claims

1. A method for preparing an interconnected substrate, the method comprises the following steps: Prepare a detachable bracket; Attach a tape layer to the detachable bracket; Attach a metal sheet to the tape layer; Attach a dry film to the metal sheet; Etch the dry film to form a plurality of etched dry films; Etch the metal sheet to form a plurality of metal pads; Remove the plurality of etched dry films to form a preformed intermediate element; Load a metal plate and the preformed intermediate element onto a molding groove, with the metal pads facing the metal plate and having a preset space therebetween; By injecting a molded composite layer into the filling space between the metal plate, the plurality of metal pads and the tape layer, the molded composite layer encapsulates most of the plurality of metal pads to form a molded interconnected substrate; And After removing the molded interconnected substrate assembly from the molding groove, remove the tape layer and the detachable bracket; Connect a plastic housing to the metal plate, the molded composite layer covers the entire central area of the bottom metal plate and extends to touch the side wall of the plastic housing, the edge of the molded composite layer is aligned with the inner side wall of the plastic housing, and the length of the molded composite layer is shorter than the length of the bottom metal plate.

2. The method according to claim 1, further comprising a step of applying a splitting process to separate the interconnected substrate from an adjacent interconnected substrate after removing the tape layer and the detachable bracket.

3. The method according to claim 1, wherein the metal plate is made of a first copper material; wherein the molded composite layer is made of resin; and wherein the plurality of metal pads are made of a second copper material.

4. The method according to claim 1, wherein the thickness of each metal pad in the plurality of metal pads is less than the thickness of the molded composite layer.

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