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WO1999063588A1 - Method for remelting solder layers - Google Patents

Method for remelting solder layers Download PDF

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Publication number
WO1999063588A1
WO1999063588A1 PCT/EP1999/003800 EP9903800W WO9963588A1 WO 1999063588 A1 WO1999063588 A1 WO 1999063588A1 EP 9903800 W EP9903800 W EP 9903800W WO 9963588 A1 WO9963588 A1 WO 9963588A1
Authority
WO
WIPO (PCT)
Prior art keywords
solder
wiring
solder layers
remelting
melted
Prior art date
Application number
PCT/EP1999/003800
Other languages
German (de)
French (fr)
Inventor
Rolf Aschenbrenner
Joachim KLÖSER
Erik Jung
Luc Boone
Hubert De Steur
Marcel Heerman
Jozef Van Puymbroeck
Original Assignee
Siemens S.A.
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 Siemens S.A. filed Critical Siemens S.A.
Publication of WO1999063588A1 publication Critical patent/WO1999063588A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K1/00—Soldering, e.g. brazing, or unsoldering
    • B23K1/005—Soldering by means of radiant energy
    • B23K1/0056—Soldering by means of radiant energy soldering by means of beams, e.g. lasers, E.B.
    • 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
    • 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
    • H05K3/3473—Plating of solder
    • 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
    • H05K3/3494—Heating methods for reflowing of solder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/36—Electric or electronic devices
    • B23K2101/42—Printed circuits
    • 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
    • H01L2224/15—Structure, shape, material or disposition of the bump connectors after the connecting process
    • H01L2224/16—Structure, shape, material or disposition of the bump connectors after the connecting process of an individual bump connector
    • H01L2224/161—Disposition
    • H01L2224/16151—Disposition the bump connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/16221—Disposition the bump connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/16225—Disposition the bump connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation
    • 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
    • H01L2224/80—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
    • H01L2224/81—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 using a bump connector
    • H01L2224/8119—Arrangement of the bump connectors prior to mounting
    • H01L2224/81192—Arrangement of the bump connectors prior to mounting wherein the bump connectors are disposed only on another item or body to be connected to the semiconductor or solid-state body
    • 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
    • H05K2203/04—Soldering or other types of metallurgic bonding
    • H05K2203/043—Reflowing of solder coated conductors, not during connection of components, e.g. reflowing solder paste
    • 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
    • H05K2203/10—Using electric, magnetic and electromagnetic fields; Using laser light
    • H05K2203/107—Using laser light

Definitions

  • the reliability of electronic devices depends to a large extent on the quality of the installed circuit boards.
  • the quality of the printed circuit boards is strongly dependent on the quality of the plated-through holes, their layer bonding and the soldering friendliness of the printed circuit board surface.
  • solder layers In order to facilitate the soldering work on printed circuits, their conductor tracks, which are made of copper, are often provided with a solder layer by galvanic deposition of tin or tin-lead, which is intended to prevent oxidation of the copper surfaces.
  • This solder layer is then remelted by a heating process, for example by exposure to infrared radiation or by immersion in a hot oil bath (cf. DE-A-25 02 900). This remelting process is necessary because such electrodeposited solder layers cannot be soldered or can only be soldered poorly.
  • the invention is based on the finding that the remelting of solder layers applied to the conductor pattern of a wiring can be carried out selectively with the aid of a laser beam without heating the entire wiring. Since the solder layers can also be melted extremely quickly with the aid of a laser beam, the wiring is subjected to minimal thermal stress. Due to the locally limited remelting process which can be carried out within a time period of less than 0.1 seconds, the laser remelting can also be carried out in the case of wiring whose circuit carriers have only a low temperature resistance.
  • MID Molded Interconnection Devices
  • laser remelting can also melt solder layers applied by chemical metal deposition or, for example, solder layers applied by screen printing.
  • the embodiment according to claim 3 enables the formation of solder bumps on connection pads of a wiring by laser remelting.
  • solder layers are melted on the connection pads and on conductor areas leading away from them and constricted in their width, the solder melted on these conductor areas flowing to the connection pads and the volume of the solder bumps that arise as a result of the melting on themselves being correspondingly increased.
  • the width of the conductor areas serving as solder supply structures must be reduced in order to prevent the solder from flowing off over the subsequent conductor runs of the wiring. This eliminates the need to apply a solder resist to the corresponding areas of the wiring.
  • the development according to claim 4 enables a very rapid remelting of the solder layers with a particularly low thermal load on the circuit carriers.
  • Nd: YAG lasers with a wavelength of 1.06 ⁇ m have proven particularly good for remelting solder layers.
  • the laser remelting of solder layers can in principle also be carried out with a diode laser array or with a strip-shaped laser beam.
  • laser remelting with the aid of a deflectable laser beam is preferred, since this results in a very high degree of flexibility and also enables a targeted selection of the areas to be melted.
  • the areas of a solder layer to be melted can be scanned extremely quickly with a deflectable laser beam.
  • Figures 1 to 6 show different stages of the process in the production of wiring and the formation of solder bumps on the connection pads of this wiring.
  • FIG. 7 shows the finished wiring after a semiconductor component has been soldered on.
  • FIG. 1 shows an electrically insulating substrate S with a metallization M applied on one side.
  • This metallization M is a thin copper lamination or a layer applied by chemical metal deposition of copper.
  • the metallization M is then structured with an Nd-YAG laser with a wavelength of 1.06 ⁇ m, this laser structuring being indicated in FIG. 1 by a laser beam LSI.
  • connection pads P and conductor lines, LZ are produced in the laser structuring, the connection pads P being connected to the further conductor lines via conductor regions LB of reduced width.
  • the wiring also has a collecting line SL, which is connected to the individual connection pads P via solder supply structures LS, which are also reduced in width compared to the conductor tracks LZ.
  • the SL collecting line enables cathodic contacting of the entire conductor pattern and thus galvanic metal deposition on the conductor pattern.
  • a reinforcing layer V made of copper and a solder layer L made of a tin-lead alloy are applied in succession to the conductor pattern by galvanic metal deposition.
  • the electrical separation of the collecting line SL from the rest of the conductor pattern is initiated by a laser beam indicated in FIG. 3 by an arrow LS2. in this connection
  • REPLACEMENT SHEET (RE3EL8 ⁇ ) the Nd-YAG laser with a wavelength of 0.355 ⁇ or 1.06 ⁇ m is used to remove the solder layer L in the areas of the solder feed structures LS directly adjacent to the collecting line SL, whereupon the copper of the reinforcing layer V and the metallization M thereby exposed, as shown in FIG. 4 is removed by etching up to the surface of the substrate S.
  • FIG. 4 also shows a deflectable laser beam LS3, with which the solder layer L is melted simultaneously on a connection pad P, on the conductor area LB leading away therefrom and on the solder supply structure LS leading away therefrom.
  • a deflectable laser beam LS3 with which the solder layer L is melted simultaneously on a connection pad P, on the conductor area LB leading away therefrom and on the solder supply structure LS leading away therefrom.
  • an Nd-YAG laser with a wavelength of 1.06 ⁇ m is used, the laser beam LS3 of which is strongly out of focus.
  • the liquid solder flows from the narrow solder supply structure LS and from the narrow conductor region LB to the connection pad P, so that a solder bump LH is automatically created there according to FIG.
  • the volume of the solder bump LH can optionally be further increased by additional, narrow solder feed structures leading away from the connection pad P and ending blindly.
  • FIG. 6 shows the arrangement of a bumpless semiconductor component HB on the wiring, the connection surfaces AF of which, for example, consist of a layer sequence of aluminum, nickel and gold, lie directly on the tips of the associated solder bumps LH. If all the solder bumps LH assigned to the semiconductor module HB are subsequently melted simultaneously, for example by reflow soldering or by laser soldering, reliable soldered connections with the concave shape of the solder bumps LH shown in FIG. 7 result.
  • solder layers L can of course also be carried out.
  • solder dots instead of the high solder bumps LH on the connection pads.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Engineering (AREA)
  • Ceramic Engineering (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Power Engineering (AREA)
  • Manufacturing Of Printed Wiring (AREA)
  • Electric Connection Of Electric Components To Printed Circuits (AREA)
  • Laser Beam Processing (AREA)

Abstract

Solder layers (L) which are at least partially deposited on the conductor pattern of a wiring by electrodeposition, by chemical deposition or also by serigraphy must be remelted in order to improve their solderability. This remelting is selectively carried out with the assistance of a laser beam (LS3). In doing this, the wiring is subjected to only a minimal thermal stress.

Description

Beschreibungdescription
Verfahren zum Umschmelzen von LotschichtenProcess for remelting solder layers
Die Zuverlässigkeit von elektronischen Geräten hängt in hohem Maße von der Qualität der eingebauten Leiterplatten ab. Die Qualität der Leiterplatten wiederum ist stark abhängig von der Qualität der Durchkontaktierungen, ihrer Lagenverklebung sowie der Lotfreudigkeit der Leiterplattenoberfläche.The reliability of electronic devices depends to a large extent on the quality of the installed circuit boards. The quality of the printed circuit boards, in turn, is strongly dependent on the quality of the plated-through holes, their layer bonding and the soldering friendliness of the printed circuit board surface.
Zur Erleichterung der Lötarbeiten auf gedruckten Schaltungen werden deren aus Kupfer bestehenden Leiterzüge häufig durch galvanische Abscheidung von Zinn oder Zinn-Blei mit einer Lotschicht versehen, welche eine Oxidation der Kupferoberflä- chen verhindern soll. Anschließend wird diese Lotschicht durch einen Wärmeprozeß, beispielsweise durch Einwirkung von Infrarotstrahlung oder durch Eintauchen in ein heißes Ölbad, umgeschmolzen (vgl. DE-A- 25 02 900). Dieser Umschmelzprozeß ist notwendig, da derartige galvanisch abgeschiedene Lot- schichten nicht oder allenfalls nur schlecht lötbar sind.In order to facilitate the soldering work on printed circuits, their conductor tracks, which are made of copper, are often provided with a solder layer by galvanic deposition of tin or tin-lead, which is intended to prevent oxidation of the copper surfaces. This solder layer is then remelted by a heating process, for example by exposure to infrared radiation or by immersion in a hot oil bath (cf. DE-A-25 02 900). This remelting process is necessary because such electrodeposited solder layers cannot be soldered or can only be soldered poorly.
Durch die thermische Belastung der Leiterplatten beim Umschmelzen der galvanisch aufgebrachten Lotschichten treten mechanische Spannungen auf und die Haftung zwischen Harz und Kupfer nimmt ab. Als Folge dieser Erscheinungen können sich eine Delamination der Leiterplatte und auch ein Abriß der Durchkontaktierungen ergeben. Zur Vermeidung derartiger Beschädigungen der Leiterplatten durch thermische Belastung wurde in der EP-A-0 330 922 vorgeschlagen, das Umschmelzen der galvanisch abgeschiedenen Lotschichten in einem Überdruckbehälter bei erhöhtem Gasumgebungdruck durchzuführen. Die beim Umschmelzen durch verschiedene Wärmeausdehnungskoeffizienten der verschiedenen Materialien auftretenden mechanische Spannungen werden dabei durch den erhöhten und in allen Richtungen wirkenden Gasumgebungsdruck weitgehend kompensiert. Der im Anspruch 1 angegebenen Erfindung liegt das Problem zugrunde, ein Verfahren zum Umschmelzen von auf das Leitermuster einer Verdrahtung zumindest partiell aufgebrachten Lot- schichten zu schaffen, welches ohne schädliche thermische Belastung der Verdrahtung einfach und schnell durchgeführt werden kann.Due to the thermal load on the printed circuit boards when the galvanically applied solder layers are melted, mechanical stresses occur and the adhesion between resin and copper decreases. As a result of these phenomena, delamination of the printed circuit board and also tearing off of the plated-through holes can result. In order to avoid such damage to the printed circuit boards due to thermal stress, it was proposed in EP-A-0 330 922 to carry out the remelting of the electrodeposited solder layers in an overpressure container at elevated ambient gas pressure. The mechanical stresses that occur during remelting due to different coefficients of thermal expansion of the different materials are largely compensated for by the increased gas ambient pressure acting in all directions. The invention specified in claim 1 is based on the problem of creating a method for remelting solder layers which are at least partially applied to the conductor pattern of a wiring, and which can be carried out simply and quickly without harmful thermal stress on the wiring.
Der Erfindung liegt die Erkenntnis zugrunde, daß das Um- schmelzen von auf das Leitermuster einer Verdrahtung aufgebrachten Lotschichten ohne Erhitzung der gesamten Verdrahtung selektiv mit Hilfe eines Laserstrahls vorgenommen werden kann. Da das Aufschmelzen der Lotschichten mit Hilfe eines Laserstrahls außerdem extrem schnell vorgenommen werden kann, ergibt sich eine minimale thermische Belastung der Verdrahtungen. Durch den örtlich begrenzten und innerhalb einer Zeitdauer von weniger als 0,1 Sekunden durchführbaren Um- schmelzvorgang kann das Laseru schmelzen auch bei Verdrahtungen durchgeführt werden, deren Schaltungsträger nur eine ge- ringe Temperaturbeständigkeit aufweisen. Somit kann das Laserumschmelzen bei allen Arten von Verdrahtungen, insbesondere auch bei flexiblen Verdrahtungen, bei nach der MID- Technologie (MID = Molded Interconnection Devices) hergestellten Spritzgießteilen mit integrierten Leiterzügen und bei den beispielsweise aus der WO-A-9609646 bekannten Polymer Stud Grid Arrays (PSGA) angewandt werden. Durch das Laserumschmelzen können außer galvanisch abgeschiedene Lotschichten aber auch durch chemische Metallabscheidung aufgebrachte Lotschichten oder beispielsweise auch durch Siebdruck aufge- brachte Lotschichten aufgeschmolzen, werden.The invention is based on the finding that the remelting of solder layers applied to the conductor pattern of a wiring can be carried out selectively with the aid of a laser beam without heating the entire wiring. Since the solder layers can also be melted extremely quickly with the aid of a laser beam, the wiring is subjected to minimal thermal stress. Due to the locally limited remelting process which can be carried out within a time period of less than 0.1 seconds, the laser remelting can also be carried out in the case of wiring whose circuit carriers have only a low temperature resistance. Laser remelting can thus be used in all types of wiring, in particular also in flexible wiring, in injection molded parts produced using MID technology (MID = Molded Interconnection Devices) with integrated conductor tracks and in the polymer stud grid arrays known from WO-A-9609646, for example (PSGA) are applied. In addition to electrodeposited solder layers, laser remelting can also melt solder layers applied by chemical metal deposition or, for example, solder layers applied by screen printing.
Vorteilhafte Ausgestaltungen des erfindungsgemäßen Verfahrens zum Umschmelzen von auf das Leitermuster einer Verdrahtung aufgebrachten Lotschichten sind in den Ansprüchen 2 bis 6 an- gegeben . Die Ausgestaltung nach Anspruch 2 ermöglicht eine weitere Reduzierung der thermischen Belastung, da das Umschmelzen nur an den Stellen einer Verdrahtung vorgenommen wird, an denen später eine gute Lötbarkeit gewährleistet sein muß.Advantageous refinements of the method according to the invention for remelting solder layers applied to the conductor pattern of a wiring are specified in claims 2 to 6. The embodiment according to claim 2 enables a further reduction in the thermal load, since the remelting is carried out only at those points in the wiring where later good solderability must be ensured.
Die Ausgestaltung nach Anspruch 3 ermöglicht die Bildung von Lothöckern auf Anschluß-Pads einer Verdrahtung durch Laserum- schmelzen. Dabei werden Lotschichten auf den Anschluß-Pads und auf davon wegführenden, in der Breite eingeschnürten Lei- terbereichen aufgeschmolzen, wobei das auf diesen Leiterbereichen aufgeschmolzene Lot zu den Anschluß-Pads hin fließt und das Volumen der durch das Aufschmelzen von selbst entstehenden Lothöcker entsprechend vergrößert. Die als Lotzufuhrstrukturen dienenden Leiterbereiche müssen dabei in ihrer Breite reduziert sein, um ein Abfließen des Lot über die anschließenden Leiterzüge der Verdrahtung zu verhindern. Das Aufbringen eines Lötstoplackes auf die entsprechenden Bereiche der Verdrahtung kann hierdurch entfallen.The embodiment according to claim 3 enables the formation of solder bumps on connection pads of a wiring by laser remelting. In this case, solder layers are melted on the connection pads and on conductor areas leading away from them and constricted in their width, the solder melted on these conductor areas flowing to the connection pads and the volume of the solder bumps that arise as a result of the melting on themselves being correspondingly increased. The width of the conductor areas serving as solder supply structures must be reduced in order to prevent the solder from flowing off over the subsequent conductor runs of the wiring. This eliminates the need to apply a solder resist to the corresponding areas of the wiring.
Die Weiterbildung nach Anspruch 4 ermöglicht ein sehr rasches Umschmelzen der Lotschichten mit einer besonders geringen thermischen Belastung der Schaltungsträger.The development according to claim 4 enables a very rapid remelting of the solder layers with a particularly low thermal load on the circuit carriers.
Gemäß Anspruch 5 haben sich für das Umschmelzen von Lot- schichten Nd:YAG Laser mit einer Wellenlänge von 1,06 μm besonders gut bewährt. Das Laserumschmelzen von Lotschichten kann prinzipiell auch mit einem Diodenlaser-Array oder mit einem streifenförmigen Laserstrahl vorgenommen werden. Gemäß Anspruch 6 wird jedoch das Laserumschmelzen mit Hilfe eines ablenkbaren Laserstrahls bevorzugt, da sich hierdurch eine sehr hohe Flexibilität ergibt und zudem eine gezielte Auswahl der aufzuschmelzenden Bereiche ermöglicht wird. Außerdem können mit einem ablenkbaren Laserstrahl die aufzuschmelzenden Bereiche einer Lotschicht extrem schnell abgerastert werden. Ein Ausführungsbeispiel der Erfindung ist in der Zeichnung dargestellt und wird im folgenden näher beschrieben.According to claim 5, Nd: YAG lasers with a wavelength of 1.06 μm have proven particularly good for remelting solder layers. The laser remelting of solder layers can in principle also be carried out with a diode laser array or with a strip-shaped laser beam. According to claim 6, however, laser remelting with the aid of a deflectable laser beam is preferred, since this results in a very high degree of flexibility and also enables a targeted selection of the areas to be melted. In addition, the areas of a solder layer to be melted can be scanned extremely quickly with a deflectable laser beam. An embodiment of the invention is shown in the drawing and will be described in more detail below.
Die Figuren 1 bis 6 zeigen verschiedene Verfahrensstadien bei der Herstellung einer Verdrahtung und der Bildung von Lothök- kern auf den Anschluß-Pads dieser Verdrahtung.Figures 1 to 6 show different stages of the process in the production of wiring and the formation of solder bumps on the connection pads of this wiring.
Die Figur 7 zeigt die fertige Verdrahtung nach dem Auflöten eines Halbleiterbausteins.FIG. 7 shows the finished wiring after a semiconductor component has been soldered on.
Figur 1 zeigt ein elektrisch isolierendes Substrat S mit einer einseitig aufgebrachten Metallisierung M. Bei dieser Metallisierung M handelt es sich um eine dünne Kupferkaschie- rung oder um eine durch chemische Metallabscheidung von Kup- fer aufgebrachte Schicht. Die Metallisierung M wird dann mit einem Nd-YAG Laser mit einer Wellenlänge von 1,06 μm strukturiert, wobei diese Laserstrukturierung in Figur 1 durch einen Laserstrahl LSI angedeutet ist.FIG. 1 shows an electrically insulating substrate S with a metallization M applied on one side. This metallization M is a thin copper lamination or a layer applied by chemical metal deposition of copper. The metallization M is then structured with an Nd-YAG laser with a wavelength of 1.06 μm, this laser structuring being indicated in FIG. 1 by a laser beam LSI.
Gemäß Figur 2 entstehen bei der Laserstrukturierung Anschluß- Pads P und Leiterzüge, LZ, wobei die Anschluß-Pads P jeweils über in der Breite reduzierte Leiterbereiche LB mit den weiterführenden Leiterzügen verbunden sind. Die Verdrahtung weist außerdem eine Sammelleitung SL auf, die über in der Breite gegenüber den Leiterzügen LZ ebenfalls reduzierte Lotzufuhrstrukturen LS mit den einzelnen Anschluß-Pads P verbunden ist. Die Sammelleitung SL ermöglicht eine kathodische Kontaktierung des gesamten Leitermusters und damit eine galvanische Metallabscheidung auf das Leitermuster.According to FIG. 2, connection pads P and conductor lines, LZ are produced in the laser structuring, the connection pads P being connected to the further conductor lines via conductor regions LB of reduced width. The wiring also has a collecting line SL, which is connected to the individual connection pads P via solder supply structures LS, which are also reduced in width compared to the conductor tracks LZ. The SL collecting line enables cathodic contacting of the entire conductor pattern and thus galvanic metal deposition on the conductor pattern.
Gemäß Figur 3 werden auf das Leitermuster nacheinander durch galvanische Metallabscheidung eine Verstärkungsschicht V aus Kupfer und eine Lotschicht L aus einer Zinn-Blei-Legierung aufgebracht. Die elektrische Trennung der Sammelleitung SL vom übrigen Leiterbild wird durch einen in Figur 3 durch einen Pfeil LS2 angedeuteten Laserstrahl eingeleitet. HierbeiAccording to FIG. 3, a reinforcing layer V made of copper and a solder layer L made of a tin-lead alloy are applied in succession to the conductor pattern by galvanic metal deposition. The electrical separation of the collecting line SL from the rest of the conductor pattern is initiated by a laser beam indicated in FIG. 3 by an arrow LS2. in this connection
ERSATZBLATT (RE3EL8Θ) wird mit einem Nd-YAG Laser mit einer Wellenlänge von 0,355 μ oder 1,06 μm die Lotschicht L in den unmittelbar an die Sammelleitung SL angrenzenden Bereichen der Lotzufuhrstrukturen LS entfernt, worauf das hierdurch freigelegte Kupfer der Verstärkungsschicht V und der Metallisierung M gemäß Figur 4 durch Ätzen bis zur Oberfläche des Substrats S abgetragen wird.REPLACEMENT SHEET (RE3EL8Θ) the Nd-YAG laser with a wavelength of 0.355 μ or 1.06 μm is used to remove the solder layer L in the areas of the solder feed structures LS directly adjacent to the collecting line SL, whereupon the copper of the reinforcing layer V and the metallization M thereby exposed, as shown in FIG. 4 is removed by etching up to the surface of the substrate S.
Figur 4 zeigt ferner einen ablenkbaren Laserstrahl LS3, mit welchem jeweils die Lotschicht L auf einem Anschluß-Pad P, auf dem davon wegführenden Leiterbereich LB und auf der davon wegführenden Lotzufuhrsstruktur LS gleichzeitig aufgeschmolzen wird. Hierfür wird ein Nd-YAG Laser mit einer Wellenlänge von 1,06 μm verwendet, dessen Laserstrahl LS3 stark außer Fo- kus gestellt ist.FIG. 4 also shows a deflectable laser beam LS3, with which the solder layer L is melted simultaneously on a connection pad P, on the conductor area LB leading away therefrom and on the solder supply structure LS leading away therefrom. For this purpose, an Nd-YAG laser with a wavelength of 1.06 μm is used, the laser beam LS3 of which is strongly out of focus.
Bei dem geschilderten Laserumschmelzen der Lotschicht L fließt das flüssige Lot von der schmalen Lotzufuhrstruktur LS und von dem schmalen Leiterbereich LB zum Anschluß-Pad P hin, so daß dort gemäß Figur 5 von selbst ein Lothöcker LH entsteht. Das Volumen des Lothöckers LH kann ggf. durch zusätzliche, schmale, vom Anschluß-Pad P wegführende und blind endende Lotzufuhrstrukturen weiter vergrößert werden.In the case of the laser remelting of the solder layer L as described, the liquid solder flows from the narrow solder supply structure LS and from the narrow conductor region LB to the connection pad P, so that a solder bump LH is automatically created there according to FIG. The volume of the solder bump LH can optionally be further increased by additional, narrow solder feed structures leading away from the connection pad P and ending blindly.
Figur 6 zeigt die Anordnung eines höckerlosen Halbleiterbausteins HB auf der Verdrahtung, dessen beispielsweise aus einer Schichtenfolge von Aluminium, Nickel und Gold bestehenden Anschlußflächen AF unmittelbar auf den Kuppen der zugeordneten Lothöcker LH aufliegen. Werden anschließend alle dem Halbleiterbaustein HB zugeordneten Lothöcker LH beispielsweise durch Reflow-Löten oder durch Laser-Löten gleichzeitig geschmolzen, so ergeben sich zuverlässige Lötverbindungen mit der aus Figur 7 ersichtlichen konkaven Form der Lothöcker LH.FIG. 6 shows the arrangement of a bumpless semiconductor component HB on the wiring, the connection surfaces AF of which, for example, consist of a layer sequence of aluminum, nickel and gold, lie directly on the tips of the associated solder bumps LH. If all the solder bumps LH assigned to the semiconductor module HB are subsequently melted simultaneously, for example by reflow soldering or by laser soldering, reliable soldered connections with the concave shape of the solder bumps LH shown in FIG. 7 result.
Bei gewöhnlichen Leitermustern ohne in der Breite reduzierte Leiterbereiche LB und ohne in der Breite reduzierte Lotzu-With ordinary conductor patterns without width-reduced conductor areas LB and without width-reduced solder
ERSATZBLÄTT(REGEL26) fuhrstrukturen LS kann das geschilderte Laserumschmelzen von Lotschichten L selbstverständlich ebenfalls durchgeführt werden. Hier ergeben sich dann auf den Anschluß-Pads nur flache Lotkuppen anstelle der hohen Lothöcker LH. SPARE BLADE (RULE 26) driving structures LS, the described laser remelting of solder layers L can of course also be carried out. Here then there are only flat solder dots instead of the high solder bumps LH on the connection pads.

Claims

Patentansprüche claims
1. Verfahren zum Umschmelzen von auf das Leitermuster einer Verdrahtung zumindest partiell aufgebrachten Lotschichten (L), dadurch g e k e n n z e i c h n e t , daß die Lotschichten (L) selektiv mit Hilfe eines Laserstrahls (LS3) aufgeschmolzen werden.1. A method for remelting solder layers (L) which are at least partially applied to the wiring pattern of a wiring, by means of the fact that the solder layers (L) are selectively melted using a laser beam (LS3).
2. Verfahren nach Anspruch 1, dadurch g e k e n n z e i c h n e t , daß die Lotschichten (L) selektiv im Bereich von Anschluß- Pads (P) der Verdrahtung aufgeschmolzen werden.2. The method according to claim 1, characterized in that the solder layers (L) are selectively melted in the area of connection pads (P) of the wiring.
3. Verfahren nach Anspruch 1, dadurch g e k e n n z e i c h n e t , daß die Lotschichten (L) zur Bildung von Lothöckern (LH) auf Anschluß-Pads (P) der Verdrahtung selektiv im Bereich der Anschluß-Pads (P) und davon wegführenden, in der Breite einge- schnürten Leiterbereichen (LB, LS) aufgeschmolzen werden.3. The method according to claim 1, characterized in that the solder layers (L) to form solder bumps (LH) on connection pads (P) of the wiring selectively in the area of the connection pads (P) and leading away, in the width - Laced conductor areas (LB, LS) are melted.
4. Verfahren nach einem der vorhergehenden Ansprüche, dadurch g e k e n n z e i c h n e t , daß die Lotschichten (L) mit Hilfe eines stark außer Fokus gestellten Laserstrahls (LS3) aufgeschmolzen werden.4. The method according to any one of the preceding claims, characterized in that the solder layers (L) are melted with the aid of a laser beam (LS3) which is strongly out of focus.
5. Verfahren nach einem der vorhergehenden Ansprüche, dadurch g e k e n n z e i c h n e t , daß die Lotschichten (L) mit dem Laserstrahl (LS3) eines Nd.YAG Lasers mit einer Wellenlänge von 1,06 μm aufgeschmolzen werden.5. The method according to any one of the preceding claims, characterized in that the solder layers (L) are melted with the laser beam (LS3) of a Nd.YAG laser with a wavelength of 1.06 μm.
6. Verfahren nach einem der vorhergehenden Ansprüche, dadurch g e k e n n z e i c h n e t , daß die Lotschichten (L) mit Hilfe eines ablenkbaren Laserstrahls (LS3) aufgeschmolzen werden. 6. The method according to any one of the preceding claims, characterized in that the solder layers (L) are melted using a deflectable laser beam (LS3).
PCT/EP1999/003800 1998-06-02 1999-06-01 Method for remelting solder layers WO1999063588A1 (en)

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DE19824635 1998-06-02

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US5194137A (en) * 1991-08-05 1993-03-16 Motorola Inc. Solder plate reflow method for forming solder-bumped terminals
US5279045A (en) * 1990-01-31 1994-01-18 Hitachi, Ltd. Minute particle loading method and apparatus
US5565119A (en) * 1995-04-28 1996-10-15 International Business Machines Corporation Method and apparatus for soldering with a multiple tip and associated optical fiber heating device

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EP0355478A1 (en) * 1988-08-22 1990-02-28 International Business Machines Corporation Improved lift-off process for terminal metals
US5279045A (en) * 1990-01-31 1994-01-18 Hitachi, Ltd. Minute particle loading method and apparatus
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