KR102668129B1 - System and method for improved electronic component interconnections - Google Patents

Abstract

Systems and methods are provided for improved interconnections to electronic components using ACAs. The methods involve using magnets that are specific for each component to be connected and optimized in terms of size and strength and position relative to the substrate and component. Ovens adapted for use with the methods and systems and kits providing parts of the system for use with existing ovens are also provided.

Description

System and method for improved electronic component interconnections

Cross-reference to related applications

This application claims priority to U.S. Provisional Patent Application No. 62/586,815, filed November 15, 2017, which is incorporated herein by reference in its entirety.

field of invention

This application generally relates to establishing electrical connections of components in electronic circuitry. More specifically, this disclosure relates to improved methods of connecting components to a substrate using anisotropic conductive adhesives.

As modern demands for technology increase, the number of electronic devices continues to increase, the availability and adoption of these devices continues to increase, the size of these devices continues to decrease, and the interconnection of electronic components required to manufacture these devices The number of interconnects has increased significantly. Moreover, in many fields previously analog devices have all but disappeared as these devices have been replaced by electronics, and while the size of electronic devices has shrunk dramatically, their power continues to expand rapidly.

As modern components become smaller and more powerful, more circuitry exists in smaller spaces on these components (i.e., circuitry density increases), allowing, for example, between different aspects of a given chip or component. Tolerances became much tighter (i.e. the pitch became smaller - becoming "ultra-small pitch").

Therefore, modern components are often more sensitive to temperature and pressure, either of which can cause problems and cause failure of the component and the entire device of which it is a part. Unfortunately, current means of creating interconnects between components and their substrates, for example, all have limitations and drawbacks for certain applications.

There are a number of interconnection means (such as traditional solders, anisotropic conductive films (ACFs), and anisotropic conductive adhesives (ACAs)), each with their own advantages and limitations. Those skilled in the art will appreciate that each of them provides options that can meet the requirements for specific interconnections for specific applications, components, or devices.

Traditional soldering involves exposing the connected components to large amounts of localized heat and pressure. Exposure of these components to these unfavorable or unsupportable conditions can result in apparent failure, poor or unreliable performance, or greatly reduced lifespan.

As an effort to improve interconnects for a variety of applications, ACFs have been developed. These conductive films can reduce the local heat required for connection by soldering, but can still require significant heat. Additionally, both heat and pressure are commonly applied to the components, which can be a significant limitation for sensitive components. ACFs also have limitations regarding the pitch of interconnections that are suitable or acceptable.

ACAs have also been developed to provide alternative solutions for creating difficult interconnects in certain applications. Like ACFs, these adhesives provide electrical conductivity only in the z-axis. ACAs, such as those produced by SunRay Scientific, contain magnetically alignable particles that form interconnects between components when the particles are 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 fix the interconnection. Because no pressure is required, ACAs are good candidates for pressure sensitive components. Additionally, curing can be accomplished at low heat for temperature sensitive components. Moreover, ACAs allow finer pitch applications than can be achieved using ACFs.

Prior art applications of ACAs typically employed a magnetic field applied across the entire substrate using electromagnets. This field covers all components residing on the substrate, but may be disadvantaged in applications where one or more components on the substrate are sensitive to magnetic fields. In addition, the applied magnetic field over a large area includes the entire magnetic field including magnetic flux lines that are generally not perfectly perpendicular to the x-y plane.

Although creating interconnects with ACAs is simple and easy, there is nonetheless a need for improved systems and methods for creating and optimizing interconnects using ACAs in specific applications.

The inventors have discovered methods that provide unexpected improvements in ACA-based electronic interconnects for specific applications and developed a system that implements the methods. The methods select appropriate ACA properties, use separate magnets positioned for each component to be interconnected, and select the properties of the magnets used for alignment of the ACA for each specific component residing on the substrate. Thus, it provides several advantages based on optimizing the creation of z-axis connections (in terms of height, number and direction of z-axis columns). The methods allow the construction of what the inventors refer to as a 'magnetic palette' that provides consistent optimal alignment and curing of ACA-based interconnects. The methods can provide improved interconnect consistency, reduced failures, improved lifetime and increased yields of functional connections compared to existing methods of forming interconnects.

In a first aspect, the present disclosure provides novel methods for aligning and curing ACA-based interconnects in digital devices, electronics, etc. Methods for establishing an interconnect between a substrate and an electronic component residing thereon using a magnetically alignable anisotropic conductive adhesive (ACA) generally include:

a) establishing dimensions and location on the substrate of a first electronic component to be disposed on and connected to the substrate;

b) determining a placement location of the first magnet that corresponds to the dimensions and location established for the component in step a);

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

d) mapping the magnetic flux lines of the magnetic field to the magnet.

Steps a) through d) are repeated for each additional component to be placed on and connected to the substrate to determine the properties and placement location for each additional magnet required;

The method is,

f) creating a magnetic tray and securing each magnet to its respective placement location on the tray;

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

h) placing the substrate on an alignment tray;

i) applying ACA to the substrate at locations suitable for interconnecting each component to be placed on the substrate;

j) populating the ACA-applied first component and each additional component onto the substrate;

k) assembling the alignment tray and the magnetic tray;

l) allowing columns to be formed in the z-axis with ACA; and

m) curing the ACA, thereby establishing interconnects between the substrate and the first component and each additional component.

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

In a second aspect, a system is provided for creating interconnects between a substrate and electronic components attached to the substrate using a magnetically alignable anisotropic conductive adhesive (ACA). The systems generally include a magnet tray comprising a non-magnetic tray adapted to receive and retain each of one or more magnets disposed therein at locations corresponding to the locations of one or more electronic components on the substrate to which the components are to be connected.

The systems also include an alignment tray adapted to hold a substrate housing one or more components to be connected to the substrate with the ACA during alignment and curing of the ACA.

The systems also include ACA containing magnetically alignable particles that can form conductive interconnections in the z-axis.

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

In presently preferred embodiments, the magnets are permanent magnets. Generally, for each magnet in a magnet tray, the magnetic flux lines are substantially parallel to each other and substantially perpendicular to the x-y plane in an area corresponding to the area of the substrate where the component and ACA are located. In the presently preferred embodiment, the magnetic flux lines essentially consist of lines parallel to each other and perpendicular to the area of the substrate where the components and ACA are located.

In a third aspect, the present disclosure provides a kit for creating interconnects between a substrate and electronic components attached to the substrate using a magnetically alignable anisotropic conductive adhesive. Kits generally:

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

Sufficient magnets to complete a magnetic tray - each magnet of the desired size and strength to make interconnections between components and boards using ACA;

at least one alignment tray adapted to receive and retain the substrate and components residing thereon during alignment and curing of the ACA to form the interconnect; and

Optionally, include an ACA suitable for use with the kit to create at least one interconnect between the component and the substrate using the kit.

In the provided kits, the magnetic tray and alignment tray are configured to be oriented perpendicularly to each other. These are assembled such that the electronic components placed on the substrate on the alignment tray (to be connected to the substrate with the ACA) are vertically aligned with the magnets on the magnet tray when the magnet tray and alignment tray are assembled in such a way. Each component requiring connection (interconnect) has a corresponding magnet to align each component when the trays are assembled.

In currently preferred embodiments of the kits, the magnets include rare earth magnets, or other permanent magnets.

In another aspect, the present disclosure provides oven systems designed to create interconnections between a substrate and an electronic component to be disposed on the substrate and connected to the substrate using ACA. Oven systems typically include a curing oven and one or more shelves or racks, each of which includes:

a magnetic tray disposed on a substrate and in which one or more magnets, each disposed at a location corresponding to a location of an electronic component to be connected to the substrate, are fitted using ACA; and

and an alignment tray adapted to receive and hold a substrate populated by one or more components to be disposed on and connected to the substrate via the ACA.

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

1 is a cross-sectional schematic diagram of one embodiment of a system for magnetically aligning and curing ACA interconnects showing a magnet tray in which magnets are positioned, an alignment tray, a substrate, and components residing on the substrate.
2 is a flow diagram illustrating the steps of a method for magnetically aligning and curing components to a substrate using ACA to create electrical connections.
Figure 3 is a diagram illustrating one embodiment of an alignment tray for use with the present invention. The tray includes a plurality of substrates, each substrate having a habitable component to be disposed on and connected to the substrate.
4 is a diagram illustrating one embodiment of an oven employing a magnetic pallet system. A. Multiple magnetic tray and alignment tray assemblies are shown within a batch oven. The external dimensions of the alignment and magnet trays are dictated by the oven dimensions but otherwise each magnet tray or each alignment tray need not be identical. Accordingly, a single oven can be used to align and cure multiple interconnects for multiple electronic components on different substrates or devices. B. Shows an enlarged view of the assembly including the alignment tray and magnet tray along with the orientation means (alignment holes). C. Shows a close-up overhead view of a magnetic tray serving as a rack in the oven.

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

Definitions and Acronyms

Unless explicitly defined otherwise, all technical and scientific terms, technical terms, and initials used in this specification will be understood by those skilled in the art in the field(s) of the present invention in which the terms are used. It has meanings that are commonly understood. In accordance with this description, the following abbreviations and definitions apply.

Abbreviations

Unless otherwise indicated, the following abbreviations apply:

AC: alternating current;

ACA: Anisotropic conductive adhesive;

ACF: Anisotropic conductive film;

DC: direct current;

Gs: Gauss, magnetic field unit;

NIB: neodymium-iron-boron;

PCB: printed circuit board; and

T: Tesla, unit of magnetic field (SI).

definitions

As used herein, “substantially” can mean a greater or lesser amount than the reference item. Preferably, substantially greater (or more) or less (or less) means at least about 10% to about 100% more than the corresponding reference item. More preferably, "substantially" in these instances means at least about 20% to about 100% more, greater or less than the reference item. As will be understood by those skilled in the art, the term 'substantially' means greater than 51%, preferably 60%, 67%, 70%, 75%, 80%, 85%, 90% of the referenced item, number, or quantity. Can also be used as in "substantially all," meaning exceeding more than %. “Substantially all” can also mean greater than 90%, including 91, 92, 93, 94, 95, 96, 97, 98, 99 or more percent of the referenced item, number, or quantity.

As used herein, singular forms include plural and vice versa unless the context clearly dictates otherwise. Accordingly, references to “a,” “an,” and “the” generally include plural forms of the respective terms. For example, reference to “electrode” or “diode” includes a plurality of such “electrodes” or “diodes.”

The words “including” and “including” should be construed as inclusive and not exclusive. Similarly, the terms “comprising,” “comprising,” and “or” should be construed as inclusive unless the context clearly prohibits such construction. Moreover, forms of the terms “comprising” or “comprising” are intended to include embodiments encompassed by the phrases “consisting essentially of” and “consisting of.” Likewise, the phrase “consisting essentially of” is intended to include embodiments encompassed by the phrase “consisting of.”

When used herein, ranges are given as abbreviations to avoid listing and describing each and every value within the range. Any suitable value within the range may be selected as the upper limit, lower limit, or terminus of the range, as appropriate.

The formulations, compositions, methods and/or other advances disclosed herein are not limited to the specific techniques, protocols, and/or components described herein, as those of ordinary skill in the art will understand. This is because it is variable. Moreover, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to, and does not, limit the scope of the disclosure or claimed.

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

Any references, including any patents, patent applications, or other publications, technical and/or academic papers, cited or referred to herein are incorporated by reference in their entirety to the extent permitted under applicable law. Included in the disclosure. Any discussion of those references is intended merely to summarize the arguments made in those references. No admission is made that any of these patents, patent applications, publications or references are prior art, or that any portion thereof is either material or relevant to the patentability of the matter claimed herein. Applicant specifically reserves the right to challenge the accuracy and appropriateness of any claim that these patents, patent applications, publications, and other references are prior art, related material, and/or material.

As used herein, “alignment” means aligning a magnetic material or composition containing magnetic particles. In general, alignment refers to the arrangement of magnetic particles along the z-axis under the influence of a magnetic field. Sorting is a process in which columns are formed along the z-axis. As will be clear from the context, sometimes 'alignment' is also used herein to refer to ensuring the proper orientation of two things - such as an alignment tray and a magnetic tray, or a substrate and an alignment tray - with respect to each other.

As used herein, “columns” refers to structures formed by magnetic particles in the composition in the z-axis under the influence of a magnetic field. The process of column formation is sometimes called 'sorting'. Column properties (eg, height, diameter, etc.) will be determined by the properties of the ACA, including the strength of the magnets and the size and amount of magnetic particles in the ACA, and the viscosity and other physical properties of the ACA matrix. Columns can and will form within seconds after exposure to a suitable magnetic field.

A “magnet,” as used herein, can generate a “magnetic field,” including any magnetic field, whether generated by an electromagnet or a permanent magnet. The "strength" of a magnet can be measured in Gs (or Ts). Those skilled in the art will understand how to determine the strength of any given magnet, or how to determine the desired magnetic strength for a given magnet. “Magnetic field mapping” as used herein means determining the specific shape of the magnetic field and the path of the magnetic field lines. Those skilled in the art will understand how to map the magnetic field of any magnet through a variety of means.

As used herein, “permanent magnet” means a magnet that does not require an electric current to flow in order to have a persistent magnetic field. Permanent magnets for use herein may include iron, nickel, cobalt, and rare earth metals. Certain currently preferred embodiments of the present disclosure utilize rare earth magnets, such as those containing lanthanoid elements. Magnets containing neodymium, or salts thereof, may be useful herein due to their magnetic strength. In one embodiment, the magnets include neodymium, iron, and boron (“NIB magnets”). Samarium, gadolinium, and even dysprosium, and their salts may be used in certain 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. Interconnects herein generally reflect electrical and physical connections, for example, between two components or a component and a substrate. A “substrate” is any material used to hold or contain other electronic components that are connected to the substrate for use in an electronic system or device, such as a printed circuit board ('PCB'). Substrates may be flexible or rigid. Preferred rigid substrates include, for example, PCBs, composites, and rigid polymers; Preferred flexible supports include, for example, soluble polymers.

As used herein, "parallel" means that two lines, such as lines representing magnetic flux, are always the same distance apart, never touch each other, and lie in the same plane, that is, they lie at zero angles with respect to each other. It means that it is in the province. Parallel lines herein are generally reference flux lines in the z-axis, which are generally perpendicular (i.e., 90 degrees) to the x-y plane of the substrate. Because of the difficulty of having lines of magnetic flux that are completely parallel throughout a full range of applications involving multiple magnets, the parallel lines in various embodiments herein are "substantially parallel" to each other and/or in X-Y. It may include substantially vertical lines. These lines may be located, for example, at about -30 degrees to about 30 degrees relative to each other and/or at about 60 degrees to about 120 degrees with respect to the Z-Y plane. More preferably these lines may be positioned, for example, at about -15 degrees to about 15 degrees relative to each other and/or at about 75 degrees to about 105 degrees with respect to the Z-Y plane. Even more preferably the substantially parallel magnetic flux lines are positioned, for example, at about -5 degrees to about 5 degrees with respect to each other, and/or at about 85 degrees to about 95 degrees with respect to the x-y plane of the substrate. Even more preferably the substantially parallel lines are positioned within about 0 degrees to about 2 degrees of each other and/or within about 0 degrees to about 2 degrees of the x-y plane of the substrate. The more lines of magnetic flux are approximately parallel to each other and perpendicular to the A person skilled in the art will understand that there will be fewer damaging short circuits and other defects.

As used herein, “z-axis” means the direction perpendicular to the principal plane in which the substrate lies, i.e., the x-y plane.

Detailed Description of Exemplary Embodiments

Systems and methods for creating improved and more consistent electronic interconnects with ACAs in electronic circuits are provided in this disclosure. These systems typically include individual magnets placed at locations corresponding to each component being connected. The size and strength of each magnet is determined based on the component, substrate, ACA being used, and the application in question. Only components connected to the ACA are exposed to any magnetic fields, meaning that sensitive components are not exposed to unnecessary magnetic fields. Advantageously, optimized interconnects provide better yields, fewer shorts and other failures, and longer lives/more cycles. The inventors have surprisingly discovered that the consistency and quality of interconnects can be substantially improved by employing strategic selection of magnet size, strength, and placement. Accordingly, methods and systems for improving the creation of interconnects using ACAs are disclosed herein.

In a first aspect the present disclosure provides novel methods for aligning and curing ACA based interconnects in digital devices, circuit boards, electronics, etc. Methods for establishing an interconnect between a substrate and an electronic component residing thereon using a magnetically alignable anisotropically conductive adhesive (ACA) generally include the following steps:

a) establishing dimensions and location on the substrate of a first electronic component to be disposed on and connected to the substrate;

b) determining a placement location of the first magnet that corresponds to the dimensions and location established for the component in step a);

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

d) Mapping the magnetic field lines of flux for the magnet.

Steps a) through d) are repeated for each additional component to be placed on and connected to the substrate to determine the properties and placement location for each additional magnet required. Those skilled in the art will understand that there are various methods referred to herein, with various steps being referred to throughout the specification. In all cases where these steps are not strictly required to be performed in the order described, the methods are equivalent to performing the steps in a different order than will most facilitate the achievement of successful interconnections without altering the overall purpose and result. Please note that this can be done.

The method includes creating a magnetic tray and binding each magnet to each placement location of each magnet on the tray; and creating an alignment tray and adapting the alignment tray to maintain the substrate during alignment (i.e., column formation) and curing of the ACA in the z-axis.

The substrate is then placed on an alignment tray. ACA is applied to the substrate on which the components will be placed. The substrate is then populated by the first and each additional component.

An alignment tray (containing the substrate, components to be attached, and applied ACA) and a magnetic tray are assembled to expose the ACA to the magnets. In ACA sufficient exposure time is provided to allow columns to be formed in the z-axis; The ACA is then cured, establishing interconnects between the substrate and the first and each additional component.

Typically, the alignment tray and magnetic tray are made of non-magnetic materials, such as aluminum, or thermally stable materials, such as plastics or composites. The magnet tray is generally adapted to receive the first and each additional magnet at their respective placement locations on the tray. The completed assembly, including a magnet tray with the magnets and an alignment tray with the substrate housing the components and ACA, can be placed in a curing oven.

In various embodiments, the magnets include permanent magnets. The magnets include rare earth magnets in one currently preferred embodiment. Rare earth magnets including neodymium or NIB magnets are used in one embodiment.

The inventor has discovered that the size and strength of the magnets for creating the interconnections can be determined empirically for each application to optimize the consistency and quality of the interconnects formed. Those skilled in the art will understand that selecting the size and strength of a particular magnet will be related to the process of forming the column, and that magnet selection will be influenced by the desired properties of the columns, such as the height, diameter, and strength of the column. Moreover, the connections of the column to both the component and the substrate are also affected by the magnetic properties.

Accordingly, in certain embodiments, the size and strength of the magnets are determined to optimize or address the properties of the column or final interconnects. These attributes may include the height of the columns, the strength of the interconnections, the number of resulting shorts, the expected life of the finished device or board, the yield of usable product, or the number of failures or rejections resulting from the process of creating the interconnects. You can.

The inventors have also determined that distinct advantages arise from using magnetic flux lines that are substantially parallel to each other and/or substantially perpendicular to the x-y plane in a region corresponding to the region of the substrate where the component and ACA are located. In various embodiments the magnetic flux lines consist essentially of these parallel and/or perpendicular lines.

In various embodiments, the ACA forms columns that are substantially uniform in terms of height and diameter as a result of using the methods provided. In presently preferred embodiments, the ACA forms substantially uniform columns substantially perpendicular to the x-y plane of the component and substrate.

To further optimize the method, to further improve consistency and to make the method more robust, in one embodiment, the geometry of the portion of the alignment tray that receives and/or holds the substrate is such that the substrate is aligned in only one orientation. It is configured to be placed on a tray. This allows technicians to reproducibly place substrates on alignment trays for production.

In other embodiments, the alignment tray includes alignment means, such as positioning pins, complementary structures, etc., to ensure that the magnetic tray and alignment tray can be assembled only in the proper orientation with respect to each other. Alternatively, the alignment and geometry of the magnetic trays allow assembly with only one (appropriate orientation). Those skilled in the art will understand that there are a number of simple methods to provide proper orientation. Again, these features will further increase consistency and allow any technician to use the production method.

As discussed above, generally, the methods allow the assembly including the positioned magnet tray and alignment tray to be placed directly into the curing oven. Preferably the alignment tray and magnet tray include materials that can withstand curing conditions for curing the ACA. In one embodiment, the trays are aluminum or thermally stable, capable of withstanding temperatures, e.g., 50-70 C, 60-80 C, 70-100 C, 75-120 C, 100-140 C, or even higher. These are non-magnetic materials. It is expected that low temperature curing methods will continue to be developed in which the materials used for alignment and magnetic trays can be modified accordingly.

The methods can be more fully understood with reference to the drawings. Figure 2 shows a flow diagram for one embodiment 200 of the methods described herein. As can be seen, the methods generally begin with understanding the substrate and the components to be disposed on the substrate and connected to the substrate using ACA, as noted in step 210. The dimensions and location of each component can be mapped to allow design of the magnet tray and determination 220 of the required placement location for each magnet.

The size and strength of each magnet can be determined based on application specifications (225). Properties of the magnetic field, such as magnetic flux lines for each magnet, can be determined or mapped (230). A person skilled in the art will understand how to determine the size, strength, and magnetic flux lines for each magnet required. Those skilled in the art will also understand that the order of the foregoing steps may be varied as desired for a given application.

Those skilled in the art will further understand that the properties of the magnet(s) will affect the development and formation of columns in the z-axis within the ACA. Stronger magnets will allow higher columns to form more quickly, but it is undesirable for the magnet to be too strong. In various embodiments, the ideal properties of magnets are determined empirically for any given application.

A magnetic tray is created (235) and the magnets selected for work are bound to their respective locations (240). It is understood that the magnet tray is designed to receive each of the magnets at their respective locations by any useful means that does not change the position or magnetic field of the magnets relative to the component and substrate. In one embodiment, the magnetic tray is made of aluminum with holes cut into locations where each of the magnets will be placed. The magnets can again be bound in place by any means without changing the magnet strength or magnetic flux lines (240). Adhesives may be conveniently used to bind the magnets to the magnet tray in certain embodiments.

An alignment tray is created 245 to serve as a carrier for the substrate and components and to ensure that the substrate and each component residing on the substrate are aligned with their corresponding magnets in the magnet tray. The alignment tray is adapted to receive and hold the substrate during alignment and subsequent curing of the ACA (250). The tray may be adapted by any means for holding the substrate together during the process of creating the interconnects. In one embodiment, a concave region complementary to the shape of the substrate is created to passively receive and retain the substrate during processing. In the presently preferred embodiment, the substrate is received in only one orientation in the alignment tray, thereby minimizing the risk of misalignment with the magnets in the magnet tray.

ACA is applied (265) to the substrate at the locations where the components will be placed (260). In some embodiments contemplated herein the steps may vary, for example, the components may reside and the ACA may be applied simultaneously. Those skilled in the art will also appreciate that the order of operations may be so varied herein, provided that the end result is that each component is positioned exactly at the desired location on the substrate with the desired amount of ACA between them.

The alignment tray and magnetic tray are then brought close to each other. In the presently preferred embodiment, the trays should be aligned, positioned perpendicularly to each other. This is enhanced by a structure that prevents the alignment tray from slipping with the substrate across the magnetic fields of the magnets in the magnet tray and initiating improper column formation. By requiring the magnet tray and alignment tray to be proximate in this way, the column formation is substantially optimized and limited to the z-axis. The trays 270 ('assembly' or magnetic pallet assembly) so assembled can then be placed in an oven for curing under appropriate conditions. Because the assembled trays fit together in a way that optimizes the formation of z-axis (i.e., perpendicular) columns that are parallel to each other and because the assembly can be moved without substantially interfering with the columns, the oven allows the assemblies to It may be a batch oven that is moved manually in and out of the oven, or it may be semi-continuous or even continuous, such as a reflow oven in which the assemblies are moved along a conveyor through the oven. There is little risk of affecting the column structure after the ACA has cured; That is, the columns are stable in cured ACA.

It should also be noted that a phenomenon referred to herein as 'chip flipping' may occur with certain components. If a component is magnetically polarized—that is, if it has, for example, two magnetic poles separated—when exposed to the magnetic field of a magnet tray, the component will 'flip' to align itself with the field. Because the ACA has not yet aligned or cured when the system is exposed to the magnetic tray, there is nothing to prevent the chip(s) from doing so. In extreme cases, the component may be completely pulled from the board. This only happens in certain components, but if it exists, it is a problem. The inventor has developed a simple solution to solve this problem if these components exist. This requires the inclusion of an additional 'tacking' step to bind the components/chips together prior to exposure to the magnetic tray. Typically, the components of interest are coupled to a substrate. One useful method is to apply a small amount of epoxy to hold sensitive components in place in the presence of a magnetic field. The methods herein involve the use of UV curable epoxy applied in small quantities sufficient to bind the components, followed by brief exposure to UV light of sufficient intensity and duration to ensure that the epoxy cures. The assembly of substrate, components, and ACA can then be placed in appropriate proximity to the magnetic tray to allow z-axis columns to be formed without concern about flipping of components/chips.

In a second of several aspects herein, the present disclosure provides a system for creating interconnects between a substrate and electronic components attached to the substrate using a magnetically alignable anisotropic conductive adhesive (ACA). The system includes a magnet tray comprising a non-magnetic tray adapted to receive and retain each of one or more magnets disposed therein at locations corresponding to the locations of one or more electronic components on the substrate to which the components are to be connected.

The system also includes an alignment tray adapted to receive a substrate housing one or more components to be connected to the substrate with an ACA. An alignment tray can hold the substrate during alignment and curing of the ACA.

The system also includes ACA containing magnetically alignable particles capable of forming conductive interconnections in the z-axis. ACA formulations may vary depending on specific applications, which may be dictated by the characteristics of the electronic components or the device to which the components are interconnected. ACAs can, for example, be formulated with electromagnetic/conductive particles in different sizes for applications with different pitch requirements.

In preferred embodiments herein, the alignment tray and magnetic tray may be made of non-magnetic materials. In one embodiment, the substrates may be placed in only one orientation on the alignment tray to avoid confusion and mistakes and allow non-technical staff to assist with production.

Generally, the magnet tray and the alignment tray are adapted to be arranged vertically together in a releasable manner such that the components on the substrate are vertically aligned with the magnets in the magnet tray, and the magnetic flux lines are substantially perpendicular to the x-y plane defining the substrate. is exposed to a magnetic field. This arrangement is preferably maintained until curing of the ACA is complete.

The magnets in various embodiments of this system are permanent magnets. Rare earth magnets, including magnets containing neodymium, such as NIB magnets, are useful for many applications herein. These magnets can provide strong magnetic fields.

The assembly including the magnet tray, alignment tray, and substrate upon which the components reside may be placed directly into the curing oven in one embodiment. This allows the aligned ACA to harden with minimal movement when exposed to a magnetic field, with little risk of disturbing the columns formed in the z-axis. In other embodiments the assembly and/or magnetic tray acts as a rack that can be slid directly into the oven and does not require any support shelves or additional racks for use. In other embodiments, the assembly may be placed on a conveyor mechanism for use with a semi-continuous or continuous process oven. In these embodiments, the conveyor is a plurality of different assemblies, each with its own magnetic tray designed according to the specifications and components and substrates to be interconnected, the same for different configurations of substrates and components. may include.

In various embodiments for each magnet in the magnet tray of the system, the magnetic flux lines are substantially parallel to each other and substantially perpendicular to the x-y plane in a region corresponding to the region of the substrate where the component and ACA are located. Optimal interconnections can result from these arrangements. The ACA forms substantially uniform columns that are substantially perpendicular to the x-y plane of the component and substrate in various embodiments.

With further reference to the drawings, FIG. 1 depicts an embodiment 100 of a system for magnetically aligning and curing ACA interconnects illustrating certain features of the system. A cross-sectional view of an embodiment for magnetically aligning and curing ACA interconnects is shown, showing a non-magnetic magnet tray 110 with a plurality of magnets 120 positioned therein. Magnet tray 110 has openings (unnumbered for convenience and clarity) to receive magnets 120 that do not alter magnetic flux lines or otherwise interfere with magnets 120 . It may be fastened within the magnetic tray 110 using adhesive (not shown) or other fastening means. Alignment tray 130 has a recess to receive substrate 140 that is held in place during alignment and curing of the ACA to form interconnects. Substrate 140 has a plurality of electronic components 150 positioned on the substrate. ACA (not shown) is applied/positioned (or potentially applied) between components 150 and substrate 140 . As can be seen, the placement of each of the magnets 120 corresponds to the location of the component 150 on the substrate 140 such that the magnets 120 are vertically aligned with the components 150 . In this configuration, the magnetic field provides the 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 of the magnets 120 is larger than the area covered by the corresponding component 150, so system 100 can be used as a prior art device to cover the entire surface of the substrate. Provides more optimal and consistent alignment compared to electromagnets, or magnets of the same size as the component.

Figure 3 depicts one embodiment of an alignment tray 300 illustrating various aspects. The single tray 310 depicted includes a plurality of substrates (not shown) each having a single component 320. In other size-dependent embodiments (not shown), a single alignment tray may hold a single substrate with one or more components. In this embodiment the presence of alignment means 330, which are holes in the magnet tray (not shown), ensures that the magnet tray and alignment tray are vertically aligned and that the magnets in the magnet tray are aligned with corresponding components to be interconnected to the substrate on the alignment tray. ), allowing appropriate alignment using, for example, pins or rods. Because proper alignment is critical to the successful formation of interconnects, in various embodiments the alignment trays have complementary structures in the magnet tray to ensure that the alignment tray and magnet tray can only be aligned in a single orientation with respect to each other. along with simple features such as various hole geometries, hole patterns or offsets, different hole sizes, combinations of holes and pins. Those skilled in the art will understand that there are many technically recognized methods for achieving proper alignment between these two objects.

In another aspect, the present disclosure provides kits for creating interconnects between a substrate and electronic components attached to the substrate using a magnetically alignable anisotropic conductive adhesive. Kits generally:

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

Sufficient magnets to complete a magnetic tray - each magnet of the desired size and strength to make interconnections between components and boards using ACA; and

and at least one alignment tray adapted to receive and retain the substrate and components residing thereon during alignment and curing of the ACA to form the interconnect.

Optionally, the kits further include an ACA suitable for use with the kit to create interconnects between components and the substrate using the kit.

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

In the presently preferred embodiment the oriented and assembled magnet tray and alignment tray (“assembly”) can be placed into a curing oven. In one embodiment, the magnetic tray or assembled trays function as a rack within an oven, or for transport into a semi-continuous or continuous oven, such as a reflow oven, or a curing tunnel.

In various embodiments, when the magnet tray and alignment tray are assembled together, for each magnet in the magnet tray, the magnetic flux lines are substantially parallel to each other and extend x-y in a region corresponding to the region of the substrate where the component is located. is substantially perpendicular to the plane. Generally, when the trays are oriented and assembled, the ACA positioned between the substrate and the component on the substrate forms substantially uniform columns that are substantially perpendicular to the x-y plane of the component and the substrate.

In yet a further aspect, the present disclosure provides oven systems for creating interconnections between a substrate and an electronic component to be disposed on the substrate and connected to the substrate using an ACA. The systems operate generally as and according to the methods described above for the other systems described herein. Typically, oven systems include a curing oven and one or more shelves or racks, each shelf or rack having one or more magnets disposed on a substrate and each positioned at a location corresponding to the location of an electronic component to be connected to the substrate. Magnetic tray fitted using ACA; and an alignment tray adapted to receive and hold a substrate residing one or more components to be disposed on and connected to the substrate via the ACA.

The magnets in one embodiment are permanent magnets. Rare earth magnets, including magnets containing neodymium, such as NIB magnets, are useful for many applications herein.

In various embodiments of oven systems, for each magnet in a magnet tray of the system, the magnetic flux lines are substantially parallel to each other and substantially perpendicular to the x-y plane in a region corresponding to the region of the substrate where the component and ACA are located. am. The ACA forms substantially uniform columns, which in various embodiments are 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 magnetic tray 410 and alignment tray 420 serves as a rack 425 in a batch oven 401 generally designed to accommodate a plurality of such racks 425. can do. An enlarged view of assembly 450 is shown as inset FIG. 4B, which shows the substrate, components, and ACA (generally 430) during alignment of the columns in the z-axis and throughout the curing process. It includes an assembled magnet tray 410 and an alignment tray 420 that hold. Alignment holes 435 ensure that the assembly can only be assembled in the proper orientation. The inset of FIG. 4C shows a separate magnet tray 410 showing a plurality of permanent magnets 415 in place.

The scope of the invention is recited in the claims appended to the detailed description, which may be affected, for example, by language limitations. Although specific terms are employed to describe the invention, they are used in a generic and descriptive sense and not for purposes of limitation. Moreover, while certain currently preferred embodiments of the claimed invention have been described in this disclosure, those skilled in the art will understand that such embodiments are provided by way of example only. In light of the teachings provided in this disclosure, certain variations, modifications, and substitutions will occur to those skilled in the art. It is therefore understood that the invention may be practiced otherwise than as specifically described and that such methods of practicing the invention are within the scope of the claims or equivalent to those claimed and do not depart from the scope and spirit of the invention as claimed. It has to be.

Claims (20)

1. A method of establishing an interconnect between a substrate and an electronic component residing thereon using a magnetically alignable anisotropic conductive adhesive (ACA), comprising:
a) establishing dimensions and location on the substrate of a first component to be disposed on and connected to the substrate;
b) determining a placement location of a first magnet that corresponds to the dimensions and location established for the component in step a);
c) determining the dimensions and strength of the magnet required in step b);
d) mapping magnetic flux lines of the magnetic field to the magnet;
e) repeating steps a) to d) for each additional component to be disposed on and connected to the substrate to determine the properties and placement location for each additional magnet required;
f) creating a magnet tray and securing each magnet to its respective placement location on the magnet tray;
g) creating an alignment tray and adapting the alignment tray to hold the substrate during alignment and curing;
h) placing the substrate on the alignment tray;
i) applying the ACA on the substrate to one or more locations where components will be placed;
j) populating the first and each additional component on the substrate;
k) assembling the alignment tray and the magnet tray;
l) allowing columns to be formed in the z-axis with the ACA; and
m) curing the ACA, thereby establishing interconnects between the substrate and the first and each additional component.
Includes,
The alignment tray and the magnet tray are made of a non-magnetic material and the magnet tray is adapted to receive the first and each additional magnet at respective placement locations of the first and each additional magnet on the magnet tray. ; A method wherein an assembly comprising the magnet tray with magnets, the alignment tray with a substrate on which the components reside, and an ACA can be placed in a curing oven. The method of claim 1, wherein the magnets comprise permanent magnets. 3. The method of claim 2, wherein the magnets comprise rare earth magnets. 4. The method of claim 3, wherein the size and strength of each magnet are adjusted to optimize the height of the columns, to optimize interconnection strength, to reduce the number of shorts, and to increase the expected life of the completed device or board. , a method, independently determined, to increase the yield of usable product, or to reduce failures or rejections as a result of creating interconnections. 5. The method of claim 4, wherein for each magnet in the magnet tray, the magnetic flux lines are parallel to each other and perpendicular to the x-y plane in an area corresponding to the area of the substrate where the component and ACA are located. The method of claim 1, wherein the ACA forms columns that are uniform in terms of height and diameter. The method of claim 1, wherein the ACA forms uniform columns, the columns being perpendicular to the x-y plane of the component and the substrate. The method of claim 1, wherein the substrate can be placed in only one orientation in the alignment tray. 2. The method of claim 1, wherein the alignment tray includes alignment means to ensure that the magnet tray and the alignment tray can be assembled only in the proper orientation with respect to each other. The method of claim 1, wherein the alignment tray and the magnet tray comprise materials capable of withstanding curing conditions for curing the ACA. A system for creating interconnects between a substrate and electronic components attached to the substrate using a magnetically alignable anisotropic conductive adhesive (ACA), comprising:
a magnet tray comprising a non-magnetic tray adapted to receive and retain each of the one or more magnets disposed therein at a location corresponding to the location of one or more electronic components on the substrate to which the components are to be connected;
an alignment tray adapted to hold the substrate residing one or more components to be connected to the substrate with the ACA during alignment and curing of the ACA; and
ACA comprising magnetically alignable particles capable of forming conductive interconnections in the z-axis
Includes,
the alignment tray and the magnetic tray are made of non-magnetic material;
The magnet tray and the alignment tray are arranged vertically together in a detachable manner such that the components on the substrate are vertically aligned with the magnets in the magnet tray, and the magnetic flux lines are perpendicular to the xy plane defining the substrate. ACA is exposed to magnetic fields;
The system of claim 1, wherein the substrate can be placed on the alignment tray in only one orientation. 12. The system of claim 11, wherein the magnets are permanent magnets. 12. The system of claim 11, wherein the magnets are rare earth magnets. 14. The system of claim 13, wherein for each magnet in the magnet tray, the magnetic flux lines are parallel to each other and perpendicular to the x-y plane in an area corresponding to the area of the substrate where the component and ACA are located. 12. The system of claim 11, wherein the ACA forms uniform columns, the columns being perpendicular to the x-y plane of the component and the substrate where the magnets are located. 12. The system of claim 11, wherein the assembly including the magnet tray, the alignment tray, and the substrate upon which the components reside can be transported or placed directly into a curing oven. 17. The system of claim 16, wherein the assembly or magnetic tray serves as a rack that can be slid or carried directly into the oven and does not require any support shelves, additional racks, or other supports. A kit for creating interconnects between a substrate and electronic components attached to the substrate using a magnetically alignable anisotropic conductive adhesive, comprising:
at least one magnet tray including a non-magnetic tray adapted to hold one or more magnets using the ACA at locations corresponding to the desired placement of the electronic component on the substrate and connection of the component to the substrate;
Sufficient magnets to complete the magnet tray, each magnet of the desired size and strength to achieve interconnection between the component and the substrate using the ACA;
at least one alignment tray adapted to receive and retain the substrate and components residing on the substrate during alignment and curing of the ACA to form the interconnect; and
Optionally, an ACA suitable for use with the kit to create at least one interconnect between a component and a substrate using the kit.
Includes,
The magnet tray and the alignment tray are configured to be oriented and assembled perpendicular to each other, such that when the magnet tray and the alignment tray are so oriented and assembled, the electronic component disposed on the substrate on the alignment tray is aligned with the magnet on the magnet tray. Kit, vertically aligned. 19. The kit of claim 18, wherein the oriented and assembled magnet tray and alignment tray can be placed or transported directly into a curing oven. 20. The kit of claim 19, wherein the magnetic tray or assembled trays function as a rack within the oven.

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