Mold half for transfer molding encapsulation of electronic components mounted on a carrier including a dual support surface, mold method, and method for using the same

Abstract

The present invention relates to a mold half for a transfer molding mold that encapsulates an electronic component mounted on a carrier, wherein the mold half for supporting the carrier has a contact surface comprising a primary carrier supporting surface and a secondary surface surrounding the primary carrier supporting surface, and the surrounding secondary surface is supported by a drive for adjusting the height of the secondary surface relative to the height of the primary carrier supporting surface. Such a mold half can be used for the transfer molding of an electronic component and relatively easily provides horizontal support for the carrier and compensates for any thickness variation of the carrier. The present invention also provides a mold having at least two mold half and a method for transfer molding encapsulation of an electronic component mounted on a carrier using such a mold.

Description

Technology Field

[0001] The present invention relates to a mold half for a transfer molding mold that encapsulates an electronic component mounted on a carrier. The present invention also relates to a transfer molding mold that encapsulates an electronic component mounted on a carrier, comprising such a mold half, as well as a method for transfer molding encapsulation of an electronic component mounted on a carrier using such a mold half or the mold. Background Technology

[0002] The encapsulation of electronic components mounted on a carrier, commonly referred to as a substrate, which delivers molding material into one or more mold cavities is a known technique. On an industrial scale, these electronic components are provided with encapsulation, typically in cured epoxy or resin, to which filler material is added. In the market, there is a trend toward the simultaneous transfer molding encapsulation of larger quantities of electronic components with varying dimensions and increasing precision requirements. This can also result in products having a heterogeneous combination of electronic components in a single package. Electronic components such as semiconductors (chips, although LEDs are also considered semiconductors in this regard) that are generally becoming smaller can be conceived herein. After the molding material is delivered, the collectively encapsulated electronic components are placed in an encapsulation section (package) that is positioned on one side of the carrier, but sometimes on two sides as well. The molding or encapsulation material often takes the form of a flat layer connected to the carrier, in which the electronic components are wholly or partially embedded / encapsulated. The carrier may consist of a lead frame, a wafer, a multilayer carrier partially made of epoxy (also referred to as a board or substrate, etc.), or other carrier structures.

[0003] During the transfer encapsulation of an electronic component mounted on a carrier, generally according to the prior art, an encapsulation press is used that has at least two mold halves, each having at least one or more mold cavities concave. After placing a carrier having the electronic component to be encapsulated between the mold halves, the mold halves are positioned toward each other, for example, to clamp the carrier. Typically, a heated liquid molding material is then supplied into the mold cavities by transfer molding. After at least partial (chemical) curing of the molding material in the mold cavities, the carrier having the encapsulated electronic component is removed from the transfer molding encapsulation press, and the encapsulated products can be separated from each other for further processing. A foil may be used during the encapsulation process, particularly to shield a portion of the electronic component to prevent the foil-covered portion of the electronic component from being covered by the molding material. Electronic components covered at least partially by molding material (electronic components that are not overmolded are referred to as "bare die" or "exposed die" products) can be used in various applications, such as various types of sensor components, ultra-low packages, or heat dissipating components. These transfer encapsulation methods are implemented on a large industrial scale and enable well-controlled encapsulation of electronic components. A problem with the conventional transfer encapsulation process of electronic components is that molding quality depends heavily on the accuracy of the carrier thickness, particularly when mold clamping occurs on the carrier. Variations in carrier thickness can lead to flash and / or bleed of the molding material (especially in the case of relatively thin carriers) or damage to the carrier due to increased clamping pressure of the mold on the carrier.

[0004] U.S. Patent No. 6,471,51 discloses a mold for press-molding a semiconductor device having a lower mold and an upper mold. The lower mold includes an outer die as well as an inner die, wherein the inner die carries the semiconductor device and a resin tablet, and the outer die surrounds the inner die in a manner that allows it to move up and down relative to the inner die. During operation, the press plate of the upper mold first engages with the outer die of the lower mold in an unlocked state to achieve precise positioning of the press plate of the upper mold and the inner die of the lower mold. After fixing the position of the press plate of the upper mold and melting the resin tablet, the press plate is pushed further toward the inner die of the lower mold while simultaneously lowering the outer die, thereby reducing the space formed by the lower die, the outer die, and the press plate.

[0005] The present invention aims to provide an alternative mold and method for transfer molding that encapsulates electronic components that are less sensitive to changes in carrier thickness and easier to control.

[0006] To provide a molding solution for transfer molding that encapsulates an electronic component mounted on a carrier and is less sensitive to changes in carrier thickness, the present invention provides a mold half for a transfer molding that encapsulates an electronic component mounted on a carrier, wherein the mold half for supporting the carrier has a contact surface, the contact surface includes a primary carrier support surface and a secondary surface surrounding the primary carrier support surface, and the secondary surface surrounding the carrier is supported by a drive for adjusting the height of the secondary surface relative to the height of the primary carrier support surface. Such a mold half may include a mold half base fixedly connected to the primary carrier support surface and adjustablely connected to the secondary surface surrounding the carrier via the height adjustment drive. Thus, the primary carrier support surface can be implemented as a rigid (and simple) structure that is relatively easy to provide a leveled support (a flat and even surface) for the carrier, and the displacement of the secondary surface can compensate for any change in the thickness of the carrier as described below in relation to the molding method according to the present invention. Additionally, the primary carrier support surface can be easily produced. In addition, the relative arrangement of the primary and secondary surfaces of the mold half can compensate for any changes caused by temperature variations in the mold half (e.g., changes in expansion and / or contraction due to temperature changes in the mold half). The primary carrier support surface and the secondary surface will typically be parallel. An additional advantage of this mold half is the enhanced flexibility provided during use. Thus, for example, the secondary surface can be lowered to the level of the primary carrier support surface or lowered to allow for easy cleaning of the primary carrier support surface (since the entire primary surface is easily accessible), and, for example, the primary carrier support surface can be inspected with grazing light (this type of inspection can also visualize very small particles of about 10 to 100 µm).Another advantage is that lowering the secondary surface can provide easy access to the side of the carrier positioned on the primary carrier support surface. This allows, for example, the molded carrier to be simply picked up. The mold according to the present invention also provides an opportunity to prevent relative tilting of the mold half at the moment of closing, particularly at the moment of double contact with the carrier. Relative tilting of the mold half during closing (even if very limited) can lead to uneven loading on the carrier, which can lead to a risk of carrier damage. By bringing the secondary surface into contact with the opposing mold before contacting the carrier, the opposing mold portion can be "guided" to a more parallel position (as opposed to a limited tilted relative position). In particular, actual developments in the market for wafers, which are increasingly used as carriers for electronic components to be molded, make the advantages of the present invention even more significant, as the primary support surface is stable and robust, enabling the necessary precise placement of the wafer. Furthermore, high accuracy in the ability to inspect small dust particles is highly welcome when processing high-sensitivity wafers.

[0007] The drive for height adjustment of the secondary surface relative to the height of the primary carrier support surface may be pressure (or load). With pressure-controlled height adjustment, the molding process can be controlled independently of the carrier thickness; and closure can be controlled by pressure instead of position. This makes the process more stable and limits the possibility of carrier damage (e.g., cracking) due to applied high pressure, as well as the possibility of leakage (e.g., flash, bleed) due to applied low pressure. As an alternative to pressure (load)-controlled height adjustment of the secondary surface, the height adjustment of the secondary surface may also be position-controlled. The present invention also enables closing the mold half first (where the secondary surface of the mold half does not absorb any closing force) when closing the carrier, and subsequently moving the secondary surface to the closed position to provide additional protection against leakage.

[0008] The drive for height adjustment of the secondary surface may include at least one movable wedge that can be displaced using a pneumatic or hydraulic cylinder, a spindle drive, a toothed and rack system, or any other type of precise linear drive. Using one or more wedges for height adjustment of the secondary surface enables the prevention of unwanted deformation of the secondary surface, in addition to accurately positioning the large support surface of the secondary surface. An additional advantage of using wedges is that they can carry a substantial load while requiring relatively limited force for displacement. In particular, but not exclusively, when wedges with smaller angles are applied, the wedges can be self-inhibitory, which not only makes adjustments difficult in process control but also helps further limit the possibility of carrier cracking. Pneumatic or hydraulic cylinders for wedge displacement provide the function of easy pressure-controlled closure of the secondary surface and are readily available as off-the-shelf products. As an alternative to using a wedge, a linear drive can also be directly coupled to a secondary surface so that the displacement direction of the secondary surface matches the drive system used (see also FIG. 2). In addition to the drive mentioned herein, other drives such as, for example, a spindle drive system, a rack and pinion wheel drive, etc. may also be used.

[0009] The secondary surface can also carry at least one guide for transfer molding the encapsulated material. This allows the secondary surface to be used for the placement of a so-called "top edge" molding material feeder. A top edge molding material feeder is a known technique used to bring molding material into a carrier, pass through the side of the carrier without the possibility of leakage, and also to keep the molding material from being placed on the boundary (rim / edge) of the carrier. The top edge molding material feeder of the prior art typically requires a separate top edge feed support, which can now be integrated with the secondary surface, making the configuration of the molding device simpler, more reliable, and cheaper.

[0010] In additional embodiments, the primary surface and the secondary surface may be at least movable between a position where the primary surface and the secondary surface are at the same level (or lower) and a position where the secondary surface is greater than the thickness of the carrier above the primary surface. The advantage of the primary surface and the secondary surface being at the same level or lower has already been mentioned (easy carrier access, ease of cleaning and inspection). It may be advantageous to provide a gasket between the primary surface and the secondary surface to prevent leakage of molding material between the joints of the primary surface and the secondary surface. Such a gasket can be further optimized by making it controllable (operable), for example, by selecting an inflatable gasket, so that it functions only as a gasket when sealing capacity is required. The use of a gasket or a controllable gasket is implemented to prevent leakage, which not only allows pressure to be applied in the molding cavity but also prevents contamination (dust-free) and, in certain embodiments, prevents the passage of (liquid) molding material.

[0011] The mold half may also include a measurement sensor for measuring the relative positions of the primary surface and the secondary surface. Measuring the relative positions of the primary surface and the secondary surface can be used as a measurement signal for the thickness of individual carriers processed in the mold half, and thus provides additional product information that is used, for example, as subsequent process steps and / or product-related information.

[0012] The present invention also provides a transfer molding mold for encapsulating electronic components mounted on a carrier, comprising at least two mold parts displaceable relative to each other, including a mold half portion and a counter clamping mold portion as described above, according to the present invention. At least one mold cavity is provided on the contact side of the at least one mold cavity, and the contact side of the counter clamping mold portion having at least one mold cavity is configured to be coupled to the carrier surrounding the electronic components to be encapsulated. With such a mold, the advantages described above with respect to the mold half portion according to the present invention can be realized. The counter mold half portion contacts the carrier so that the mold cavity mold is allocated around the electronic components to be encapsulated, and the clamping force of the mold half portion can be limited to a level where leakage (bleed and flash) is at least prevented; higher pressure is not required. A secondary support surface can be used to maintain the position of the carrier on the primary carrier support surface and for additional closure (second barrier) against leakage. A supply channel for molding material may also be provided on the contact side of the opposing clamping mold portion; thus, the molding material can be supplied over the top of the carrier where the opposing mold portion is clamped to the carrier. This transfer molding technique is also referred to as "top edge" molding.

[0013] In another embodiment of a transfer molding mold that encapsulates electronic components mounted on a carrier, a molding material supply portion (top edge) is provided between opposing clamping mold portions, and at least one clamping mold portion has an opening for holding the molding material supply portion at a clamped position of the opposing clamping mold portion. This molding material supply portion may be supported by a second support surface of a lower mold half portion. By proper support, and thus by proper placement of the second support surface, any excessive pressure on the carrier that could lead to carrier cracking (wafer cracking) can be successfully prevented.

[0014] The present invention also provides a method for transfer molding encapsulation of electronic components mounted on a carrier using a mold half portion according to the present invention and as described above, the method comprising: a) a step of placing a carrier on a primary surface of a carrier-supporting mold half portion such that the electronic components face a mold cavity, wherein a secondary support surface is located on the same side as the primary support surface and the electronic components carrying surface of the carrier; b) a step of moving the mold portions toward one another so that the mold cavity surrounds the electronic components to be encapsulated, thereby causing the mold portions to clamp the carrier between the primary support surface and the mold cavity concave contact side; c) a step of moving the secondary support surface toward the mold cavity concave contact side of the opposing clamping mold portion; d) a step of transferring a liquid molding material to the mold cavity through a supply channel on the mold cavity concave contact side; e) a step of curing the molding material at least partially; f) a step of moving the mold portions apart from one another; and g) a step of removing a carrier having molded electronic components from a primary support surface of a mold half portion supporting the carrier. After the mold half portion is moved apart, the secondary support surface may be moved below the surface carrying the electronic components of the carrier (i.e., moved further away from the opposing mold portion than the surface carrying the electronic components of the carrier). During step c), until a specific closing pressure level of the secondary support surface is reached, the secondary support surface may be moved toward the concave contact side of the mold cavity of the opposing mold portion. In this way, the molding process "predicts" the carrier thickness. This molding process is particularly suitable for transfer molding; a molding cavity is formed and subsequently, a liquid molding material is supplied to the molding cavity through a supply channel for the molding material, preferably toward the contact side of the opposing clamping mold portion.This process can be performed independently of the precise thickness of the carrier, which affects the result (quality of the molded electronic components), and the process is also more robust and stable to execute.

[0015] In the molding method according to the present invention, the position of a secondary support surface relative to a primary support surface can be registered and, for example, fed back to automatic process control. This information regarding the relative positions of the primary carrier support surface and the secondary surface can be used to provide information regarding the dimensions (thickness) of the carrier, and thus the provided measurement information forms an additional advantage of the present invention. Brief explanation of the drawing

[0016] The present invention will be further described based on the non-limiting and exemplary embodiments shown in the drawings below. Herein: FIG. 1 is a schematic exploded perspective view of a mold portion according to the present invention. FIG. 2 is a schematic exploded perspective view of an alternative embodiment of a mold part according to the present invention. FIGS. 3a to 3g are schematic diagrams illustrating subsequent steps of a molding method according to the present invention. FIG. 4 is a cross-sectional view of a mold schematically shown according to the present invention. FIG. 5 is a schematic diagram of the steps of an alternative (topmost edge) molding method according to the present invention. Specific details for implementing the invention

[0017] FIG. 1 shows a mold portion (1) for carrying a carrier (not shown in this figure) having electronic components, wherein the mold portion (1) has a primary carrier support surface (2) that is solidly integrated with the mold half-base (3). The primary carrier support surface (2) is surrounded by a secondary surface (4), and the secondary surface (4) is supported by a wedge (5). The height of the secondary surface (4) relative to the primary carrier support surface (2) can be adjusted by moving the wedge (5) according to arrow P1 (in a direction parallel to the primary carrier support surface (2) and the secondary surface (4). The side of the secondary surface (2) facing the wedge (5) is chamfered (6) to cooperate with the wedge (5).

[0018] An alternative mold part (10) is shown in FIG. 2. The mold part (10) has a primary carrier support surface (11) that is rigidly integrated with the mold half-base (12). The primary carrier support surface (11) is surrounded by a secondary surface (13), the secondary surface (13) is supported by a cylinder (14), and the cylinder (e.g., a hydraulic or pneumatic cylinder) is integrated into the mold half-base (12). By operating the cylinder (14) according to arrow P2 (in a direction perpendicular to the primary carrier support surface (2) and the secondary surface (4)), the height of the secondary surface (13) relative to the primary carrier support surface (11) can be adjusted.

[0019] FIG. 3a shows a mold half (20) having a primary carrier support surface (21) rigidly integrated with a mold half base (22). The primary carrier support surface (21) is surrounded by a secondary surface (23), and the secondary surface (23) is supported by a wedge (24) displaceable by an electric drive spindle (25). The secondary surface (23) is leveled with, for example, the primary carrier support surface (21) to enable easy access to the primary carrier support surface (21), for example, for cleaning and / or inspection purposes.

[0020] In FIG. 3b, the mold half (20) of FIG. 3a is shown again with the carrier (26) of the electronic component (27) placed on the primary carrier support surface (21). The secondary surface (23) is still at a lower position as shown in FIG. 3a.

[0021] In FIG. 3c, the second mold portion (28) (here, the upper mold portion) is closed according to arrow P3 on the carrier (26) so that a concave molding cavity (29) on the contact side (30) of the second mold (30) surrounds the electronic component (27) to be encapsulated.

[0022] In FIG. 3d, the secondary surface (23) is moved along arrow P4 with respect to the contact surface (30) of the second mold part (28) to further confine the carrier (26) having the electronic component (27). In the subsequent FIG. 3e, the molding material (31) is supplied to the molding cavity (29). After curing as shown in FIG. 3f, the second mold part (28) can be removed (moved away from the mold half (20) having the primary carrier support surface (21), thereby freeing the molded electronic component (32) on the carrier (26) from the second mold part (28).

[0023] In FIG. 3g, the secondary surface (23) is moved downward along with the spindle (25) drive wedge (24) according to arrow P5 to allow access to the side of the carrier (26), for example, allowing a gripper (33) to enter (see arrow P6) and remove the molded electronic component (32) on the carrier (26) from the primary carrier support surface (21).

[0024] FIG. 4 shows a cross-section of an additional alternative mold (40) having a mold base (41) and an integrated primary carrier support surface (42), and the integrated primary carrier support surface (42) is surrounded by a secondary surface (43). The height of the secondary surface (43) can be adjusted by moving the wedge (44, 45) (see arrows P8, P9) (see arrow P7). A gasket (48) is positioned between the base (46) of the secondary surface (43) and the base (47) of the primary carrier support surface (42) to prevent dust from passing through and to establish pressure on the carrier (49), thereby preventing any unexpected leakage of molding material. Additionally, as shown in this drawing, the rim (50) of the carrier (49) is round, and in the embodiment shown herein, the rim (50) is at a certain distance from the secondary surface (43), so that the gripper can grasp the carrier (49) even if the secondary surface (43) is at a higher position.

[0025] FIG. 5 illustrates a step of a folding processor, wherein a bottom mold half (20) having a primary carrier support surface (21) corresponds to the initiation of a bottom mold portion as shown in FIG. 3a through 3g. Since the bottom half (20) corresponds, the same reference numeral is also used for this part of the mold. Here, a second mold portion (50) having an opening (51) for holding an individually movable molding material supply portion (52) is different. This molding material supply portion (52) is also referred to as the "top edge." The molding material supply portion (52) is used to deliver molding material to the carrier (26), passing through the side of the carrier (26) without leakage problems while keeping the molding material from being on the edge of the carrier (26). For proper placement, the molding material supply portion (52) is moved toward the carrier (26) (arrow P 10 (Reference) It comes into contact with the carrier (26). The problem with this contact may be that the carrier (26) is damaged (cracked). An important advantage of the present invention is that the secondary surface (23) can be moved upward (by moving the wedge (24) as described herein in relation to FIG. 3a) so that the secondary surface (23) becomes somewhat horizontal with respect to the upper side of the carrier. After that, the secondary surface (23) is used as a support for the molding material supply unit (52), so the possibility of damage to the carrier (26) due to contact with the molding material supply unit (52) is now very limited.

Claims

Claim 1 A mold half for a transfer molding mold that encapsulates electronic components mounted on a carrier, wherein the mold half for supporting the carrier has a contact surface, said contact surface includes a primary carrier support surface and a secondary surface around said primary carrier support surface, said secondary surface around said secondary surface is supported by a drive for adjusting the height of said secondary surface with respect to the height of said primary carrier support surface, said drive for adjusting the height of said secondary surface includes a wedge supporting said secondary surface, said height of said secondary surface is adjusted by a horizontal displacement of said wedge. Claim 2 The mold half portion according to claim 1, wherein the mold half portion includes a mold half portion base, and the mold half portion base is stationarily connected to the primary carrier support surface and is adjustablely connected to the surrounding secondary surface through the height adjustment drive. Claim 3 A mold half portion according to claim 1 or 2, wherein the height adjustment drive of the secondary surface relative to the height of the primary carrier support surface is pressure or position controlled. Claim 4 delete Claim 5 A mold half portion according to claim 1 or 2, characterized in that the height adjustment drive of the secondary surface comprises at least one pneumatic or hydraulic cylinder. Claim 6 A mold half portion according to claim 1 or 2, wherein the secondary surface also carries at least one guide for encapsulating a material. Claim 7 A mold half portion according to claim 1 or 2, wherein the primary carrier support surface and the secondary surface are at least movable between a position where the primary carrier support surface and the secondary surface are at the same level and a position where the secondary surface is greater than or equal to the thickness of the carrier higher than the primary carrier support surface. Claim 8 A mold half portion according to claim 1 or 2, characterized in that a gasket is positioned between the primary carrier support surface and the secondary surface. Claim 9 A mold half portion according to claim 8, characterized in that the gasket between the primary carrier support surface and the secondary surface is an operable gasket. Claim 10 A mold half portion according to claim 1 or 2, characterized in that the mold half portion includes a measuring sensor for measuring the relative position of the primary carrier support surface and the secondary surface. Claim 11 A transfer molding mold for encapsulating electronic components mounted on a carrier, comprising at least two mold parts displaceable relative to each other, including a mold half portion and an opposing clamping mold portion according to claim 1 or 2. Claim 12 A transfer molding mold for encapsulating electronic components, characterized in that, in claim 11, at least one opposing clamping mold portion has at least one mold cavity concave on the contact side, and the contact side of the opposing clamping mold portion having the at least one mold cavity is configured to be coupled to the carrier surrounding the electronic components to be encapsulated. Claim 13 A transfer molding mold for encapsulating electronic components, characterized in that, in claim 12, the contact side of the opposing clamping mold portion also has a supply channel for molding material. Claim 14 A transfer molding mold for encapsulating electronic components, characterized in that, in claim 11, a molding material supply portion (topmost edge) is provided between the opposing clamping mold portions, and at least one of the clamping mold portions has an opening for holding the molding material supply portion at the clamped position of the opposing clamping mold portions. Claim 15 A method for transfer molding encapsulation of electronic components mounted on a carrier using a mold according to claim 11, comprising: a) placing a carrier on the primary carrier support surface of the carrier support mold half portion such that the electronic components face the mold cavity, wherein the secondary surface is located on the same side as the primary carrier support surface and the surface of the carrier carrying the electronic components; b) clamping the carrier between the primary carrier support surface and the mold cavity concave contact side by moving the mold portions toward each other so that the mold cavity surrounds the electronic components to be encapsulated; c) moving the secondary surface toward the mold cavity concave contact side of the opposing clamping mold portion through a horizontal displacement of the wedge supporting the secondary surface; d) transferring a liquid molding material to the mold cavity through a supply channel of the mold cavity concave contact side; and e) at least partially A method for encapsulation comprising: a step of curing; f) a step of moving the mold portions apart from each other; and g) a step of removing the carrier having molded electronic components from the primary carrier support surface of the mold half portion supporting the carrier. Claim 16 An encapsulation method according to claim 15, characterized in that, after moving the mold portions apart, the secondary surface is moved further away from the opposing clamping mold portion than the surface having the electronic components of the carrier. Claim 17 A method of encapsulation according to claim 15, characterized in that, during step c), the secondary surface is moved toward the mold cavity concave contact side of the opposing clamping mold part until a specific closing pressure level of the secondary surface is reached. Claim 18 A method for transfer molding encapsulation of electronic components mounted on a carrier using a mold half portion according to claim 15, characterized in that the position of the secondary surface relative to the primary carrier support surface is registered and fed back to automatic process control.

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