GB2330689A - Method of attaching solder bumps to a die - Google Patents

Method of attaching solder bumps to a die Download PDF

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Publication number
GB2330689A
GB2330689A GB9722301A GB9722301A GB2330689A GB 2330689 A GB2330689 A GB 2330689A GB 9722301 A GB9722301 A GB 9722301A GB 9722301 A GB9722301 A GB 9722301A GB 2330689 A GB2330689 A GB 2330689A
Authority
GB
United Kingdom
Prior art keywords
substrate
article
flowable
die
medium
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Withdrawn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
GB9722301A
Other versions
GB9722301D0 (en
Inventor
Kenneth Kaskoun
Erik Jung
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.)
Motorola Solutions Inc
Original Assignee
Motorola Inc
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 Motorola Inc filed Critical Motorola Inc
Priority to GB9722301A priority Critical patent/GB2330689A/en
Publication of GB9722301D0 publication Critical patent/GB9722301D0/en
Publication of GB2330689A publication Critical patent/GB2330689A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
    • H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
    • H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
    • H05K3/3457—Solder materials or compositions; Methods of application thereof
    • H05K3/3478—Applying solder preforms; Transferring prefabricated solder patterns
    • 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
    • H01L24/01—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
    • H01L24/10—Bump connectors ; Manufacturing methods related thereto
    • H01L24/11—Manufacturing methods
    • 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
    • H01L2224/10—Bump connectors; Manufacturing methods related thereto
    • H01L2224/12—Structure, shape, material or disposition of the bump connectors prior to the connecting process
    • H01L2224/13—Structure, shape, material or disposition of the bump connectors prior to the connecting process of an individual bump connector
    • H01L2224/13001—Core members of the bump connector
    • H01L2224/13099—Material
    • 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
    • H01L2924/01075—Rhenium [Re]
    • 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
    • H01L2924/01082—Lead [Pb]
    • 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
    • H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
    • H01L2924/161—Cap
    • H01L2924/1615—Shape
    • H01L2924/16152—Cap comprising a cavity for hosting the device, e.g. U-shaped cap
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/10—Details of components or other objects attached to or integrated in a printed circuit board
    • H05K2201/10613—Details of electrical connections of non-printed components, e.g. special leads
    • H05K2201/10621—Components characterised by their electrical contacts
    • H05K2201/10674—Flip chip
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/03—Metal processing
    • H05K2203/0338—Transferring metal or conductive material other than a circuit pattern, e.g. bump, solder, printed component
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/07—Treatments involving liquids, e.g. plating, rinsing
    • H05K2203/0756—Uses of liquids, e.g. rinsing, coating, dissolving
    • H05K2203/0776—Uses of liquids not otherwise provided for in H05K2203/0759 - H05K2203/0773
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/15—Position of the PCB during processing
    • H05K2203/159—Using gravitational force; Processing against the gravity direction; Using centrifugal force

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Computer Hardware Design (AREA)
  • Power Engineering (AREA)
  • Wire Bonding (AREA)

Abstract

A substrate 2 is provided with solder bumps 4 and a die 10 is aligned and brought into contact with the substrate. The substrate is bonded to the die by heating the solder bumps to form an assembly. To separate the die from the substrate the assembly is placed in a bath of non oxidizing fluid 20 (eg a mixture of glycerol and iso-propyl alcohol) with the dies lowermost. The fluid is heated to melt the solder bumps and the dies together with the solder bumps separate from the substrate and sink to the bottom of the bath.

Description

METHOD OF ATTACHING RE-FLOWABLE CONTACTS TO AN ARTICLE FIELD OF INVENTION This invention relates to attaching re-flowable contacts to articles and particularly, though not exclusively, to providing articles such as semiconductor die or wafers with re-flowable contacts such as solder bumps.
BACKGROUND It is well known in the electronics industry to attach solder bumps to a semiconductor die or wafer in order for the die or wafer to be subsequently "surface-mounted" to a printed circuit board using "flip-chip" technology. In surface-mounting a solder-bumped die or wafer to a printed circuit board, the board and the die or wafer are placed together with the solder bllmps contacting the board in predetermined alignment, and the assembly is heated until the solder bumps melt sufficiently to adhere to the board; the assembly is then cooled to allow the solder to solidify and form lasting mechanical and electrical bonds between the printed circuit board and the die or wafer. The die or wafer is thus surface-mounted to the printed circuit board without the need for further machine or manual-processes of electrical soldering or mechanical attachment.
One method to be able to solder-bump the die or wafer (i.e., in order to provide the die or wafer with solder bumps attached at predetermined positions) is to first provide solder bumps at predetermined positions on a substrate, and then to bring the die or wafer into contact with the substrate. The assembly is then heated until the solder bumps melt sufficiently to adhere to the die or wafer. This structure is then cooled so that a solid contact is made between the die or wafer and the substrate.
The structure is then reheated to the melting point and the substrate and the die or wafer are separated. The surface areas of pads to which the solder bumps adhere on the die or wafer are chosen to be greater than the surface areas of similar pads on the substrate, so that at separation most of the solder remains on the larger surface area pads of the die or wafer.
The most important and challenging part of this operation is the release and transfer of the solder bumps from the substrate to the die or wafer. Known techniques for separating the substrate and the die or wafer have involved manually prizing or shearing the components apart when a predetermined temperature has been reached. Such known techniques have often resulted in poor consistency in adequately releasing and transferring the solder bumps from the substrate to the die or wafer or in damage to the bumps or the substrate, preventing its re-use.
There is a need for a process whereby the separation of the substrate and the die or wafer occurs in such a manner that the release and transfer of the solder bumps from the substrate to the die or wafer is effected reliably and repeatably.
SUMMARY OF INVENTION In accordance with the invention, there is provided a method of attaching re-flowable contacts to an article as claimed in claim 1.
BRIEF DESCRIPTION OF DRAWINGS One method of providing a semiconductor product die with solder bumps will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 shows a product die and a substrate with solder bumps to be transferred.
FIG. 2 shows the product die and the substrate of FIG. 1 assembled during processing.
FIGS. 3 and 4 show the assembled product die and substrate of FIG. 2 immersed in glycerol or a mixture of glycerol and ispropyl alcohol during the transfer and release step of the process in accordance with the present invention.
FIGS. 5 shows, alternatively to FIG. 2, an assembly of the product die and the substrate of FIG. 1 with a weight attached to the product die.
FIG. 6 shows the assembled product die and substrate of FIG. 4 immersed in glycerol or a mixture of glycerol and iso-propyl alcohol during the transfer and release step of the process in accordance with the present invention.
DESCRIPTION OF PREFERRED EMBODIMENT Referring now firstly to FIG. 1, in a process for attaching solder bumps to a semiconductor device, a substrate 2 is provided with solder bumps 4 attached to pads 6 which are arranged at predetermined positions on the substrate 2 and coupled to the active layer or layers (not shown) that are part of the semiconductor device. The bumps 4, which are of conventional lead/tin (Pb/Sn) solder material, may be put on the substrate by any of a number of known technologies such as plating, screen printing, etc.
A semiconductor device 10 in the form of a semiconductor die or wafer has similar pads 12 (which, as will be discussed below, are of greater surface area than the pads 6 of the substrate 2) which are coupled to the active layer or layers (not shown) that are part of the semiconductor device 10.
Two or more such semiconductor devices 10 and the substrate 2 are brought together, with their pads in alignment and facing opposite each other, so that the solder bumps 4 on the substrate 2 touch the pads 12 of each of the semiconductor devices 10. The touching substrate 2 and semiconductor devices 10 are held together and heated to a temperature which allows the solder of the bumps 4 to melt (as shown by the bumps' dashed-line boundaries in FIG. 2) and form a bond between the substrate and the device, resulting in the assembly 16 shown in FIG. 2. At this point, burn-in or any necessary testing of the devices 10 may be performed on the assembled devices.
Referring now also to FIG. 3, the assembly 16 of the substrate and its devices is then immersed in a bath 18 containing glycerol or a nonoxidizing mixture of glycerol and iso-propyl alcohol (G/IPA) 20. The assembly is arranged with the substrate 2 uppermost and supported at its periphery on a frame 22, the devices 10 hanging down from substrate and supported therefrom only by the bonded solder bumps 4. Thus, the substrate 2 and the devices 10 individually experience different forces (apart from the bonding provided by the solder bumps 4 and apart from buoyancy effects): the substrate experiencing no net force (its own weight being counteracted by the reactive force provided by the supporting frame 18) and the devices 10 experiencing only their own weight.
The bath 18 is located on a hot plate 24 which is used to heat the bath and its contents. As the temperature of the glycerol or G/IPA inedium 20 reaches the melting point of the solder bumps 4, the solder begins to melt. As the solder bumps 4 become molten, they cease to hold the devices 10 to the substrate 2, and when the weight of the devices overcomes surface tension effects of the molten solder bumps, the devices separate from the substrate 2 and fall gently to the bottom of the bath 18.
As mentioned above, the surface areas of the pads 12 on the devices 10 are greater than those of the pads 6 on the substrate 2. The effect of this difference in surface areas is that when the devices 10 separate from the substrate (when the solder bumps 4 melt), most of the solder comes away on the larger of the pads (i.e., those of the devices 10). In this way the solder bumps 4 are transferred from the substrate 2 to the devices 10. The separated devices 10 are subsequently removed from the bottom of the bath 16 and may be used for flip-chip surface-mounting as is well known, with the transferred solder bumps being re-flowed to make final electrical and mechanical bonds for the device.
Referring now also to FIG. 5, it will be appreciated that if there are a large number of solder bumps to be transferred to a particular device 26, the resultant combined surface tension effects of the molten solder may make it difficult for the device to satisfactorily separate from the substrate.
In this case, it may be desirable to attach a weight 28 (such as, for example, a metal slug weighing approximately 10mg per solder bump) to the device 26 on its side remote from that to which solder bumps are to be transferred. The weight 28 may be attached by any convenient means, such as high-temperature tape or adhesive (e.g., epoxy or glue).
The remainder of the transfer and release process takes place as described above, but now when the solder melts, the weight 28 promotes positive separation and, as shown in FIG. 6, the solder-bumped devices 26 fall to the bottom of the bath. When the solder-bumped devices 24 are removed from the bath, the weights 22 may be removed from the devices (using acetone, or another suitable solvent, if necessary) and re-used.
It will be appreciated that the above-described transfer and release process has many advantages. It is simple, low-cost, has very few process steps and requires very little equipment. It is automatic in that separation and transfer occur when the temperature of the solder reaches melting point and surface tension effects of the molten solder are overcome. The separation produced is slow but sure, and results in good, consistent and repeatable solder bump transfer. The process can also be high-speed because both full wafers and individual semiconductor chips can be processed simultaneously in the same amount of time. Further, since the separation takes place in a non-oxidizing environment glycerol or (the G/IPA medium) the transferred solder bumps are not oxidized during the transfer process and remain of high quality.
It will also be understood that variations in the above described solder bump transfer and release process can be made. For example, if the weight of the devices allows, the density of the heating medium may be arranged so that the devices float to the surface upon separation (the substrate being held down in the medium) so that the solder-bumped devices may be skimmed from the surface.

Claims (10)

  1. CLAIMS 1. A method of attaching re-flowable contacts to an article, the method comprising the steps of: providing the article having thereon predetermined areas in which the re-flowable contacts are to be attached; providing a substrate having thereon predetermined areas containing bumps of flowable contact material; bringing the article into contact with the substrate, with the predetermined areas of the substrate and the article in alignment and opposition, to form an assembly; containing the assembly in a medium in which the substrate and the article individually experience different forces; raising the temperature of the medium containing the assembly to a point at which the contact material flows; allowing the substrate and the article to separate when the contact material flows from the substrate to the article and the difference between the forces experienced by the substrate and the article overcomes surface tension effects; and removing the separated articles with attached re-flowable contacts from the medium.
  2. 2. A method as claimed in claim 1 wherein the substrate is held in the medium, allowing the article to separate from the substrate by floating or sinking
  3. 3. A method as claimed in claim 2 wherein the density of the medium is less than that of the article whereby the article sinks from the substrate.
  4. 4. A method as claimed in claim 3 further comprising attaching a weight to the article to promote separation of the article from the substrate.
  5. 5. A method as claimed in any preceding claim wherein the flowable contact material is solder.
  6. 6. A method as claimed in claim 5 wherein the solder is a Pb/Sn composition.
  7. 7. A method as claimed in any preceding claim wherein the medium is non-ondlzmg.
  8. 8. A method as claimed in claim 7 wherein the medium contains glycerol or a mixture of glycerol and iso-propyl alcohol.
  9. 9. A method as claimed in any preceding claim wherein a plurality of the articles have re-flowable contacts transferred from a single substrate.
  10. 10. A method of attaching re-flowable contacts to an article substantially as hereinbefore described with reference to the accompanying drawings.
GB9722301A 1997-10-23 1997-10-23 Method of attaching solder bumps to a die Withdrawn GB2330689A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9722301A GB2330689A (en) 1997-10-23 1997-10-23 Method of attaching solder bumps to a die

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9722301A GB2330689A (en) 1997-10-23 1997-10-23 Method of attaching solder bumps to a die

Publications (2)

Publication Number Publication Date
GB9722301D0 GB9722301D0 (en) 1997-12-17
GB2330689A true GB2330689A (en) 1999-04-28

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Family Applications (1)

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GB9722301A Withdrawn GB2330689A (en) 1997-10-23 1997-10-23 Method of attaching solder bumps to a die

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5219117A (en) * 1991-11-01 1993-06-15 Motorola, Inc. Method of transferring solder balls onto a semiconductor device
US5381946A (en) * 1992-03-04 1995-01-17 Mcnc Method of forming differing volume solder bumps

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5219117A (en) * 1991-11-01 1993-06-15 Motorola, Inc. Method of transferring solder balls onto a semiconductor device
US5381946A (en) * 1992-03-04 1995-01-17 Mcnc Method of forming differing volume solder bumps

Also Published As

Publication number Publication date
GB9722301D0 (en) 1997-12-17

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)