WO2012066465A1 - Connexion soudée comportant une couche métallique mouillable et non mouillable - Google Patents

Connexion soudée comportant une couche métallique mouillable et non mouillable Download PDF

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Publication number
WO2012066465A1
WO2012066465A1 PCT/IB2011/055072 IB2011055072W WO2012066465A1 WO 2012066465 A1 WO2012066465 A1 WO 2012066465A1 IB 2011055072 W IB2011055072 W IB 2011055072W WO 2012066465 A1 WO2012066465 A1 WO 2012066465A1
Authority
WO
WIPO (PCT)
Prior art keywords
component
soldering
substrate
layer
wetting
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.)
Ceased
Application number
PCT/IB2011/055072
Other languages
English (en)
Inventor
Raimond Louis Dumoulin
Gordon Patrick Rudolf Elger
Hendrik Elisabeth Jozef Gijsbers
Johan Frans Justin Maria Caers
Xiu Juan Zhao
Adrianus Marinus De Jong
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.)
Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
Original Assignee
Philips Intellectual Property and Standards GmbH
Koninklijke Philips Electronics NV
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 Philips Intellectual Property and Standards GmbH, Koninklijke Philips Electronics NV filed Critical Philips Intellectual Property and Standards GmbH
Publication of WO2012066465A1 publication Critical patent/WO2012066465A1/fr
Anticipated expiration legal-status Critical
Ceased 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
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/11—Printed elements for providing electric connections to or between printed circuits
    • H05K1/111—Pads for surface mounting, e.g. lay-out
    • 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
    • H05K2201/20—Details of printed circuits not provided for in H05K2201/01 - H05K2201/10
    • H05K2201/2081—Compound repelling a metal, e.g. 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
    • 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
    • H05K2203/048—Self-alignment during soldering; Terminals, pads or shape of solder adapted therefor
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to an assembly including a substrate and a component fixed to the substrate and to a method of forming an assembly of a component on a substrate.
  • a first object in the present case the component, which may be an optical and/or electrical component, is fixed to a second object, presently termed a substrate, by providing a molten solder material between the two objects.
  • a mechanically stable connection is formed by adhesion of the solder material to the two objects.
  • the present invention is concerned on one hand with exact placement and alignment of a component on the substrate and on the other hand with obtaining good heat conduction between the component and the substrate. Both aspects are particularly important in optical applications, in particular where the component comprises a light source generating heat that needs to be dissipated.
  • US 6,709,898 describes a microelectronic package.
  • a microelectronic die is accurately placed on a heat spreader while providing thermal conduction.
  • a first plurality of solder bumps is formed on a wafer by applying a wetting layer to the back surface of the wafer.
  • a removable solder dam such as a photo resist, is patterned over the wetting layer.
  • the solder bumps may be formed by screen printing a paste into openings of the photo resist and reflowing the paste to form solder bumps.
  • a second plurality of solder bumps is formed on the heat spreader with a wetting layer and a removable solder dam.
  • the microelectronic die is then placed on the heat spreader.
  • the heat spreader is then heated to reflow the solder bumps, so that capillary action between the bumps aligns the die on the heat spreader.
  • the substrate on which the component is mounted comprises at least two covering layers arranged on the surface where the component is mounted. It is possible to provide the substrate with only these two layers, e.g. a first layer directly on a substrate material and a second layer directly on the first layer, where the second layer forms an exposed outer layer. However, as will become apparent, the invention is not strictly limited to this two-layer structure; it is possible that further layers are disposed below, in between and/or on top of the first and second covering layers.
  • Both the first and second covering layers are made of metal.
  • the first, lower layer is non-wetting for a solder material
  • the second outer layer is made from a material that is wetting for the solder material. Wetting describes the ability of the solder material when melted to contact the surface of the layers.
  • solder materials which may or may not contain Lead (Pb), and contain one or more of Tin (Sn), Copper (Cu), Silver (Ag), Bismuth (Bi), Indium (In), Zinc (Zn) and Antimony (Sb)
  • the first layer is wetting, such that the solder material spreads on the surface of this layer, whereas the second surface is non- wetting, such that the solder material does not spread on this surface.
  • wetting material for the second layer examples include Gold (Au) and Silver (Ag); examples of the non-wetting material for the first layer are Nickel (Ni), Titanium (Ti), Titanium Tungsten alloy (TiW), Palladium (Pd) and Platinum (Pt).
  • a cut-out is formed in the second layer, such that a solder dam exposing said non-wetting first layer is formed delimiting a portion of the surface as a soldering pad.
  • a soldering pad may be of any desired shape, such as rounded, rectangular etc..
  • the second, wetting layer does no longer cover the first, non-wetting layer, such that solder material is confined to the soldering pad by the adhesive/cohesive intermo- lecular forces governing the wetting/non-wetting behaviour.
  • a component is fixed to the substrate by a soldering connection.
  • Soldering material is arranged on the soldering pad and fixes the component to the soldering pad, thus forming a rigid mechanical connection.
  • the connection thus formed has on one hand the advantage of good thermal contact between the component and the substrate.
  • the solder material and the first and second covering layers are of metal material, such that good heat conduction is ensured.
  • the structure of the assembly allows an efficient manufactur- ing process while obtaining high precision in positional and directional alignment of the component on the substrate. Alignment of the component may be achieved along the soldering pad, i.e. by the cut-out formed in the second covering layer.
  • both the lower surface of the component contacting the substrate and the upper surface of the substrate contacting the component are flat, planar surfaces.
  • the substrate is a heat spreader, i.e. a body consisting of a metal material for good heat conduction (such as Aluminium (Al), Copper (Cu), etc.) and extends beyond the soldering pad for heat dissipation.
  • the heat spreader may comprise heat dissipation structures such as cooling fins etc..
  • the component comprises at least one optical element, in particular a light source, reflector and/or a lens. For such an optical element, exact alignment may be critical. In particular for a light source, especially an LED or laser source, both exact alignment and good thermal contact have decisive advantages.
  • a cut-out in the second covering layer is formed by first providing a complete layer and then ablating the layer to form the cut-out.
  • a directed beam for ablating the second layer This could be a particle beam, such as e.g. an electron beam, but preferably laser irradiation is used.
  • Direction of such a beam, in particular a laser beam may be effected in a very exact manner by optical means.
  • positioning of the soldering pad on the surface of the substrate may be easily achieved with very high precision.
  • soldering pad After the soldering pad is formed, it is preferred to fix the component to the soldering pad by reflow soldering.
  • solder material is dosed on the soldering pad and the component is placed on top. The soldering pad is then heated to melt the solder material for forming the soldering connection. It is particularly preferred to place the component loosely on the soldering pad, i.e. setting it on the soldering pad and solder material with- out fixing it in position and orientation.
  • the loosely placed component will automatically align itself on the solder pad by intermolecular forces acting between the solder material and the component.
  • the component will automatically achieve a defined position aligned relative to the borders of the soldering pad, i.e. the soldering dam.
  • the soldering dam i.e. the soldering dam.
  • the component is fixed to the substrate not only at a single soldering pad, but at a plurality of soldering pads.
  • Each of the soldering pads are preferably formed next to each other on the surface of the substrate by forming, as described above, cut-outs in the second, wetting covering layer.
  • individual soldering pads may be separated by solder dams.
  • Providing a plurality of soldering pads can contribute to exact alignment of the component. Further, for covering a larger surface evenly with soldering material it has proven advantageous to separate portions of the surface into different soldering pads to achieve better uniformity of the distribution of the solder material.
  • each soldering pad substantially the same amount of solder material per unit surface of the soldering pad.
  • the amount of solder material will thus be at least substantially equal (where "substantially” equal is understood to mean that the amount of solder material on a given soldering pad will not differ by more than 20% from the average amount over all soldering pads of the same component, preferably by no more than 10%).
  • Such equal distribution of the solder material minimizes the possible amount of tilt of the component relative to the surface of substrate, which is particularly important in optical applications.
  • the lower surface of the component i.e. the surface facing the soldering pads, will preferably comprise a metal material with wetting properties for the solder material. It is further preferred that on the lower component surface, one or more soldering pads are formed. Particularly, it is preferred that the number, size and arrangement of the positioning pads on the component correspond to the number, size and arrangement of soldering pads formed on the substrate. This serves to provide exact positioning. Individual positioning pads on the lower surface of the component may again be delimited by solder dams exposing non- wetting material, e.g. ceramic material of the component.
  • Fig. 1 shows a perspective view of a substrate with covering layers
  • Figs. 2, 3 show sectional views (not to scale) of the substrate of fig. 1 with the section taken along line A.. A;
  • Fig. 4 shows a perspective view of placement of a component on thesubstrate
  • Fig. 5 shows a sectional view (not to scale) with the section taken along line A.. A in fig. 4
  • Figs. 6-8 show different steps of placement of the component in sectional views
  • Fig. 1 shows a heat sink as a substrate 10, onto which an electro/optical component 12 (see fig. 4) is to be mounted.
  • the electro/optical component 12 is an LED module comprising four high power LEDs 14 mounted on a ceramic plate 16.
  • the substrate 10 as shown in the cross-sectional view of fig. 2, is comprised of a main body 18 of Copper (Cu) or another material of good heat conduction which is covered by a first covering layer 20, which in the present example is a Nickel layer, on top of which a second covering layer 22, which in the present example is a Gold (Au) layer, is provided.
  • a first covering layer 20 which in the present example is a Nickel layer
  • a second covering layer 22 which in the present example is a Gold (Au) layer
  • the layer thickness here appears much larger than it actually is as compared to the thickness of the body 18 for illustrative purposes.
  • the covering layers 20 and 22 may be provided on the body 18 in a plurality of different ways, such as electrolytic plating or electrode-less plating processes. Their thickness will generally range from 0.01 ⁇ ⁇ 10 ⁇ . Thicker layers will work also, but at increased cost.
  • the covering layers 20, 22 are on one hand provided for corrosion protection. On the other hand, they are used to mount the component 12 onto the flat upper surface of the substrate 10 as will be described.
  • solder connection using a solder material.
  • solder material A variety of different solder materials, including Lead- containing as well as Lead-free solder material may be used. Preferred solder materials are predominantly (i.e. above 60 %) based on Tin (Sn), such as e.g. SAC based solders, SnAg based solders, or SnAu based solders.
  • the first layer 20 consisting of Nickel is non-wetting and the second layer 22 consisting of Gold is wetting, i.e. the solder material, when melted, will contact the second Gold layer easily (small contact angle of a drop of liquid material on the surface), whereas the first Nickel layer will not be easily contacted (large contact angle).
  • these properties direct the flow of molten solder material in configurations where both wetting and non- wetting surfaces are involved.
  • the solder material will follow the wetting surface material and will not run out into the bordering surface areas of non-wetting material.
  • it is necessary that the sec- ond layer 22 is better wetting than the first layer 20, i.e. is more easily contacted by the solder material.
  • soldering pads 24 are formed delimited by soldering dams 26.
  • the soldering dams 26 are formed by partially removing the second layer 22 forming longitudinal grooves 26 where the first Nickel layer 20 is exposed.
  • the thus formed soldering pads 24 have a surface comprised of the Gold layer 22 and are bordered on all sides by exposed Nickel material of the first layer 20.
  • the grooves 26, where the material of the second layer 22 has been completely removed to expose the first layer 20 beneath are preferably formed by irradiation with a laser beam 28. Intensity and duration of the laser irradiation should be carefully controlled to securely remove, within the grooves 26, the second layer 22. Generally, the process will be controlled to evaporate within the grooves 26 the second layer 22 completely and also a part of the first layer 20. However, at least a minimal thickness of the first layer 20 will be left. Such treatment may easily be achieved to a high degree of precision using a high intensity laser 28 directed by suitably controlled optics.
  • any type of laser system capable to ablate the layer 22 may be used. Preferably, a laser system based on short pulses and matching frequencies of laser light is employed.
  • the grooves 26 need to be provided in a width sufficient to ensure that soldering material provided on each soldering pad 24 will, due to the non- wetting properties of the first Nickel layer 20, not spread beyond the solder dam. Generally, this should be ensured by providing grooves of e. g. 30 ⁇ ⁇ 500 ⁇ thickness.
  • solder material 30 is then dosed onto the solder pads 24 (fig. 4, fig. 5). In the preferred example, as shown in the figures, four solder pads 24 of equal size are formed. Also, about equal amounts of solder material 30 are dosed onto each of the solder pads 24.
  • the solder material 30 may be applied as blobs of solder paste or, alternatively, in a printing process.
  • the component 12 is then placed onto the thus prepared substrate 10.
  • positioning pads 32 are formed which equal in size, number and arrangement the four solder pads 24 formed on the surface of the substrate 10.
  • the component 12 is loosely placed onto the surface of substrate 10 to then be fixed in a reflow soldering process.
  • the placement of the component 12 need not be exact.
  • An offset between the soldering pads 24 and positioning pads 32 is tolerable.
  • the whole assembly is heated to melt the solder material 30. Due to the wetting/non-wetting properties, intermolecular forces act between the solder material 30 and the positioning pads 32 to exactly align positioning pads 32 on soldering pads 24, and thus very accurately aligning component 12 onto the surface of the substrate 10 (see fig. 8).
  • a mechanically stable soldering connection is formed fixing the component 12 to the substrate 10.
  • Thermal contact of the component 12 to the substrate 10 is excellent due to good heat con- duction properties of the involved metal materials.
  • the degree of precision achieved in positioning of the component 12 largely corresponds to the degree of precision achieved with the ablating laser 28, so that positional accuracy of the component 12 is very high.
  • solder material 30 and positioning pads 32 will correct, as illustrated in fig. 7/fig. 8, any linear misalignment as well as a rotation of the component 12 with regard to the substrate 10 (as long as the initial positioning is precise enough to have largely overlapping positioning pads 32 and soldering pads 24, which should be easy to achieve).
  • solder material 30 By providing substantially the same amount of solder material 30 on each soldering pad 24, four uniform solder connections are formed leading to exact alignment of the component 12 without tilt relative to the surface of the substrate 10.
  • the electro-optical component 12 is an LED module 12 to be mounted to a heat sink 10.
  • a plurality of such LED modules 12 may be mounted to the same heat sink, preferably side by side on the same surface.
  • solder pads 24 are formed not only for a first LED module 12, but also for other LED modules to be mounted. All LED modules 12 may then be fixed to the heat sink 10 at the same time by a single reflow soldering process.
  • a module of multiple LED light sources may be obtained, where the individual light sources are aligned with high precision and a good thermal contact is ensured.
  • the substrate 10 is an outer surface of a water cooler.
  • LED modules 12 instead of LED modules 12 as shown in the above examples, a plurality of laser modules are mounted on the surface of the substrate 10. Again, the good thermal contact allows efficient cooling of the laser modules by the water cooler. Additionally, the very exact alignment al- lows forming a uniform laser light zone in front of the assembly.
  • the substrate 10 is a standoff including a flat mounting surface for a group of laser modules as well as a mounting surface for micro lenses. Both can be fixed to the standoff by the described method, so that very exact placement and thus good optical alignment is achieved.
  • the wettability of the second layer 22 is substantially better than the wettability of the first layer 20.
  • solder connection may be used as a purely mechanical contact, but could also serve as an electrical contact, e.g. for providing operating power to an LED module 12.
  • the substrate 10 may be a printed circuit board (PCB), preferably a metal core printed circuit board (MC-PCB), where electrically isolated from the metal layers 20, 22 conductive tracks are provided for electrical connection of the mounted component(s).
  • PCB printed circuit board
  • MC-PCB metal core printed circuit board

Landscapes

  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Electric Connection Of Electric Components To Printed Circuits (AREA)
  • Semiconductor Lasers (AREA)

Abstract

L'invention concerne un ensemble comprenant un substrat (10) comportant une première couche de couverture (20) et une seconde couche de couverture (22). La première couche de couverture (20) est faite dans un matériau métallique qui ne peut pas être mouillé par un matériau de soudure. La seconde couche de couverture (22) est faite dans un matériau métallique qui peut être mouillé par le matériau de soudure (30). Une découpe (26) est formée dans la seconde couche (22) pour former une digue de soudure (26) qui délimite une pastille de soudage (24). Un composant (12) est fixé sur le substrat (10) par une connexion soudée formée par le matériau de soudure (30) entre la pastille de soudage (24) et le composant (12).
PCT/IB2011/055072 2010-11-19 2011-11-14 Connexion soudée comportant une couche métallique mouillable et non mouillable Ceased WO2012066465A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP10191895.1 2010-11-19
EP10191895 2010-11-19

Publications (1)

Publication Number Publication Date
WO2012066465A1 true WO2012066465A1 (fr) 2012-05-24

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2011/055072 Ceased WO2012066465A1 (fr) 2010-11-19 2011-11-14 Connexion soudée comportant une couche métallique mouillable et non mouillable

Country Status (2)

Country Link
TW (1) TW201240035A (fr)
WO (1) WO2012066465A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10706880B1 (en) * 2019-04-02 2020-07-07 Seagate Technology Llc Electrically conductive solder non-wettable bond pads in head gimbal assemblies
US20230064063A1 (en) * 2019-12-16 2023-03-02 Hitachi Astemo, Ltd. Manufacturing method for semiconductor device and semiconductor device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3851223A (en) * 1971-12-06 1974-11-26 Nippon Electric Co Microcircuit board
US4600970A (en) * 1984-05-29 1986-07-15 Rca Corporation Leadless chip carriers having self-aligning mounting pads
US6362435B1 (en) * 1999-12-20 2002-03-26 Delphi Technologies, Inc. Multi-layer conductor pad for reducing solder voiding

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3851223A (en) * 1971-12-06 1974-11-26 Nippon Electric Co Microcircuit board
US4600970A (en) * 1984-05-29 1986-07-15 Rca Corporation Leadless chip carriers having self-aligning mounting pads
US6362435B1 (en) * 1999-12-20 2002-03-26 Delphi Technologies, Inc. Multi-layer conductor pad for reducing solder voiding

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
ANONYMOUS: "Laser defined solderable area for circuit boards", RESEARCH DISCLOSURE, MASON PUBLICATIONS, HAMPSHIRE, GB, vol. 433, no. 8, 1 May 2000 (2000-05-01), XP007126054, ISSN: 0374-4353 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10706880B1 (en) * 2019-04-02 2020-07-07 Seagate Technology Llc Electrically conductive solder non-wettable bond pads in head gimbal assemblies
US10964342B1 (en) 2019-04-02 2021-03-30 Seagate Technology Llc Methods of controlling a shape and size of solder joints of magnetic recording heads
US20230064063A1 (en) * 2019-12-16 2023-03-02 Hitachi Astemo, Ltd. Manufacturing method for semiconductor device and semiconductor device

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