US20020145181A1 - Method for integrated circuit packaging - Google Patents
Method for integrated circuit packaging Download PDFInfo
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- US20020145181A1 US20020145181A1 US09/829,208 US82920801A US2002145181A1 US 20020145181 A1 US20020145181 A1 US 20020145181A1 US 82920801 A US82920801 A US 82920801A US 2002145181 A1 US2002145181 A1 US 2002145181A1
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- Prior art keywords
- receptacle
- microelectronic device
- cavity
- leadframe
- continuous strip
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/02—Containers; Seals
- H01L23/04—Containers; Seals characterised by the shape of the container or parts, e.g. caps, walls
- H01L23/043—Containers; Seals characterised by the shape of the container or parts, e.g. caps, walls the container being a hollow construction and having a conductive base as a mounting as well as a lead for the semiconductor body
- H01L23/047—Containers; Seals characterised by the shape of the container or parts, e.g. caps, walls the container being a hollow construction and having a conductive base as a mounting as well as a lead for the semiconductor body the other leads being parallel to the base
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/50—Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/16—Fillings or auxiliary members in containers or encapsulations, e.g. centering rings
- H01L23/18—Fillings characterised by the material, its physical or chemical properties, or its arrangement within the complete device
- H01L23/24—Fillings characterised by the material, its physical or chemical properties, or its arrangement within the complete device solid or gel at the normal operating temperature of the device
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
- H01L24/93—Batch processes
- H01L24/95—Batch processes at chip-level, i.e. with connecting carried out on a plurality of singulated devices, i.e. on diced chips
- H01L24/97—Batch processes at chip-level, i.e. with connecting carried out on a plurality of singulated devices, i.e. on diced chips the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
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- 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
- H01L2224/45117—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 400°C and less than 950°C
- H01L2224/45124—Aluminium (Al) as principal constituent
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- 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
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- 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
- H01L2224/4805—Shape
- H01L2224/4809—Loop shape
- H01L2224/48091—Arched
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- 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
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- H—ELECTRICITY
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- 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
- H01L2924/01—Chemical elements
- H01L2924/01079—Gold [Au]
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- H01—ELECTRIC ELEMENTS
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- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/10—Details of semiconductor or other solid state devices to be connected
- H01L2924/11—Device type
- H01L2924/12—Passive devices, e.g. 2 terminal devices
- H01L2924/1204—Optical Diode
- H01L2924/12042—LASER
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- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/10—Details of semiconductor or other solid state devices to be connected
- H01L2924/11—Device type
- H01L2924/14—Integrated circuits
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- H—ELECTRICITY
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- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T83/00—Cutting
- Y10T83/04—Processes
- Y10T83/0605—Cut advances across work surface
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T83/00—Cutting
- Y10T83/141—With means to monitor and control operation [e.g., self-regulating means]
- Y10T83/159—Including means to compensate tool speed for work-feed variations
Definitions
- the present invention relates to methods for fabricating packages for microelectronic devices.
- microelectronic devices such as integrated circuits in chip carrier packages or overmolded packages. These packages protect the microelectronic device from the environment, and provide means for electrically and mechanically attaching the microelectronic device in the intended system.
- the conventional technique for forming these packages comprises transfer molding.
- the leadframes are separated into sections for a predetermined number of packages, and microelectronic devices are attached to the leadframes.
- Transfer molding is a batch process that has been used in the electronics industry for many years, where leadframes are transferred to a molding machine, a mold cavity is formed around the leadframe and device, and plastic is injected into the mold to form the package.
- chip carrier type packages can be filled with an encapsulant and then sealed.
- the leads for plastic packages are then plated. This entails a complex set of processes which can be incompatible with other packaging process steps, and therefore requires more careful and expensive treatment to prevent damage to the sealed package.
- dambar acts as a dam to prevent the leakage of plastic.
- the dambars are cut away with a series of precision cutting tools. This is conventionally done at the stage when the packages, typically in strip form, are subsequently separated into individual packages. These cutting tools are expensive because of the need for precision and tight tolerances in the microelectronic devices.
- this invention provides a method of forming microelectronic packages of the type including a microelectronic device, a receptacle formed of an insulative material and defining a cavity for receipt of the microelectronic device, and a leadframe formed of a conductive material and facilitating electrical and mechanical connection of the microelectronic device to an external circuit.
- the packages are formed in a continuous process comprising: moving a continuous strip of an electrically conductive substrate material along a feed path to a removal station and removing material from the continuous strip to define a series of successive connected leadframes from the remaining material with each leadframe including a series of leads; at a forming station along the feed path, forming a receptacle of electrically insulative material on the substrate strip at a respective leadframe, and attaching a device in the cavity at an attachment station.
- a continuous strip of successively connected cavity packages, each containing a device are formed.
- Another aspect of the invention is to include one or more additional processing steps along the feed path.
- the process can be extended to include: a wire bonding step whereby the microelectronic device is electrically connected to the leads via a plurality of wires; a liquid fill station where each cavity is filled with a liquid encapsulant; a curing station for setting the liquid encapsulant; a sealing station for sealing the package with a lid; a marking station for labeling each package; and a separation station for the separation of the continuous strip of packages into discrete strips containing a desired number of packages.
- the continuous process of the invention facilitates selected addition of the recited steps depending upon the requirements of a particular package design or the availability of particular production equipment.
- FIG. 1 is a cutaway view of a package with a microelectronic device therein;
- FIG. 2 is a diagram of a section the strip of metal including leadframes after etching
- FIG. 3 is a diagram of packages during a stage of fabrication
- FIG. 4 is a diagram of the process for production of the packages of FIGS. 1 and 3;
- FIG. 5 is a diagram of the mold housing attached to a leadframe
- FIG. 6 is a process flow chart for production of the packages of FIGS. 1 and 3.
- microelectronic device packages are preferably formed of a hard, durable material and encapsulate the microelectronic device.
- FIG. 1 depicts a cutaway view of a package 10 which includes a microelectronic device 12 .
- the microelectronic device 12 may comprise, e.g., an integrated circuit or “chip.”
- the microelectronic device 12 is positioned in a cavity 14 defined by a receptacle 16 which is covered by a lid 18 .
- a plurality of leads 20 extend through a wall of the receptacle 16 and into the cavity, a further plurality of leads 20 extend through an opposite wall of the receptacle and into the opposite side of the cavity.
- the device 12 is connected to the leads 20 by thin wires 22 .
- the wires 22 are bonded to the microelectronic device at bonding pads 24 on the microelectronic device.
- Leads 20 facilitate electrical connection of the device 12 to an external circuit.
- the leads 20 are provided by leadframes 30 , FIG. 2, and are strips of metal that have been etched or stamped, such that the remaining material defines the leads 20 and a die pad 32 positioned between the opposing leads 20 .
- the leadframes are produced in strip form, then cut into discrete sections for fabrication of packages by batch processing.
- the package die is produced in a continuous manufacturing process.
- FIG. 3 depicts a diagram of a strip of packages 10 during a stage in the continuing manufacturing process.
- Each package includes the receptacle 16 for receiving the device, as well as a leadframe 30 which provides the leads 20 in the finished package providing connections to an external circuit.
- the leadframes are fabricated from a continuous strip of metal 42 , typically copper (Cu).
- the leadframe is formed from the strip 42 by cutting or etching to a desired configuration, where material is cut away leaving the leads 20 .
- the receptacle 16 is fabricated from a thermoplastic and defines a cavity 14 for receiving a microelectronic device.
- Leads 20 include an exterior portion 34 which extends through the sides of the receptacle 16 to an interior portion 36 having a paddle configuration and positioned within the cavity.
- the package may also include metal die pad 32 fabricated during the production of the leadframes from the strip 42 .
- the die pad 32 is positioned in the cavity 14 .
- FIG. 4 is the overall diagrammatic view of the continuous process of the invention.
- the continuous copper strip 42 of electrically conductive substrate begins at a supply station 100 where the strip is supplied from a reel 44 .
- the continuous strip 42 proceeds to a removal station 104 where the continuous strip 42 is etched to create a series of successive connected leadframes.
- the removal station includes a resist section 46 for applying a resist to the strip 42 in a desired pattern, an etching bath 48 for removal of the material on the continuous strip 42 not covered by the resist, and a rinse section 50 for removing the resist and any residual etchant, thus forming a continuous strip of connected leadframes 30 .
- the strip 42 now in the form of a continuous strip of connected leadframes 30 , continues to a plating section 108 where the strip 42 proceeds through a series of plating baths 54 and rinsing baths 56 .
- the continuous strip of leadframes is plated in a first plating bath containing a nickel (Ni) solution.
- the first plating bath deposits a layer of nickel on the copper leadframes 30 .
- the continuous strip of leadframes is rinsed and proceeds through a second plating bath.
- the second plating bath contains a palladium (Pd) solution and deposits a layer of palladium over the nickel layer on the continuous strip of leadframes.
- the continuous strip of leadframes is rinsed and proceeds through a third plating bath (not shown).
- the third plating bath contains a gold (Au) solution and deposits a layer of gold over the palladium layer.
- the leadframes are rinsed and proceed to the next station.
- the continuous strip 42 proceeds to a receptacle formation station 112 .
- the receptacle formation is performed with thermoplastic injection molding that forms a receptacle integral with each leadframe.
- a mold housing 60 FIG. 5, is used for fabricating the receptacle in a continuous thermoplastic injection molding process.
- the mold housing 60 has an upper and lower part that engage on the leadframe.
- the mold housing 60 includes two parts, an “A” side part 62 and a “B” side part 64 .
- the mold housing B side part 64 has teeth 70 that are tapered and fit between the leads 20 on the leadframe 30 .
- the teeth 70 are tapered and help guide the leadframe 30 into a correct position.
- the moldhousing A side part 62 has teeth 68 that are shaped to mesh with the teeth 70 of the B side part 64 .
- the teeth 68 of the A side part 62 are designed to leave a gap where the leads 20 from the leadframe sit.
- the tapered teeth 68 , 70 help close the mold 60 and provide a sufficient seal to prevent plastic from leaking out of the mold 60 .
- the mold housing has two sets of offset steel teeth 68 , 70 that protrude into the spaces between the leads 20 , come together and seal the spaces between the leads 20 .
- the design permits the fabrication of dambarless leadframes. Creating receptacles without dambars eliminates expensive dambar removal steps.
- Thermoplastic is injected and fills the mold housing 60 to create the receptacle 16 , such that the receptacle defines a cavity 14 and encapsulates each leadframe 30 , wherein the leads 20 extend from the cavity 14 to the exterior of the receptacle 16 .
- the thermoplastic sets and the mold housing is automatically removed.
- the receptacle 16 is fabricated from a thermoplastic, and a preferred plastic is a liquid crystal polymer (LCP) material.
- LCP liquid crystal polymer
- a variety of plastics are available for use with this process, among them are polyimides.
- the continuous strip of receptacles 16 proceeds to a device attachment station 116 .
- a device attachment station 116 microelectronic devices 12 are placed in the receptacles 16 .
- An adhesive is applied to the device 12 , or the die pad 32 , or both prior to insertion of the device 12 into the receptacle 16 .
- the continuous strip of leadframes proceeds to the separation station 114 , and then the continuous strip of leadframes is cut into discrete sections 66 containing a desired number of packages.
- the leadframe can be another electrically conductive material, such as aluminum (Al).
- the substrate is stamped to define the desired leadframe features.
- stamping or etching will depend on the thickness of the substrate as well as other features of a particular fabrication design.
- the choice, order, and number of plating baths 54 will depend on the end use, and the type of metal used for wires 22 . Factors influencing the choice of plating material include corrosion resistance and solderability.
- the continuous processing feature of the present invention may also include additional steps in the fabrication of packages prior to separation.
- the process commences with the supply of a continuous strip of substrate from the supply station 100 , proceeds to the removal station 104 , the plating station 108 , the receptacle formation station 112 , the device attachment station 116 , and then continues to a wire bonding station 124 .
- an adhesive is applied to either the die pad 32 in each receptacle 16 , or the microelectronic device 12 , or both.
- a microelectronic device 12 is positioned and attached to each die pad 32 in each receptacle 16 on the continuous strip.
- adhesive depends on the particular device and its intended function. Factors affecting the choice of adhesive are whether the device needs to be insulated from the environment, or thermally or electrically connected to an external environment. Typical adhesives selected for microelectronic applications are silver-filled epoxy and silver-filled polyimide.
- the continuous strip of packages 10 thereafter proceeds to a snap cure station 120 where the adhesive is cured in an oven.
- An aspect of this automation is curing in a pass-through oven.
- each device 12 is electrically connected to the inner portion 36 of the leads 20 in the corresponding package 10 on the continuous strip 42 via a plurality of wires 22 .
- Wires are affixed by conventional wire bonding techniques. These include aluminum wire bonding through ultrasonic bonding, or gold wire bonding through thermosonic or thermocompression bonding methods.
- each package 10 is filled with an encapsulating liquid which may be either a liquid epoxy or a silicone gel filling material.
- an encapsulating liquid which may be either a liquid epoxy or a silicone gel filling material.
- the choice of fill material depends on the characteristics of the die.
- the continuous strip of packages 10 remains unfilled as may be desired in the case where the microelectronic device comprises a pressure sensor.
- An aspect of this invention is the application to making sensor device packages. Sensor device packages are not able to be made with the conventional method of attaching the devices and overmolding the device and leadframe, and therefore require more costly and time consuming processing.
- the continuous strip of packages 10 thereafter proceeds to an epoxy cure station 132 where the adhesive is cured in an oven.
- An aspect of this automation is curing in a pass-through oven.
- the continuous strip of packages 10 thereafter proceeds to a sealing station 136 where a protective lid 18 is affixed to each package using a polyimide adhesive.
- a polyimide adhesive The choice of adhesive will depend on the choice of thermoplastic used for the receptacle.
- the lid material is typically a dark plastic material suitable for marking with a laser.
- the continuous strip of packages 10 thereafter proceeds to a laser marking station 140 where each package is marked with information as desired to identify the encapsulated microelectronic device therein.
- the continuous strip of packages then proceeds to the separation station 114 for separation from the continuous strip into individual packages, or into strips containing a desired number of packages.
- a buffer area is provided for creating and taking up slack in the continuous strip.
- the buffer area includes a series of reels that have springs and guides to provide a constant tension and allow movement of the reels as slack is either created or taken up.
- the metal die pad 32 may be encapsulated with the thermoplastic material of the receptacle or, alternatively, may be exposed to the external environment in which case a heat source may be applied to the metal die pad for transfer of heat through the die pad 32 and the device 12 to the bonding pads 24 on the device 12 . Heating the bonding pads 24 is necessary in the case of gold wire bonding.
- the exposed metal die pad 32 may also be affixed to a heat sink. This enhances thermal management of the package and the device contained therein.
- An important feature of this invention is the ability to select the desired stations in the production process. This invention can be applied for the expansion of existing package manufacturing systems bringing stations on-line as equipment becomes available.
Abstract
Description
- The present invention relates to methods for fabricating packages for microelectronic devices.
- In the electronic industry, it is conventional to encapsulate microelectronic devices such as integrated circuits in chip carrier packages or overmolded packages. These packages protect the microelectronic device from the environment, and provide means for electrically and mechanically attaching the microelectronic device in the intended system.
- The conventional technique for forming these packages comprises transfer molding. The leadframes are separated into sections for a predetermined number of packages, and microelectronic devices are attached to the leadframes. Transfer molding is a batch process that has been used in the electronics industry for many years, where leadframes are transferred to a molding machine, a mold cavity is formed around the leadframe and device, and plastic is injected into the mold to form the package.
- Subsequently, chip carrier type packages can be filled with an encapsulant and then sealed. The leads for plastic packages are then plated. This entails a complex set of processes which can be incompatible with other packaging process steps, and therefore requires more careful and expensive treatment to prevent damage to the sealed package.
- Additionally, in conventional molding of plastic packages, when the mold is closed around the leadframe, there are spaces between the leads from which the plastic can leak from the mold. In order to prevent this, a section of the leadframe called a dambar acts as a dam to prevent the leakage of plastic. After the plastic package has been set and cured, the dambars are cut away with a series of precision cutting tools. This is conventionally done at the stage when the packages, typically in strip form, are subsequently separated into individual packages. These cutting tools are expensive because of the need for precision and tight tolerances in the microelectronic devices.
- Despite these disadvantages, it is desirable to create a die package for a semiconductor device which is essentially a molded package. This is because a molded package is sturdy and cost effective. Additionally, the electronic industry is accustomed to the molded package in that the product design and assembly processes are set up to use molded die packages. It would be advantageous to have improved methods for forming the plastic packages.
- In one aspect, this invention provides a method of forming microelectronic packages of the type including a microelectronic device, a receptacle formed of an insulative material and defining a cavity for receipt of the microelectronic device, and a leadframe formed of a conductive material and facilitating electrical and mechanical connection of the microelectronic device to an external circuit.
- According to the invention, the packages are formed in a continuous process comprising: moving a continuous strip of an electrically conductive substrate material along a feed path to a removal station and removing material from the continuous strip to define a series of successive connected leadframes from the remaining material with each leadframe including a series of leads; at a forming station along the feed path, forming a receptacle of electrically insulative material on the substrate strip at a respective leadframe, and attaching a device in the cavity at an attachment station. As such, a continuous strip of successively connected cavity packages, each containing a device are formed. This method has the advantage of providing a continuous production of packages resulting in a savings of fabrication time and material.
- Another aspect of the invention is to include one or more additional processing steps along the feed path. The process can be extended to include: a wire bonding step whereby the microelectronic device is electrically connected to the leads via a plurality of wires; a liquid fill station where each cavity is filled with a liquid encapsulant; a curing station for setting the liquid encapsulant; a sealing station for sealing the package with a lid; a marking station for labeling each package; and a separation station for the separation of the continuous strip of packages into discrete strips containing a desired number of packages. The continuous process of the invention facilitates selected addition of the recited steps depending upon the requirements of a particular package design or the availability of particular production equipment.
- Other objects, advantages and applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.
- These and other features, aspects, and advantages of the present invention will become apparent with reference to the following description, appended claims, and accompanying drawings where:
- FIG. 1 is a cutaway view of a package with a microelectronic device therein;
- FIG. 2 is a diagram of a section the strip of metal including leadframes after etching;
- FIG. 3 is a diagram of packages during a stage of fabrication;
- FIG. 4 is a diagram of the process for production of the packages of FIGS. 1 and 3;
- FIG. 5 is a diagram of the mold housing attached to a leadframe; and
- FIG. 6 is a process flow chart for production of the packages of FIGS. 1 and 3.
- The present invention provides a new method for producing microelectronic device packages. Such microelectronic device packages are preferably formed of a hard, durable material and encapsulate the microelectronic device.
- For purpose of background, a typical package for a microelectronic device will be described. FIG. 1 depicts a cutaway view of a
package 10 which includes amicroelectronic device 12. Themicroelectronic device 12 may comprise, e.g., an integrated circuit or “chip.” Themicroelectronic device 12 is positioned in acavity 14 defined by areceptacle 16 which is covered by alid 18. A plurality ofleads 20 extend through a wall of thereceptacle 16 and into the cavity, a further plurality ofleads 20 extend through an opposite wall of the receptacle and into the opposite side of the cavity. Thedevice 12 is connected to theleads 20 bythin wires 22. Thewires 22 are bonded to the microelectronic device at bondingpads 24 on the microelectronic device.Leads 20 facilitate electrical connection of thedevice 12 to an external circuit. Theleads 20 are provided byleadframes 30, FIG. 2, and are strips of metal that have been etched or stamped, such that the remaining material defines theleads 20 and adie pad 32 positioned between theopposing leads 20. - Conventionally, the leadframes are produced in strip form, then cut into discrete sections for fabrication of packages by batch processing.
- According to the invention, the package die is produced in a continuous manufacturing process. FIG. 3 depicts a diagram of a strip of
packages 10 during a stage in the continuing manufacturing process. Each package includes thereceptacle 16 for receiving the device, as well as aleadframe 30 which provides theleads 20 in the finished package providing connections to an external circuit. The leadframes are fabricated from a continuous strip ofmetal 42, typically copper (Cu). The leadframe is formed from thestrip 42 by cutting or etching to a desired configuration, where material is cut away leaving theleads 20. Thereceptacle 16 is fabricated from a thermoplastic and defines acavity 14 for receiving a microelectronic device.Leads 20 include anexterior portion 34 which extends through the sides of thereceptacle 16 to aninterior portion 36 having a paddle configuration and positioned within the cavity. The package may also includemetal die pad 32 fabricated during the production of the leadframes from thestrip 42. The diepad 32 is positioned in thecavity 14. - FIG. 4 is the overall diagrammatic view of the continuous process of the invention. The
continuous copper strip 42 of electrically conductive substrate begins at asupply station 100 where the strip is supplied from areel 44. - The
continuous strip 42 proceeds to aremoval station 104 where thecontinuous strip 42 is etched to create a series of successive connected leadframes. The removal station includes a resist section 46 for applying a resist to thestrip 42 in a desired pattern, anetching bath 48 for removal of the material on thecontinuous strip 42 not covered by the resist, and a rinse section 50 for removing the resist and any residual etchant, thus forming a continuous strip of connectedleadframes 30. - The
strip 42, now in the form of a continuous strip of connectedleadframes 30, continues to aplating section 108 where thestrip 42 proceeds through a series of platingbaths 54 and rinsingbaths 56. The continuous strip of leadframes is plated in a first plating bath containing a nickel (Ni) solution. The first plating bath deposits a layer of nickel on thecopper leadframes 30. The continuous strip of leadframes is rinsed and proceeds through a second plating bath. The second plating bath contains a palladium (Pd) solution and deposits a layer of palladium over the nickel layer on the continuous strip of leadframes. The continuous strip of leadframes is rinsed and proceeds through a third plating bath (not shown). The third plating bath contains a gold (Au) solution and deposits a layer of gold over the palladium layer. The leadframes are rinsed and proceed to the next station. - The
continuous strip 42 proceeds to areceptacle formation station 112. The receptacle formation is performed with thermoplastic injection molding that forms a receptacle integral with each leadframe. A mold housing 60, FIG. 5, is used for fabricating the receptacle in a continuous thermoplastic injection molding process. The mold housing 60 has an upper and lower part that engage on the leadframe. The mold housing 60 includes two parts, an “A”side part 62 and a “B”side part 64. The mold housingB side part 64 hasteeth 70 that are tapered and fit between theleads 20 on theleadframe 30. Theteeth 70 are tapered and help guide theleadframe 30 into a correct position. The moldhousingA side part 62 hasteeth 68 that are shaped to mesh with theteeth 70 of theB side part 64. Theteeth 68 of theA side part 62 are designed to leave a gap where the leads 20 from the leadframe sit. The taperedteeth steel teeth leads 20, come together and seal the spaces between the leads 20. The design permits the fabrication of dambarless leadframes. Creating receptacles without dambars eliminates expensive dambar removal steps. Thermoplastic is injected and fills the mold housing 60 to create thereceptacle 16, such that the receptacle defines acavity 14 and encapsulates eachleadframe 30, wherein theleads 20 extend from thecavity 14 to the exterior of thereceptacle 16. The thermoplastic sets and the mold housing is automatically removed. Thereceptacle 16 is fabricated from a thermoplastic, and a preferred plastic is a liquid crystal polymer (LCP) material. A variety of plastics are available for use with this process, among them are polyimides. - The continuous strip of
receptacles 16 proceeds to a device attachment station 116. At the attachment station 116,microelectronic devices 12 are placed in thereceptacles 16. An adhesive is applied to thedevice 12, or thedie pad 32, or both prior to insertion of thedevice 12 into thereceptacle 16. - Following the receptacle formation and attachment of the microelectronic device, the continuous strip of leadframes proceeds to the separation station114, and then the continuous strip of leadframes is cut into discrete sections 66 containing a desired number of packages.
- In one process alternative, the leadframe can be another electrically conductive material, such as aluminum (Al).
- In another process alternative, the substrate is stamped to define the desired leadframe features. The choice of stamping or etching will depend on the thickness of the substrate as well as other features of a particular fabrication design.
- In another process alternative, the choice, order, and number of plating
baths 54 will depend on the end use, and the type of metal used forwires 22. Factors influencing the choice of plating material include corrosion resistance and solderability. - The continuous processing feature of the present invention may also include additional steps in the fabrication of packages prior to separation. In the expanded process of FIG. 6, the process commences with the supply of a continuous strip of substrate from the
supply station 100, proceeds to theremoval station 104, theplating station 108, thereceptacle formation station 112, the device attachment station 116, and then continues to awire bonding station 124. At the die attachment station 116, an adhesive is applied to either thedie pad 32 in eachreceptacle 16, or themicroelectronic device 12, or both. Amicroelectronic device 12 is positioned and attached to each diepad 32 in eachreceptacle 16 on the continuous strip. The choice of adhesive depends on the particular device and its intended function. Factors affecting the choice of adhesive are whether the device needs to be insulated from the environment, or thermally or electrically connected to an external environment. Typical adhesives selected for microelectronic applications are silver-filled epoxy and silver-filled polyimide. - The continuous strip of
packages 10 thereafter proceeds to asnap cure station 120 where the adhesive is cured in an oven. An aspect of this automation is curing in a pass-through oven. - At the
wire bonding station 124, eachdevice 12 is electrically connected to theinner portion 36 of theleads 20 in thecorresponding package 10 on thecontinuous strip 42 via a plurality ofwires 22. Wires are affixed by conventional wire bonding techniques. These include aluminum wire bonding through ultrasonic bonding, or gold wire bonding through thermosonic or thermocompression bonding methods. - The continuous strip of packages thereafter proceeds to a
liquid fill station 128 where eachpackage 10 is filled with an encapsulating liquid which may be either a liquid epoxy or a silicone gel filling material. The choice of fill material depends on the characteristics of the die. In an alternative, the continuous strip ofpackages 10 remains unfilled as may be desired in the case where the microelectronic device comprises a pressure sensor. An aspect of this invention is the application to making sensor device packages. Sensor device packages are not able to be made with the conventional method of attaching the devices and overmolding the device and leadframe, and therefore require more costly and time consuming processing. - The continuous strip of
packages 10 thereafter proceeds to an epoxy cure station 132 where the adhesive is cured in an oven. An aspect of this automation is curing in a pass-through oven. - The continuous strip of
packages 10 thereafter proceeds to a sealing station 136 where aprotective lid 18 is affixed to each package using a polyimide adhesive. The choice of adhesive will depend on the choice of thermoplastic used for the receptacle. The lid material is typically a dark plastic material suitable for marking with a laser. - The continuous strip of
packages 10 thereafter proceeds to alaser marking station 140 where each package is marked with information as desired to identify the encapsulated microelectronic device therein. - The continuous strip of packages then proceeds to the separation station114 for separation from the continuous strip into individual packages, or into strips containing a desired number of packages.
- When different stations require different speeds, known processes for matching the different speeds of the different stations are applied. One such method entails the use of multiple substations along the continuous strip, such as using several device attachment substations. In addition, between each process station, a buffer area is provided for creating and taking up slack in the continuous strip. The buffer area includes a series of reels that have springs and guides to provide a constant tension and allow movement of the reels as slack is either created or taken up.
- The metal die
pad 32 may be encapsulated with the thermoplastic material of the receptacle or, alternatively, may be exposed to the external environment in which case a heat source may be applied to the metal die pad for transfer of heat through thedie pad 32 and thedevice 12 to thebonding pads 24 on thedevice 12. Heating thebonding pads 24 is necessary in the case of gold wire bonding. The exposedmetal die pad 32 may also be affixed to a heat sink. This enhances thermal management of the package and the device contained therein. - An important feature of this invention is the ability to select the desired stations in the production process. This invention can be applied for the expansion of existing package manufacturing systems bringing stations on-line as equipment becomes available.
- The operation and construction of the system for the continuous fabrication of microelectronic die packages is apparent from the foregoing description. The method of operation and structure of the system described has been characterized as being preferred. Obvious changes and modifications may be made therein and it is not intended that it be limited to the above description, but rather only to the extent set forth in the following claims.
Claims (18)
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US09/829,208 US6472251B1 (en) | 2001-04-09 | 2001-04-09 | Method for integrated circuit packaging |
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US09/829,208 US6472251B1 (en) | 2001-04-09 | 2001-04-09 | Method for integrated circuit packaging |
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US6472251B1 US6472251B1 (en) | 2002-10-29 |
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Cited By (3)
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US20100052125A1 (en) * | 2008-08-29 | 2010-03-04 | Sanyo Electric Co., Ltd. | Resin sealing type semiconductor device and method of manufacturing the same, and lead frame |
CN112345845A (en) * | 2020-09-25 | 2021-02-09 | 华东光电集成器件研究所 | Microminiature encapsulation circuit aging clamp |
CN114040563A (en) * | 2021-11-05 | 2022-02-11 | 上海杰瑞兆新信息科技有限公司 | Packaging structure and packaging method of electronic product with high heat dissipation performance |
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KR101340512B1 (en) * | 2006-12-01 | 2013-12-12 | 삼성디스플레이 주식회사 | Semiconductor chip package and printed circuit board assembly having the same |
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Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
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US20100052125A1 (en) * | 2008-08-29 | 2010-03-04 | Sanyo Electric Co., Ltd. | Resin sealing type semiconductor device and method of manufacturing the same, and lead frame |
CN102244016A (en) * | 2008-08-29 | 2011-11-16 | 三洋电机株式会社 | Resin sealing type semiconductor device and method of manufacturing the same, and lead frame |
US8704342B2 (en) * | 2008-08-29 | 2014-04-22 | Semiconductor Components Industries, Llc | Resin sealing type semiconductor device and method of manufacturing the same, and lead frame |
US9171761B2 (en) | 2008-08-29 | 2015-10-27 | Semiconductor Components Industries, Llc | Resin sealing type semiconductor device and method of manufacturing the same, and lead frame |
US9905497B2 (en) | 2008-08-29 | 2018-02-27 | Semiconductor Components Industries, Llc | Resin sealing type semiconductor device and method of manufacturing the same, and lead frame |
CN112345845A (en) * | 2020-09-25 | 2021-02-09 | 华东光电集成器件研究所 | Microminiature encapsulation circuit aging clamp |
CN114040563A (en) * | 2021-11-05 | 2022-02-11 | 上海杰瑞兆新信息科技有限公司 | Packaging structure and packaging method of electronic product with high heat dissipation performance |
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