A method for processing the appearance of an epoxy resin encapsulated circuit

Abstract

The present invention belongs to the technical field of integrated circuit manufacturing and processing, and specifically relates to a method for processing the appearance of an epoxy resin encapsulated circuit. By using a CNC milling machine to remove the encapsulated shell after encapsulation, rough-processing the components, removing the excess encapsulating material on the periphery of a single product, and retaining the circuit appearance processing allowance according to the length of the plastic-encapsulated device pin direction, the milling process is prevented from generating mechanical stress on the device pins. At the same time, the high-speed CNC milling machine has the advantage of simultaneous multi-spindle processing, and can complete the rough processing of 4-6 products at one time. After CNC programming, the operator only needs to clamp according to a specific mold, and the processing consistency and processing efficiency are greatly improved; then, the grinding liquid is used in combination with the grinding iron disk to perform precision grinding on the five surfaces to be processed, so as to achieve low-stress and low-heat appearance processing of the circuit product, avoid cracking and delamination of the circuit during subsequent processing and assessment, and improve the later reliability of the circuit.

Description

Technical Field

[0001] The invention belongs to the technical field of integrated circuit manufacturing and processing, and particularly relates to a shape processing method for an epoxy resin encapsulated circuit. Background Art

[0002] Three-dimensional stacked circuits use epoxy potting compound to encapsulate the stacked components. The interconnection between the functional leads is then achieved vertically through metallization on the outer sidewalls. Prior to this interconnection, the epoxy-encapsulated 3D stacked circuit must be formed to fully expose the leads of the stacked components within the molded and cured resin block. The encapsulated circuit has a cubic structure, with the external leads extending from the bottom. Traditional machining processes such as turning, milling, and cutting impose high stresses, causing microscopic damage to the side leads of the encapsulated components. This can lead to failures such as cracking and delamination at the interface between the lead terminals and the potting compound during temperature cycling tests. Furthermore, epoxy-potted circuits require an epoxy glass cloth substrate for support before potting. The laminated glass cloth substrate deforms when exposed to coolant, weakening the connection between the substrate and the potting compound. Without coolant during machining, the accumulated cutting heat poses a risk to circuit reliability. Direct grinding has low efficiency due to the large peripheral margin of circuit potting (generally 5mm to 10mm per side). In addition, traditional turning, milling and cutting can only clamp one product for processing at a time. One product needs to process 5 sides, and the production efficiency is extremely low. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for processing the outer shape of an epoxy resin encapsulated circuit to solve the problems of easy damage caused by traditional mechanical processing technology and low grinding efficiency of traditional grinding methods.

[0004] To achieve the above object, the present invention proposes the following technical solutions:

[0005] A method for processing the outer shape of an epoxy resin encapsulated circuit comprises the following steps:

[0006] Step 1: Make the shell removal tooling according to the shell with the shell potting circuit;

[0007] Step 2: Bind the shell removal tooling, embed the potted circuit with the shell into the groove of the shell removal tooling, and remove the shell of the potted circuit with the shell by a CNC milling machine to obtain the shelled potted circuit;

[0008] Step 3: Make rough milling tooling according to the circuit structure after shelling and potting;

[0009] Step 4: Bind the rough milling tooling, fix the shelled potted circuit to the rough milling tooling, and use a CNC milling machine to mill the shelled potted circuit to obtain the rough milled circuit;

[0010] Step 5: Grind the rough-milled circuit to obtain a ground circuit.

[0011] Preferably, in step one, the shell-encapsulated circuit includes a shell, a potting body, external leads and two positioning holes; the external leads and the positioning holes are located on the same side of the shell-encapsulated circuit, and there is an external lead area on the shell-encapsulated circuit; the external leads are located inside the external lead area, and the positioning holes are located outside the external lead area.

[0012] Preferably, in step 1, the shell removal tool includes a first plate and a second plate;

[0013] The first board is provided with a plurality of mold binding holes, which are distributed in an L-shape at the edge of the first board; pin binding holes are provided at the diagonal corners of the first board; the first board is provided with an internal cavity, the length and width of the internal cavity of the first board are consistent with the length and width of the outer contour of the housing of the potted circuit with the housing, and a processing hole is provided at each of the four inner corners of the internal cavity of the first board;

[0014] The length and width of the second board are consistent with the length and width of the first board, and the second board has the same layout, number and size of the die binding holes and the pin binding holes as the first board. The second board is provided with a second board internal cavity. Compared with the first board internal cavity, each side of the second board internal cavity is at least 5mm smaller than the corresponding side of the first board internal cavity, and each side is at least 2mm larger than the corresponding side of the outer lead area of the potted circuit after shelling;

[0015] The first plate and the second plate are stacked together and fixed with pins passing through the pin binding holes, with the first plate on top and the second plate on the bottom.

[0016] Preferably, the total thickness of the first board is greater than or equal to one third of the height of the encapsulated circuit with the shell; the total thickness of the second board is greater than the height of the external lead extending out of the bottom plate.

[0017] Preferably, in step 2, the shell removal tooling is nailed to the table of the multi-axis CNC milling machine, and there is no visible gap between the shell removal tooling and the table; the shell encapsulated circuit is embedded in the groove of the shell removal tooling, and the side of the shell encapsulated circuit with external leads faces downward.

[0018] Preferably, in step three, the rough milling tooling is composed of a rough milling tooling base plate, the upper portion of the rough milling tooling base plate is provided with a mold binding hole, two circuit mounting holes, a pin binding hole and an external lead protection groove, a plurality of mold binding holes are distributed in an L-shape at the edge of the rough milling tooling base plate, the pin binding hole is provided at a diagonal position of the rough milling tooling base plate, the positions of the two circuit mounting holes and the external lead protection groove correspond to the two positioning holes and the external lead positions on the potted circuit after shelling, and the pins pass through the plurality of pin binding holes of the rough milling tooling base plate to form the rough milling tooling;

[0019] The outer lead protection groove is at least 1 mm larger than the length and width of the outer lead of the corresponding potted circuit after shelling.

[0020] Preferably, the circuit mounting hole of the rough milling tooling and the positioning hole of the potted circuit after shelling are fixed together by pins.

[0021] Preferably, the length dimension of the circuit after rough milling is required to be 0.4mm larger than the distance between the farthest ends of the pins of the plastic-encapsulated components inside the circuit extending outward, and the width dimension of the circuit after rough milling is 1mm larger than the overall dimension required by the drawing in this direction of the circuit.

[0022] Preferably, in step 4, if the thickness of the potted circuit after shelling is less than 6 mm, a milling cutter with a diameter greater than or equal to 2 mm is selected; if the thickness of the potted circuit after shelling is greater than or equal to 6 mm and less than or equal to 12 mm, a milling cutter with a diameter greater than or equal to 3 mm is selected.

[0023] Preferably, in step five, a grinding iron disc with a mesh size of 300 to 500 is selected and ground with a green silicon carbide grinding fluid with a particle size of greater than 10 μm and less than 14 μm.

[0024] The present invention is beneficial in that:

[0025] Due to the characteristics of various metal materials and other non-metallic materials encapsulated within the epoxy organic material, a CNC milling machine is used in steps 2 and 4 to retain a certain dimensional margin. This ensures that the pins of the internally encapsulated plastic-encapsulated components are not touched during cutting, and the amount of grinding is minimized, avoiding the cutting damage caused by the traditional one-step cutting method. At the same time, the effective area of the circuit product is separated from the potted component.

[0026] The divided single circuit is ground surface by surface using a vertical surface grinder, exposing the lead terminals encapsulated in the potting compound while grinding the circuit to the dimensions required by the drawing. Grinding fluid is added during grinding to improve grinding efficiency while preventing heat generated during the grinding process from affecting the chips inside the circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 This is a schematic diagram of a potting circuit with a housing;

[0029] Figure 2 This is a schematic diagram of plate No. 1;

[0030] Figure 3 This is the schematic diagram of plate No. 2;

[0031] Figure 4 This is the superimposed image of plate 1 and plate 2;

[0032] Figure 5 Schematic diagram of tooling for shell removal;

[0033] Figure 6 A schematic diagram of the tooling for removing the potting circuit housing from the housing;

[0034] Figure 7 This is a schematic diagram of the potting circuit after shelling;

[0035] Figure 8 This is a schematic diagram of the rough milling tooling;

[0036] Figure 9 This is a schematic diagram of installing the potted circuit on the rough milling tooling after shelling;

[0037] Figure 10 This is the schematic diagram of the entire circuit after rough milling;

[0038] Figure 11 A perspective view of the internally encapsulated plastic package device;

[0039] Figure 12 This is the circuit diagram after rough milling;

[0040] Figure 13 This is the schematic diagram of the circuit after grinding;

[0041] Figure 14 The figure is a flow chart of a method for processing the appearance of an epoxy resin encapsulated circuit.

[0042] In the figure, 1 is the housing, 2 is the external leads, 3 is the positioning hole, 4 is board 1, 5 is board 2, 6 is the pin binding hole, 7 is the internal cavity of board 1, 8 is the internal cavity of board 2, 9 is the machining hole, 10 is the tooling for removing the housing, 11 is the potted circuit with the housing, 12 is the potted circuit after shell removal, 13 is the base plate for rough milling tooling, 14 is the external lead protection groove, 15 is the circuit mounting hole. 16 is the circuit after rough milling, 17 is the circuit after grinding, 18 is the rough milling tooling, 19 is the mold binding hole, 20 is the internally encapsulated plastic-encapsulated device, 21 is the pin of the plastic-encapsulated device, and 22 is the potting body. DETAILED DESCRIPTION

[0043] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0044] The following detailed description is an exemplary description and is intended to provide further detailed description of the present invention. Unless otherwise indicated, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present invention belongs. The terms used in the present invention are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention.

[0045] Example 1:

[0046] See also Figure 1 As shown, the present invention provides a method for processing the appearance of an epoxy resin encapsulated circuit.

[0047] Figure 1 The encapsulated circuit 11 with a shell shown in the figure is provided with a shell 1, a potting body 22, an external lead 2 and a positioning hole 3; the external lead 2 and the positioning hole 3 are located on the same surface of the encapsulated circuit 11 with a shell, and there is an external lead area on the encapsulated circuit 11 with a shell. The external lead 2 is located inside the external lead area, and the positioning hole 3 is located outside the external lead area.

[0048] Taking the housing 11 of the encapsulated circuit as an example, a method for processing the outer shape of the epoxy resin encapsulated circuit includes the following steps:

[0049] like Figure 2 As shown, the first board 4 is designed and uses epoxy glass cloth substrate;

[0050] A plurality of die binding holes 19 are provided on the first plate, and are distributed in an L-shaped pattern at the edge of the first plate 4, with at least two die binding holes 19 being provided on each side of the L-shape;

[0051] A pin binding hole 6 is designed at each diagonal corner of the No. 1 plate for fixing the multi-layer substrate;

[0052] An internal opening 7 of plate No. 1 is provided on plate No. 1 4. The length and width of the internal opening 7 of plate No. 1 are consistent with the length and width of the outer contour of the shell 1 with the shell encapsulated circuit 11, and a processing hole 9 is provided at each of the four inner corners of the internal opening 7 of plate No. 1. The diameter of the processing hole 9 is not less than the diameter of the milling cutter used for processing the inner groove.

[0053] like Figure 3 As shown, the second board 5 is designed and adopts an epoxy glass cloth substrate. The length and width of the second board 5 are consistent with the length and width of the first board, and it has the same layout, number and size of mold binding holes 3 and pin binding holes 6 as the first board 4. The second board 5 is provided with a second board internal cavity 8. Each side of the second board internal cavity 8 is at least 5 mm smaller than the No. 1 board internal cavity 7, and each side is at least 2 mm larger than the corresponding side of the external lead area of the shell encapsulated circuit 11.

[0054] like Figure 4 As shown, several No. 1 plates 4 and several No. 2 plates 5 are stacked together and fixed with pins through the pin binding holes 6, with No. 1 plate 4 on top and No. 2 plate on the bottom, forming a Figure 5 The housing removal tool 10 is shown;

[0055] The total thickness of the shell excluding the No. 1 plate 4 on the tooling 10 is greater than or equal to one-third of the height of the potted circuit 11 with the shell removed, and less than or equal to the height of the potted circuit 11 with the shell minus the thickness of the bottom of the shell 1;

[0056] The total thickness of the second plate 5 is greater than the height of the external lead 2 extending out of the bottom plate;

[0057] Alternatively, only one No. 1 plate 4 with sufficient thickness and one No. 2 plate 5 with sufficient thickness may be used.

[0058] The shell removal tool 10 is stapled to the multi-axis CNC milling machine table through the die binding holes 19 to ensure that there is no visible gap between the shell removal tool 10 and the table;

[0059] According to the equipment model and specifications, if it is a 2-axis one, two sets of shell removal tooling 10 are made and bound according to the same positioning rule.

[0060] like Figure 6 As shown, the outer lead 2 of the housing potting circuit 11 is placed downward and embedded in the groove of the housing removal tool 10.

[0061] A CNC milling program is compiled according to the outer contour dimensions and thickness of the shell 1 with the encapsulated circuit 11, and the four sides and bottom of the shell 1 are cut off. The milling cutter path in the program follows the center line of the encapsulated shell to ensure that the milling cutter cutting path completely separates the bottom of the shell 1 from the surrounding areas.

[0062] The milled housing potting circuit 11 is taken out from the housing removal tool 10, and the four-side housing and the bottom housing that have been cut off are separated from the potting body 22 with pliers to obtain the following: Figure 7 The circuit 12 is shown as potted after shelling.

[0063] According to the structure of the encapsulated circuit 12 after shelling, the rough milling tool 18 is designed, such as Figure 8 As shown: the rough milling tooling substrate 13 adopts an epoxy glass cloth substrate, and a mold binding hole 19, a circuit mounting hole 15, a pin binding hole 6, and an external lead protection groove 14 are provided on the upper part of the rough milling tooling substrate 13, wherein the position of the circuit mounting hole 15 corresponds to the position of the positioning holes 3 at both ends of the potted circuit 12 after shelling, and the diameter of the circuit mounting hole 15 is consistent with the diameter of the positioning holes 3 at both ends of the potted circuit 12 after shelling. At least one pin binding hole 6 is designed at each diagonal corner of the rough milling tooling substrate 13 for fixing multiple substrates; based on the position of the circuit mounting hole 15, the slotting position of the external lead protection groove 14 corresponds to the position of the external lead 2 of the potted circuit after shelling, and the external lead protection groove 14 is at least 1 mm larger than the width and length of the external lead 2 of the corresponding potted circuit 12 after shelling. The rough milling tool 18 is composed of a single rough milling tool base plate 13 of sufficient thickness or multiple rough milling tool base plates 13 stacked with pins. The thickness of the rough milling tool 18 should be greater than the height of the external lead 2 extending from the bottom plate surface.

[0064] like Figure 9 As shown, the rough milling tool 18 is installed and fixed on the processing table of the multi-axis CNC milling machine through the mold binding hole 19, and then the external lead 2 on the shelled potted circuit 12 is facing downward, and the positioning hole 3 of the shelled potted circuit 12 is fixed with the circuit mounting hole 15 using a pin.

[0065] Prepare milling data according to the structure and size of the potting circuit 12 after shelling, such as Figure 11 As shown, the length direction dimension requirement of the circuit is 0.4mm larger than the distance between the farthest ends of the plastic-encapsulated device pins 21 of the plastic-encapsulated device 20 encapsulated inside the circuit, and 0.2mm larger on one side. The width direction dimension of the circuit is 1mm larger than the required dimension requirement of the circuit in this direction as a whole, and 0.5mm larger on one side.

[0066] According to the compiled milling data, the milling cutter with scale teeth is selected. The diameter of the milling cutter is selected according to the thickness of the potting circuit 12 after shelling:

[0067] The diameter of the milling cutter selected for the shelled potted circuit 12 with a thickness of less than 6 mm should be ≥ 2.0 mm and ≤ (the distance between the multiple circuits encapsulated in the shelled potted circuit 12 - 2) / 2;

[0068] The diameter of the milling cutter selected for the shelled potted circuit 12 with a thickness of 6 mm or less and a thickness of 12 mm should be ≥3.0 mm and ≤(the distance between the multiple circuits encapsulated in the shelled potted circuit 12 - 2) / 2;

[0069] The length of the milling cutter blade should be at least 1 mm longer than the thickness of the potting circuit 12 after shelling.

[0070] After rough milling, the entire circuit is as follows Figure 10 shown.

[0071] After the rough milling of the milling type is completed, the circuit 16 is as follows Figure 12 shown.

[0072] For a single circuit that has been decomposed, clamp it on the corresponding grinding tool with any side except the side where lead 2 is located facing outward. Use a vertical surface grinder, install a grinding iron disc with a mesh size of 300-500 mesh, and add green silicon carbide grinding fluid with a particle size of 10μm-14μm in real time. Apply a pressure of about 5kg on the surface of the tool disc. The grinding disc is driven by the pulley to rotate, and the tool disc rotates to generate grinding force to remove the excess of the single circuit after rough milling. After completing the processing of one side, replace the grinding tool and complete the grinding of the remaining four sides except the side where lead 2 is located in the same way. Finally, grind the circuit to the size required by the drawing, and obtain the following Figure 13 Circuit 17 after grinding is shown.

[0073] The flow chart is as follows Figure 14 shown.

[0074] In view of the characteristics of various metal materials and other non-metallic materials encapsulated in epoxy organic materials, the present invention adopts a PCB multi-axis CNC milling machine with a scaly carbide milling cutter to efficiently complete side cutting, so that the effective area of the circuit product is separated from the potting component; after the separation, the single piece is grinded by a vertical surface grinder to grind the circuit surface by surface, so that the lead terminals encapsulated in the potting material are exposed and the lead terminals are grinded to the required size of the drawing. Grinding fluid is added during grinding to improve grinding efficiency while preventing heat generated during the grinding process from affecting the chips inside the circuit.

[0075] It is understood from common technical knowledge that the present invention may be implemented by other embodiments that do not depart from its spirit or essential features. Therefore, the embodiments disclosed above are, in all respects, merely illustrative and not exclusive. All modifications within the scope of the present invention or equivalent to the scope of the present invention are intended to be encompassed by the present invention.

Claims

1. A method for processing the shape of an epoxy resin encapsulated circuit, characterized in that: The steps include: Step 1: Making a shell removal tool (10) based on the shell (1) with the shell potting circuit (11); The shell removal tool (10) includes a first plate (4) and a second plate (5); A plurality of mold binding holes (19) are provided on the first board (4), and the plurality of mold binding holes (19) are distributed in an L-shape at the edge of the first board (4); a pin binding hole (6) is provided at the diagonal corner of the first board; a first board internal opening (7) is provided on the first board, and the length and width of the first board internal opening (7) are consistent with the length and width of the outer contour of the housing (1) on the housing potting circuit (11), and a processing hole (9) is provided at each of the four inner corners of the first board internal opening (7); The length and width of the second board (5) are consistent with the length and width of the first board, and the second board (5) has the same layout, number and size of the mold binding holes (19) and the pin binding holes (6) as the first board (4). The second board (5) is provided with a second board internal opening (8). Compared with the first board internal opening (7), each side of the second board internal opening (8) is at least 5 mm smaller than the corresponding side of the first board internal opening (7), and each side is at least 2 mm larger than the corresponding side of the outer lead area of the potted circuit (12) after shelling. The first plate (4) and the second plate (5) are stacked together, and the pins are passed through the pin binding holes (6) for fixing, with the first plate (4) on top and the second plate (5) on the bottom; Step 2: Binding the shell removal tool (10), embedding the shell-encapsulated circuit (11) in the groove of the shell removal tool (10), and removing the shell of the shell-encapsulated circuit (11) by a CNC milling machine to obtain the shelled encapsulated circuit (12); Step 3: Make a rough milling tool (18) according to the structure of the potting circuit (12) after shelling; the rough milling tool (18) is composed of a rough milling tool base plate (13), and the upper part of the rough milling tool base plate (13) is provided with a mold binding hole (19), two circuit mounting holes (15), a pin binding hole (6) and an external lead protection groove (14). Step 4: Binding the rough milling tool (18), fixing the shelled potting circuit (12) to the rough milling tool (18), and milling the shelled potting circuit (12) by a CNC milling machine to obtain the rough milled circuit (16); Step 5: Grinding the rough-milled circuit (16) to obtain a ground circuit (17).

2. The method for processing the outer shape of an epoxy resin encapsulated circuit according to claim 1, wherein: In step 1, the encapsulated circuit (11) with a housing comprises a housing (1), a encapsulating body (22), an external lead (2) and two positioning holes (3); the external lead (2) and the positioning holes (3) are located on the same surface of the encapsulated circuit (11) with a housing, and an external lead area exists on the encapsulating body (22); the external lead (2) is located inside the external lead area, and the positioning holes (3) are located outside the external lead area.

3. The method for processing the outer shape of an epoxy resin encapsulated circuit according to claim 2, wherein: The total thickness of the first board (4) is greater than or equal to one third of the height of the encapsulated circuit (11) with the housing, and less than or equal to the height of the encapsulated circuit (11) with the housing minus the bottom thickness of the housing 1; the total thickness of the second board (5) is greater than the height of the external lead (2) extending out of the bottom plate.

4. The method for processing the outer shape of an epoxy resin encapsulated circuit according to claim 2, wherein: In step 2, the shell removal tool (10) is nailed to the table of the multi-axis CNC milling machine, and there is no visible gap between the shell removal tool (10) and the table; the shell encapsulation circuit (11) is embedded in the groove of the shell removal tool (10), and the side of the shell encapsulation circuit (11) with the external lead (2) faces downward.

5. The method for processing the outer shape of an epoxy resin encapsulated circuit according to claim 2, wherein: In step 3, a plurality of mold binding holes (19) are distributed in an L-shape at the edge of the rough milling tooling substrate (13), a pin binding hole (6) is provided at a diagonal position of the rough milling tooling substrate (13), the positions of the two circuit mounting holes (15) and the external lead protection groove (14) correspond to the two positioning holes and the positions of the external lead (2) on the potting circuit (12) after shelling, and the pins pass through the plurality of pin binding holes (6) of the rough milling tooling substrate (13) to form the rough milling tooling (18); The outer lead protection groove (14) is at least 1 mm larger than the length and width of the outer lead of the corresponding shell-removed potting circuit (12).

6. The method for processing the outer shape of an epoxy resin encapsulated circuit according to claim 5, wherein: The circuit installation hole (15) of the rough milling tool (18) and the positioning hole (3) of the potting circuit (12) after shelling are fixed together by pins.

7. The method for processing the outer shape of an epoxy resin encapsulated circuit according to claim 5, wherein: The lengthwise dimension C of the circuit (16) after rough milling is required to be 0.4 mm larger than the distance between the two farthest ends of the pins (21) of the plastic-encapsulated device (20) encapsulated inside the circuit, and the widthwise dimension of the circuit (16) after rough milling is 1 mm larger than the overall dimension required by the drawing in this direction of the circuit.

8. The method for processing the outer shape of an epoxy resin encapsulated circuit according to claim 1, wherein: In step 4, if the thickness of the potted circuit (12) after shelling is less than 6 mm, a milling cutter with a diameter greater than or equal to 2 mm is selected; if the thickness of the potted circuit (12) after shelling is greater than or equal to 6 mm and less than or equal to 12 mm, a milling cutter with a diameter greater than or equal to 3 mm is selected.

9. The method for processing the outer shape of an epoxy resin encapsulated circuit according to claim 1, wherein: In step five, a grinding iron disc with a mesh size of 300 to 500 is selected and ground with a green silicon carbide grinding fluid with a particle size of greater than 10 μm and less than 14 μm.

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