US20010028117A1 - Method and structure for preventing adhesive bleed onto surfaces - Google Patents
Method and structure for preventing adhesive bleed onto surfaces Download PDFInfo
- Publication number
- US20010028117A1 US20010028117A1 US09/881,466 US88146601A US2001028117A1 US 20010028117 A1 US20010028117 A1 US 20010028117A1 US 88146601 A US88146601 A US 88146601A US 2001028117 A1 US2001028117 A1 US 2001028117A1
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- wire bond
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- noble metal
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- 239000000853 adhesive Substances 0.000 title claims abstract description 23
- 230000001070 adhesive effect Effects 0.000 title claims abstract description 23
- 238000000034 method Methods 0.000 title claims abstract description 11
- 239000000758 substrate Substances 0.000 claims abstract description 33
- 239000000203 mixture Substances 0.000 claims abstract description 25
- 239000013545 self-assembled monolayer Substances 0.000 claims abstract description 25
- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 22
- 239000000126 substance Substances 0.000 claims abstract description 22
- 239000004593 Epoxy Substances 0.000 claims abstract description 16
- 150000002430 hydrocarbons Chemical group 0.000 claims abstract description 16
- BWGNESOTFCXPMA-UHFFFAOYSA-N Dihydrogen disulfide Chemical compound SS BWGNESOTFCXPMA-UHFFFAOYSA-N 0.000 claims abstract description 5
- 230000000740 bleeding effect Effects 0.000 claims abstract description 5
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 claims description 16
- 125000000217 alkyl group Chemical group 0.000 claims description 8
- 239000002094 self assembled monolayer Substances 0.000 claims description 7
- 239000011368 organic material Substances 0.000 claims description 4
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical group C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 3
- 239000005977 Ethylene Chemical group 0.000 claims description 3
- 150000001356 alkyl thiols Chemical class 0.000 claims description 2
- 125000004414 alkyl thio group Chemical group 0.000 claims 1
- 238000000682 scanning probe acoustic microscopy Methods 0.000 claims 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 abstract description 33
- 229910052737 gold Inorganic materials 0.000 abstract description 33
- 239000010931 gold Substances 0.000 abstract description 33
- 229910052751 metal Inorganic materials 0.000 abstract description 10
- 239000002184 metal Substances 0.000 abstract description 10
- 239000004215 Carbon black (E152) Substances 0.000 abstract description 8
- 229930195733 hydrocarbon Natural products 0.000 abstract description 8
- 238000009736 wetting Methods 0.000 abstract description 8
- 150000003573 thiols Chemical class 0.000 abstract description 7
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 abstract description 6
- 229920006332 epoxy adhesive Polymers 0.000 abstract description 6
- 229910052717 sulfur Inorganic materials 0.000 abstract description 6
- 239000011593 sulfur Substances 0.000 abstract description 6
- LSDPWZHWYPCBBB-UHFFFAOYSA-N Methanethiol Chemical compound SC LSDPWZHWYPCBBB-UHFFFAOYSA-N 0.000 abstract description 2
- 238000005476 soldering Methods 0.000 abstract 1
- 239000000463 material Substances 0.000 description 6
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 4
- 150000002019 disulfides Chemical class 0.000 description 4
- QJAOYSPHSNGHNC-UHFFFAOYSA-N octadecane-1-thiol Chemical compound CCCCCCCCCCCCCCCCCCS QJAOYSPHSNGHNC-UHFFFAOYSA-N 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
- 239000003351 stiffener Substances 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 230000002209 hydrophobic effect Effects 0.000 description 3
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 2
- 239000003989 dielectric material Substances 0.000 description 2
- 229910052731 fluorine Inorganic materials 0.000 description 2
- 239000011737 fluorine Substances 0.000 description 2
- 229910052763 palladium Inorganic materials 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- OAYXUHPQHDHDDZ-UHFFFAOYSA-N 2-(2-butoxyethoxy)ethanol Chemical compound CCCCOCCOCCO OAYXUHPQHDHDDZ-UHFFFAOYSA-N 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical class S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000010420 art technique Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 150000002343 gold Chemical class 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000012044 organic layer Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 125000004434 sulfur atom Chemical group 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
Images
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- 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 potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/48—Manufacture or treatment of parts, e.g. containers, prior to assembly of the devices, using processes not provided for in a single one of the subgroups H01L21/06 - H01L21/326
- H01L21/4814—Conductive parts
- H01L21/4846—Leads on or in insulating or insulated substrates, e.g. metallisation
- H01L21/4864—Cleaning, e.g. removing of solder
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
- H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
- H01L23/498—Leads, i.e. metallisations or lead-frames on insulating substrates, e.g. chip carriers
- H01L23/49866—Leads, i.e. metallisations or lead-frames on insulating substrates, e.g. chip carriers characterised by the materials
- H01L23/49894—Materials of the insulating layers or coatings
-
- 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
- H01L24/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
-
- 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
- H01L2924/01—Chemical elements
- H01L2924/01006—Carbon [C]
-
- 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
- H01L2924/01—Chemical elements
- H01L2924/01029—Copper [Cu]
-
- 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
- H01L2924/01—Chemical elements
- H01L2924/01033—Arsenic [As]
-
- 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
- H01L2924/01—Chemical elements
- H01L2924/01046—Palladium [Pd]
-
- 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
- H01L2924/01—Chemical elements
- H01L2924/01047—Silver [Ag]
-
- 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
- H01L2924/01—Chemical elements
- H01L2924/01078—Platinum [Pt]
-
- 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
- H01L2924/01—Chemical elements
- H01L2924/01079—Gold [Au]
-
- 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
- H01L2924/01—Chemical elements
- H01L2924/01087—Francium [Fr]
-
- 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
- H01L2924/013—Alloys
- H01L2924/014—Solder alloys
-
- 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
- H01L2924/10—Details of semiconductor or other solid state devices to be connected
- H01L2924/11—Device type
- H01L2924/14—Integrated circuits
Definitions
- This invention relates generally to the prevention of bleeding of organic material onto a metal substrate and, more particularly, to preventing bleeding of adhesive or components thereof onto a noble metal substrate. In even more particular aspects, this invention relates to the prevention of the bleeding of any components of a die attach adhesive onto noble metal circuitry on a dielectric substrate and, specifically, onto gold wire bond surfaces on a chip carrier or other noble metal circuitry on an I/C chip mounting substrate.
- one technique of mounting utilizes a two-part epoxy adhesive to bond the chip either to gold plating on a planar surface of a substrate, or onto copper or some dielectric material in a cavity formed in an electrical substrate, which substrate also has electrical contacts or wire bond surfaces on the surface thereof.
- One particular problem encountered when using such bond techniques is the tendency of the components of the epoxy adhesive to “bleed” and spread onto the wire bond surfaces, such as the wire bond pads or other noble metal surfaces, such as ground rings or voltage rings, and adhere thereto.
- This “bleed” causes the surface of the bond pads or other metal surfaces to be unreceptive to the bonding of the wire bonds necessary to electrically connect the wire bond surfaces to the contacts on the I/C chip. This, of course, results in unsatisfactory electrical contacts and, thus, contributes to an unsatisfactory chip package.
- One prior art technique for solving this problem is to treat the part with a CF 4 plasma.
- the plasma reacts with the organic portion of the substrate, and the fluorine containing moieties settle on the gold surface of the wire bond pads and other gold surfaces and make them less susceptible to being wetted by bleed from the adhesive.
- this is not a completely satisfactory treatment in all instances in that the fluorine containing moieties are not strongly bonded to the gold but are only lightly adhered thereto. Therefore, they can be easily removed with organic solvents during processing before attachment of the I/C chip takes place, but not easily removed with aqueous systems during processing.
- the CF 4 plasma tends, in many cases, to adversely affect the dielectric material for subsequent application of encapsulating material.
- an object of the present invention to provide a method and structure for substantially reducing or eliminating the wettability of metal surfaces, particularly noble metal surfaces, and specifically gold or other noble metal surfaces, to organic materials, particularly any components of an adhesive, such as an epoxy used for attaching an I/C chip to a substrate, and which I/C chip is subsequently bonded thereto.
- a method and structure for preventing wetting or bleed of an adhesive, such as an epoxy, onto a metal surface and particularly wire bond surfaces on the surface of a dielectric substrate is provided.
- This invention is particularly useful in preventing bleed from any components of an adhesive for attaching an I/C chip or a die to a substrate, and more particularly when a two-part epoxy adhesive is used.
- the method includes treating the surfaces of the wire bond pads with a chemical composition that prevents wetting of, or bleed onto, the wire bond surfaces by a component of the epoxy used to attach the die to the substrate surface.
- the chemical composition is a chemical which will provide “Self-Assembled Monolayers” (SAMs) on the surface of the gold.
- compositions are characterized by a molecule having at least one group, such as a mercaptan or disulfide, connected to a hydrocarbon or substituted hydrocarbon moiety, such as (CH 2 ) n chain.
- a particular molecule that is useful for this is 1-octadecanethiol [HS—(CH 2 ) 17 —CH 3 ].
- the thiol or sulfur-containing portion of the molecule has an affinity for gold or other noble metals, such as palladium, platinum and silver, and chemically bonds to the metal surface, leaving the hydrocarbon segment oriented away from the surface.
- the affinity of the thiol or sulfur-containing portion of the molecule chemically bonding with the metals provides a relatively strong attachment of the molecule to the metal surface.
- the hydrocarbon segment oriented away from the surface presents a surface on the metal which has the characteristics of the hydrocarbon portion of the molecule which has a low surface tension, and, thus, prevents wetting of the gold or other noble metal by an epoxy adhesive component.
- Other chemical moieties such as disulfides having a general formula of R—S—S—R′, where R and R′ are the same or different hydrocarbon moieties, such as (CH 2 ) x or substituted chains, could be used to form the SAMs.
- the SAMs once they provide protection from the bleed of the die attach adhesives, self desorb or are otherwise removed from the gold surface during the wire bonding temperatures, thus rendering the gold surface free from any organic layer which would interfere with wire bonding process.
- the composition is applied as a coating, preferably in a solvent such as butylcarbitol.
- FIG. 1 is a top plan view of a planar chip carrier after coating the gold surfaces thereon to form a SAM according to this invention and before the attachment of an I/C chip;
- FIG. 2 is a sectional view taken substantially along the plane designated by the line 2 - 2 of FIG. 1;
- FIG. 3 is a view similar to FIG. 1 with an I/C chip attached;
- FIG. 4 is a top plan view of a chip carrier with a cavity configuration for the reception of an I/C chip after treatment of the gold surfaces to form a SAM according to this invention
- FIG. 5 is a sectional view taken substantially along the plane designated by the line 55 of FIG. 4;
- FIG. 6 is a view similar to FIG. 4 with an I/C chip attached thereto.
- the chip carrier includes an organic dielectric substrate 10 which has formed thereon a central die attach pad 12 which is connected to a ground ring 14 by fingers 16 .
- a voltage or power ring 18 is also provided, as well as wire bond pads 20 on the surface of the substrate 10 .
- All of the central die pad 12 , ground ring 14 , fingers 16 , voltage or power ring 18 , and wire bond pads 20 preferably are formed of gold, although other noble metals, such as palladium, platinum or silver, may be used in some instances. However, gold is the preferred material for these structures.
- an adhesive (not shown) is applied to the surface of the central die attach pad 12 , and the die 24 is then mounted to the central die attach pad 12 .
- a particularly useful adhesive for attaching the die 24 is a two part epoxy adhesive, such as Ablestick 965-IL, manufactured by Ablestick Corp. During this mounting process, there is a tendency for the adhesive to bleed during the attach period and to spread out from the attach surface 12 onto the fingers 16 , the ground ring 14 .
- Ground ring 14 is the first wire bondable gold surface that the die attach adhesive comes in contact with but, depending on how the substrate is configured, gold surfaces 18 and 20 may be affected.
- the surface of the central die attach 12 , the ground ring 14 , fingers 16 , the voltage ring 18 , and the wire bond pads 20 are treated with a chemical composition which will produce on the gold surface a “Self-Assembled Monolayer” (SAM) 26 (FIG. 2).
- SAM Self-Assembled Monolayer
- the chemical composition is generally characterized by a group that has an affinity to bond to gold or other noble metal, and is connected to one or more hydrocarbon groups, which terminate in hydrophobic and oleophobic groups.
- the groups that bond to the gold are thiol or other sulfur containing groups, such as disulfides.
- compositions have the general formulae of HS—R or R—S—S—R′, where R and R′ may be the same or different, and are hydrocarbon moieties such as (CH 2 ) n or substituted (CH 2 ) n chains which may be terminated with a methyl or fluorinated methyl group, which have hydrophobic and oleophobic characteristics.
- R and R′ may be the same or different, and are hydrocarbon moieties such as (CH 2 ) n or substituted (CH 2 ) n chains which may be terminated with a methyl or fluorinated methyl group, which have hydrophobic and oleophobic characteristics.
- the HS group attaches to the gold.
- compositions are described in the publication “Thin Films, Self Assembled Monolayers of Thiols”, edited by Abraham Ulman, Vol. 24, at pages 14-17, which is incorporated herein by reference.
- the hydrocarbon groups listed on page 15 under low-energy surfaces produce such low-energy surfaces.
- Alkyl thiols and disulfides that terminate in nonpolar groups absorb onto gold and other noble metal surfaces and have hydrophobic and oleophobic characteristics. Thus, these are the preferred compositions.
- a particularly useful thiol is 1-octadecanethiol [HS—(CH 2 ) 17 —CH 3 ].
- This chemical composition preferably is applied either by spraying or dipping or otherwise coating the entire surface of the substrate 10 with the chemical composition that forms the SAM 26 .
- the SAM 26 on the gold surfaces will protect the gold surfaces from any bleed from the adhesive wetting the gold surfaces when an I/C chip 24 is attached, as shown in FIG. 3. SAMs will not form on the organic substrate material 10 .
- the SAM material 26 When it is time to perform the wire bonding, which is at a temperature of at least about 120° C. and higher for compressive wire bonding, the SAM material 26 will desorb from the various gold surfaces and allow the wire bond to take place, as shown in FIG. 3, one of which wires is shown at 27 extending from pad 28 on I/C chip 24 to a wire bond pad 20 . It is to be understood that wire bonding can take place between the pads 28 on the chip 24 and either or both the ground ring 14 or voltage ring 18 .
- FIGS. 4 through 6 another embodiment of a laminate chip carrier is shown.
- This chip carrier is of the cavity type with the chip being mounted in the cavity.
- the chip carrier includes a substrate 30 which includes a stiffener 32 having an adhesive 34 which attaches a polyimide dielectric sheet of material 36 thereto.
- a second layer of adhesive 38 attaches a soldermask 40 thereto, and a dielectric laminate 42 is attached to the soldermask 40 .
- the stiffener 32 is preferably formed of copper or nickel clad copper.
- the laminate preferably is an FR-4 material comprised of a glass filled epoxy, as is well known in the art.
- a cavity 44 extends through the laminate 42 , the soldermask 40 , the adhesive 38 , the polyirnide 36 , the adhesive 34 , to the stiffener 32 , on which the die or I/C chip 24 will be mounted, as will be described presently.
- the laminate 42 has a gold band 46 formed on interior surface 48 thereof, which surrounds the upper portion of the cavity 44 .
- Laminate 42 also has a top surface 50 on which is formed a ground ring 52 , a voltage ring 54 and wire bond pads 56 , which are separated by soldermask 58 .
- the ground ring 52 , the voltage ring 54 and wire bond pads 56 which are wire bond surfaces, all are metal, preferably gold.
- an I/C chip 24 is bonded to the top surface 62 of stiffener 32 , (i.e. the surface is exposed in the cavity 44 of the substrate 30 ) by an epoxy 64 .
- the epoxy 64 preferably is a two component epoxy, such as Ablestick 965 - 1 L, the same as the epoxy described with respect to FIG. 3.
- all of the surfaces of the gold band 46 , the ground ring 52 , voltage ring 54 and gold wire bond pads 56 are treated with a chemical composition which will form a SAM 26 (FIG. 5) in the same manner and with the same composition as described with respect to FIGS. 1 - 3 . This will prevent bleed from the epoxy 64 from wetting the surface of the various gold or other noble metal surfaces since the sulfur or thiol moieties will adhere to the surface with a chemical bond, thus presenting an outward low surface tension surface of hydrocarbon to the surrounding space.
- the SAM 26 will desorb from the gold surfaces and allow the wire bond to take place, as shown in FIG. 6, one of which wires is shown at 27 extending from pad 28 on the I/C chip 24 to wire bond pad 56 .
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Abstract
Description
- 1. Field of the Invention
- This invention relates generally to the prevention of bleeding of organic material onto a metal substrate and, more particularly, to preventing bleeding of adhesive or components thereof onto a noble metal substrate. In even more particular aspects, this invention relates to the prevention of the bleeding of any components of a die attach adhesive onto noble metal circuitry on a dielectric substrate and, specifically, onto gold wire bond surfaces on a chip carrier or other noble metal circuitry on an I/C chip mounting substrate.
- 2. Background Information
- In the mounting of integrated circuit (I/C) chips on substrates having electrical connections, such as wire bond pads thereon, one technique of mounting utilizes a two-part epoxy adhesive to bond the chip either to gold plating on a planar surface of a substrate, or onto copper or some dielectric material in a cavity formed in an electrical substrate, which substrate also has electrical contacts or wire bond surfaces on the surface thereof. One particular problem encountered when using such bond techniques is the tendency of the components of the epoxy adhesive to “bleed” and spread onto the wire bond surfaces, such as the wire bond pads or other noble metal surfaces, such as ground rings or voltage rings, and adhere thereto. This “bleed” causes the surface of the bond pads or other metal surfaces to be unreceptive to the bonding of the wire bonds necessary to electrically connect the wire bond surfaces to the contacts on the I/C chip. This, of course, results in unsatisfactory electrical contacts and, thus, contributes to an unsatisfactory chip package.
- One prior art technique for solving this problem is to treat the part with a CF4 plasma. The plasma reacts with the organic portion of the substrate, and the fluorine containing moieties settle on the gold surface of the wire bond pads and other gold surfaces and make them less susceptible to being wetted by bleed from the adhesive. However, this is not a completely satisfactory treatment in all instances in that the fluorine containing moieties are not strongly bonded to the gold but are only lightly adhered thereto. Therefore, they can be easily removed with organic solvents during processing before attachment of the I/C chip takes place, but not easily removed with aqueous systems during processing. Moreover, the CF4 plasma tends, in many cases, to adversely affect the dielectric material for subsequent application of encapsulating material.
- It is, therefore, an object of the present invention to provide a method and structure for substantially reducing or eliminating the wettability of metal surfaces, particularly noble metal surfaces, and specifically gold or other noble metal surfaces, to organic materials, particularly any components of an adhesive, such as an epoxy used for attaching an I/C chip to a substrate, and which I/C chip is subsequently bonded thereto.
- According to the present invention, a method and structure for preventing wetting or bleed of an adhesive, such as an epoxy, onto a metal surface and particularly wire bond surfaces on the surface of a dielectric substrate is provided. This invention is particularly useful in preventing bleed from any components of an adhesive for attaching an I/C chip or a die to a substrate, and more particularly when a two-part epoxy adhesive is used. The method includes treating the surfaces of the wire bond pads with a chemical composition that prevents wetting of, or bleed onto, the wire bond surfaces by a component of the epoxy used to attach the die to the substrate surface. The chemical composition is a chemical which will provide “Self-Assembled Monolayers” (SAMs) on the surface of the gold. These compositions are characterized by a molecule having at least one group, such as a mercaptan or disulfide, connected to a hydrocarbon or substituted hydrocarbon moiety, such as (CH2)n chain. A particular molecule that is useful for this is 1-octadecanethiol [HS—(CH2)17—CH3]. The thiol or sulfur-containing portion of the molecule has an affinity for gold or other noble metals, such as palladium, platinum and silver, and chemically bonds to the metal surface, leaving the hydrocarbon segment oriented away from the surface. The affinity of the thiol or sulfur-containing portion of the molecule chemically bonding with the metals provides a relatively strong attachment of the molecule to the metal surface. The hydrocarbon segment oriented away from the surface presents a surface on the metal which has the characteristics of the hydrocarbon portion of the molecule which has a low surface tension, and, thus, prevents wetting of the gold or other noble metal by an epoxy adhesive component. Other chemical moieties, such as disulfides having a general formula of R—S—S—R′, where R and R′ are the same or different hydrocarbon moieties, such as (CH2)x or substituted chains, could be used to form the SAMs.
- The SAMs, once they provide protection from the bleed of the die attach adhesives, self desorb or are otherwise removed from the gold surface during the wire bonding temperatures, thus rendering the gold surface free from any organic layer which would interfere with wire bonding process. The composition is applied as a coating, preferably in a solvent such as butylcarbitol.
- FIG. 1 is a top plan view of a planar chip carrier after coating the gold surfaces thereon to form a SAM according to this invention and before the attachment of an I/C chip;
- FIG. 2 is a sectional view taken substantially along the plane designated by the line2-2 of FIG. 1;
- FIG. 3 is a view similar to FIG. 1 with an I/C chip attached;
- FIG. 4 is a top plan view of a chip carrier with a cavity configuration for the reception of an I/C chip after treatment of the gold surfaces to form a SAM according to this invention;
- FIG. 5 is a sectional view taken substantially along the plane designated by the line55 of FIG. 4; and
- FIG. 6 is a view similar to FIG. 4 with an I/C chip attached thereto.
- Referring now to the drawings, and, for the present, to FIG. 1, a planar chip carrier for use in the present invention is shown The chip carrier includes an organic
dielectric substrate 10 which has formed thereon a centraldie attach pad 12 which is connected to aground ring 14 byfingers 16. A voltage orpower ring 18 is also provided, as well aswire bond pads 20 on the surface of thesubstrate 10. All of thecentral die pad 12,ground ring 14,fingers 16, voltage orpower ring 18, andwire bond pads 20, preferably are formed of gold, although other noble metals, such as palladium, platinum or silver, may be used in some instances. However, gold is the preferred material for these structures. - To attach an I/C chip or die24 (FIG. 3), an adhesive (not shown) is applied to the surface of the central
die attach pad 12, and thedie 24 is then mounted to the centraldie attach pad 12. A particularly useful adhesive for attaching thedie 24 is a two part epoxy adhesive, such as Ablestick 965-IL, manufactured by Ablestick Corp. During this mounting process, there is a tendency for the adhesive to bleed during the attach period and to spread out from theattach surface 12 onto thefingers 16, theground ring 14.Ground ring 14 is the first wire bondable gold surface that the die attach adhesive comes in contact with but, depending on how the substrate is configured,gold surfaces - To overcome this problem, the surface of the central die attach12, the
ground ring 14,fingers 16, thevoltage ring 18, and thewire bond pads 20, are treated with a chemical composition which will produce on the gold surface a “Self-Assembled Monolayer” (SAM) 26 (FIG. 2). The chemical composition is generally characterized by a group that has an affinity to bond to gold or other noble metal, and is connected to one or more hydrocarbon groups, which terminate in hydrophobic and oleophobic groups. Preferably, the groups that bond to the gold are thiol or other sulfur containing groups, such as disulfides. These compositions have the general formulae of HS—R or R—S—S—R′, where R and R′ may be the same or different, and are hydrocarbon moieties such as (CH2)n or substituted (CH2)n chains which may be terminated with a methyl or fluorinated methyl group, which have hydrophobic and oleophobic characteristics. In the case of the HS—R molecule, the HS group attaches to the gold. In the case of a disulfide molecule, the bond between the sulfur atoms is believed to cleave, leaving two molecules, both of which can attach through the sulfur to the gold depending upon the resulting (CH2)n or substituted (CH2)n chain lengths as to which will predominate. The gold surface then takes on the characteristics of the hydrocarbon surface, which can have a surface tension as low as about 18 dynes/cm, which is lower than the surface tension of the epoxy used. A particularly useful class of compounds are those in the classes (HS(CH2)nX) wherein n is an integer preferably from 1 to 21, and x is methyl, ethylene or fluorinated methyl terminated group. Such compositions are described in the publication “Thin Films, Self Assembled Monolayers of Thiols”, edited by Abraham Ulman, Vol. 24, at pages 14-17, which is incorporated herein by reference. The hydrocarbon groups listed on page 15 under low-energy surfaces produce such low-energy surfaces. Alkyl thiols and disulfides that terminate in nonpolar groups absorb onto gold and other noble metal surfaces and have hydrophobic and oleophobic characteristics. Thus, these are the preferred compositions. A particularly useful thiol is 1-octadecanethiol [HS—(CH2)17—CH3]. (Mercaptans tend to oxidize to disulfides if left standing for a period of time.) This chemical composition preferably is applied either by spraying or dipping or otherwise coating the entire surface of thesubstrate 10 with the chemical composition that forms theSAM 26. TheSAM 26 on the gold surfaces, as shown in FIG. 2, will protect the gold surfaces from any bleed from the adhesive wetting the gold surfaces when an I/C chip 24 is attached, as shown in FIG. 3. SAMs will not form on theorganic substrate material 10. - When it is time to perform the wire bonding, which is at a temperature of at least about 120° C. and higher for compressive wire bonding, the
SAM material 26 will desorb from the various gold surfaces and allow the wire bond to take place, as shown in FIG. 3, one of which wires is shown at 27 extending frompad 28 on I/C chip 24 to awire bond pad 20. It is to be understood that wire bonding can take place between thepads 28 on thechip 24 and either or both theground ring 14 orvoltage ring 18. - Referring now to FIGS. 4 through 6, another embodiment of a laminate chip carrier is shown. This chip carrier is of the cavity type with the chip being mounted in the cavity. The chip carrier includes a
substrate 30 which includes astiffener 32 having an adhesive 34 which attaches a polyimide dielectric sheet ofmaterial 36 thereto. A second layer of adhesive 38 attaches asoldermask 40 thereto, and adielectric laminate 42 is attached to thesoldermask 40. Thestiffener 32 is preferably formed of copper or nickel clad copper. The laminate preferably is an FR-4 material comprised of a glass filled epoxy, as is well known in the art. Acavity 44 extends through the laminate 42, thesoldermask 40, the adhesive 38, thepolyirnide 36, the adhesive 34, to thestiffener 32, on which the die or I/C chip 24 will be mounted, as will be described presently. The laminate 42 has agold band 46 formed oninterior surface 48 thereof, which surrounds the upper portion of thecavity 44.Laminate 42 also has atop surface 50 on which is formed aground ring 52, avoltage ring 54 andwire bond pads 56, which are separated bysoldermask 58. Theground ring 52, thevoltage ring 54 andwire bond pads 56, which are wire bond surfaces, all are metal, preferably gold. - As can be seen in FIGS. 5 and 6, an I/
C chip 24 is bonded to thetop surface 62 ofstiffener 32, (i.e. the surface is exposed in thecavity 44 of the substrate 30) by anepoxy 64. The epoxy 64 preferably is a two component epoxy, such as Ablestick 965-1L, the same as the epoxy described with respect to FIG. 3. As previously described, in order to prevent bleed of the epoxy 64, all of the surfaces of thegold band 46, theground ring 52,voltage ring 54 and goldwire bond pads 56, are treated with a chemical composition which will form a SAM 26 (FIG. 5) in the same manner and with the same composition as described with respect to FIGS. 1-3. This will prevent bleed from the epoxy 64 from wetting the surface of the various gold or other noble metal surfaces since the sulfur or thiol moieties will adhere to the surface with a chemical bond, thus presenting an outward low surface tension surface of hydrocarbon to the surrounding space. - As described previously, where bonding takes place, the
SAM 26 will desorb from the gold surfaces and allow the wire bond to take place, as shown in FIG. 6, one of which wires is shown at 27 extending frompad 28 on the I/C chip 24 to wirebond pad 56. - It is to be understood that various modifications of the above-described embodiments can be made, for example, rather than relying on the processing temperatures during wire bonding.
Claims (25)
Priority Applications (1)
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US09/881,466 US6420253B2 (en) | 2000-03-28 | 2001-06-14 | Method for preventing adhesive bleed onto surfaces |
Applications Claiming Priority (2)
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US09/537,959 US6252307B1 (en) | 2000-03-28 | 2000-03-28 | Structure for preventing adhesive bleed onto surfaces |
US09/881,466 US6420253B2 (en) | 2000-03-28 | 2001-06-14 | Method for preventing adhesive bleed onto surfaces |
Related Parent Applications (1)
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US09/537,959 Division US6252307B1 (en) | 2000-03-28 | 2000-03-28 | Structure for preventing adhesive bleed onto surfaces |
Publications (2)
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US20010028117A1 true US20010028117A1 (en) | 2001-10-11 |
US6420253B2 US6420253B2 (en) | 2002-07-16 |
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US09/537,959 Expired - Fee Related US6252307B1 (en) | 2000-03-28 | 2000-03-28 | Structure for preventing adhesive bleed onto surfaces |
US09/881,466 Expired - Fee Related US6420253B2 (en) | 2000-03-28 | 2001-06-14 | Method for preventing adhesive bleed onto surfaces |
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US09/537,959 Expired - Fee Related US6252307B1 (en) | 2000-03-28 | 2000-03-28 | Structure for preventing adhesive bleed onto surfaces |
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Cited By (1)
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US20090023243A1 (en) * | 2004-12-28 | 2009-01-22 | Mitsumasa Koyanagi | Method and apparatus for fabricating integrated circuit device using self-organizing function |
Families Citing this family (11)
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JP2001168223A (en) * | 1999-12-07 | 2001-06-22 | Fujitsu Ltd | Semiconductor device |
TW511414B (en) * | 2001-04-19 | 2002-11-21 | Via Tech Inc | Data processing system and method, and control chip, and printed circuit board thereof |
US20060043587A1 (en) * | 2004-08-31 | 2006-03-02 | Lsi Logic Corporation, A Delaware Corporation | Apparatus and method for reducing signal cross talk between wire bonds of semiconductor packages |
US20060065983A1 (en) * | 2004-09-30 | 2006-03-30 | Lsi Logic Corporation | Semiconductor package with wire bond arrangement to reduce cross talk for high speed circuits |
TWI265095B (en) * | 2005-08-16 | 2006-11-01 | Ind Tech Res Inst | Nozzle plate |
US20070099346A1 (en) * | 2005-11-01 | 2007-05-03 | International Business Machines Corporation | Surface treatments for underfill control |
US20090035455A1 (en) * | 2007-07-31 | 2009-02-05 | Endicott Interconnect Technologies, Inc. | Adhesive bleed prevention method and product produced from same |
MY165210A (en) * | 2009-12-04 | 2018-03-05 | Oclaro Tech Ltd | Surface treatments and coatings |
WO2012082863A1 (en) | 2010-12-15 | 2012-06-21 | Advanced Bionics Ag | Protection for implanted gold surfaces |
ITUB20159489A1 (en) | 2015-12-28 | 2017-06-28 | St Microelectronics Srl | METHOD FOR THE SURFACE TREATMENT OF A SEMICONDUCTOR SUBSTRATE |
EP3722741A1 (en) * | 2019-04-08 | 2020-10-14 | Nokia Technologies Oy | An apparatus comprising a cantilever |
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CA1197325A (en) | 1984-06-04 | 1985-11-26 | Beverley W. Gumb | Masking of holes in circuit patterns on circuit boards prior to flow soldering |
US4803124A (en) | 1987-01-12 | 1989-02-07 | Alphasem Corporation | Bonding semiconductor chips to a mounting surface utilizing adhesive applied in starfish patterns |
US5635047A (en) * | 1992-07-28 | 1997-06-03 | Iowa State University Research Foundation, Inc. | Electrochemical method of controlling thiolate coverage on a conductive substrate such as gold |
US5900160A (en) | 1993-10-04 | 1999-05-04 | President And Fellows Of Harvard College | Methods of etching articles via microcontact printing |
US5514501A (en) | 1994-06-07 | 1996-05-07 | The United States Of America As Represented By The Secretary Of Commerce | Process for UV-photopatterning of thiolate monolayers self-assembled on gold, silver and other substrates |
US5523878A (en) | 1994-06-30 | 1996-06-04 | Texas Instruments Incorporated | Self-assembled monolayer coating for micro-mechanical devices |
US5598193A (en) * | 1995-03-24 | 1997-01-28 | Hewlett-Packard Company | Treatment of an orifice plate with self-assembled monolayers |
US5731547A (en) | 1996-02-20 | 1998-03-24 | International Business Machines Corporation | Circuitized substrate with material containment means and method of making same |
US5719087A (en) | 1996-03-07 | 1998-02-17 | Taiwan Semiconductor Manufacturing Company, Ltd. | Process for bonding pad protection from damage |
-
2000
- 2000-03-28 US US09/537,959 patent/US6252307B1/en not_active Expired - Fee Related
-
2001
- 2001-06-14 US US09/881,466 patent/US6420253B2/en not_active Expired - Fee Related
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20090023243A1 (en) * | 2004-12-28 | 2009-01-22 | Mitsumasa Koyanagi | Method and apparatus for fabricating integrated circuit device using self-organizing function |
US8283208B2 (en) * | 2004-12-28 | 2012-10-09 | Mitsumasa Koyanagi | Method and apparatus for fabricating integrated circuit device using self-organizing function |
US8722460B2 (en) | 2004-12-28 | 2014-05-13 | Mitsumasa Koyanagi | Method and apparatus for fabricating integrated circuit device using self-organizing function |
Also Published As
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US6252307B1 (en) | 2001-06-26 |
US6420253B2 (en) | 2002-07-16 |
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