The present invention generally relates to an improved method for manufacturing encapsulated semiconductor devices. More specifically, the present invention relates to a method for facilitating singulation or segmentation of a strip-shaped array of encapsulated semiconductor integrated circuit (IC) devices into a plurality of discrete encapsulated IC devices.
Semiconductor devices, for example, integrated circuit (IC) devices, are typically fabricated in the form of small, thin, and thus fragile, dies or chips which are electrically connected to a lead frame or other mounting means via a plurality of very fine, fragile wires, and then protected from physical damage, environmentally-induced corrosion or degradation, etc., by means of an encapsulant material which surrounds the die or chip and associated lead frame or mounting. Referring to FIG. 1, which is a schematic plan view of an elongated device mounting strip for illustrating conventional large-scale manufacturing technology, the upper surface 1U of a common substrate 1, e.g., a flexible, elongated strip typically comprised of a polymeric material, e.g., an about 25 to about 150 xcexcm thick sheet or film of polyimide or other polymer-based flexible tape, includes a plurality of spaced-apart device mounting areas 2 (illustratively from about 4 to about 20 mm wide and from about 4 to about 20 mm long and spaced-apart from about 0.5 to about 3 mm) for mounting thereon a corresponding plurality of IC dies or chips 3, with each mounting area 2 including circuitry (not shown for illustrative simplicity) for providing electrical connection to the die or chip 3 mounted thereat. A plurality of symmetrically opposed pairs of slots 4A, 4B (illustratively from about 0.2 to about 2 mm wide) extending through substrate 1 from the upper surface 1U to the lower surface 1L thereof, with their respective facing termini 4TA, 4TB in close proximity (illustratively from about 1 to about 30 mm apart) are formed by cleanly pre-cutting through substrate 1 prior to mounting of die or chip 3, so as to substantially, but not completely, surround a respective device mounting area 2 at the periphery thereof, in order to facilitate segmentation of substrate 1 during singulation of the strip into a plurality of discrete encapsulated devices by reducing, e.g., minimizing, the amount of substrate 1 material to be removed. Referring now to the schematic, cross-sectional view of FIG. 2, to perform encapsulation, a bead 6 of liquid encapsulant, typically comprised of an epoxy-based material, is applied via a dispenser to the spaces 5 between the smaller periphery of each die or chip 3 and the larger periphery of each device mounting area 2, adjacent the inner edge of each of the pairs of slots 4A, 4B. However, in typical practice, the bead 6 of liquid encapsulant disadvantageously flows, aided by surface tension effects, etc., into slots 4A, 4B prior to hardening. Such encapsulant flow (also known as xe2x80x9cflashingxe2x80x9d) necessitates placement of a sheet 7, termed a xe2x80x9ccoverlay filmxe2x80x9d, on the lower surface 1L of substrate 1 in order to prevent encapsulant 6 which penetrates the substrate from adhering to any underlying mechanical support utilized during curing, transport, etc., thereby adding to process cost and complexity. After encapsulation, the strip is segmented, as by cutting through the substrate to remove the small amount of substrate 1 material between each of the pairs of facing termini 4TA, 4TB of each pair of slots 4A, 4B to thereby singulate the array of devices on the common strip into a plurality of discrete, encapsulated IC device packages, wherein the pre-cut pairs of opposing slots 4A, 4B facilitate segmentation by minimizing the amount of substrate 1 material required to be removed by cutting. However, the ease of singulation provided by the pre-cut slots 4A, 4B is either completely lost, or at least diminished, when the latter are filled, or even partially filled, with hardened encapsulant 6, as illustrated in FIG. 2.
Accordingly, there exists a need for improved methodology for reliable manufacture of encapsulated semiconductor devices, e.g., chip- or die-based IC devices, employing pre-cut flexible strip-shaped substrates, which methodology avoids the drawbacks attendant upon fabrication according to the above-described conventional manufacturing processing and effectively addresses and solves problems associated with segmentation of elongated strips of encapsulated semiconductor devices, as by cutting of pre-cut or pre-slotted flexible strips. Further, there exists a need for improved methodology for alleviating the above-described problems yet is fully compatible with the throughput requirements of mass-manufacturing techniques.
The present invention, wherein the pre-cut slots are formed by cutting through the flexible, strip-shaped substrate from the lower surface towards the upper surface thereof in a manner so as to form burrs or flaps which seal off, or at least substantially reduce the width of the slots at the upper surface of the strip, thereby substantially preventing, or at least minimizing, penetration (xe2x80x9cflashingxe2x80x9d) of liquid encapsulant into the slots, effectively addresses and solves the above-described problems attendant upon encapsulation and singulation processing of strip-shaped device arrays. Further, the methodology provided by the present invention provides a significant process simplification by eliminating the need for placement of the xe2x80x9ccoverlayxe2x80x9d sheet 7 over the lower surface 1L of the substrate 1 in order to prevent flow, and adhesion, etc., of the encapsulant 6 to underlying mechanical support surfaces. Finally, the inventive methodology is not limited to use with devices comprising semiconductor IC dies or chips, but rather enjoys diverse utility in the manufacture of all manner of encapsulated electrical devices and components.
An advantage of the present invention is an improved method of making an encapsulated device.
Another advantage of the present invention is an improved method of making an encapsulated semiconductor device utilizing a pre-cut flexible strip substrate.
Yet another advantage of the present invention is an improved method for performing segmentation processing of a strip-shaped array of encapsulated semiconductor devices to singulate the array into a plurality of discrete encapsulated devices.
Additional advantages and other features of the present invention will be set forth in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present invention. The advantages of the present invention may be realized and obtained as particularly pointed out in the appended claims.
According to one aspect of the present invention, the foregoing and other advantages are obtained in part by a method of manufacturing an encapsulated device, which method comprises the sequential steps of:
(a) providing a substrate including a pair of opposed upper and lower major surfaces;
(b) forming at least one slot extending through the substrate from the upper surface to the lower surface thereof, the at least one slot defining a device mounting area of the upper surface, the at least one slot extending substantially, but not completely, around the periphery of the device mounting area, the forming of the at least one slot comprising cutting the substrate such that burrs or flaps are formed at the upper surface thereof which seal off or at least substantially reduce the width of the at least one slot at the upper surface of the substrate;
(c) positioning a device on the upper surface of the substrate within the device mounting area, the periphery of the device being smaller than the periphery of the device mounting area; and
(d) applying a liquid encapsulant material in at least the space between the device periphery and the device mounting area periphery, wherein penetration of the liquid encapsulant into the at least one slot is substantially prevented, or at least minimized, by the presence of the burrs or flaps of the at least one slot at the upper surface of the substrate.
According to embodiments of the present invention, step (a) comprises providing a flexible substrate, e.g., an elongated, strip-shaped, polymer-based substrate; step (b) comprises forming the at least one slot, e.g., a pair of slots arranged in symmetrically opposed relation, by cutting through the substrate in the direction from the lower surface to the upper surface, e.g., by cutting the substrate utilizing a die and punch configured to form a burr or flap at the upper surface of the substrate.
According to further embodiments of the present invention, step (a) comprises providing a substrate including electrical circuitry on the upper surface thereof within the device mounting area; and step (c) comprises positioning an electrical device within the device mounting area and electrically connecting leads extending from the device to the electrical circuitry.
According to still further embodiments of the present invention, step (c) comprises providing a semiconductor device within the device mounting area, e.g., a semiconductor integrated circuit (IC) die or chip; and step (d) comprises applying a liquid encapsulant comprising a polymer-based or polymerizable material, e.g., an epoxy resin based material.
According to yet further embodiments of the present invention:
step (a) comprises providing an elongated, strip-shaped substrate including a plurality of spaced-apart device mounting areas arranged on the upper surface thereof, each mounting area including electrical circuitry;
step (b) comprises forming, for each device mounting area, at least one slot extending through the substrate from the upper surface to the lower surface thereof, the at least one slot substantially, but not completely, surrounding the periphery of the device mounting area, the forming of each slot comprising forming burrs or flaps at the upper surface of the substrate which seal off, or at least substantially reduce the width of each slot at the upper surface;
step (c) comprises positioning an electrical device, e.g., a semiconductor IC die or chip, within each device mounting area and electrically connecting leads extending therefrom to the electrical circuitry of the respective device mounting area; and
step (d) comprises applying a liquid encapsulant material, e.g., an epoxy resin-based material, in at least the space between the periphery of each device and the periphery of the respective device mounting area, wherein entry of encapsulant into each of the slots is substantially prevented, or at least minimized by the presence of the burrs or flaps at the upper surface of the substrate.
According to an embodiment of the present invention, the method comprises the further step of:
(e) segmenting the strip-shaped substrate by cutting the substrate in the spaces between adjacent mounting areas to singulate the strip into a plurality of discrete encapsulated devices.
According to another aspect of the present invention, a method of manufacturing at least one encapsulated semiconductor device comprises the sequential steps of:
(a) providing a flexible, elongated, strip-shaped substrate having a pair of opposed upper and lower major surfaces, the substrate including a plurality of spaced-apart device mounting areas arranged on the upper surface, each mounting area including electrical circuitry;
(b) forming, at each device mounting area, a pair of slots extending through the substrate from the upper surface to the lower surface thereof, the slots being arranged in symmetrically opposed relation so as to substantially, but not completely, surround the periphery of the device mounting area, the forming of the pair of slots comprising forming burrs or flaps at the upper surface of the substrate which seal off, or at least substantially reduce the width of each of the slots at the upper surface of the substrate;
(c) positioning a semiconductor device on the upper surface of the substrate within each device mounting area and electrically connecting leads extending therefrom to the electrical circuitry of the respective device mounting area, the periphery of the semiconductor device being smaller than the periphery of the device mounting area; and
(d) applying a liquid encapsulant in at least the space between the periphery of each semiconductor device and the periphery of the respective device mounting area, wherein entry of encapsulant into each of the slots is substantially prevented, or at least minimized, by the presence of the burrs or flaps at each of said slots at the upper surface of the substrate.
According to embodiments of the present invention, the method comprises the further step of:
(e) segmenting the strip-shaped substrate by cutting the substrate in the spaces between adjacent device mounting areas to singulate the strip into a plurality of discrete encapsulated semiconductor devices.
According to particular embodiments of the present invention:
step (a) comprises providing a polymer-based substrate;
step (b) comprises forming each pair of slots by cutting through the substrate in the direction from the lower surface to the upper surface thereof utilizing a die and punch configured to form a burr or flap at the upper surface;
step (c) comprises providing a semiconductor device comprising an integrated circuit (IC) die or chip; and
step (d) comprise applying a polymer-based or polymerizable material as the liquid encapsulant.
Additional advantages and aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein embodiments of the present invention are shown and described, simply by way of illustration of the best mode contemplated for practicing the present invention. As will be described, the present invention is capable of other and different embodiments, and its several details are susceptible of modification in various obvious respects, all without departing from the spirit of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as limitative.