阅读说明：本技术 热成形具有表面曲率的电子装置的技术 (Techniques for thermoforming electronic devices with surface curvature ) 是由 艾德斯格尔·康斯坦·彼得·斯米茨 简-埃里克·杰克·马丁·鲁宾厄 马尔科·鲍林 于 2019-02-18 设计创作，主要内容包括：一种制造弯曲电子装置(100)的方法及所得产品。一非传导支撑材料(12m)构成的图案化层印制在一热塑性基体(11)上以形成一支撑图样。一电路(13、14)施加到该支撑图样(12)上,其中该电路(13、14)包含电路线(13)及施加到该图样的支撑岛体(12a)上的电气组件(14),该电路线包含施加到该图样的该等支撑线(12b)上的一传导材料(13m)。一热成形程序(P)用来在该支撑材料(12m)的一相当高抗变形性维持该电路(13、14)的一结构完整性的同时,使该基体(11)变形(S)。(A method of manufacturing a curved electronic device (100) and the resulting product. A patterned layer of non-conductive support material (12m) is printed on a thermoplastic substrate (11) to form a support pattern. A circuit (13, 14) is applied on the supporting pattern (12), wherein the circuit (13, 14) comprises circuit lines (13) comprising a conductive material (13m) applied on the supporting lines (12b) of the pattern and electrical components (14) applied on the supporting islands (12a) of the pattern. A thermoforming process (P) for deforming (S) the base body (11) while a relatively high resistance to deformation of the support material (12m) maintains a structural integrity of the electrical circuit (13, 14).)

1. A method of manufacturing a curved electronic device (100), the method comprising:

-providing a matrix (11) comprising a thermoplastic material (11 m);

-printing a patterned layer of non-conductive support material (12m) to form a support pattern (12) onto the substrate (11), wherein the support pattern (12) comprises a plurality of support islands (12a) interconnected by support lines (12b) bridging open areas (11a) of the substrate (11) without the support material (12m) between the support islands (12 a);

-applying a circuit (13, 14) onto the supporting pattern (12), wherein the circuit (13, 14) comprises a plurality of circuit lines (13) comprising a conductive material (13m) applied onto the plurality of supporting lines (12b), and electrical components (14) applied onto the plurality of supporting islands (12a), the electrical components (14) being electrically interconnected by the plurality of circuit lines (13); and

-using a thermoforming process (P) at an elevated processing temperature (T) for deforming (S) a shape of the base body (11) with the support pattern (12) and the electric circuits (13, 14) according to a predetermined surface curvature (C), wherein the support material (12m) has a higher resistance to deformation (S) than the thermoplastic material (11m) of the base body (11) at the processing temperature (T), wherein deformation (S) is concentrated in the open areas (11a) between the support island bodies (12a), while the higher resistance to deformation of the support material (12m) maintains a structural integrity of the electric circuits (13, 14) applied thereon during the thermoforming process (P).

2. The method according to claim 1, wherein the support material (12m) has a higher glass transition temperature (Tg) than the thermoplastic material (11m) of the matrix (11).

3. Method according to any one of the preceding claims, wherein said thermoforming process (P) comprises heating at least said substrate (11) above a glass transition temperature (T) of said substrate (11)_g,11) Wherein the processing temperature is kept lower than a glass transition temperature (T) of the support pattern (12)_g,12)。

4. Method according to any one of the preceding claims, wherein the support material (12m) has a higher toughness than the thermoplastic material (11m) of the matrix (11) at the treatment temperature (T) at least during the thermoforming procedure (P).

5. Method according to any of the preceding claims, wherein the deforming step comprises bending, stretching and/or compressing the substrate (11) in dependence of the predetermined surface curvature (C), wherein the support pattern (12) at least partially prevents deformation (S) of the substrate (11) at a plurality of locations of the electric circuit (13, 14), wherein a number of stretches, compressions and/or bends are concentrated at the open areas (11a) of the substrate (11) not covered by the support pattern (12).

6. Method according to any of the preceding claims, wherein a first radius of curvature (R1) in the open area (11a) of the substrate (11) is smaller than a second radius of curvature (R2) of the substrate area covered by the support pattern (12), in particular the area covered by the support island body (12a), wherein the second radius of curvature (R2) is kept above a critical radius preventing structural damage to the electrical circuit (13, 14).

7. Method according to any of the preceding claims, wherein the stretching or compression at the area covered by the support pattern (12) is kept below a critical percentage to prevent structural damage to the circuitry (13, 14).

8. The method according to any of the preceding claims, wherein said support pattern (12) has a layer thickness (12t) between 5 and 50 microns, wherein said support islands (12a) have a minimum cross-sectional diameter (12d) greater than 0.5 mm and said support lines (12b) have a line width (12w) between 50 and 200 microns.

9. The method of any one of the preceding claims, wherein the circuit line (13) follows a path of the support line (12b), wherein the support line (12b) has a track width (12w) equal to or slightly larger than a width (13w) of the circuit line (13), wherein edges in the support line (12b) extending beyond edges of the circuit line (13) have an edge width (12e) of less than 100 micrometers.

10. Method according to any of the preceding claims, wherein the support lines (12b) and the circuit lines (13) follow a meandering path between the support islands (12a), wherein a length along the meandering path is at least twice larger than a shortest straight-line distance between two end points of the meandering path.

11. The method according to any one of the preceding claims, wherein the support material (12m) forming the support pattern (12) comprises a polymer material.

12. The method according to any one of the preceding claims, wherein printing the support pattern (12) comprises applying a liquid printing material (12p) onto the substrate (11) by screen printing, and hardening the printing material (12p) to form the support material (12m) of the support pattern (12).

13. Method according to any one of the preceding claims, wherein said circuit line (13) comprises a metallic ink and said electrical component (14) comprises a surface mount component (SMD) disposed before said thermoforming process (P).

14. A method according to any of the preceding claims, wherein a non-conductive top layer is applied on top of the electrical circuit (13, 14).

15. A curved electronic device (100) made by the method according to any of the preceding claims, the electronic device (100) comprising:

-a matrix (11) comprising a thermoplastic material (11 m);

-a patterned layer of non-conductive printed support material (12m) forming a support pattern (12) on said substrate (11), wherein said support pattern (12) comprises a plurality of support islands (12a) interconnected by support lines (12b) bridging open areas (11a) of said substrate (11), without support material (12m) between said support islands (12 a);

-a circuit (13, 14) applied on said supporting pattern (12), wherein said circuit (13, 14) comprises circuit lines (13) comprising a conductive material (13m) applied on said supporting lines (12b), and electrical components (14) applied on said supporting islands (12a), wherein said electrical components (14) are electrically interconnected by said circuit lines (13); and

-wherein a shape of the base body (11) with the supporting pattern (12) and the electric circuits (13, 14) is deformed by a thermoforming process (P) according to a predetermined surface curvature (C), wherein the supporting material (12m) has a higher resistance to deformation (S) than the thermoplastic material (11m) of the base body (11), wherein deformation (S) is concentrated in the open areas (11a) between the supporting islands (12a), while the higher resistance to deformation of the supporting material (12m) maintains a structural integrity of the electric circuits (13, 14) applied thereon during the thermoforming process (P).

Technical field and background

The present disclosure relates to a method of manufacturing a curved electronic device by a thermoforming process and products resulting therefrom.

The present inventors have discovered that current printed in-mold (inmold) electronic component structures may have reliability problems due to substrate instability during the molding process. For example, it is difficult to reliably join complex (heavy) components to structures to be in-molded. One solution may include avoiding the bonding of complex component (QFN, LED) packages to thermoformable substrates, or may find more stretchable electrical components and interconnect materials. Other solutions may involve using foils such as PET/PEN that are used to build up the electronic components containing the assembly, cutting the foils into the correct pattern, and applying the foil body to a substrate to thermoform the entire stack. However, cutting small patterns from a foil can be very difficult.

US 2016/316570 a1 describes a method for manufacturing a non-flat printed circuit board assembly in which damage to the circuit traces is avoided by curing the pattern only after thermoforming. However, this has limitations on the handling of the unformed PCB and limits material use and process conditions. By way of further background, US 2005/206047 a1 describes a contoured circuit board, and JP 2004356144 a describes a component mounted flexible circuit board.

It is desirable to improve the flexibility and process conditions in the manufacture of electronic devices having very small components and connections while preventing circuit damage that may occur, particularly during thermoforming or thereafter.

Disclosure of Invention

The present disclosure provides improved methods of manufacturing a curved electronic device and resulting products. A patterned layer of a non-conductive support material is printed to form a support pattern onto a substrate comprising a thermoplastic material. The support pattern comprises a plurality of support islands interconnected by support lines bridging open areas of the thermoplastic matrix, the support islands being free of support material therebetween. A circuit is applied on the support pattern. The circuit includes circuit lines with a conductive material applied to the support lines. Electrical components are applied on the support islands where they are interconnected by circuit lines. A thermoforming process with elevated processing temperatures is used to deform the shape of a substrate having the support pattern and circuitry according to a predetermined surface curvature.

By printing the support pattern instead of cutting the pattern from a foil, the method is more easily flexible, more accurate and more suitable for increasingly smaller circuit patterns. The support material may have a higher resistance to deformation than the thermoplastic material of the substrate. In this manner, deformation can be concentrated in the open areas between the support islands, while the higher resistance to deformation of the support material maintains a structural integrity of the electrical circuit applied thereto during the thermoforming process. For example, the support material may be a relatively hard material that may be easily bent or stretched during the thermoforming process, such as a thermoplastic matrix. For example, the support material may have a relatively high glass transition or melting temperature compared to the thermoplastic material, so the support material remains relatively stiff and/or more viscous during the thermoforming process.

Drawings

These and other features, aspects, and advantages of the apparatus, systems, and methods of the present disclosure will become better understood with regard to the following description, appended claims, and accompanying drawings where:

FIGS. 1A and 1B schematically illustrate top views of steps in manufacturing one embodiment of a curved electronic device;

fig. 2A-2E schematically illustrate cross-sectional views of other or additional steps in manufacturing the embodiment of the curved electronic device.

Detailed Description

The terminology used to describe particular embodiments is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the content clearly indicates otherwise. The term "and/or" includes any and all combinations of one or more of the associated listed items. It will be understood that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features but does not preclude the presence or addition of one or more other features. It will be further appreciated that when a particular step of a method is referred to as being subsequent to another step, unless otherwise indicated, the particular step may be immediately subsequent to the other step, or one or more intermediate steps may be performed before the particular step is performed. Similarly, it will be understood that when a connection is described between structures or elements, it can be directly established or passed through intermediate structures or elements unless otherwise indicated.

The present invention is described more fully with reference to the accompanying drawings, in which several embodiments of the invention are shown. In the drawings, the absolute and relative sizes of systems, components, layers and regions may be exaggerated for clarity. Several embodiments may be described with reference to potentially advantageous embodiments of the invention and to schematic illustrations and/or cross-sectional illustrations of intermediate structures. Like element numbers refer to like elements throughout the specification and drawings. Relative terms and their derivatives should be construed to mean the same as the orientation described below or shown in the drawings to which it is being discussed. Unless otherwise specified, these relative terms are for convenience of description and do not require that the system be interpreted or operated in a particular orientation.

FIGS. 1A and 1B schematically illustrate top views of steps in manufacturing one embodiment of a curved electronic device. Fig. 2A-2E schematically illustrate cross-sectional views of other or additional steps in manufacturing an embodiment of the curved electronic device.

In one embodiment, such as illustrated in FIG. 2A, a substrate 11 is provided that comprises or consists essentially of a thermoplastic material 11 m. It will be appreciated that a thermoplastic or thermo-softening plastic is a plastic material that can be bent or molded above a particular temperature and that can (re) solidify upon cooling. Thus, thermoplastics can be reshaped by heating and are typically used to make shaped parts through various polymer processing techniques, such as injection molding, compression molding, calendaring, and extrusion. A preferred thermoplastic material 11m described herein for the substrate 11 is Polymethylmethacrylate (PMMA), also known as acrylic, a transparent thermoplastic. Another preferred material is polyethylene terephthalate (PET), also known as PETG, or Polycarbonate (PC), preferably with added glycol. Other examples of thermoplastics may include, for example, Acrylonitrile Butadiene Styrene (ABS), nylon or polyamide, polylactic acid (PLA), polybenzimidazole, polyethersulfone, polyoxymethylene, polyetheretherketone, polyetherimide, polyethylene, polyphenylene oxide, polyphenylene sulfide, polypropylene, polystyrene, polyvinyl chloride.

In one embodiment, as illustrated in FIG. 2A, a patterned layer of non-conductive support material 12m is applied by printing onto substrate 11. This forms a supporting pattern 12. In one embodiment, the supporting pattern 12 comprises a polymer material. It will be appreciated that the polymer is a macromolecule or macromolecule, consisting of many repeating subunits. Polymers are typically produced via polymerization of many small molecules called monomers. They typically yield particular physical properties relative to the macromolecular mass of small molecule compounds, including toughness, viscoelasticity, and the tendency to form glasses and semi-crystalline structures that are amorphous. Preferably, the supporting pattern 12 comprises an amorphous to semi-crystalline medium-crosslinked polymer. Preferably, the cross-linking is sufficient to ensure that the film exhibits a high melting point, while its brittle fracture properties remain low. For example, the support pattern 12 may include epoxy, acrylic, or polyimide. In a preferred embodiment, a reactive epoxy resin is used. It will be appreciated that a polymer formed from an epoxide precursor may be referred to as an epoxy resin, even though such materials may no longer contain epoxy groups or contain only some residual epoxy groups that remain unreacted in the formation of the resin.

In a preferred embodiment, such as shown in fig. 1A, the support pattern 12 comprises a plurality of support islands 12 a. In the illustrated embodiment, the base 11 also has open areas 11a without support material 12m between the support islands 12 a. In another or further preferred embodiment, also as shown in fig. 1A, the support islands 12a may be interconnected by support lines 12b, thus serving to bridge the open areas 11A.

In one embodiment, such as shown in fig. 2C and 2D, a circuit 13, 14 is applied to the support pattern 12. This is also illustrated in FIG. 1B. In the embodiment shown, the circuit includes circuit lines 13 comprising a conductive material 13m applied to support lines 12 b. In the embodiment shown, the circuit also includes an electrical component 14 applied to the support island 12 a. These electrical components 14 may be electrically interconnected through circuit lines 13 as illustrated in fig. 1B.

In a preferred embodiment, as shown in fig. 2E, a thermoforming process P is used to deform S the shape of the substrate 11 with the support pattern 12 and the circuits 13, 14. For example, the shape changes from a flat shape to a curved shape according to a predetermined surface curvature C. Of course, many concave and/or convex curvatures are contemplated. Typically the thermoforming process involves applying an elevated process temperature T suitable for the thermoforming process. For example, the processing temperature is above 50 degrees celsius, typically above 80 degrees or higher, for example between 100 and 200 degrees.

In a preferred embodiment, the support material 12m has a higher resistance to deformation than the thermoplastic material 11m of the matrix 11. In this way, the deformation is concentrated in the open areas 11a between the supporting islands 12a, while the higher resistance to deformation of the supporting material 12m maintains the structural integrity of the circuits 13, 14 applied to the supporting material during the thermoforming process P. In fig. 2E, deformation is illustrated by arrows S, which may generally include a change in curvature and/or length (tension/compression) of the substrate primarily along one or more dimensions.

In one embodiment, the support material 12m has a higher toughness than the thermoplastic material 11m of the matrix 11, for example at least higher than 10%, preferably at least higher than 50%, at least twice or higher. The higher the relative toughness of the support pattern material relative to the substrate material, the less deformation at the substrate area covered by the support pattern. Preferably, the toughness is higher at least during the thermoforming process P when deformation occurs, and more preferably also after, so that the deformation S is at least partially continuously prevented in the area where the circuit is applied.

Elastic modulus is considered to be a material property that quantifies or measures the resistance of an object or substance to elastic deformation (non-permanent) when a pressure is applied. Generally, a stiffer material will have a higher modulus of elasticity. Specifying how pressure and stress are measured, including orientation, allows different types of elastic modulus to be defined, including Young's modulus (E), shear or stiffness modulus (G or μ), and volume modulus (K). In a preferred embodiment, the support pattern comprises or consists essentially of a support material 12m having a relatively high modulus of elasticity, as defined above, of one or more, preferably all, of the above-defined moduli, at least in comparison with the thermoplastic material 11 m.

In one embodiment, the support material 12m has a higher glass transition temperature Tg than the thermoplastic material 11m of the substrate 11. It will be appreciated that glass transition can be a process that can occur between a range of temperatures. Several different operationally defined glass transition temperatures may be used, which may differ by several kjeldahl temperatures for a particular material. Nevertheless, the glass transition temperature according to any definition may be relatively lower or higher. For example, a definition in connection with the present invention refers to adhesion, e.g. fixing the glass transition temperature Tg at 10¹²The value of pas. In an embodiment, the glass transition temperature of the support material 12m is at least 10 degrees celsius, preferably at least 20 degrees celsius, at least 30 degrees celsius, or at least 50 degrees celsius higher than the thermoplastic material 11m as defined. It will be appreciated that the processing temperature of the thermoforming procedure may be suitably selected from among a sufficiently different glass transition temperature.

In one embodiment, the thermoforming process P comprises heating at least the substrate 11 above the glass transition temperature Tg of the substrate 11_,11A processing temperature T, wherein the processing temperature is kept lower than the glass transition temperature Tg of the support pattern 12_,12Or at least below a melting temperature of the support pattern 12. Of course, it is also possible that the support material 12m does not have a glass transition phenomenon, wherein the glass transition temperature may be considered as being maximum, or the melting or decomposition temperature of the support material 12m may be substituted. Preferably, the support pattern 12 is not subjected to glass transformation or at least during the thermoforming procedure PAnd will not melt. At least, the support pattern 12 preferably has a higher melting temperature than the substrate 11. Alternatively or additionally, the supporting pattern 12 may have at least a higher viscosity than the substrate 11 during the thermoforming process P.

Preferably, the thermoplastic material 11m of the substrate 11 has a glass transition temperature that is not so high, for example, below 300 ℃, or below 200 ℃, at least below a damage temperature of the electrical component 14. Preferably, the thermoplastic material 11m has a glass transition temperature that is not so low, e.g., above 70 degrees celsius, preferably above 100 degrees celsius, at least high enough to prevent unintended deformation of the electronic device 100 after manufacture during normal use. For example, the commercial grade Tg of PMMB is generally between 85 and 165 ℃.

In several preferred embodiments, the deformation comprises bending the substrate 11 according to a predetermined surface curvature C. For example, the substrate 11 is deformed using a mold 15, as shown in FIG. 2E, which determines the predetermined surface curvature C. The mold 15 may also be a component of the electronic device 100 in some embodiments, or another support structure may be provided in addition to the mold. Molding or thermoforming procedures other than those shown are also contemplated for deforming the substrate, support layer and circuit pattern.

In several preferred embodiments, the supporting pattern 12 covers some areas of the substrate 11, while leaving other areas 11a between the covered areas open, i.e. without the supporting pattern 12. The open area may provide the majority of the deformation. In some embodiments, deformation, such as bending, includes stretching and/or compressing different regions of the substrate 11. Advantageously, the supporting pattern 12 may at least partially prevent deformation S of the substrate 11 at the location of the electrical circuits 13, 14. For example, the deformation S is preferably concentrated in the open area 11a between the support patterns 12 in the base 11. Thus, an amount of stretching, compressing and/or bending concentrates on the open areas 11a in the substrate 11 not covered by the support pattern 12.

In some embodiments, as schematically shown in fig. 2E, a first radius of curvature R1 at the open region 11 of the substrate 11 is smaller than a second radius of curvature R2 of the substrate region covered by the support pattern 12, particularly the region covered by the support islands 12 a. In other words, the curvature at the open area 11a may be greater than the covered area. For example, the first radius of curvature R1 may be less than 1 meter, less than 0.5 meter, or less, such as between 1 and 10 centimeters. For example, the second radius of curvature R2 may be more than ten percent greater than the first radius of curvature R1 (i.e., a magnification of 1.1), in some cases higher than 20% or even more, such as 50% or even twice as great. In some embodiments, the second radius of curvature R2 remains above a critical radius to prevent structural damage to the circuits 13, 14. For example, the support pattern 12 maintains the second radius of curvature R2 above a threshold value of 1 meter, 2 meters, or even higher, such as maintaining a substantially flat shape, particularly at the support island 12 a. The flatter the area of the support pattern 12 where the circuitry 13, 14 is applied, the more damage can be avoided. Typically, the depicted circuit patterns 13, 14 disposed on top of the support pattern 12 experience a third radius of curvature R3 that is equal to or greater than the second radius of curvature R2 (i.e., less curvature).

In some embodiments, the substrate 11 has a greater amount of tension or compression in its open area 11a than the area of the substrate covered by the support pattern 12, particularly the area covered by the support islands 12 a. In other words, particularly the stretching or compressing along the surface of the base body can be concentrated particularly on the open regions 11a between the supporting island bodies 12 a. For example, the stretching or compressing in the area covered by the supporting pattern 12 may be kept below a critical percentage to avoid structural damage to the circuits 13, 14. For example, the support pattern 12 maintains a length parallel to the substrate surface along one or more dimensions within 20% (i.e., stretches the length at a rate less than 1.2 or compresses the length at a rate greater than 0.8), preferably within 10%, more preferably within 5%, or even less than 1%, or substantially no stretch/compression. More stretching and compression along the surface at least along a length of the support lines 12b and circuit lines 13 or along the dimension of the support island body 12a can be avoided, and more damage can be avoided. It will be appreciated that stretching (or bending) of the open areas 11a between the supporting islands 12a does not necessarily result in much stretching (or bending transverse to the length) along the length of the supporting wires 12b, especially if the islands are provided with a buffer structure, such as a meandering line.

In some embodiments, such as shown in the figures, the support pattern 12 includes a plurality of support islands 12a, such as where the circuitry includes electrical components 14 disposed on the support islands 12 a. In some embodiments, as illustrated in FIG. 1A, support island 12a has a minimum cross-sectional diameter 12d along a surface of the substrate, e.g., greater than 0.5 mm, greater than 1 mm, greater than 0.5 cm, greater than 1 cm or more. In other or further embodiments, as illustrated in FIG. 1B, the support island body 12a provides a minimum margin 12r around the respective one or more electrical components 14 on the island body. Preferably, the minimum margin 12r of support island 12a between the respective one or more assemblies 14 and the edge of island 12 is, for example, greater than 0.5 mm, greater than 1 mm, greater than 0.5 cm or more. The inventors have found that a larger margin may be preferable to protect the individual components from deformation, especially when the components are arranged in the center of or near the individual island.

The inventors have found that larger island bodies are less prone to shifting during the thermoforming process. Thus, increasing the island size ensures relative positioning of the assembly to a predetermined position, which is particularly advantageous for assemblies such as LEDs and/or buttons that provide signal processing or interact with the exterior of the electronic device 100. In addition to the electrical components 14, electrical (external) connectors to the circuitry are also preferably provided on the relatively large support island. This ensures a more predictable arrangement of connectors, making it easier to form a connection to the electronic device 100.

In some embodiments, such as shown in the figures, the support pattern 12 comprises a plurality of support lines 12b, e.g. wherein the circuitry comprises circuit lines 13, i.e. several conductive tracks forming electrical interconnections on top of the support lines 12 b. Preferably, the support lines 12b follow respective paths imposed on respective corresponding circuit lines 13 on top thereof. In other words, the path of the circuit line 13 is preferably parallel to the path of the support line 12 b. In the illustrated embodiment, the circuit lines 13 form electrical interconnections between several electrical components 14. Similarly, support wires 12b may form support interconnects between several support islands 12 a.

In some embodiments, as depicted in fig. 1A, the support lanes or lines 12b have a lane width 12w, such as at least 10 microns, preferably at least 50 microns, such as between 100 and 500 microns, preferably less than 200 microns. On the one hand, the support lines are preferably wide enough to provide sufficient support and protect the circuit lines 13 from damage. On the other hand, the support lines are preferably narrow enough not to prevent the flexibility that can be provided by the pattern of circuit lines 13, such as the meandering pattern shown. In some preferred embodiments, the trace width 12w is (nearly) equal to or only slightly greater than the width 13w of the circuit lines 13. For example, the edge of the support line 12b extending beyond the edge of the circuit line 13 has an edge width 12e in a range of less than 100 micrometers, preferably less than 50 micrometers, less than 20 micrometers or less, for example, between no edge and an edge of less than 10 micrometers. In other or further embodiments, the width 13w of the circuit traces 13 (along a surface of the substrate) may be less than 200 microns, preferably less than 100 microns, such as between 10 and 50 microns. A relatively narrow support wire may provide preferred elasticity while preventing stretching of the circuit wire 13 along its length.

In a preferred embodiment, the support lines 12b and overlying circuit lines 13 comprise a buffer structure, such as shown in FIG. 1A, following a tortuous or meandering path between the support islands 12 a. Typically, a length along the meandering or curved path may be greater than a shortest straight distance between two end points of the path (not along the path), for example, may be greater than at least 0.5 times, preferably at least two times, at least three times, at least five times or more. The higher the ratio between the length along the path and the linear distance between the ends, the more the path can be reconfigured or stretched (unfolded) without damaging the circuit lines 13.

In some embodiments, the tortuous path changes its direction in the opposite direction a plurality of times, such as at least two times, preferably at least three times, four times or more. This may allow the path to expand providing additional flexibility. In some embodiments, as shown in FIG. 1A, the direction may change by an angle of at least 40 degrees of the planar angle each time, preferably at least 90 degrees, at least 130 degrees, or even 180 degrees or more (e.g., exhibit a swirl). In some embodiments, the direction may be changed back and forth. For example, in the illustrated embodiment, the trace support pattern 12b between the support islands 12a is followed by a left turn of about 90 degrees, followed by a top turn of about 180 degrees, followed by a bottom turn of about 180 degrees, followed by a right turn of about 90 degrees. Other meander patterns are of course also conceivable.

In some embodiments, as shown, for example, in fig. 2B, the support pattern 12 has a certain layer thickness 12t, for example, between 1 to 100 microns, preferably between 5 to 50 microns, more preferably between 10 to 20 microns. In some embodiments (not shown), the layer thickness may vary, for example, being thicker in the support island 12a than in the support lines 12 b. Preferably, at least the support pattern 12 can maintain the dimensional uniformity of the electronic circuit on top. Also preferably, at least the support wires 12b and the circuit wires 13 at the top may have limited stretch. For example, the support pattern 12 has an elongation of at least 10% before breaking, such as a length along the lane that allows the support lane to be extended 1.1 times without breaking and/or losing substantial functionality of the circuit. For example, the support pattern 12 may have at least some elasticity that allows for recoverable deformation, such as recovery to an original form condition when extended at least 1%, i.e., 1.01 times, or more, such as between 2 and 5%. For example, in some embodiments, the support material 12m has a Young's modulus between 100MPa and 10 GPa. Also preferably, the support pattern 12 does not soften or melt significantly during the thermoforming process, which may cause an undesirably large reduction in Young's modulus.

In the context of this disclosure, the support pattern 12 preferably comprises or is formed from a printable or printable material. In some embodiments, printing of the support pattern 12 includes applying a (liquid) printing material 12p to the substrate 11. In other or further embodiments, the printing material 12p may be hardened to form the supporting pattern 12 made of the supporting material 12 m. For example, the printing material 12p may comprise a precursor (e.g., a monomer), and the curing step may comprise polymerizing or at least partially cross-linking the precursor to form the supporting pattern 12. For example, the printing material 12p includes a solvent, and the hardening step includes drying the solvent to leave the supporting pattern 12. Likewise, further or other procedures are contemplated to harden the printing material 12p, such as thermal treatment and/or hardening with light, such as UV. Suitable processes for printing the support pattern 12 may include, for example, screen printing. This can be done on a chip-by-chip basis, but can also be done in a continuous roll-to-roll manner using a stop and go (stop and go) procedure. Alternatively, a rotary screen printing process may be utilized.

As noted herein, the circuit lines 13 may comprise a conductive material. Accordingly, wherein the circuit lines 13 are configured to conduct electricity, for example, between a plurality of electrical components 14 and/or between the components and (external) electrical connections. In a preferred embodiment, the circuit line 13 comprises a metal ink, more preferably silver paste. In some embodiments, the circuit lines 13 may be deposited on top of the support lines 12b, for example by printing. Preferably, the circuit lines 13 provide an elongation before breaking of at least 1%, preferably at least 5%, or even 10% or more, without losing substantial functionality. Preferably, the circuit lines 13 can be bent transversely to their length by at least 1 meter, at least 0.5 meter or less by a limited radius, for example allowing the lines to be bent by a radius of 10 cm without the circuit losing substantial functionality.

In some embodiments, the electrical component 14 comprises a Surface Mount Device (SMD). For example, the electrical component 14 comprises an integrated circuit, or a transducer such as a Light Emitting Device (LED), or an interface component such as a button, switch, or any other functional component of the electronic device 100. For example, the electrical component 14 may be provided, e.g., soldered or otherwise bonded to a bond pad of a circuit, e.g., a circuit trace, using a conductive adhesive such as ICA. For example, the setting step may involve picking and placing, light-induced positive transfer (LIFT), or other setting methods.

In some embodiments, it may be preferable to apply a recess, for example, between the electrical connections or between the bond pads of the circuit, before disposing the electrical component 14. The recess fill, for example, fills a space between the support island 12 and the electrical component 14. In some embodiments, the recessed filler is also preferably printed using the same material as the supporting pattern 12. In some embodiments, the electrical component 14 itself may be a printed component or otherwise built from a build-up material.

In some embodiments (not shown), a non-conductive top layer is applied on top of the circuitry 13, 14. Optionally, the top layer comprises another support pattern having the same or similar pattern as the support pattern 12 under the circuit. Alternatively or additionally, the top layer may comprise another thermoplastic matrix, and circuitry may be sandwiched between the matrices.

The methods described herein may provide a correspondingly curved electronic device 100. In one embodiment, the electronic device 100 includes a substrate 11 of a thermoplastic material 11 m. In another or further embodiment, a patterned layer of non-conductive printable support material 12m is included which forms a support pattern 12 on the substrate 11. The circuits 13, 14 may be applied on the support pattern 12. Notably, the shape of the substrate 11 having the supporting pattern 12 and the circuits 13, 14 is formed in accordance with a predetermined surface curvature C through a thermoforming process P. In one application, the electronic device 100 comprises a curved dashboard for a vehicle, wherein electrical components 14, such as lights and buttons, are integrated into the dashboard. Of course many other applications are conceivable.

For purposes of clarity and conciseness of description, features are described herein as part of the same or separate embodiments, however, it will be understood that the scope of the invention may include embodiments having combinations of all or part of the features described. Of course, it is to be understood that any one of the above-described embodiments or methods may be combined with one or more other embodiments or methods to provide even further improvements in finding and matching designs and advantages. It will be appreciated that the present disclosure provides particular advantages for fabricating electronic devices having curved surfaces in a thermoforming process, and may be applied generally to any application in which electronic circuitry is protected from deformation of an underlying substrate by a support pattern.

In some embodiments, the present solution may include printing a polymer electrical insulation film (dielectric) under a complete circuit during the thermoforming process, ensuring a reliable well-defined substrate. For example, films with (high) rupture strength (e.g., > 10% ultimate elongation and > 1% elastic strain) compared to PEN/PET/PI are preferred to ensure the dimensional integrity of the electronic circuitry and components on top of it. Preferably, at least the support structure does not melt, which may cause a large decrease in young's modulus at the thermoforming temperature. This may lead to an undefined redistribution of the printed circuit during the thermoforming process. To ensure that critical areas of the circuit remain in place, a thin mechanical buffer structure in a meandering configuration may be included to accommodate the local extensions. The structures may be designed according to mechanical rules, wherein the width of the structures may be limited to reduce the force required for deformation.

It will be appreciated that some aspects of the present solution may provide a print-only method while ensuring reliability of the molding system within a layer-by-layer basis. These solutions can combine manufacturing simplicity with high reliability. In addition, there may be less stringent requirements on the metal inks and interconnect materials used. The use of a print-only approach enables smaller mechanical buffer structures (i.e., meandering mesh lines) to provide performance that is superior to conventional lamination-based approaches. A step may include defining a design that has been adjusted for the structure to be thermoformed. In this regard, it may be useful to include sufficient redundant wiring on the components to be thermoformed.

The choice of support material to be printed, such as a polymer dielectric film, may define the possible yield strength, young's modulus and fracture strength. Preferably an amorphous to semi-crystalline medium cross-linked polymer with low filler loading. For example, the total dry film thickness may be on the order of 10 to 20 μm. In the case of the meander line structure, the width is preferably about 100-200 μm to provide a high degree of stretchability. The support layer, for example a polymer film, may be only on the bottom, but it is conceivable to print the support layer on both sides.

For metallization, a slightly stretchable/formable metallic silver ink is advantageous to ensure that possible elongation of the metallic structure on the film during formation can be compensated. On the other hand, conventional silver paste or even pure metal films with appropriate design rules, such as electroless copper plating, may also be utilized.

Electrical components, such as SMDs, can be placed in areas with low mechanical stress, which ensure as low a shear force on the component as possible during formation. The bonding may be achieved, for example, by ICA or welding. Alternatively, a high young's modulus underfill material may be printed under the SMD component after bonding. This ensures that there is no structural deformation under the bond pad. The SMD components bonded on the film can have a stable structure that reduces the probability of deformation under the bonding pads. The solution can also be combined with electroless printing to enable pure metal electrical structures. Using a meander, more deformation is applied than with a printed structure alone, since the structure may reconfigure itself. This may enable new options for more extreme configurations.

In interpreting the appended claims, it should be understood that the term "comprising" does not exclude the presence of other elements or acts than those listed in a particular claim; the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements; any reference signs in the claims do not limit their scope; several "means" may be represented by the same or different items or implementing structures or functions; the disclosed devices, or any of their portions, may be combined or divided into further portions, unless otherwise specified. When one request is directed to another, this may indicate a multiplication advantage achieved through a combination of their respective features. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Such embodiments may therefore include all available combinations of the claimed items, where each claimed item may in principle refer to any preceding claimed item unless the context clearly dictates otherwise.