CN111512708A

CN111512708A - System and method for improving electronic component interconnection

Info

Publication number: CN111512708A
Application number: CN201880073739.1A
Authority: CN
Inventors: 安德鲁·斯特默埃尔曼
Original assignee: Sunshine Science Co ltd
Current assignee: Sunshine Science Co ltd
Priority date: 2017-11-15
Filing date: 2018-11-15
Publication date: 2020-08-07
Also published as: JP7193168B2; KR20200111162A; EP3711463A1; WO2019099754A1; AU2018368939B2; AU2018368939A1; CA3082894A1; JP2021503186A; SG11202004250RA; JP7440120B2; JP2023025166A; AU2023274124A1

Abstract

Systems and methods for improving the interconnection of electronic components using ACAs are provided. The method involves the use of magnets that are specific to each component to be connected and are optimized in terms of size and strength and position relative to the substrate and the component. An oven adapted for use with the method and system and a kit of parts providing the system for use with an existing oven are also provided.

Description

System and method for improving electronic component interconnection

Cross Reference to Related Applications

This application claims the benefit of U.S. provisional patent application No. 62/586,815 filed on 2017, 11, 15, which is incorporated herein by reference in its entirety.

Technical Field

This generally relates to establishing electrical connections of components in an electronic circuit. More particularly, this relates to an improved method for connecting a component to a substrate using an anisotropic conductive adhesive.

Background

As modern demands for technology increase, the number of electronic devices continues to increase, the availability and adoption of such devices continues to increase, the size of such devices continues to decrease, and the number of interconnections of electronic components required to manufacture such devices has greatly increased. Furthermore, previously analog devices have almost disappeared in many fields as such devices have been replaced by electronic apparatuses, and the size of electronic devices has dropped dramatically even when the power of those devices has continued to expand rapidly.

As modern components have become smaller and more powerful, more circuitry is present on such components in smaller and smaller spaces (i.e., the density of the circuitry has increased), while tolerances between, for example, different aspects of a given chip or component have become tighter (i.e., the pitch has become smaller- "ultra-fine pitch").

Modern components are therefore often more susceptible to temperatures and pressures, any of which may cause problems and even failure of the component and the entire apparatus of which it is a part. Unfortunately, current approaches to creating interconnects between, for example, components and their substrates have limitations and disadvantages for certain applications.

The skilled practitioner will recognize that there are many interconnection means, such as conventional soldering, Anisotropic Conductive Film (ACF), and Anisotropic Conductive Adhesive (ACA), each of which has benefits and limitations, and each of which provides options that can meet the specific interconnection requirements of a particular application, component, or device.

Conventional welding involves exposing the joined components to locally significant amounts of heat and pressure. Exposing such components to these adverse or unsustainable conditions may result in complete failure, poor or unreliable performance, or greatly reduced lifetime.

As an effort to improve interconnects for various applications, ACFs have been developed. These conductive films can reduce the local heat required for connection by soldering, but they may still require a large amount of heat. Furthermore, heat and pressure are typically applied to the components, which can be a significant limitation for sensitive components. An ACF also has limitations in the pitch of the interconnects it is adapted to or able to accommodate.

ACAs have also been developed to provide alternative solutions for creating difficult interconnects in certain applications. Like ACFs, these adhesives provide conductivity only in the Z-axis. ACAs such as those produced by SunRay Scientific contain magnetically alignable particles that form interconnections between components when aligned along the Z-axis by exposure to a magnetic field. The adhesive matrix is then cured, for example by exposure to heat, to complete and secure the interconnection. No pressure is required, making ACA a good candidate for pressure sensitive components. In addition, for temperature sensitive parts, curing can be accomplished in low heat. Furthermore, ACA allows finer pitch applications than can be achieved using ACF.

Prior art applications of ACAs have typically employed magnetic fields applied across the entire substrate using electromagnets. While such a field covers all components filled on the substrate, it may be disadvantageous in applications where one or more components on the substrate are sensitive to magnetic fields. Furthermore, the magnetic field applied over a large area includes the entire magnetic field, including lines of flux that are not substantially very perpendicular to the X-Y plane.

While it is simple and easy to create interconnects with ACA, there remains a need for improved systems and methods for using ACA to create and optimize interconnects in specific applications.

Disclosure of Invention

The inventors have discovered methods of providing unexpected improvements in ACA-based electronic interconnects for specific applications and have developed systems that implement these methods. These methods provide several advantages based on the following steps: the creation of the Z-axis connection (in terms of height, number and direction of the Z-axis posts) is optimized by selecting the appropriate ACA characteristics, using separate magnets positioned for each component to be interconnected, and selecting the characteristics of the magnets used for alignment of the ACA for each specific component populated on the substrate. These methods allow for the construction of what the inventors call "magnetic pallets" (which provide consistent and optimal alignment and curing of ACA-based interconnects) to be achieved. These methods can provide improved interconnect consistency, reduced failures, improved lifetime, and increased functional connection yield as compared to existing methods of forming interconnects.

In a first aspect, the present disclosure provides a novel method of aligning and curing ACA-based interconnects in digital equipment, electronic devices, and the like. Methods for establishing interconnections between a substrate and electronic components populated on the substrate using a magnetically alignable Anisotropic Conductive Adhesive (ACA) typically include the steps of:

a) establishing a size and a position on the substrate of a first electronic component to be placed on and connected to the substrate;

b) determining a placement position of the first magnet corresponding to the size and position established for the component in step a);

c) determining the size and strength of the magnet required in step b); and

d) the flux lines of the magnetic field of the magnet are plotted.

Repeating steps a) -d) for each additional component to be placed on and connected to the substrate in order to determine the required characteristics and placement position of each additional magnet;

the method further comprises the steps of:

f) creating a magnetic tray and fixing each magnet in its respective placement position on the tray;

g) creating an alignment tray and adapting the alignment tray to hold the substrate during alignment and curing;

h) placing a substrate on an alignment tray;

i) applying the ACA to the substrate in a position suitable for interconnecting each component to be placed on the substrate;

j) filling the substrate with the first component and each additional component where ACA has been applied;

k) assembling the alignment tray and the magnetic tray;

l) allowing the formation of pillars in the Z-axis in ACA; and

m) curing the ACA to establish interconnections between the substrate and the first component and each additional component.

The alignment tray and the magnetic tray are made of a non-magnetic material. The magnet tray is adapted to receive and retain the first magnet and each additional magnet in their respective positions of placement on the tray. The assembled magnet tray (with magnets in place) and alignment tray (with substrate filled with components and ACA) can be placed directly into the curing oven as an assembly.

In a second aspect, provided herein is a system for creating an interconnect between a substrate and an electronic component attached to the substrate using a magnetically alignable Anisotropic Conductive Adhesive (ACA). The system generally includes a magnet tray including a non-magnetic tray adapted to receive and retain each of one or more magnets placed therein in a position corresponding to a position of one or more electronic components on a substrate to which the components are to be attached.

The system further comprises an alignment tray adapted to hold the substrate during alignment and curing of the ACA, the substrate being filled with one or more components to be connected to the substrate with the ACA.

The system also includes an ACA including magnetically alignable particles capable of forming interconnects that are electrically conductive in the Z-axis.

Both the alignment tray and the magnetic tray are preferably made of a non-magnetic material. In various embodiments, the substrates can only be placed in the alignment tray in one orientation.

In a presently preferred embodiment, the magnet is a permanent magnet. Typically, for each magnet in the magnet tray, the lines of magnetic flux are substantially parallel to each other and substantially perpendicular to the X-Y plane in an area corresponding to the area of the component and the substrate on which the ACA is located. In a presently preferred embodiment, the lines of magnetic flux are substantially constituted by lines parallel to each other and perpendicular to the component and to the area of the substrate on which the ACA is located.

In a third aspect, the present disclosure provides a kit for creating an interconnection between a substrate and an electronic component attached to the substrate using a magnetically alignable anisotropic conductive adhesive.

The kit generally comprises:

at least one magnetic tray including a non-magnetic tray adapted to hold one or more magnets in a position corresponding to a desired position of an electronic component on a substrate and a connection of the component to the substrate using an ACA;

sufficient magnets to complete the magnet tray, each magnet of a desired size and strength for making interconnections between the component and substrate using ACA;

at least one alignment tray adapted to receive and hold the substrate and the components filled on the substrate to form the interconnections during aligning and curing the ACA;

and optionally an ACA adapted for use with the kit to create at least one interconnection between the component and the substrate using the kit.

In the provided kit, the magnet tray and the alignment tray are configured to be vertically oriented with respect to each other. They are assembled such that when the magnet tray and the alignment tray are assembled in that manner, the electronic components (to be connected to the substrate using the ACA) placed on the substrate on the alignment tray are vertically aligned with the magnets on the magnet tray. Each component that needs to be connected (interconnected) has a corresponding magnet, with which each component will align when the pallet is assembled.

In a presently preferred embodiment of the kit, the magnet comprises a rare earth magnet or other permanent magnet.

In yet another aspect, the present disclosure provides an oven system designed to create an interconnection between a substrate and an electronic component to be placed on the substrate and connected to the substrate using ACA. The oven system typically includes a curing oven and one or more shelves or racks, each of which includes:

a magnetic tray equipped with one or more magnets, each magnet being placed in a position corresponding to a position of an electronic component to be placed on a substrate and connected to the substrate using an ACA; and

an alignment tray adapted to receive and hold a substrate filled with one or more components to be placed on the substrate and connected via an ACA.

These and/or additional aspects, features and advantages of the present invention will become apparent to those skilled in the art in view of this disclosure.

Drawings

FIG. 1: a cross-sectional overview of an embodiment of a system for magnetically aligning and curing ACA interconnects showing a magnet tray with magnets positioned therein, an alignment tray, a substrate, and components populated on the substrate.

FIG. 2: a flow chart illustrating steps of a method of using an ACA to magnetically align and cure a component to a substrate to create an electrical connection is shown.

FIG. 3: a drawing of an embodiment of an alignment tray for use therewith is shown. The tray includes a plurality of substrates, each having a filler member to be placed on and connected to the substrate.

FIG. 4: a plot of an embodiment of an oven employing a magnetic pallet system is shown. A. A plurality of magnet trays and alignment tray assemblies are shown in the batch oven. The outer dimensions of the alignment tray and the magnet tray are dictated by the oven dimensions, but otherwise not required to be the same for each magnet tray or each alignment tray. Thus, a single oven can be utilized to align and cure multiple interconnects for multiple electronic components on different substrates or devices. B. An enlarged view of an assembly comprising an alignment tray with orientation means (alignment holes) and a magnet tray is shown. C. A close-up top view of a magnet tray used as a rack in an oven.

Detailed Description

Provided herein are methods and systems for using ACAs to provide improved and more consistent interconnections for electronic components.

Definitions and abbreviations

Unless otherwise specifically defined, all technical and scientific terms, terms of art, and acronyms used herein have the same meanings as commonly understood by one of ordinary skill in the art in the field of the invention or in the field of using the same. Following abbreviations and definitions apply in accordance with this description.

Acronyms

Unless otherwise indicated, the following abbreviations apply:

AC: exchanging;

ACA: an anisotropic conductive adhesive;

ACF: an anisotropic conductive film;

DC: d, direct current;

gs: gauss, magnetic field unit;

NIB: neodymium-iron-boron;

PCB: a printed circuit board; and

t: tesla, magnetic field units, SI.

Definition of

As used herein, "substantially" may mean an amount greater than or less than the referenced item. Preferably, substantially greater (or more) or less (or less) means at least about 10% to about 100% or more different from the corresponding referenced item. More preferably, "substantially" in such instances means at least about 20% to about 100% or more greater or less than the referenced item. As the skilled person will recognise, the term "substantially" can also be used as "substantially all", "substantially all" means more than 51%, preferably more than 60%, 67%, 70%, 75%, 80%, 85%, 90% or more of the referenced item, quantity or amount. "substantially all" can also mean greater than 90% of the referenced item, quantity, or amount, including 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more.

As used herein, the singular form of a word includes the plural, and vice versa, unless the context clearly dictates otherwise. Thus, references to "a/an" and "the" generally include plural reference terms. For example, reference to "an electrode" or "a diode" includes a plurality of such "electrodes" or "diodes".

The words "comprising", "including" and "comprising" are to be construed as inclusive and not exclusive. Likewise, the terms "comprising," "including," and "or" should all be construed as inclusive, unless such a construction is clearly prohibited from the context. Additionally, the forms of the terms "comprising" or "including" are intended to include embodiments encompassed by the phrases "consisting essentially of," and "consisting of. Similarly, the phrase "consisting essentially of is intended to include embodiments encompassed by the phrase" consisting of.

Where used herein, ranges are provided in a shorthand manner, so as to avoid having to enumerate and describe each and every value within the range. Any suitable value within the range can be selected as an upper value, a lower value, or a landmark of the range, where appropriate.

The formulations, compositions, methods, and/or other advancements disclosed herein are not limited to the particular methodologies, protocols, and/or components described herein as these may vary, as will be recognized by the skilled artisan. In addition, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to, indeed, limit the scope of the disclosed or claimed embodiments.

Although any formulation, composition, method, or other means or materials similar or equivalent to those described herein can be used in the practice of the present invention, the preferred formulations, compositions, methods, or other means or materials are described herein.

Any reference cited or referenced herein, including any patent, patent application, or other publication, technology, and/or academic article, is hereby incorporated by reference in its entirety to the extent allowed under applicable law. Any discussion of those references is intended merely to summarize the assertions made therein. No admission is made that any such patents, patent applications, publications or references are prior art, or that any portion thereof is relevant or decisive for the patentability claimed herein. Applicants specifically reserve the right to challenge the accuracy and pertinency of any claims in which such patents, patent applications, publications, and other references are prior art or are relevant and/or conclusive.

As used herein, "aligning" means aligning a magnetic material or composition comprising magnetic particles. In general, alignment refers to the alignment of magnetic particles in the Z-axis under the influence of a magnetic field. Alignment is the process used to form the posts in the Z-axis. As will be clear from the context, sometimes "alignment" is also used herein to refer to ensuring proper orientation of two things, such as an alignment tray and a magnetic tray or a substrate and an alignment tray, relative to each other.

As used herein, "pillar" refers to a structure formed in the Z-axis by magnetic particles in a composition under the influence of a magnetic field. The process of column formation (column formation) is sometimes referred to as "alignment". The column properties (e.g., height, diameter, etc.) will be determined by the strength of the magnet and the characteristics of the ACA, including the size and amount of magnetic particles in the ACA as well as the viscosity and other physical properties of the ACA matrix. The pillars can and will form within seconds of exposure to a suitable magnetic field.

A "magnet" can generate a "magnetic field" that, as used herein, includes any magnetic field, whether generated by an electromagnet or a permanent magnet. The "strength" of a magnet can be measured with Gs (or Ts). The skilled person will recognize how to determine the strength of any given magnet, or how to determine the desired magnetic strength of a given magnet. As used herein, "mapping a magnetic field" means determining the specific shape of the magnetic field and the path of the magnetic field lines. The skilled person will recognize how to map the magnetic field of any magnet by various means.

As used herein, "permanent magnet" means a magnet that does not require a flow of current in order to have a permanent magnetic field. Permanent magnets for use herein can include iron, nickel, cobalt, and rare earth metals. Certain presently preferred embodiments herein utilize rare earth magnets, such as lanthanide-containing rare earth magnets. Magnets comprising neodymium or its salts may be useful herein because of their magnetic strength. In one embodiment, the magnet comprises neodymium, iron, and boron ("NIB magnet"). Samarium, gadolinium and even dysprosium and salts thereof can be used for specific applications. Other types of permanent magnets, such as ceramic magnets and other composite magnets, and even flexible magnets, may be suitable for use herein for other specific applications.

As used herein, an "interconnect" is generally a connection between any two aspects of a system. The interconnections herein generally reflect, for example, electrical and physical connections between two components or a component and a substrate. A "substrate" is a substrate for holding or containing other electronic components, such as a printed circuit board ("PCB"), connected thereon for use in an electronic system or device. The substrate may be flexible or rigid. Preferred rigid substrates include, for example, PCBs, composites, and rigid polymers; preferred flexible supports include, for example, flexible polymers.

As used herein, "parallel" means that two lines, such as the lines representing magnetic flux, are always separated by the same distance and never contact each other and exist in the same plane, i.e., they are at 0 degrees with respect to each other. The parallel lines herein are generally reference flux lines in the Z axis that are generally perpendicular (i.e., 90 degrees) to the X-Y plane of the substrate. Due to the difficulty of having completely parallel lines of magnetic flux in all applications involving multiple magnets, parallel lines in various embodiments herein may include lines that are "substantially parallel" to each other and/or substantially perpendicular to X-Y. Such lines may be positioned, for example, at about-30 to about 30 degrees relative to each other, and/or about 60 to about 120 degrees relative to the Z-Y plane. More preferably, such lines are positioned, for example, at about-15 to about 15 degrees relative to each other, and/or about 75 to about 105 degrees relative to the Z-Y plane. Even more preferably, the substantially parallel lines of magnetic flux are positioned, for example, at about-5 to about 5 degrees relative to each other and/or about 85 to about 95 degrees relative to the X-Y plane of the substrate. Even more preferably, the substantially parallel lines will be positioned within about 0 to about 2 degrees of each other and/or within about 0 to about 2 degrees of being perpendicular to the X-Y plane. The skilled person will recognize that the closer the flux lines are parallel to each other and perpendicular to the X-Y plane, the more ACAs will form parallel pillars during alignment that will underlie the interconnect and the less will there be shorts and other defects that negatively impact the functionality or durability of the interconnect so formed.

As used herein, "Z-axis" means a direction perpendicular to the main plane, i.e., the X-Y plane, in which the substrate lies.

Detailed description of illustrative embodiments

Systems and methods are provided herein for utilizing ACAs in electronic circuits to create improved and more consistent electronic interconnects. Such systems typically include individual magnets placed in positions corresponding to each component being connected. The size and strength of each magnet is determined based on the component, the substrate, the ACA in use, and the application mentioned. Only components that are being connected using ACA are exposed to any magnetic field, meaning that sensitive components are not exposed to unwanted magnetic fields. Preferably, the optimized interconnects provide better yield, fewer shorts and other failures, and longer life/more cycles. The inventors have surprisingly found that by employing strategic selection of magnet size, strength and placement, the uniformity and quality of the interconnection can be greatly improved. Accordingly, disclosed herein are methods and systems for improving the creation of interconnects using ACAs.

In a first aspect, the present disclosure provides a novel method of aligning and curing ACA-based interconnects in digital equipment, circuit boards, electronic devices, and the like. Methods for establishing interconnections between a substrate and electronic components filled on the substrate using a magnetically alignable Anisotropic Conductive Adhesive (ACA) typically comprise the steps of:

c) determining the size and strength of the magnet required in step b); and

d) the flux lines of the magnetic field of the magnet are plotted.

Repeating steps a) -d) for each additional component to be placed on and connected to the substrate in order to determine the required characteristics and placement position of each additional magnet. The skilled artisan will recognize that throughout the specification there are various methods set forth herein in which various steps are set forth. It should be noted that where it is not strictly necessary to perform such steps in the order described, the methods can likewise be performed by performing the steps in a different order, as this facilitates a successful interconnection without altering the overall objectives and results.

The method further comprises the steps of: creating a magnetic tray and securing each magnet in its respective placement position on the tray; and creating an alignment tray and adapting the alignment tray to hold the substrate during aligning (i.e., post forming) and curing the ACA in the Z-axis.

The substrate is then placed on an alignment tray. The ACA is applied to the substrate where the component is to be placed. The substrate is then filled with the first component and each additional component.

The alignment tray (including the substrate, the components to be attached and the applied ACA) and the magnetic tray are assembled to expose the ACA to the magnet. Sufficient exposure time is provided to allow the formation of pillars in the Z-axis in ACA; and then curing the ACA to establish interconnections between the substrate and the first component and each of the additional components.

Typically, the alignment tray and the magnetic tray are made of a non-magnetic material such as aluminum or a thermally stable material such as plastic or a composite material. The magnet tray is typically adapted to accommodate the first magnet and each additional magnet in their respective placement positions on the tray. The completed assembly, including the magnet tray with magnets and the alignment tray with the substrate filled with components and ACA, can be placed in a curing oven.

In various embodiments, the magnet comprises a permanent magnet. The magnets in one presently preferred embodiment comprise rare earth magnets. In one embodiment rare earth magnets are used, including neodymium or NIB magnets.

The inventors have found that the size and strength of the magnets used to create the interconnect can be determined empirically for each application to optimize the consistency and quality of the formed interconnect. The skilled person will appreciate that the selection of the size and strength of a particular magnet will be relevant to the process of column formation, and that the magnet selection will be influenced by the desired characteristics of the column, such as the height, diameter and strength of the column. Furthermore, the connection of the post to both the component and the substrate is also affected by the magnet properties.

Thus, in certain embodiments, the size and strength of the magnets are determined to optimize or account for the properties of the posts or the final interconnect. Such attributes may include the height of the posts, the strength of the interconnect, the number of resulting shorts, the expected life of the completed device or board, the yield of usable product, or the failure rate or number of failures resulting from the process of creating the interconnect.

The inventors have also determined that a significant benefit results from utilizing magnetic flux lines that are substantially parallel to each other and/or substantially perpendicular to the X-Y plane in an area corresponding to an area of the substrate on which the component and the ACA are located. In various embodiments, the flux lines consist essentially of such parallel and/or perpendicular lines.

In various embodiments, the ACA forms a column that is substantially uniform in height and diameter as a result of utilizing the provided methods. In a presently preferred embodiment, the ACA forms substantially uniform pillars substantially perpendicular to the X-Y plane of the component and substrate.

In order to further optimize the method, to further improve the consistency and to make the method simpler and more reliable, the geometry of the part of the alignment tray that accommodates and/or holds the substrate is in one embodiment configured such that the substrate can only be placed in one orientation in the alignment tray. This enables a technician to reproducibly place the substrate in the alignment tray for production.

In other embodiments, the alignment tray includes alignment means such as placement pins (complementary structures), etc. to ensure that the magnetic tray and the alignment tray can only be assembled in the proper orientation relative to each other. Alternatively, the geometry of the alignment tray and the magnetic tray allows assembly in only one (proper orientation). The skilled person will recognise that there are many simple ways to provide the appropriate orientation. Again, such features would further improve consistency and allow any skilled person to adapt the method to production.

As discussed above, typically, these methods allow the assembly including the positioned magnet tray and the alignment tray to be placed directly into the curing oven. Preferably, the alignment tray and the magnet tray comprise materials capable of withstanding the curing conditions used to cure the ACA. In one embodiment, the trays are aluminum or thermally stable non-magnetic materials capable of withstanding temperatures of, for example, 50-70C, 60-80C, 70-100C, 75-120C, 100-140C, or even greater. It is expected that a low temperature curing method will continue to be developed, in which case the materials used for the alignment tray and the magnet tray can be revised accordingly.

These methods can be more fully appreciated by reference to the figures. FIG. 2 shows a flow diagram of one embodiment 200 of the method described herein. As can be seen, the methods generally begin with an understanding of the substrate and the components to be placed on the substrate and connected to the substrate using ACA, as indicated in step 210. The size and location of each component can be mapped to allow the magnet tray to be designed and the placement location 220 for each magnet required to be determined.

The size and strength of each magnet can be determined 225 based on the details of the application. The characteristics of the magnetic field, such as the flux lines of each magnet, can be determined or mapped 230. The skilled person will understand how to determine the size, strength and flux lines of each magnet required. The skilled person will also recognise that the order of the preceding steps may be altered as may be preferred in a given application.

The skilled artisan will further recognize that the characteristics of the magnets will affect the development and formation of the pillars in the Z-axis within the ACA. Stronger magnets will allow for taller pillars to be formed faster, however making the magnets too strong is not desirable. In various embodiments, the desired characteristics of the magnet are determined empirically for any given application.

A magnet tray 235 is created and the magnets selected for this work are fixed in their respective positions 240. It should be understood that the magnet tray is designed to accommodate each magnet in its respective position by any useful means that does not alter the position or magnetic field of the magnet relative to the component and substrate. In one embodiment, the magnetic tray is made of aluminum, with holes being opened at the locations where each magnet will be placed. The magnet may again be secured in place 240 by any means so long as it does not alter the strength or flux lines of the magnet. An adhesive can be conveniently used in some embodiments to secure the magnets in the magnet tray.

The alignment tray 245 is created to serve as a carrier for the substrate and components and to ensure that the substrate and each component filled on the substrate is aligned with a corresponding magnet in the magnet tray. The alignment tray is adapted 250 to receive and hold the substrate during alignment and subsequent curing of the ACA. The tray can be adapted by any means to secure the substrate during the process of creating the interconnect. In one embodiment, a recessed area complementary to the shape of the substrate is created to passively accommodate and constrain the substrate during the process. In a presently preferred embodiment, the substrate can only be received in the alignment tray in one orientation, minimizing the risk of misalignment with the magnets in the magnet tray.

The ACA is applied 265 to the substrate at the location where the component is to be placed 260. The steps may vary in some embodiments contemplated herein, for example, the components may be filled and the ACA may be applied simultaneously. The skilled person will also appreciate that the order of the operations herein may be varied as long as the end result is that each component is correctly placed in the desired position on the substrate with the desired amount of ACA in between.

The alignment tray and the magnet tray are then brought into proximity with each other. In a presently preferred embodiment, the trays must be aligned when vertically positioned relative to each other. This is implemented by a structure that prevents the alignment tray from sliding with the substrate across the magnetic field of the magnets in the magnet tray and causing improper post formation. By requiring the magnet tray and the alignment tray to be close in this way, the column formation is optimized and limited to substantially the Z-axis. The thus assembled tray 270 ("assembly" or magnet pallet assembly) can then be placed in an oven to cure under the appropriate conditions. Because the assembled trays fit together in a manner that optimizes the formation of Z-axis (i.e., vertical) posts that are parallel to each other and because the components can be moved without substantially interfering with the posts, the oven can be a batch oven (batch oven) in which the components are manually moved into and out of the oven, or it can be a semi-continuous or even continuous oven, such as a reflow oven in which the components travel along a conveyor belt through the oven. After the ACA has cured, there is little risk of affecting the pillar structure; that is, the pillars are stable in the cured ACA.

It should also be noted that some components may experience what is referred to herein as "chip flipping". If the component is magnetic-poled, i.e., if the component has, for example, two separate magnetic poles, the component will "flip" when exposed to the magnetic field of the magnet tray to align itself with the magnetic field. Because the ACA is not yet aligned or cured when the system is exposed to the magnet tray, nothing prevents the chip from doing so. In extreme cases the component may be pulled entirely out of the substrate. While this only occurs on certain components, it can cause problems if present. The inventors have developed a simple solution to this problem in the presence of such components. It needs to include an additional "paste" step to hold the component/chip before exposure to the magnet tray. Typically, the component of interest is secured to the substrate. One useful way is to apply a small amount of epoxy in the presence of a magnetic field to hold sensitive components in place. Current methods include the use of uv-curable epoxy applied as a paint sufficient to secure the part, followed by brief exposure to uv light of sufficient intensity and duration to ensure curing of the epoxy. The assembly of substrate, component and ACA can then be placed in proper proximity to the magnet tray to allow the formation of Z-axis posts without concern for component/chip flipping.

In a second of its several aspects, the present disclosure provides a system for creating an interconnect between a substrate and an electronic component attached to the substrate using a magnetically alignable Anisotropic Conductive Adhesive (ACA). The system includes a magnet tray including a non-magnetic tray adapted to receive and hold each of one or more magnets placed therein in a position corresponding to a position of one or more electronic components on a substrate to which the components are to be connected.

The system also includes an alignment tray adapted to receive a substrate that is populated with one or more components to be connected to the substrate with the ACA. The alignment tray is capable of holding the substrate during alignment and curing of the ACA.

The system also includes an ACA including magnetically alignable particles capable of forming interconnects that are electrically conductive in the Z-axis. The ACA formulation can be varied for specific applications as may be dictated by the nature of the electronic components or the equipment interconnecting these components. For applications with different pitch requirements, the ACA may be formulated with, for example, different sized electromagnetic/conductive particles.

In a presently preferred embodiment, the alignment tray and the magnetic tray are made of a non-magnetic material. In one embodiment, the substrate can only be placed in the alignment tray in one orientation to avoid confusion and error and to allow non-technical staff to assist in production.

Typically, the magnet tray and the alignment tray are adapted to be removably vertically arranged together such that the components on the substrate are vertically aligned with the magnets in the magnet tray and the ACA is exposed to the magnetic field such that the flux lines are substantially perpendicular to the X-Y plane defining the substrate. This arrangement is preferably maintained until the solidification of the ACA is completed.

In various embodiments of the system, the magnet is a permanent magnet. Rare earth magnets are useful in many applications herein, including magnets comprising neodymium, such as NIB magnets. These magnets can provide a strong magnetic field.

In one embodiment, the assembly comprising the magnet tray, the alignment tray, and the component-filled substrate can be placed directly into a curing oven. This enables the aligned ACA to solidify with minimal movement and low risk of disturbing the pillars formed in the Z-axis when exposed to a magnetic field. In another embodiment, the assembly and/or magnet tray serves as a stand that can be slid directly into the oven without the need for any supporting shelves or additional stands for use. In other embodiments, the assembly can be placed on a conveyor mechanism for use with a semi-continuous or continuous process oven. In such embodiments, the conveyor belt may comprise a plurality of different assemblies of the same or different configurations of substrates and components-each assembly mating with its own detailing magnetic tray and components and substrates to be interconnected.

In various embodiments, for each magnet in the magnet tray of the system, the lines of magnetic flux are substantially parallel to each other and substantially perpendicular to the X-Y plane in an area corresponding to an area of the component and the substrate on which the ACA is located. An optimal interconnection can result from such an arrangement. The ACA forms substantially uniform pillars that are, in various embodiments, substantially perpendicular to the X-Y plane of the component and substrate.

With further reference to the figures, fig. 1 depicts an embodiment 100 of a system for magnetically aligning and curing ACA interconnects illustrating certain features of the system. Shown is a cross-sectional view showing an embodiment of a non-magnetic magnet tray 110 having a plurality of magnets 120 positioned therein for magnetically aligning and curing an ACA interconnect. The magnet tray 110 has openings (not numbered for convenience and clarity) to accommodate the magnets 120, which magnets 120 may be secured in the magnet tray 110 using an adhesive (not shown) or other securing means that does not alter the flux lines or otherwise interfere with the magnets 120. The alignment tray 130 has recesses that receive substrates 140 that are held in place during alignment and curing of the ACA to form the interconnects. The substrate 140 has a plurality of electronic components 150 positioned thereon. An ACA (not shown) is applied/positioned (or likely already applied) between the component 150 and the substrate 140. As can be seen, the placement of each magnet 120 corresponds to the position of the component 150 on the substrate 140 such that the magnets 120 are vertically aligned with the component 150. In this configuration the magnetic field provides a force to align the electromagnetic particles of the ACA (not shown) to form a Z-axis column. As can be seen, the area covered by each magnet 120 is larger than the area covered by the corresponding component 150, so that the system 100 provides better and consistent alignment compared to prior art electromagnets that cover the entire surface of the substrate or magnets that are the same size as the components.

Fig. 3 depicts an embodiment of an alignment tray 300 illustrating various aspects thereof. The depicted single tray 310 includes a plurality of substrates (not shown), each having a single component 320. In other embodiments (not shown), a single alignment tray may hold a single substrate with one or more components, depending on size. The alignment means 330, in this embodiment holes, allow for proper alignment with a magnet tray (not shown) using, for example, pins or rods, such that the magnet tray and alignment tray are arranged vertically and the magnets in the magnet tray are aligned with corresponding components for interconnection to the substrates on the alignment tray. Because proper alignment is important to the successful formation of the interconnection, the alignment tray may include simple features in various embodiments, such as varying hole geometries, hole patterns or offsets, different hole sizes, combinations of holes and pins, and complementary structures in the magnet tray that ensure that the alignment tray and the magnet tray can only be aligned in a single orientation relative to each other. The skilled person will recognise that there are many technically-accepted methods for achieving proper alignment between two such objects.

In yet another aspect, the present disclosure provides a kit for creating an interconnection between a substrate and an electronic component attached to the substrate using a magnetically alignable anisotropic conductive adhesive. The kit generally comprises:

at least one magnetic tray including a non-magnetic tray adapted to hold one or more magnets in a position corresponding to a desired placement of an electronic component on a substrate and connection of the component to the substrate using an ACA;

sufficient magnets to complete the magnet tray, each magnet of desired size and strength for making interconnections between the component and the substrate using the ACA; and

at least one alignment tray adapted to receive and hold a substrate and a component filled on the substrate to form an interconnect during aligning and curing of the ACA.

Optionally, the kit further comprises an ACA adapted for use with the kit to create an interconnection between the component and the substrate using the kit.

The magnet tray and the alignment tray are typically configured to be vertically oriented with respect to each other and can be assembled such that when the magnet tray and the alignment tray are so oriented and assembled, the electronic components placed on the substrate on the alignment tray are vertically aligned with the magnets on the magnet tray. This configuration is used in various embodiments for both the alignment and curing processes.

In a presently preferred embodiment, the oriented and assembled magnet tray and alignment tray ("assembly") can be placed into a curing oven. In one embodiment, the magnet tray or assembled tray is used as a rack in an oven, or a rack for transport into a semi-continuous or continuous oven such as a reflow oven or curing tunnel.

In various embodiments, when the magnet tray and the alignment tray are assembled together, for each magnet in the magnet tray, the lines of magnetic flux are substantially parallel to each other and substantially perpendicular to the X-Y plane in a region corresponding to a region of the substrate on which the component is located. Typically, the ACA positioned between the substrate and the components thereon form substantially uniform columns that are substantially perpendicular to the X-Y plane of the components and substrate when the tray is oriented and assembled.

In yet another aspect, the present disclosure provides an oven system for creating an interconnection between a substrate and an electronic component to be placed on the substrate and connected to the substrate using ACA. These systems generally operate as described above for the other systems described herein and in accordance with these methods. Typically the oven system comprises: a curing oven and one or more shelves or racks, each shelf or rack comprising: a magnetic tray equipped with one or more magnets, each magnet being placed in a position corresponding to a position of an electronic component to be placed on a substrate and connected to the substrate using an ACA; and an alignment tray adapted to receive and hold a substrate filled with one or more components to be placed on the substrate and connected via the ACA.

The magnet is in one embodiment a permanent magnet. Rare earth magnets are useful in many applications herein, including magnets comprising neodymium, such as NIB magnets.

In various embodiments of the oven system, for each magnet in the magnet tray of the system, the lines of magnetic flux are substantially parallel to each other and substantially perpendicular to the X-Y plane in an area corresponding to the area of the component and the substrate on which the ACA is located. The ACA forms substantially uniform pillars that are, in various embodiments, substantially perpendicular to the X-Y plane of the component and substrate.

An embodiment 400 of an oven system is shown in fig. 4. As can be seen, each assembly 450 of magnet tray 410 and alignment tray 420 can be used as a rack 425 in batch oven 401, which is typically designed to accommodate a plurality of such racks 425. An enlarged view of the assembly 450 is shown as inset 4B, which includes the assembled magnet tray 410 and the alignment tray 420 that holds the substrate, components, and ACA (generally 430) during alignment of the posts in the Z-axis and throughout the curing process. The alignment holes 435 ensure that the components can only be placed together in the proper orientation. The inset 4C shows an individual magnet tray 410, the individual magnet tray 410 showing a plurality of permanent magnets 415 in place.

The scope of the invention is set forth in the following claims, e.g., limited by language. Although the invention has been described in language specific to particular terms, those terms are used in a generic and descriptive sense only and not for purposes of limitation. Additionally, while certain presently preferred embodiments of the claimed invention have been described herein, those skilled in the art will recognize that such embodiments are provided by way of example only. Certain alterations, modifications, and substitutions will occur to those skilled in the art in view of the teachings provided herein. It is therefore to be understood that the invention may be practiced otherwise than as specifically described and that such manner of practicing the invention is within the scope of the appended claims, or is equivalent to the scope of the claims, and does not depart from the scope and spirit of the invention as claimed.

Claims

1. A method of establishing an interconnection between a substrate and an electronic component filled on the substrate using a magnetically alignable Anisotropic Conductive Adhesive (ACA), the method comprising the steps of:

a) establishing a size and a position on the substrate of a first component to be placed on the substrate and connected to the substrate;

b) determining a placement position of a first magnet corresponding to the size and position established for the component in step a);

c) determining the size and strength of the magnet required in step b);

d) plotting flux lines of the magnetic field of the magnet;

e) repeating steps a) -d) for each additional component to be placed on and connected to the substrate to determine the characteristics and placement positions for each additional magnet required;

h) placing the substrate on the alignment tray;

i) applying the ACA on the substrate in one or more locations where components are to be placed;

j) filling the substrate with the first component and each additional component;

k) assembling the alignment tray and the magnetic tray;

l) allowing the formation of pillars in the ACA in the Z-axis; and

m) curing the ACA, thereby establishing the interconnections between the substrate and the first and each additional component;

wherein the alignment tray and the magnetic tray are made of a non-magnetic material and the magnetic tray is adapted to accommodate the first magnet and each additional magnet in their respective placement positions on the tray; and wherein an assembly comprising the magnet tray with magnets, the alignment tray with component-filled substrate and ACA can be placed in a curing oven.

2. The method of claim 1, wherein the magnet comprises a permanent magnet.

3. The method of claim 2, wherein the magnet comprises a rare earth magnet.

4. The method of claim 3, wherein the size and strength of each magnet is determined independently and empirically to optimize the height of the posts, to optimize interconnect strength, to reduce the number of short circuits, to improve the expected life of a finished device or board, to improve yield of usable product, or to reduce failure or scrap due to creating the interconnects.

5. The method of claim 4, wherein for each magnet in the magnet tray, the lines of magnetic flux are substantially parallel to each other and substantially perpendicular to an X-Y plane in an area corresponding to an area of the substrate on which the component and ACA are located.

6. The method of claim 1, wherein said ACA forms a column that is substantially uniform in height and diameter.

7. The method of claim 1, wherein the ACA forms substantially uniform pillars that are substantially perpendicular to an X-Y plane of the component and the substrate.

8. The method of claim 1, wherein the substrate can only be placed in the alignment tray in one orientation.

9. The method of claim 1, wherein the alignment tray includes an alignment device to ensure that the magnetic tray and the alignment tray can only be assembled in the proper orientation relative to each other.

10. The method of claim 1, wherein the alignment tray and the magnet tray comprise a material capable of withstanding curing conditions for curing the ACA.

11. A system for creating an interconnect between a substrate and an electronic component attached to the substrate using a magnetically alignable Anisotropic Conductive Adhesive (ACA), the system comprising:

a magnet tray comprising a non-magnetic tray adapted to receive and hold each of one or more magnets placed therein in a position corresponding to a position of one or more electronic components on a substrate to which the components are to be attached;

an alignment tray adapted to hold a substrate filled with one or more components to be connected to the substrate with an ACA during alignment and curing of the ACA;

and an ACA comprising magnetically alignable particles capable of forming interconnects that are electrically conductive in the Z-axis;

wherein the alignment tray and the magnetic tray are made of a non-magnetic material;

wherein the magnet tray and the alignment tray are removably vertically arranged together such that the components on the substrate are vertically aligned with the magnets in the magnet tray and the ACA is exposed to the magnetic field such that the flux lines are substantially perpendicular to an X-Y plane defining the substrate; and

wherein the substrate can only be placed in the alignment tray in one orientation.

12. The system of claim 11, wherein the magnet is a permanent magnet.

13. The system of claim 11, wherein the magnet is a rare earth magnet.

14. The system of claim 13, wherein for each magnet in the magnet tray, the lines of magnetic flux are substantially parallel to each other and substantially perpendicular to the X-Y plane in an area corresponding to an area of the substrate on which the component and ACA are located.

15. The system of claim 11, wherein the ACA forms a substantially uniform column that is substantially perpendicular to an X-Y plane of the component and the substrate in the presence of the magnet.

16. The system of claim 11, wherein the assembly comprising the magnet tray, the alignment tray, and the component-filled substrate can be placed or transferred directly into a curing oven.

17. The system of claim 16, wherein the assembly or the magnet tray serves as a rack that can be slid directly into or transferred into the oven and does not require any support shelves, additional racks, or other supports.

18. A kit for creating an interconnection between a substrate and an electronic component attached to the substrate using a magnetically alignable anisotropic conductive adhesive, the kit comprising:

sufficient magnets to complete the magnet tray, each magnet of a desired size and strength for making interconnections between the component and the substrate using the ACA;

at least one alignment tray adapted to receive and hold the substrate and components filled on the substrate during aligning and curing the ACA to form the interconnect;

and optionally an ACA adapted for use with the kit to create at least one interconnection between a component and a substrate using the kit;

wherein the magnet tray and the alignment tray are configured to be vertically oriented with respect to each other and assembled such that electronic components placed on a substrate on the alignment tray are vertically aligned with magnets on the magnet tray when the magnet tray and the alignment tray are so oriented and assembled.

19. The kit of claim 18, wherein the oriented and assembled magnet tray and alignment tray can be placed or transferred directly into a curing oven.

20. The kit of claim 19, wherein the magnet tray or assembled tray serves as a rack in the oven.