Molded electronic package with angled sides - Patents.com

Abstract

An electronic device (100) includes a molded package structure (108) and conductive leads (110, 120) partially exposed outside the package structure (108), the package structure having lateral sides (101, 102, 103, 104) extending at angles (θ1, θ2) greater than 15 degrees and less than 25 degrees to facilitate mold cavity filling during package molding and to mitigate mold voids within the electronic device (100). A method of manufacturing an electronic device includes attaching a die (150) to a leadframe, electrically coupling conductive terminals of the die (150) to the conductive leads, and performing a molding process with a mold having cavity sidewalls with a draft angle greater than 15 degrees and less than 25 degrees to form a package structure (108) surrounding the die (150) and partially surrounding the conductive leads (110, 120).

Description

[Technical field]

[0001] Packaged electronic devices often include one or more semiconductor dies, conductive leads, and electrical interconnects to form an electrical circuit that can be connected to conductive pads on a host printed circuit board. The package is molded to surround the die and some of the leads. Unbalanced flow of molding material can occur during the molding process, especially for high voltage molding compounds used to create tall packages. This can result in incomplete filling during molding, creating mold voids or gaps in the molded package structure. Mold voids can be addressed by optimizing molding parameters, but this increases manufacturing costs and complexity. Summary of the Invention

[0002] In one aspect, an electronic device includes a molded package structure and conductive leads partially exposed outside the package structure, the package structure having sides that extend at an angle of greater than 15 degrees and less than 25 degrees to facilitate mold cavity filling during package molding and to mitigate mold voids in the electronic device.

[0003] In another aspect, a method of manufacturing an electronic device includes attaching a die to a lead frame, electrically coupling conductive terminals of the die to the conductive leads, and performing a molding process with a mold having cavity sidewalls with a draft angle greater than 15 degrees and less than or equal to 25 degrees to form a package structure surrounding the die and partially surrounding the conductive leads. [Brief description of the drawings]

[0004] [Figure 1] FIG. 1 is a perspective view of an electronic device having a molded package structure with high draft angle sidewalls and gull-wing leads.

[0005] [Figure 1A] FIG. 2 is a partial side view of the electronic device of FIG.

[0006] [Figure 1B] FIG. 2 is a plan view of the electronic device of FIGS. 1 and 1A.

[0007] [Figure 1C] FIG. 2 is a front view of the electronic device of FIGS. 1 to 1B.

[0008] [Figure 1D] FIG. 2 is a side view of the electronic device of FIGS. 1 to 1C.

[0009] [Diagram 2] 1 is a flow chart of a method for manufacturing an electronic device.

[0010] [Diagram 3] 1-1D after being processed according to the method of FIG. 2. [Figure 4] 1-1D after being processed according to the method of FIG. 2. [Diagram 5] 1-1D after being processed according to the method of FIG. 2. [Figure 6] 1-1D after being processed according to the method of FIG. 2. [Figure 7] 1-1D after being processed according to the method of FIG. 2. [Figure 8] 1-1D after being processed according to the method of FIG. 2.

[0011] [Figure 9] FIG. 2 is a partial side view of another electronic device having J-shaped leads.

[0012] [Figure 10]FIG. 1 is a partial side view of a quad flat no-lead (QFN) electronic device having a molded package structure with high draft angle sidewalls.

[0013] [Figure 11] 1 is a partial side view of another electronic device having a molded packaging structure with upper and lower portions of unequal heights.

[0014] [Figure 12] 1 is a partial side view of another electronic device having a molded packaging structure with upper and lower portions of unequal heights and with different draft angles. FIG.

[0015] [Figure 13] 1 is a partial side view of another electronic device having a molded packaging structure with upper and lower portions with different draft angles. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] In the drawings, like reference numerals refer to like elements throughout, and the various features are not necessarily drawn to scale. Also, the term "couple" includes an indirect or direct electrical or mechanical connection, or a combination thereof. For example, when a first device couples to or is coupled to a second device, the connection may be through a direct electrical connection, or may be through an indirect electrical connection via one or more intervening devices and connections.

[0017] Referring first to Figures 1-1D, Figure 1 illustrates an electronic device 100 with a molded package structure 108 having high draft angle sidewalls and gull wing leads. Figure 1A illustrates a partial side view of electronic device 100, Figure 1B illustrates a top view of electronic device 100, Figure 1C illustrates a front view of electronic device 100, and Figure 1D illustrates a side view of electronic device 100. Electronic device 100 is shown in an example position in three-dimensional space having respective first, second, and third mutually orthogonal directions X, Y, and Z. As best shown in Figure 1, electronic device 100 includes opposing first and second sides 101 and 102 extending along a second direction Y and spaced apart from one another along a first direction X. The electronic device 100 also includes third and fourth sides 103 and 104 spaced apart from one another along a second direction Y, a bottom side 105, and a top side 106 spaced apart from the bottom side 105 along a third direction Z. In the illustrated example, the bottom side 105 and the top side 106 are generally planar and extend in an XY plane in the first and second directions X and Y, respectively. The electronic device 100 includes gull-wing conductive leads 110 along the first side 101 and leads 120 along the opposing second side 102. The illustrated gull-wing leads 110 and 120 are or include a conductive metal, such as aluminum or copper, and have an interior portion surrounded by a molded package structure 108 and an exterior portion partially exposed outside the package structure 108.

[0018] As shown in Figures 1, 1A, and 1C, the lateral sides 101-104 of the package structure 108 have tapered portions extending at angles greater than 15 degrees and less than 25 degrees to facilitate mold cavity filling during package molding and reduce mold voids in the electronic device. The tapered surfaces of the sides 101-104 are created by corresponding tapered walls of the mold cavity during molding to form the molded package structure 108 as shown and further described hereinafter. The first side 101 has an upper first portion 111 and a lower second portion 112. The first portion 111 of the first side 101 extends at a first angle θ1 from a first plane P1YZ in respective second and third directions Y and Z to the sixth side 106. The second portion 112 of the first side 101 extends from the first plane P1YZ in the respective second and third directions Y and Z to the fifth side 105. In one example, the first angle θ1 is greater than 15 degrees, and the first angle θ1 is 25 degrees or less. In these or other examples, the second portion 112 of the first side 101 extends from the first plane P1YZ in the respective second and third directions Y and Z to the fifth side 105 at a second angle θ2. In one implementation, the second angle θ2 is greater than 15 degrees, and the second angle θ2 is 25 degrees or less. In one example, the first angle θ1 is approximately equal to the second angle θ2. In other implementations, the first angle θ1 and the second angle θ2 are different (e.g., Figures 12 and 13 below).

[0019] 1 and 1C, the second side 102 has an upper first portion 121 and a lower second portion 122. The first portion 121 of the second side 102 extends from a second YZ plane P2YZ to the sixth side 106 at a first angle θ1 in the respective second and third directions Y and Z. The second portion 122 of the second side 102 extends from the second YZ plane P2YZ to the fifth side 105. In one example, the second portion 122 of the second side 102 extends from the second YZ plane P2YZ to the fifth side 105 at a second angle θ2.

[0020] As shown in FIG. 1 and FIG. 1D, the third side 103 has an upper first portion 131 and a lower second portion 132. The first portion 131 of the third side 103 extends from the first XZ plane P1XZ to the sixth side 106 at a first angle θ1 in the respective first and third directions X and Z. The second portion 132 of the third side 103 extends from the first XZ plane P1XZ to the fifth side 105. In one example, the second portion 132 of the third side 103 extends from the first XZ plane P1XZ to the fifth side 105 at a second angle θ2. In this example, the fourth side 104 has a first portion 141 and a second portion 142. A first portion 141 of the fourth side 104 extends at a first angle θ1 from a second XZ plane P2XZ to the sixth side 106 in the respective first and third directions X and Z, and a second portion 142 of the fourth side 104 extends from the second XZ plane P2XZ to the fifth side 105. In one example, the second portion 142 of the fourth side 104 extends at a second angle θ2 from the second XZ plane P2XZ to the fifth side 105.

[0021] As shown in FIG. 1A, the first portions 111, 121, 131, and 141 of the first, second, third, and fourth sides 101, 102, 103, and 104, respectively, have a first height L1 along the third direction Z. The second portions 112, 122, 132, and 142 of the first, second, third, and fourth sides 101, 102, 103, and 104, respectively, have a second height L2 along the third direction Z. In the electronic device 100 of FIGS. 1-1D, the first height L1 and the second height L2 are approximately equal. In other examples (e.g., or less than FIGS. 11 and 12), the first height L1 and the second height L2 are different. In the illustrated example, the side 101 includes an intermediate portion between the first portion 111 and the second portion 112, and the leads 110 extend substantially laterally along the first direction X from the intermediate portion of the first side 101. The other lateral sides 102-104 in this example have similar intermediate portions. In other implementations (not shown), the intermediate portion is omitted from each of the lateral sides 101-104, for example, with the upper first portions 111, 121, 131, and 141 extending to the respective second portions 112, 122, 132, and 142.

[0022] As further shown in FIG. 1, electronic device 100 includes a semiconductor die 150 mounted, for example, on a die attach pad (not shown) and enclosed within the molding material of package structure 108. Die 150 includes conductive terminals, such as conductive copper or aluminum die bond pads, some of which are electrically coupled to conductive leads 110 or 120, respectively, by conductive bond wires 152. Other examples include flip-chip die attach electrical connections, alone or in combination with bond wires, substrate interconnects, and / or other forms of electrical coupling (not shown). Leads 110 and 120 in the example of FIGS. 1-1D are gull-wing leads extending outwardly from first and second sides 101, 102, respectively, of package structure 108. In other examples, different lead types and / or shapes can be used, such as J-shaped leads (e.g., FIG. 9 below), no-lead types for quad flat no-lead (QFN) package types (e.g., FIG. 10 below). Also, in various implementations, the leads 110 , 120 may be located along one, two, three, or four sides of the electronic device 100 .

[0023] The electronic device provides increased angles θ1 and θ2 of greater than 15 degrees to promote balanced mold material flow in the mold cavity during the molding process to reduce or avoid mold voids or gaps in the material of the finished molded package structure 108. This promotes proper mechanical support and protection for the enclosed components, as well as electrical isolation and high voltage withstand capability, especially for high voltage insulating devices. In addition, the increased angles θ1 and θ2 promote uniform and void-free molding by increasing the uniformity of the mold material flow during the mold filling operation without the need to adjust or optimize mold parameters such as mold material temperature range, injection pressure and flow rate, mold material viscosity and other properties. In an example, the electronic device may be a high-profile, high-voltage device having tapered sides extending at first and second angles θ1 and θ2 of greater than 15 degrees along the third direction Z, such as a mold thickness of 3.00 mm. In some examples, angles θ1 and θ2 are 25 degrees or less, and angles exceeding this amount can reduce the thickness of the molded material of package structure 108 near each side 101-104, thereby limiting the electrical isolation distance from package structure 108 and external components or high voltage components encapsulated within the system (e.g., die 150, bond wires 152). In some examples, one or both of angles θ1 and θ2 are greater than or equal to 18 degrees and less than or equal to 22 degrees, such as about 20 degrees. In one implementation, angles θ1 and θ2 are set or controlled by the configuration of the respective mold halves or mold sections used in the molding process to create molded package structure 108.

[0024] 2-8, FIG. 2 illustrates a method 200 for manufacturing an electronic device, and FIGS. 3-8 illustrate the electronic device 100 of FIGS. 1-1D undergoing a manufacturing process according to method 200. Method 200 includes a die attach operation at 202. FIG. 3 illustrates an example in which a die attach process 300 is performed to attach a semiconductor die 150 to a die attach pad 302 of a starting leadframe that also includes potential leads 110 and 120. In one example, the starting leadframe has a plurality of potential device portions arranged in an array of rows and columns (not shown), and the die attach process 300 includes simultaneous or sequential placement of a plurality of dies 150 onto respective die attach pads of a panel array.

[0025] Method 200 continues at 204 with electrical bonding, including coupling one or more conductive terminals of die 150 to respective conductive leads 110 or 120, as well as any die-to-die connections required for a given electronic device design (e.g., die-to-die connections for a multi-chip module or MCM device, not shown). Figure 4 illustrates an example in which a wire bonding process 400 is performed to form bond wires 152 between respective conductive bond pads of semiconductor die 150 and associated ones of the conductive leads 110, 120 of the starting lead frame.

[0026] Method 200 further includes molding at 206 using a mold with high upper and lower draft angles. FIGS. 5-8 show an example of electronic device 100 undergoing molding process 500 using a mold having separable first and second mold parts 501 and 502, respectively. First mold part 501 in the example of FIGS. 5-8 has a first (e.g., upper) cavity with a first draft angle θ1, and second mold part 502 has a second (e.g., lower) cavity with a second draft angle θ2. In one example, draft angles θ1 and θ2 are both greater than 15 degrees and less than or equal to 25 degrees, and in one implementation are between 18 and 22 degrees. Mold cavity interior sidewall draft angles θ1 and θ2 correspond approximately to the respective first and second angles θ1 and θ2 of electronic device 100 after molding. The molding process 500 forms a package structure 108 that encloses the die 150 and bond wires 152, partially encloses the conductive leads 110 and 120, and leaves its outer portions exposed for subsequent trimming and forming operations. The upper and lower mold sections 501 and 502 are closed along the arrows in FIG. 5 to enclose the die 150 and future device portions of the leadframe panel array to create cavities associated with each future electronic device. Each device cavity is then filled with molten molding compound 108, as shown in FIG. 6, which solidifies as it cools, as shown in FIG. 7. The mold sections 501 and 502 are then separated along the arrows in FIG. 8, leaving a molded package structure 108 having sides at angles θ1 and θ2, as described above in connection with FIGS. 1-1D. The method 200 continues at 208 in FIG. 2 with lead trimming and forming processing (not shown) and package separation at 210 to provide individual completed packaged electronic devices 100.

[0027] 9-13 show another example electronic device having a molded package structure with a sidewall angle greater than 15 degrees and less than or equal to 25 degrees. Figure 9 shows a portion of another electronic device 900 having a molded package structure 908 having a J-shaped lead 910 along a first side 901 having a first (e.g., upper) portion 911 that extends to a top (e.g., sixth) side 906 at a first angle θ1 and a second (e.g., lower) portion 912 that extends to a bottom (e.g., fifth) side 905 at a second angle θ2. The other three lateral sides have similar first and second portions at respective angles θ1 and θ2. In one example, electronic device 900 has four lateral sides, including the illustrated side 901, and each of the four sides includes one or more conductive leads 910 that are partially exposed along the respective side and also partially exposed along a bottom (e.g., fifth) side 905 of the packaging structure 908. In another example, electronic device 900 has leads along fewer than all lateral sides.

[0028] 10 illustrates a portion of another electronic device 1000 having a quad flat molded (e.g., QFN) package structure 1008 having leads 1010 partially exposed along a first side 1001 with a first (e.g., upper) portion 1011 extending to a top (e.g., sixth) side 1006 at a first angle θ1 and a second (e.g., lower) portion 1012 extending to a bottom (e.g., fifth) side 1005 at a second angle θ2. The other three lateral sides have similar first and second portions at respective angles θ1 and θ2. In one example, electronic device 1000 has four lateral sides, including the illustrated side 1001, and each of the four sides includes one or more conductive leads 1010 that are partially exposed along the respective side and also partially exposed along a bottom (e.g., fifth) side 1005 of the packaging structure 1008. In another example, electronic device 1000 has leads along fewer than all lateral sides.

[0029] FIG. 11 shows a portion of another electronic device 1100 having a molded package structure 1108 with gulping leads 1110 along a first side 1101 having a first (e.g., top) portion 1111 extending to a top (e.g., sixth) side 1106 at a first angle θ1 and a second (e.g., bottom) portion 1112 extending to a bottom (e.g., fifth) side 1105 at a second angle θ2. In this example, the first portion 1111 of the first side 1101 has a first height L1 along a third direction Z, and the second portion 1112 has a second height L2 along the third direction Z, the first height L1 and the second height L2 being different. In the illustrated implementation, the second height L2 is smaller than the first height L1. In another example, the second height L2 is larger than the first height L1. In these examples, the other three lateral sides have similar first and second portions of the respective angles θ1 and θ2. In one example, the electronic device 1100 has four lateral sides, including the side 1101 shown, and each of the four sides includes one or more gull-wing conductive leads 1110 extending from the respective side. In another example, the electronic device 1100 has leads 1110 along fewer than all of the lateral sides. Also, in the example of FIG. 11, the first and second angles θ1, θ2 are different, and both angles θ1, θ2 are greater than 15 degrees and less than or equal to 25 degrees. In the example shown, angle θ1 is less than angle θ2. In another example, angle θ1 is greater than angle θ2.

[0030] 12 shows a portion of another electronic device 1200 having upper and lower portions with various draft angles. The electronic device 1200 has a molded package structure 1208 with gull-wing leads 1210 along a first side 1201 having a first (e.g., upper) portion 1211 that extends to a top (e.g., sixth) side 1206 at a first angle θ1 and a second (e.g., lower) portion 1212 that extends to a bottom (e.g., fifth) side 1205 at a second angle θ2. In this example, the first portion 1211 of the first side 1201 has a first height L1 along a third direction Z, and the second portion 1212 has a second height L2 along the third direction Z, where the first height L1 and the second height L2 are different. In the illustrated implementation, the second height L2 is smaller than the first height L1. In another example, the second height L2 is greater than the first height L1. In these examples, the other three lateral sides have similar first and second portions with respective angles θ1 and θ2. In one example, the electronic device 1200 has four lateral sides, including the side 1201 shown, and each of the four sides includes one or more gull-wing conductive leads 1210 extending from the respective side. In another example, the electronic device 1200 has leads 1210 along fewer than all of the lateral sides. Also, in the example of FIG. 12, the first and second angles θ1, θ2 are different, and both angles θ1, θ2 are greater than 15 degrees and less than or equal to 25 degrees. In the example shown, angle θ is less than angle θ2. In another example, angle θ1 is greater than angle θ2.

[0031] 13 illustrates another example electronic device 1300 having a molded package structure 1308 with upper and lower portions 1311 and 1312 of various draft angles. The electronic device 1300 has gull-wing leads 1310 along a first side 1301 having a first (e.g., upper) portion 1311 that extends to a top (e.g., sixth) side 1306 at a first angle θ1 and a second (e.g., lower) portion 1312 that extends to a bottom (e.g., fifth) side 1305 at a second angle θ2. In this example, the first portion 1311 of the first side 1301 has a first height L1 along a third direction Z and the second portion 1312 has a second height L2 along the third direction Z, where the first height L1 and the second height L2 are approximately equal. In this example, the other three lateral sides have similar first and second portions of the respective angles θ1 and θ2. In one example, the electronic device 1300 has four lateral sides, including the side 1301 shown, and each of the four sides includes one or more gull-wing conductive leads 1310 extending from the respective side. In another example, the electronic device 1300 has leads 1310 along fewer than all of the lateral sides. Also, in the example of FIG. 13, the first and second angles θ1, θ2 are different, and both angles θ1, θ2 are greater than 15 degrees and less than or equal to 25 degrees. In the example shown, angle θ1 is less than angle θ2. In another example, angle θ1 is greater than angle θ2.

[0032] The described embodiments and variations thereof provide advantages in that they promote complete mold filling and reduce mold voids or gaps to improve the performance and rigidity of the molded package structure. These examples allow the use of conventional molding parameter control with or without the added cost and complexity of mold parameter optimization. These solutions are advantageous for multi-chip module (MCM) packaged devices and packaged integrated circuits, for example, where mold material flow during the manufacture of single component packaged electronic devices is generally enhanced, and includes packaged integrated circuits with multiple electronic components. In addition, the described solutions provide advantages for thick package designs, including devices having package structure thicknesses (e.g., along the exemplary third direction (Z) of 3.00 mm or more). Some implementations of the described examples can reduce mold flow imbalances with high voltage mold compounds by mold modification to implement new package draft angle designs having draft angles greater than 15 degrees and less than or equal to 25 degrees. These examples also save manufacturing costs by minimizing yield loss due to external mold voids and increasing productivity by avoiding machine downtime due to mold voids without requiring further molding process optimization and by eliminating multiple learning cycles on mold flow / parameter optimization.

[0033] The above examples are merely illustrative of some possible implementations of the various aspects of the present disclosure, and equivalent changes and / or modifications will occur to others skilled in the art upon reading and understanding this specification and the accompanying drawings. Unless otherwise specified, "about," "approximately," or "substantially" preceding a value means + / - 10% of the stated value. Modifications may be made to the examples described, and other implementations are possible, within the scope of the claims of this application.

Claims

1. It is an electronic device, A package structure having a first side, a second side, a third side, a fourth side, a fifth side, and a sixth side, wherein the first side and the second side are spaced apart from each other along a first direction, the third side and the fourth side are spaced apart from each other along a second direction perpendicular to the first direction, and the fifth side and the sixth side are spaced apart from each other along a third direction perpendicular to the first and second directions, A conductive lead partially exposed on the outside of the package structure, Includes, The first side portion includes a first portion extending at a first angle from the first plane in the second and third directions to the sixth side portion, and a second portion extending from the first plane in the second and third directions to the fifth side portion, wherein the first angle is greater than 15 degrees and the first angle is 25 degrees or less. The second side portion includes a first portion extending at a first angle from the second plane in the second and third directions to the sixth side portion, and a second portion extending from the second plane in the second and third directions to the fifth side portion. The third side portion includes a first portion extending at a first angle from the first plane in the first and third directions to the sixth side portion, and a second portion extending from the first plane in the first and third directions to the fifth side portion. An electronic device wherein the fourth side portion includes a first portion extending at a first angle from a second plane in the first and third directions to the sixth side portion, and a second portion extending from the second plane in the first and third directions to the fifth side portion.

2. The electronic device according to claim 1, The second portion of the first side extends at a second angle from the first plane in the second and third directions to the fifth side, The second portion of the second side extends at the second angle from the second plane in the second and third directions to the fifth side, The second portion of the third side extends at a second angle from the first plane in the first and third directions to the fifth side, The second portion of the fourth side extends at a second angle from the second plane in the first and third directions to the fifth side, An electronic device in which the second angle is greater than 15 degrees and the second angle is 25 degrees or less.

3. The electronic device according to claim 2, An electronic device in which the first angle is approximately equal to the second angle.

4. The electronic device according to claim 3, An electronic device in which the conductive leads extend outward from a first side of the package structure.

5. The electronic device according to claim 3, An electronic device in which the conductive leads are partially exposed along the first and fifth sides of the package structure.

6. The electronic device according to claim 2, An electronic device in which the conductive leads extend outward from a first side of the package structure.

7. The electronic device according to claim 2, An electronic device in which the conductive leads are partially exposed along the first and fifth sides of the package structure.

8. The electronic device according to claim 2, An electronic device in which the first angle is 18 degrees or greater, the first angle is 22 degrees or less, the second angle is 18 degrees or greater, and the second angle is 22 degrees or less.

9. The electronic device according to claim 1, An electronic device in which the conductive leads extend outward from a first side of the package structure.

10. The electronic device according to claim 1, An electronic device in which the conductive leads are partially exposed along the first side and the fifth side of the package structure.

11. The electronic device according to claim 1, An electronic device in which the first angle is 18 degrees or greater, the first angle is 22 degrees or less, the second angle is 18 degrees or greater, and the second angle is 22 degrees or less.

12. The electronic device according to claim 1, Each of the first, second, third, and fourth sides has a first portion that is a first height along the third direction, Each of the first, second, third, and fourth sides has a second height along the third direction, An electronic device in which the first height and the second height are different.

13. The electronic device according to claim 12, The second portion of the first side extends at a second angle from the first plane in the second and third directions to the fifth side, The second portion of the second side extends at the second angle from the second plane in the second and third directions to the fifth side, The second portion of the third side extends at the second angle from the first plane in the first and third directions to the fifth side, The second portion of the fourth side extends at the second angle from the second plane in the first and third directions to the fifth side, An electronic device in which the first angle and the second angle are different.

14. The electronic device according to claim 1, The second portion of the first side extends at a second angle from the first plane in the second and third directions to the fifth side, The second portion of the second side extends at the second angle from the second plane in the second and third directions to the fifth side, The second portion of the third side extends at the second angle from the first plane in the first and third directions to the fifth side, The second portion of the fourth side extends at the second angle from the second plane in the first and third directions to the fifth side, An electronic device in which the first angle and the second angle are different.

15. The electronic device according to claim 14, Each of the first, second, third, and fourth sides has a first portion that is a first height along the third direction, Each of the first, second, third, and fourth sides has a second height along the third direction, An electronic device in which the first height is approximately equal to the second height.

16. A method for manufacturing electronic devices, Attaching the die to the lead frame, The conductive terminals of the die are electrically coupled to the conductive leads, In order to form a package structure that surrounds the die and partially encloses the conductive lead, the molding process is carried out using a mold having a cavity sidewall with a draft angle greater than 15 degrees and 25 degrees or less than that, Methods that include...

17. The method according to claim 16, A method wherein the draft angle is 18 degrees or more and 22 degrees or less.

18. The method according to claim 16, A method wherein the mold includes separable first and second mold portions, the first mold portion having a first cavity having the draft angle, and the second mold portion having a second cavity having a second draft angle.

19. The method according to claim 18, A method wherein the draft angle is approximately equal to the second draft angle.

20. The method according to claim 18, A method wherein the first draft angle is 18 degrees or greater, the second draft angle is 22 degrees or less, the third draft angle is 18 degrees or greater, and the fourth draft angle is 22 degrees or less.

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