EP0734590A1 - Integrated circuit package assembly including a window and methods of manufacturing - Google Patents

Integrated circuit package assembly including a window and methods of manufacturing

Info

Publication number
EP0734590A1
EP0734590A1 EP95938152A EP95938152A EP0734590A1 EP 0734590 A1 EP0734590 A1 EP 0734590A1 EP 95938152 A EP95938152 A EP 95938152A EP 95938152 A EP95938152 A EP 95938152A EP 0734590 A1 EP0734590 A1 EP 0734590A1
Authority
EP
European Patent Office
Prior art keywords
leadframe
package
die
opening
bonding
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95938152A
Other languages
German (de)
French (fr)
Inventor
Chillara Satya
Mostafazadeh Shahram
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
National Semiconductor Corp
Original Assignee
National Semiconductor Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by National Semiconductor Corp filed Critical National Semiconductor Corp
Publication of EP0734590A1 publication Critical patent/EP0734590A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/28—Encapsulations, e.g. encapsulating layers, coatings, e.g. for protection
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0203—Containers; Encapsulations, e.g. encapsulation of photodiodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/26—Layer connectors, e.g. plate connectors, solder or adhesive layers; Manufacturing methods related thereto
    • H01L2224/31—Structure, shape, material or disposition of the layer connectors after the connecting process
    • H01L2224/32—Structure, shape, material or disposition of the layer connectors after the connecting process of an individual layer connector
    • H01L2224/3201—Structure
    • H01L2224/32012—Structure relative to the bonding area, e.g. bond pad
    • H01L2224/32013—Structure relative to the bonding area, e.g. bond pad the layer connector being larger than the bonding area, e.g. bond pad
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/26—Layer connectors, e.g. plate connectors, solder or adhesive layers; Manufacturing methods related thereto
    • H01L2224/31—Structure, shape, material or disposition of the layer connectors after the connecting process
    • H01L2224/32—Structure, shape, material or disposition of the layer connectors after the connecting process of an individual layer connector
    • H01L2224/321—Disposition
    • H01L2224/32151—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/32221—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/32245—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/44—Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L2224/45—Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • H01L2224/45001—Core members of the connector
    • H01L2224/45099—Material
    • H01L2224/451—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof
    • H01L2224/45138—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof the principal constituent melting at a temperature of greater than or equal to 950°C and less than 1550°C
    • H01L2224/45144—Gold (Au) as principal constituent
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/481—Disposition
    • H01L2224/48151—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/48221—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/48245—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic
    • H01L2224/48247—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic connecting the wire to a bond pad of the item
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/73—Means for bonding being of different types provided for in two or more of groups H01L2224/10, H01L2224/18, H01L2224/26, H01L2224/34, H01L2224/42, H01L2224/50, H01L2224/63, H01L2224/71
    • H01L2224/732—Location after the connecting process
    • H01L2224/73251—Location after the connecting process on different surfaces
    • H01L2224/73265—Layer and wire connectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
    • H01L2924/151—Die mounting substrate
    • H01L2924/156—Material
    • H01L2924/157—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
    • H01L2924/15738—Material with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof the principal constituent melting at a temperature of greater than or equal to 950 C and less than 1550 C
    • H01L2924/15747—Copper [Cu] as principal constituent

Definitions

  • the present invention relates generally to an integrated circuit package assembly, and more particularly to an assembly wherein the assembly includes a light receiving window for exposure of a semiconductor die mounted within the package to a preselectable source of light.
  • ce ⁇ ain semiconductor dies which are mounted within an integrated circuit package assembly require exposure to a source of light at a point during their operational cycle.
  • semiconductor dies include, but are not limited to. EPROMs and light detecting ICs such as CCD imaging chips
  • the die must be enclosed in a sealed environment to protect it and us associated electrical connections from damage due to exposure to the outside environment while, at the same time, there is a need for exposure of the die l ⁇ light from a desired source external to the IC package
  • the package must therefore include a window for transmission of light from outside the package lo the die
  • FIG. 1 illustrates a prior art integrated circuit package assembh generally indicated by the reterence numeral 10.
  • the assembly incorporates a ceramic base 12. a ceramic lid 14 and a leadtrame 16 having a plurality oi leadframe leads 17
  • the leadlrame is sandwiched between upper and lower lavers ot sealing class respectively designated by reference numerals ⁇ _ and 20
  • the sealing glass bonds the ceramic lid to the ceramic base and seals the leadframe leads therebetween.
  • a light responsive semiconductor die 22 having a plurality of bonding pads 24 is bonded to ceramic base 12 by suitable bonding material 25.
  • Ceramic lid 14 includes a light transparent or at least translucent window 28 opposite semiconductor die 22 to permit the exposure of the die to a preselectable light source external to the package.
  • Leadframe leads 17 in the sealing glass layers 18 and 20 must be formed from a material, for example alloy 42, having surface characteristics which lend themselves to bonding with the sealing glass in order to properly hermetically seal the IC package.
  • Leadframes 17 typically produced for use in ceramic type packages are usually formed from such materials. These materials are more expensive to produce than some other materials, such as plated copper, which is used to make leadframes in a typical plastic IC package, but which is not compatible with sealing glass.
  • sealing a leadframe in a typical prior art plastic package is easily accomplished using a less expensive plated copper leadframe, while maintaining excellent bonding characteristics between the leadframe and the plastic.
  • the ceramic lid and base are themselves expensive to produce in comparison to, for example, plastic typically used in packages which do not require a ligh' receiving window Ceramic materials also tend to be brittle in nature and therefore significant losses are incurred due to chipping and cracking of the ceramic base and lid, further increasing the cost of manufacturing Problems due to the method of sealing the ceramic package are also encountered.
  • Package 10 is sealed by the sealing glass layers in a heating procedure during the assembly of the package. Sealing glass layers 18 and 20, and therefore the entire IC package assembly, are exposed to high temperatures to melt the sealing glass sufficiently in order to cause the glass to flow between leadframe leads 17 and bond ceramic base 12 to ceramic lid 14. A temperature of 450 degrees C for approximately ten minutes is required to perform this procedure.
  • Attrition of some of the IC assemblies is caused during the heating procedure due to splashing of the glass onto the semiconductor die.
  • Glass on the die may prevent proper operation of the die during required exposure to a light source, for example, an EPROM die can be rendered unerasable due to sealing glass on the die.
  • Contamination of the die with material from within the sealing furnace is another problem encountered during the heating procedure. This contamination is usually comprised of iron and it, in a similar fashion to glass splashing, may also prevent proper operation of the die when exposed to a light source, rendering the die unusable.
  • the heating procedure also causes problems in relation to bonding wires 26.
  • Gold bonding wires are typically used in IC packages, but due to exposure of the bonding wires to the high temperature involved during the heating procedure, gold wires cannot be used since they exhibit a propensity for disconnection when exposed to high temperature. Therefore, aluminum bonding wires must be used, since they are less sensitive to heat, but an additional problem is created in that aluminum bonding wires are more difficult to efficiently bond as compared to gold bonding wires.
  • the heating procedure required in the production of the ceramic package by introducing the need for aluminum bonding wires causes increased production costs.
  • the sealing glass is used to seal the leadframe leads and fills the spaces between adjacent leads. Since the sealing glass is positioned between the leads it has a direct influence upon the capacitance of the assembly.
  • the sealing glass has a dielectric constant of approximately 12.5, which is approximately three times the dielectric constant of the plastic used in typical plastic IC packages which do not include a window. Capacitance is directly proportional to dielectric constant and therefore the inter-lead capacitance produced when sealing glass is disposed between the leads is far greater than that produced when plastic is placed between the leads. The speed performance of the ceramic package is therefore limited by the sealing glass.
  • FIG. 2 which is taken from Patent 4,663,833 illustrates such a package assembly generally indicated by the reference numeral 30.
  • the assembly includes a leadframe 31.
  • the package is made up of a number of plastic components including: a leadframe supporting member 32 and an outer package 34 which is molded around leadframe supporting member 32.
  • a light receiving window 36 is affixed in outer package 34 opposite a light responsive semiconductor die 37.
  • the method by which the IC package assembly of Figure 2 is produced can be considered relatively complex in comparison with production steps for typical windowless plastic IC packages.
  • Leadframe 31 is positioned upon leadframe supporting member 32.
  • a precise molding operation is then carried out wherein the outer package 34 is molded around the leadframe and the leadframe supporting member.
  • Recesses 42 are formed below the leadframe supporting member by positioning pins (not shown) used in the molding procedure.
  • These recesses constitute a disadvantage in that they provide a path by which moisture may seep into the package.
  • the patent suggests that the additional step of filling recesses 38 with an epoxy resin should be taken.
  • the prior art assembly shown in Figure 2 has several advantages over the prior art assembly of Figure 1.
  • the assembly of Figure 2 is less expensive to produce, since it includes a plastic package rather than a ceramic package.
  • the heating procedure required in the method of producing the ceramic package used in the assembly shown in Figure 1 is avoided.
  • the method used to produce the plastic package shown in Figure 2 is complex and the package thereby produced is correspondingly complex and expensive in comparison to a typical windowless plastic IC package.
  • the plastic package of Figure 2 also includes an inherent disadvantage, as discussed above, due to the additional recesses formed below the leadframe supporting member.
  • IC package including a light receiving window for housing a semiconductor die requiring exposure to a light source during its operational cycle.
  • the present invention provides such a package and discloses unique method of making the package.
  • integrated circuit package assemblies which include a light receiving window and methods of producing the assemblies are herein disclosed. These assemblies, like the assembly illustrated in Figure 2, include a package having a light receiving window.
  • a leadframe is supported in a molded package.
  • the leadframe includes top and bottom surfaces, a die support section, and a plurality of leadframe leads, wherein each leadframe lead includes a support portion and a bonding portion.
  • the package is comprised of two independent but ultimately confronting sections.
  • One section is bonded and directly connected to at least the upper surface of the support portion of the leadframe leads and the other section is bonded and directly connected to at least the bottom surface of the support portions of the leadframe leads, such that the package material surrounds the bonding portions of the leadframe leads and the leadframe is sandwiched between and held in place by the two sections.
  • the package defines an internal opening above the upper surface of the die support section.
  • a semiconductor die having a plurality of bonding pads is bonded to the die support section of the leadframe within the integral opening.
  • a plurality of bonding wires electrically interconnect the bonding pads on the die to the bonding portions of the leadframe leads.
  • a light transmitting material is supported in the integral opening to form a light receiving window in the package.
  • a second embodiment of the present invention is identical to the first embodiment with the exception of the package.
  • the package in the second embodiment of the invention consists of a single annular shaped unitary body which is molded onto the support portions of the leadframe leads around the die support section whereby to define opposing top and bottom openings on opposite sides of the die support section for gaining access to the die support section.
  • the annular body completely encapsulates and seals therein the support portions of the leadframe leads
  • the bottom opening is sealed by a suitable means which may include, but is not limited to epoxy resin.
  • the top opening is ultimately closed off by means of a light transmitting window.
  • An integrated circuit package assembly including a package having a light receiving window, is manufactured by: providing a leadframe having top and bottom opposing surfaces, a die support section and a plurality of leadframe leads; molding an upper plastic package section to the top surface of the leadframe so as to define a light receiving window opening within the upper section such that the die support section and portions of said leadframe leads remain exposed through the window opening; molding a lower plastic package section to the bottom surface of the leadframe opposite the upper section with the leadframe leads in place therebetween, whereby to seal the leadframe leads, the upper, and the lower sections together; bonding a semiconductor die, through the window opening, to the die support section, the die including a plurality of bonding pads; electrically interconnecting, through the window opening, an array of bonding wires from the bonding pads on the semiconductor die to the exposed portion of the leadframe leads; and finally, sealing a light transmitting material in the window opening to
  • An integrated circuit assembly including a package having a light receiving window, is manufactured by: providing a leadframe including top and bottom opposing surfaces, a die support section and a plurality of leadframe leads, wherein each respective leadframe lead includes a support portion and a bonding portion; molding a package including top and bottom opposing surfaces around the support portions of the leadframe leads to seal the support portions of the leads within the package itself and to define respective opposing openings on opposite sides of the support section of the leadframe such that the die support section and the bonding portions of the leadframe leads are accessible through the openings and such that the leadframe is supported by the support portions of the leadframe leads; sealing the opening in the bottom surface of the package with suitable means; bonding, through the opening in the top surface of the package, the semiconductor die to the die support section; electrically interconnecting, through the opening in the top surface of the package, an array of bonding wires from the bonding pads on the semiconductor die to the exposed portion of the leadframe leads; and finally, sealing the opening in
  • FIGURE 1 is a cross-sectional elevational illustration of a ceramic package integrated circuit assembly according to the prior art
  • FIGURE 2 is a cross-sectional elevational illustration of a plastic package integrated circuit assembly according to the prior art
  • FIGURE 3A is a cross-sectional view, in elevation, illustrating a first embodiment of an integrated circuit package assembly manufactured in accordance with a first method of the present invention
  • FIGURE 3B is a plan view of the assembly of Figure 3A
  • FIGURES 4A through 4E illustrate the first method of manufacturing the IC package assembly as shown in Figures 3 A and 3B,
  • FIGURE 5A is a cross-sectional view, in elevation illustrating a second embodiment of an integrated circuit package assembly manufactured in accordance with a second method of the present invention
  • FIGURE 5B is a plan view of the assembly of Figure 5A.
  • FIGURES 6A through 6D illustrate the second method of manufacturing the IC package assembly as shown in Figures 5A and 5B.
  • FIGS 3A and 3B illustrate an integrated circuit package assembly manufactured in accordance with a first embodiment of the present invention and generally designated by reference numeral 50.
  • the assembly includes a leadframe 52 having a top surface 54, a bottom surface 56, a die support section 58, and a plurality of leadframe leads 60.
  • Each respective leadframe lead 60 includes an inner bonding portion 60a, an intermediate support portion 60b and an outer portion 60c.
  • This leadframe is typical of leadframes used within plastic packages of the prior art and may be formed of, for example, copper or plated copper material.
  • the assembly includes a package 62 consisting essentially of an upper section 64 and a lower section 66.
  • Upper section 64 is molded directly onto at least the top surface of support portions 60b of the leadframe leads and lower section 66 is molded directly onto a portion of bottom surface 56 of the leadframe so that the molding material is bonded to the bottom surface of die support section 58 and support portions 60b of the leadframe leads.
  • the molding material fills the spaces 68, shown in Figure 3B, defined between the respective leadframe leads to completely surround support portions 60b of the leads and seal them within the molding material in the completed assembly.
  • the leadframe is thereby sandwiched between and held in place by the upper and lower sections and supported in place therebetween.
  • the leadframe lead's outer portions 60c extend outside the package for connection to external components.
  • upper section 64 of package 62 defines an integral opening 70 above and around die support section 58.
  • Inner bonding portions 60a of the leadframe leads extend inwardly into opening 70 around die support section 58 for electrical connection thereto.
  • a semiconductor die 72 which is responsive to light, for example an EPROM, is bonded by suitable means, well known in the art, to the upper surface of die support section 58.
  • the die includes a plurality of bonding pads 74 electrically interconnected to respective ones of inner bonding portions 60a of the leadframe leads by a plurality of bonding wires 76.
  • a light receiving window 78 is supported and fixed in opening 70 by suitable means which may include, as shown in Figure 3A, an optional downwardly recessed step portion 80.
  • the window may be comprised of any suitable light transmitting material which, for example, may include translucent alumina.
  • the window is held in place by suitable adhesive means, which is well known in the art, applied to the step portion.
  • Figures 4A through 4E illustrate a first method of manufacturing the assembly as shown in Figures 3A and 3B, in accordance with the present invention. It is emphasized here that the order in which the various operations of the first method are performed is critical only to the extent that the final assembly produced is in accordance with the assembly as shown and described in Figures 3A and 3B.
  • the leadframe 52 is provided, as previously described.
  • the leadframe is positioned on a surface 79 against a first mold 81 having a cavity 82 appropriate for forming upper section 64 as specifically illustrated in Figure 4A.
  • a clamp 84 holds the leadframe in place and covers die support section 58 and inner bonding portions 60a of the leadframe leads to keep these areas clean during the molding operation to follow.
  • Suitable and readily providable molding material is injected into cavity 82 and upper section 64 is formed.
  • the upper section is molded to the top surface of leadframe 52 such that support portions 60b of the leadframe leads are bonded to the upper section.
  • the clamp is specially designed to allow the flow of molding material into specific areas, for example, molding material is allowed to flow into the spaces between support portions 60b of the leadframe leads and around the die support section.
  • Clamp 84 also keeps at least the upper surface of the die support section and the upper surface of the inner bonding portions of the leadframe leads free of molding material. Opening 70 in the upper section is formed by the clamp. If it is so desired, step portion 80 around opening 70 may be formed during the molding operation by appropriate shaping of the clamp or mold. In this case the mold is shown forming the step portion.
  • Molding of lower section 66 of the package is accomplished by placing the assembly shown in Figure 4A into a second mold 86, as shown in Figure 4B.
  • the second mold defines a cavity 88 appropriately shaped to form the desired outline of the lower section.
  • Clamp 84 which was used to mold the upper section of the package, may be left in position while the lower section of the package is molded.
  • lower section 66 of the package is molded by injection of a suitable molding material into cavity 88.
  • the molding process is carried out in a manner which integrally bonds the lower section to the upper section of the package and seals the support portions of the leadframe leads between the sections whereby the leadframe is supported. Note specifically that the top surfaces of support section 58 and leadframe lead portions 60a are protected against the flow of molding material by clamp 84 during formation of lower section 66, thereby insuring that these surfaces remain clean.
  • semiconductor die 72 may at this point be bonded to die support section 58 of the leadframe through opening 70, by means well known in the art. Since the molding operation for each section has been previously accomplished, problems with deposition of contaminants upon the die from the molding operations are avoided by this method.
  • bonding wires 76 are interconnected from bonding pads 74 on the die to respective inner bonding portions 60a of the leadframe leads through opening 70.
  • light receiving window 78 is properly sized to be received in opening 70.
  • the window is adhesively attached to step portion 13
  • a second embodiment of an integrated circuit assembly manufactured in accordance with a second method of the present invention is generally designated by reference numeral 100.
  • the assembly includes a leadframe 102 manufactured for use with the present invention.
  • the leadframe includes a top surface 104, a bottom surface 106, a die support section 108, and a plurality of leadframe leads 1 10.
  • Each respective leadframe lead 1 10 includes an inner bonding portion 110a, an intermediate support portion 110b and an outer portion 110c.
  • This leadframe is typical of leadframes used within windowless plastic packages of the prior art, in the same manner as leadframe 52.
  • the assembly includes a package 1 12 which is molded directly onto support portions 1 10b of the leadframe leads.
  • the support portions are entirely encapsulated in molding material.
  • Package 1 12 forms an annular body extending outwardly from top surface 104 and bottom surface 106 of the leadframe, surrounding die support section 108 of the leadframe to support the leadframe and define opposing top and bottom openings 1 14 and 1 16 respectively.
  • Bottom opening 1 16 is sealed by a suitable means 1 17, well known in the art, which may include, but is not limited to, epoxy resin.
  • inner bonding portions 1 10a of the leadframe leads extend inwardly from package 1 12 toward die support section 108 for electrical connection thereto and outer portions 1 10c extend externally beyond package 1 12 for connection to external components.
  • a semiconductor die 1 18, which is responsive to light, for example an EPROM, is bonded by suitable means, well known in the art, to the upper surface of die support section 108.
  • the die includes a plurality of bonding pads 120 electrically interconnected to respective ones of bonding portions 14
  • a light receiving window 124 is supported on the package and seals opening 1 14 by suitable means which may include, as shown in Figure 5 A, a downwardly recessed step portion 126 around the perimeter of the opening.
  • the window may be comprised of any suitable light transmitting material examples of which may include glass and translucent alumina.
  • the window is held in place by suitable adhesive means, which is well known in the art, applied to the step portion. Any method may be used to affix window 124 to the package within the scope of the invention, provided that a seal is attained between the package and the window. It is also noted that, as in the first embodiment of the invention, step portion 126 is not a requirement of the invention as claimed.
  • FIG. 6A through 6E A second method of manufacturing an integrated circuit package assembly, in accordance with the present invention, is illustrated in Figures 6A through 6E
  • This method produces an integrated circuit assembly including a light receiving window in accordance with the second embodiment of the present invention, as described immediately above in conjunction with Figures 5A and 5B. It is again emphasized here that the order in which some of the various operations of the second method are performed are critical only to the extent that the final assembly produced is in accordance with the assembly as shown in Figures 5A and 5B and described herein.
  • the leadframe 102 is provided, as previously described
  • the leadframe is placed in a mold 140 comprised of upper and lower mold pieces 140a and 140b and clamped in place by a pair of opposing upper and lower lamps 142 and 144 respectively.
  • Mold 140 along with the upper and lower clamps form an annular cavity 146 appropriately shaped to the desired outline of package 1 12 Suitable molding material is infected into cavity 146 to form package 1 12 so that the package is molded onto the support portions of the leadframe as described above
  • upper and lower clamps 142 and 144 are removed and the assembly is removed from upper and lower mold pieces 140a and 140b
  • Top opening 1 14 is defined by upper clamp 142 and bottom opening 116 is defined by lower clamp 122.
  • Molding with the clamps in place keeps die support section 108 and bonding portions 1 10a of the leadframe leads free of the molding material. Access to the bonding portions and the die support section is gained through top opening 1 14 in the package.
  • bottom opening 1 16 in the package is sealed by suitable means 1 17. Any means of sealing bottom opening 116 may be used provided that a hermetic seal of the opening is attained.
  • Semiconductor die 1 18 is then bonded, as depicted in Figure 6C, by means well known in the art, to die support section 108. The bonding is accomplished through top opening 1 14, in accordance with the method as claimed.
  • Bonding wires 122 are then electrically connected from respective ones of bonding pads 120 on the semiconductor die to respective ones of bonding portions 1 10a of the leadframe leads. Electrical interconnection of the bonding wires is, like the bonding of the die to the support section, accomplished through top opening 1 14 of package 1 12.
  • step portion 126 with adhesive means applied thereto are only one of many possible means by which the window may be affixed to seal the opening.

Abstract

An integrated circuit package assembly is disclosed herein. The assembly includes a leadframe (52) having a plurality of leadframe leads (60). A light responsive semiconductor die (72) is supported on the leadframe. A package is molded directly onto a portion of the leadframe to define an opening integral with the package for a light receiving window (78) through which the semiconductor die may be illuminated by a preselectable light source. In a first method of the invention, the package is molded to the leadframe in two separate sections with the window opening defined in one of the sections during molding. In a second method of the invention, the package is molded to the leadframe in one operation to define the window opening. In both methods the semiconductor die is bonded to the leadframe and electrically interconnected to the leadframe leads through the window opening in the package. The window opening is sealed by a suitable light transmitting material to comprise a light receiving window.

Description

INTEGRATED CIRCUIT PACKAGE ASSEMBLY
INCLUDING A WINDOW AND METHODS OF
MANUFACTURING
BACKGROUND OF THE INVENTION
The present invention relates generally to an integrated circuit package assembly, and more particularly to an assembly wherein the assembly includes a light receiving window for exposure of a semiconductor die mounted within the package to a preselectable source of light.
In the field of integrated circuits, ceπain semiconductor dies which are mounted within an integrated circuit package assembly require exposure to a source of light at a point during their operational cycle. Examples of these types of semiconductor dies include, but are not limited to. EPROMs and light detecting ICs such as CCD imaging chips The die must be enclosed in a sealed environment to protect it and us associated electrical connections from damage due to exposure to the outside environment while, at the same time, there is a need for exposure of the die lυ light from a desired source external to the IC package The package must therefore include a window for transmission of light from outside the package lo the die
In the prior art the die w as typically enclosed within a package including a ceramic base and lid. Figure I illustrates a prior art integrated circuit package assembh generally indicated by the reterence numeral 10. The assembly incorporates a ceramic base 12. a ceramic lid 14 and a leadtrame 16 having a plurality oi leadframe leads 17 The leadlrame is sandwiched between upper and lower lavers ot sealing class respectively designated by reference numerals \ _ and 20 The sealing glass bonds the ceramic lid to the ceramic base and seals the leadframe leads therebetween. A light responsive semiconductor die 22 having a plurality of bonding pads 24 is bonded to ceramic base 12 by suitable bonding material 25. A plurality of bonding wires 26 electrically interconnect leadframe leads 17 to bonding pads 24 on the die. Ceramic lid 14 includes a light transparent or at least translucent window 28 opposite semiconductor die 22 to permit the exposure of the die to a preselectable light source external to the package.
Although the prior art assembly of Figure 1 does allow for exposure of the semiconductor die to a light source through the window, due to the method of fabrication of the assembly and the materials used therein, difficulties have been encountered which prohibitively increase the cost of the package, as will be described below.
One problem encountered involves sealing leadframe leads 17 in the sealing glass layers 18 and 20. Leadframe leads 17 must be formed from a material, for example alloy 42, having surface characteristics which lend themselves to bonding with the sealing glass in order to properly hermetically seal the IC package. Leadframes 17 typically produced for use in ceramic type packages are usually formed from such materials. These materials are more expensive to produce than some other materials, such as plated copper, which is used to make leadframes in a typical plastic IC package, but which is not compatible with sealing glass. In comparison, sealing a leadframe in a typical prior art plastic package is easily accomplished using a less expensive plated copper leadframe, while maintaining excellent bonding characteristics between the leadframe and the plastic.
The ceramic lid and base are themselves expensive to produce in comparison to, for example, plastic typically used in packages which do not require a ligh' receiving window Ceramic materials also tend to be brittle in nature and therefore significant losses are incurred due to chipping and cracking of the ceramic base and lid, further increasing the cost of manufacturing Problems due to the method of sealing the ceramic package are also encountered. Package 10 is sealed by the sealing glass layers in a heating procedure during the assembly of the package. Sealing glass layers 18 and 20, and therefore the entire IC package assembly, are exposed to high temperatures to melt the sealing glass sufficiently in order to cause the glass to flow between leadframe leads 17 and bond ceramic base 12 to ceramic lid 14. A temperature of 450 degrees C for approximately ten minutes is required to perform this procedure. Attrition of some of the IC assemblies is caused during the heating procedure due to splashing of the glass onto the semiconductor die. Glass on the die may prevent proper operation of the die during required exposure to a light source, for example, an EPROM die can be rendered unerasable due to sealing glass on the die. Contamination of the die with material from within the sealing furnace is another problem encountered during the heating procedure. This contamination is usually comprised of iron and it, in a similar fashion to glass splashing, may also prevent proper operation of the die when exposed to a light source, rendering the die unusable.
The heating procedure also causes problems in relation to bonding wires 26. Gold bonding wires are typically used in IC packages, but due to exposure of the bonding wires to the high temperature involved during the heating procedure, gold wires cannot be used since they exhibit a propensity for disconnection when exposed to high temperature. Therefore, aluminum bonding wires must be used, since they are less sensitive to heat, but an additional problem is created in that aluminum bonding wires are more difficult to efficiently bond as compared to gold bonding wires. Thus, the heating procedure required in the production of the ceramic package by introducing the need for aluminum bonding wires causes increased production costs.
An additional concern arises regarding the electrical performance of a ceramic package of the type described above. In an IC package the capacitance between leads must be held to an absolute minimum since this capacitance is directly related to the speed at which the assembly is capable of operating. In this prior art ceramic package. the sealing glass is used to seal the leadframe leads and fills the spaces between adjacent leads. Since the sealing glass is positioned between the leads it has a direct influence upon the capacitance of the assembly. The sealing glass has a dielectric constant of approximately 12.5, which is approximately three times the dielectric constant of the plastic used in typical plastic IC packages which do not include a window. Capacitance is directly proportional to dielectric constant and therefore the inter-lead capacitance produced when sealing glass is disposed between the leads is far greater than that produced when plastic is placed between the leads. The speed performance of the ceramic package is therefore limited by the sealing glass.
Most IC packages having a light transmitting window have been produced using ceramic packages, as discussed above. However, it has been suggested, for example, in United States Patent 4,663,833 to use a plastic package. Figure 2, which is taken from Patent 4,663,833, illustrates such a package assembly generally indicated by the reference numeral 30. The assembly includes a leadframe 31. The package is made up of a number of plastic components including: a leadframe supporting member 32 and an outer package 34 which is molded around leadframe supporting member 32. A light receiving window 36 is affixed in outer package 34 opposite a light responsive semiconductor die 37.
The method by which the IC package assembly of Figure 2 is produced can be considered relatively complex in comparison with production steps for typical windowless plastic IC packages. Leadframe 31 is positioned upon leadframe supporting member 32. A precise molding operation is then carried out wherein the outer package 34 is molded around the leadframe and the leadframe supporting member. Recesses 42 are formed below the leadframe supporting member by positioning pins (not shown) used in the molding procedure. These recesses constitute a disadvantage in that they provide a path by which moisture may seep into the package. The patent suggests that the additional step of filling recesses 38 with an epoxy resin should be taken. The prior art assembly shown in Figure 2 has several advantages over the prior art assembly of Figure 1. The assembly of Figure 2 is less expensive to produce, since it includes a plastic package rather than a ceramic package. Also, the heating procedure required in the method of producing the ceramic package used in the assembly shown in Figure 1 is avoided. Nevertheless, the method used to produce the plastic package shown in Figure 2 is complex and the package thereby produced is correspondingly complex and expensive in comparison to a typical windowless plastic IC package. The plastic package of Figure 2 also includes an inherent disadvantage, as discussed above, due to the additional recesses formed below the leadframe supporting member.
It is desirable, in view of the prior art, to produce an economical and yet reliable
IC package including a light receiving window for housing a semiconductor die requiring exposure to a light source during its operational cycle. The present invention, as will be described hereinafter, provides such a package and discloses unique method of making the package.
SUMMARY OF THE INVENTION
As will be described in more detail hereinafter, integrated circuit package assemblies which include a light receiving window and methods of producing the assemblies are herein disclosed. These assemblies, like the assembly illustrated in Figure 2, include a package having a light receiving window. However, in accordance with a first embodiment of the present invention, a leadframe is supported in a molded package. The leadframe includes top and bottom surfaces, a die support section, and a plurality of leadframe leads, wherein each leadframe lead includes a support portion and a bonding portion. The package is comprised of two independent but ultimately confronting sections. One section is bonded and directly connected to at least the upper surface of the support portion of the leadframe leads and the other section is bonded and directly connected to at least the bottom surface of the support portions of the leadframe leads, such that the package material surrounds the bonding portions of the leadframe leads and the leadframe is sandwiched between and held in place by the two sections. The package defines an internal opening above the upper surface of the die support section. A semiconductor die having a plurality of bonding pads is bonded to the die support section of the leadframe within the integral opening. A plurality of bonding wires electrically interconnect the bonding pads on the die to the bonding portions of the leadframe leads. Finally, a light transmitting material is supported in the integral opening to form a light receiving window in the package.
A second embodiment of the present invention is identical to the first embodiment with the exception of the package. The package in the second embodiment of the invention consists of a single annular shaped unitary body which is molded onto the support portions of the leadframe leads around the die support section whereby to define opposing top and bottom openings on opposite sides of the die support section for gaining access to the die support section. The annular body completely encapsulates and seals therein the support portions of the leadframe leads The bottom opening is sealed by a suitable means which may include, but is not limited to epoxy resin. The top opening is ultimately closed off by means of a light transmitting window.
Methods for producing the above described embodiments of the invention are also disclosed hereinafter. An integrated circuit package assembly, according to the first embodiment of the present invention, including a package having a light receiving window, is manufactured by: providing a leadframe having top and bottom opposing surfaces, a die support section and a plurality of leadframe leads; molding an upper plastic package section to the top surface of the leadframe so as to define a light receiving window opening within the upper section such that the die support section and portions of said leadframe leads remain exposed through the window opening; molding a lower plastic package section to the bottom surface of the leadframe opposite the upper section with the leadframe leads in place therebetween, whereby to seal the leadframe leads, the upper, and the lower sections together; bonding a semiconductor die, through the window opening, to the die support section, the die including a plurality of bonding pads; electrically interconnecting, through the window opening, an array of bonding wires from the bonding pads on the semiconductor die to the exposed portion of the leadframe leads; and finally, sealing a light transmitting material in the window opening to form a light receiving window.
An integrated circuit assembly, according to the second embodiment of the present invention, including a package having a light receiving window, is manufactured by: providing a leadframe including top and bottom opposing surfaces, a die support section and a plurality of leadframe leads, wherein each respective leadframe lead includes a support portion and a bonding portion; molding a package including top and bottom opposing surfaces around the support portions of the leadframe leads to seal the support portions of the leads within the package itself and to define respective opposing openings on opposite sides of the support section of the leadframe such that the die support section and the bonding portions of the leadframe leads are accessible through the openings and such that the leadframe is supported by the support portions of the leadframe leads; sealing the opening in the bottom surface of the package with suitable means; bonding, through the opening in the top surface of the package, the semiconductor die to the die support section; electrically interconnecting, through the opening in the top surface of the package, an array of bonding wires from the bonding pads on the semiconductor die to the exposed portion of the leadframe leads; and finally, sealing the opening in the top surface of the package with a light transmitting material to form a light receiving window.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the present invention may best be understood by reference to the following detailed description of the presently preferred embodiments together with the accompanying drawings in which:
FIGURE 1 is a cross-sectional elevational illustration of a ceramic package integrated circuit assembly according to the prior art,
FIGURE 2 is a cross-sectional elevational illustration of a plastic package integrated circuit assembly according to the prior art,
FIGURE 3A is a cross-sectional view, in elevation, illustrating a first embodiment of an integrated circuit package assembly manufactured in accordance with a first method of the present invention,
FIGURE 3B is a plan view of the assembly of Figure 3A,
FIGURES 4A through 4E illustrate the first method of manufacturing the IC package assembly as shown in Figures 3 A and 3B,
FIGURE 5A is a cross-sectional view, in elevation illustrating a second embodiment of an integrated circuit package assembly manufactured in accordance with a second method of the present invention,
FIGURE 5B is a plan view of the assembly of Figure 5A, and
FIGURES 6A through 6D illustrate the second method of manufacturing the IC package assembly as shown in Figures 5A and 5B. DETAILED DESCRIPTION OF THE INVENTION
Methods for manufacturing the integrated circuit assemblies disclosed herein and the assemblies thereby produced will hereinafter be described in detail. Having described Figures 1 and 2 previously, attention is immediately directed to Figures 3A and 3B which illustrate an integrated circuit package assembly manufactured in accordance with a first embodiment of the present invention and generally designated by reference numeral 50. The assembly includes a leadframe 52 having a top surface 54, a bottom surface 56, a die support section 58, and a plurality of leadframe leads 60. Each respective leadframe lead 60 includes an inner bonding portion 60a, an intermediate support portion 60b and an outer portion 60c. This leadframe is typical of leadframes used within plastic packages of the prior art and may be formed of, for example, copper or plated copper material.
In accordance with the present invention, the assembly includes a package 62 consisting essentially of an upper section 64 and a lower section 66. Upper section 64 is molded directly onto at least the top surface of support portions 60b of the leadframe leads and lower section 66 is molded directly onto a portion of bottom surface 56 of the leadframe so that the molding material is bonded to the bottom surface of die support section 58 and support portions 60b of the leadframe leads. The molding material fills the spaces 68, shown in Figure 3B, defined between the respective leadframe leads to completely surround support portions 60b of the leads and seal them within the molding material in the completed assembly. The leadframe is thereby sandwiched between and held in place by the upper and lower sections and supported in place therebetween. At the same time, as illustrated best in Figure 3A, the leadframe lead's outer portions 60c extend outside the package for connection to external components.
Still referring to Figures 3A and 3B, upper section 64 of package 62 defines an integral opening 70 above and around die support section 58. Inner bonding portions 60a of the leadframe leads extend inwardly into opening 70 around die support section 58 for electrical connection thereto. A semiconductor die 72, which is responsive to light, for example an EPROM, is bonded by suitable means, well known in the art, to the upper surface of die support section 58. The die includes a plurality of bonding pads 74 electrically interconnected to respective ones of inner bonding portions 60a of the leadframe leads by a plurality of bonding wires 76. A light receiving window 78 is supported and fixed in opening 70 by suitable means which may include, as shown in Figure 3A, an optional downwardly recessed step portion 80. The window may be comprised of any suitable light transmitting material which, for example, may include translucent alumina. The window is held in place by suitable adhesive means, which is well known in the art, applied to the step portion.
Figures 4A through 4E illustrate a first method of manufacturing the assembly as shown in Figures 3A and 3B, in accordance with the present invention. It is emphasized here that the order in which the various operations of the first method are performed is critical only to the extent that the final assembly produced is in accordance with the assembly as shown and described in Figures 3A and 3B.
Referring now to Figure 4A, the leadframe 52 is provided, as previously described. The leadframe is positioned on a surface 79 against a first mold 81 having a cavity 82 appropriate for forming upper section 64 as specifically illustrated in Figure 4A. A clamp 84 holds the leadframe in place and covers die support section 58 and inner bonding portions 60a of the leadframe leads to keep these areas clean during the molding operation to follow. Suitable and readily providable molding material is injected into cavity 82 and upper section 64 is formed. The upper section is molded to the top surface of leadframe 52 such that support portions 60b of the leadframe leads are bonded to the upper section. The clamp is specially designed to allow the flow of molding material into specific areas, for example, molding material is allowed to flow into the spaces between support portions 60b of the leadframe leads and around the die support section. Clamp 84 also keeps at least the upper surface of the die support section and the upper surface of the inner bonding portions of the leadframe leads free of molding material. Opening 70 in the upper section is formed by the clamp. If it is so desired, step portion 80 around opening 70 may be formed during the molding operation by appropriate shaping of the clamp or mold. In this case the mold is shown forming the step portion.
Molding of lower section 66 of the package is accomplished by placing the assembly shown in Figure 4A into a second mold 86, as shown in Figure 4B. The second mold defines a cavity 88 appropriately shaped to form the desired outline of the lower section. Clamp 84, which was used to mold the upper section of the package, may be left in position while the lower section of the package is molded. With the clamp in place and the assembly in the second mold, lower section 66 of the package is molded by injection of a suitable molding material into cavity 88. The molding process is carried out in a manner which integrally bonds the lower section to the upper section of the package and seals the support portions of the leadframe leads between the sections whereby the leadframe is supported. Note specifically that the top surfaces of support section 58 and leadframe lead portions 60a are protected against the flow of molding material by clamp 84 during formation of lower section 66, thereby insuring that these surfaces remain clean.
Referring now to Figures 4C and 4D, semiconductor die 72 may at this point be bonded to die support section 58 of the leadframe through opening 70, by means well known in the art. Since the molding operation for each section has been previously accomplished, problems with deposition of contaminants upon the die from the molding operations are avoided by this method.
After the die is bonded to the die support section, bonding wires 76 are interconnected from bonding pads 74 on the die to respective inner bonding portions 60a of the leadframe leads through opening 70.
At this point, and shown in Figure 4E, light receiving window 78 is properly sized to be received in opening 70. The window is adhesively attached to step portion 13
80 with a suitable adhesive. Other methods may be used to affix the light transmitting material in place and, in fact, the step portion is not a requirement. All methods of affixing window 78 on the package to seal the opening are considered to be within the scope of the invention as disclosed herein.
Referring now to Figures 5A and 5B, a second embodiment of an integrated circuit assembly manufactured in accordance with a second method of the present invention is generally designated by reference numeral 100. The assembly includes a leadframe 102 manufactured for use with the present invention. The leadframe includes a top surface 104, a bottom surface 106, a die support section 108, and a plurality of leadframe leads 1 10. Each respective leadframe lead 1 10 includes an inner bonding portion 110a, an intermediate support portion 110b and an outer portion 110c. This leadframe is typical of leadframes used within windowless plastic packages of the prior art, in the same manner as leadframe 52.
In accordance with the present invention, the assembly includes a package 1 12 which is molded directly onto support portions 1 10b of the leadframe leads. The support portions are entirely encapsulated in molding material. Package 1 12 forms an annular body extending outwardly from top surface 104 and bottom surface 106 of the leadframe, surrounding die support section 108 of the leadframe to support the leadframe and define opposing top and bottom openings 1 14 and 1 16 respectively. Bottom opening 1 16 is sealed by a suitable means 1 17, well known in the art, which may include, but is not limited to, epoxy resin.
Also shown in Figures 5A and 5B, inner bonding portions 1 10a of the leadframe leads extend inwardly from package 1 12 toward die support section 108 for electrical connection thereto and outer portions 1 10c extend externally beyond package 1 12 for connection to external components. A semiconductor die 1 18, which is responsive to light, for example an EPROM, is bonded by suitable means, well known in the art, to the upper surface of die support section 108. The die includes a plurality of bonding pads 120 electrically interconnected to respective ones of bonding portions 14
1 10a of the leadframe leads by a plurality of bonding wires 122. A light receiving window 124 is supported on the package and seals opening 1 14 by suitable means which may include, as shown in Figure 5 A, a downwardly recessed step portion 126 around the perimeter of the opening. The window may be comprised of any suitable light transmitting material examples of which may include glass and translucent alumina. The window is held in place by suitable adhesive means, which is well known in the art, applied to the step portion. Any method may be used to affix window 124 to the package within the scope of the invention, provided that a seal is attained between the package and the window. It is also noted that, as in the first embodiment of the invention, step portion 126 is not a requirement of the invention as claimed.
A second method of manufacturing an integrated circuit package assembly, in accordance with the present invention, is illustrated in Figures 6A through 6E This method produces an integrated circuit assembly including a light receiving window in accordance with the second embodiment of the present invention, as described immediately above in conjunction with Figures 5A and 5B. It is again emphasized here that the order in which some of the various operations of the second method are performed are critical only to the extent that the final assembly produced is in accordance with the assembly as shown in Figures 5A and 5B and described herein.
Referring now to Figure 6A, the leadframe 102 is provided, as previously described The leadframe is placed in a mold 140 comprised of upper and lower mold pieces 140a and 140b and clamped in place by a pair of opposing upper and lower lamps 142 and 144 respectively. Mold 140 along with the upper and lower clamps form an annular cavity 146 appropriately shaped to the desired outline of package 1 12 Suitable molding material is infected into cavity 146 to form package 1 12 so that the package is molded onto the support portions of the leadframe as described above After hardening of the package, upper and lower clamps 142 and 144 are removed and the assembly is removed from upper and lower mold pieces 140a and 140b Top opening 1 14 is defined by upper clamp 142 and bottom opening 116 is defined by lower clamp 122.
Molding with the clamps in place keeps die support section 108 and bonding portions 1 10a of the leadframe leads free of the molding material. Access to the bonding portions and the die support section is gained through top opening 1 14 in the package.
Following molding of package 112, and shown in Figure 6B, bottom opening 1 16 in the package is sealed by suitable means 1 17. Any means of sealing bottom opening 116 may be used provided that a hermetic seal of the opening is attained.
Semiconductor die 1 18 is then bonded, as depicted in Figure 6C, by means well known in the art, to die support section 108. The bonding is accomplished through top opening 1 14, in accordance with the method as claimed.
Bonding wires 122, also shown in Figure 6C, are then electrically connected from respective ones of bonding pads 120 on the semiconductor die to respective ones of bonding portions 1 10a of the leadframe leads. Electrical interconnection of the bonding wires is, like the bonding of the die to the support section, accomplished through top opening 1 14 of package 1 12.
It is here again noted that contamination of the die and bonding wires is avoided by completion of package molding prior to bonding the die to the die support section and the interconnection of the bonding wires.
In Figure 6D, light receiving window 124 is then sealed to step portion 126 in the top opening. Again it is emphasized that step portion 126 with adhesive means applied thereto are only one of many possible means by which the window may be affixed to seal the opening.
It should be understood that the present invention may be embodied in many other specific forms and produced by other methods without departing from the spirit or scope of the invention. Therefore, the present examples and methods are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:
1. A method of manufacturing an integrated circuit assembly having a light receiving window through which a semiconductor die can be selectively exposed to a preselectable light source, said method comprising: a) providing a leadframe having top and bottom opposing surfaces, a die support section and a plurality of leadframe leads; b) molding an upper section to said top surface of said leadframe so as to define a light receiving window opening within said upper section such that said die support section and portions of said leadframe leads remain exposed through said window opening; c) molding a lower section to said bottom surface of said leadframe opposite said upper section with the leadframe leads in place therebetween, whereby to seal the leadframe leads, the upper, and the lower sections together; d) bonding a semiconductor die, through said window opening, to said die support section, said die including a plurality of bonding pads; e) electrically interconnecting, through said window opening, an array of bonding wires from said bonding pads on said semiconductor die to respective exposed portions of said leadframe leads; and f) sealing a light transmitting material in said window opening to form a light receiving window.
2. A method according to claim 1 wherein said die is mounted to said die support section after the upper section is molded, but before the lower section is molded.
3. A method according to claim 1 wherein said die is mounted to said die support section after the upper and lower sections are molded.
4. A method according to the method of claim I wherein said bonding step includes the step of bonding an EPROM chip to said die support section.
5. A method according to the method of claim 1 wherein said step for molding the upper section of the package further includes the step of molding an integral downwardly recessed step portion around said window opening and wherein the step for sealing a light receiving window includes the step of sealing the window onto said step portion.
6. A method of manufacturing an integrated circuit assembly according to the method of claim 1 wherein said sealing step includes the step of sealing a translucent alumina window in said window opening.
7. A method of manufacturing an integrated circuit assembly having a light receiving window through which a semiconductor die can be selectively exposed to a preselectable light source, said method comprising: a) providing a leadframe including top and bottom opposing surfaces, a die support section and a plurality of leadframe leads, wherein each respective leadframe lead includes a support portion and a bonding portion; b) molding a package including top and bottom opposing surfaces around said support portions of said leadfr-ame leads to seal the support portions of the leads within the package and to define respective opposing openings on opposite sides of the support section of said leadframe such that said die support section and said bonding portions of said leadframe leads are accessible through said openings and such that said leadframe is supported by said support portions of said leadframe leads; c) sealing said opening in the bottom surface of the package by suitable means; d) bonding, through the opening in the top surface of the package, said semiconductor die to said die support section; e) electrically interconnecting, through the opening in the top surface of the package, an array of bonding wires from said bonding pads on said semiconductor die to respective exposed portions of said leadframe leads; and
0 sealing the opening in the top surface of the package with a light transmitting material to form said light receiving window.
8. A method according to claim 7 wherein the opening in the bottom surface is sealed prior to bonding the semiconductor die to the die support section.
9. A method according to claim 7 wherein the opening in the bottom surface is sealed after bonding the semiconductor die to the die support section.
10. A method according to the method of claim 7 wherein said bonding step includes the step of bonding an EPROM chip to said die support section.
1 1. A method according to the method of claim 7 wherein said step for molding the package further includes the step of molding a downwardly recessed step portion around said opening in the top surface of the package and wherein the step of sealing a light receiving window includes the step of sealing the window onto said step portion.
12. A method according to the method of claim 7 wherein said step for sealing includes the step of sealing a translucent alumina window in said window opening.
13. An integrated circuit assembly, comprising: a) a leadframe including a top and bottom surface, a die support section, and plurality of leadframe leads, wherein each leadframe lead includes a support portion and a bonding portion; b) a package consisting essentially of two independent sections each of which is integrally molded as a single unit, one of said units being connected with and bonded directly to at least the top surface of said support portions of the leadframe leads and the other section being connected with and bonded directly to at least the bottom surface of said support portions of the leadframe leads such that the package surrounds the bonding portions of the leadframe leads and said leadframe is sandwiched between and held in place by said two sections, said package further defining a integral opening above the upper surface of the die support section; c) a semiconductor die bonded to said die support section of the leadframe within said opening, said die including a plurality of bonding pads; d) a plurality of bonding wires respectively electrically interconnecting said bonding pads on the semiconductor die to said bonding portions of said leadframe leads; and e) a light transmitting material sealing the opening in the package to comprise a light receiving window, whereby a semiconductor die can be selectively exposed to a predetermined light source through said light receiving window.
14. An integrated circuit assembly according to claim 13 wherein the package includes a downwardly recessed step portion around said opening of the package.
15. An integrated circuit assembly according to claim 14 wherein said light transmitting material is adhesively sealed to said step portion.
16. An integrated circuit assembly according to claim 13 wherein the light transmitting material is adhesively sealed to said package.
17. An integrated circuit assembly according to claim 13 wherein said light receiving window comprises translucent alumina.
18. An integrated circuit assembly, comprising: a) a leadframe including a die support section and a plurality of leadframe leads, wherein each leadframe lead includes a support portion and a bonding portion; b) a package including a single annular shaped unitary body which is molded onto said support portions of the leadframe leads around the die support section whereby to define opposing top and bottom openings on opposite sides of the die support section for gaining access thereto, said annular body encapsulating the support portions of the leadframe leads and supporting the leadframe, said package further including means for closing the bottom opening; c) a semiconductor die bonded to said die support section of the leadframe, said die including a plurality of bonding pads; d) a plurality of bonding wires respectively electrically interconnecting said bonding pads on the semiconductor die to said bonding portions of said leadframe leads; and e) a light transmitting material sealing the top opening of the package to comprise a light receiving window, whereby a semiconductor die can be selectively exposed to a predetermined light source through said light receiving window.
19. An integrated circuit assembly according to claim 18 wherein the package includes a downwardly recessed step portion around the top opening of the package.
20. An integrated circuit assembly according to claim 19 wherein said light receiving window is adhesively fixed to said step portion around the top opening.
21 . An integrated circuit assembly according to claim 18 wherein said means for closing the bottom opening includes an epoxy resin disposed therein.
22. An integrated circuit assembly according to claim 18 wherein said light receiving window comprises translucent alumina.
EP95938152A 1994-10-14 1995-10-13 Integrated circuit package assembly including a window and methods of manufacturing Withdrawn EP0734590A1 (en)

Applications Claiming Priority (3)

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US32411994A 1994-10-14 1994-10-14
PCT/US1995/012766 WO1996012303A1 (en) 1994-10-14 1995-10-13 Integrated circuit package assembly including a window and methods of manufacturing
US324119 1999-06-02

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JPS60239043A (en) * 1984-05-14 1985-11-27 Oki Electric Ind Co Ltd Manufacture of package for semiconductor device
JPS61150242A (en) * 1984-12-24 1986-07-08 Hitachi Ltd Package for semiconductor device
JPS63133653A (en) * 1986-11-26 1988-06-06 Matsushita Electronics Corp Optically erasable semiconductor storage device
JPH079951B2 (en) * 1986-12-04 1995-02-01 沖電気工業株式会社 Method for manufacturing semiconductor device
FR2667982B1 (en) * 1990-10-15 1997-07-25 Sgs Thomson Microelectronics INTEGRATED WINDOW CIRCUIT MOLD HOUSING AND MOLDING METHOD.
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