Method for printing electrically conductive layer on surface of 3D electronic component and associated 3D electronic component

Abstract

The invention relates to a method for depositing an electrically conductive layer on a surface of a three-dimensional (3D) electronic component 10A, 10B, 10C comprising at least one electronic device 14 embedded in a solid polymer material 16. The method comprises the steps of: (i) providing a 3D electronic component 10A, 10B, 10C; (ii) forming at least one flow barrier 18 in a surface of the solid polymeric material 16 of the 3D electronic component 10A, 10B, 10C; and (iii) depositing an electrically conductive layer 20A, 20B, 20C on at least a portion of the surface of the solid polymeric material 16 such that the electrically conductive layer 20A, 20B, 20C is at least partially delimited by the flow barrier 18. The invention also relates to an associated 3D electronic component 10A, 10B, 10C.

Description

[0001] The present invention relates to a method for depositing a conductive layer on a surface of a 3D electronic component such as a System-in-Package (SIP). Furthermore, the present invention relates to a 3D electronic component.

[0002] Insulating and protecting electronic components or even complete electronic circuits in polymer encapsulants, such as, for example, system-in-package (SIP), is a common technology today. The polymer encapsulant may, for example, include a molding compound, or more specifically an epoxy molding compound. Due to the high density of electrical functions built into the complete electronic circuit module, electromagnetic or electrical interference (EMI) may cause the electronic circuit to fail completely. For this reason, these electronic circuits must be shielded to suppress EMI radiation from being emitted from the electronic circuit and to suppress EMI radiation from being received by the electronic circuit.

[0003] Traditionally, SIP modules use, for example, metal housings to achieve the purpose of EMI shielding. However, metal housings violate the goal of miniaturization. Instead of using a metal housing, the functional layer can be applied, for example, by a PVD process. Alternatively, an inkjet printer can be used to deposit, for example, a silver-containing inkjet ink on the surface of the SIP module. Once the inkjet ink is printed on the surface of the SIP module, the inkjet ink is cured using, for example, UV light so as to form a continuous functional layer on the surface of the SIP module. Other curing means are conceivable, such as oven curing, IR radiation or plasma. Prior to the printing process, the surface of the SIP module can undergo a pretreatment process for cleaning purposes. Again, plasma can be used for this purpose.

[0004] US 2021 / 227697 A1 and US 2015 / 068787 A1 disclose generating grooves by laser ablation and filling the grooves with a conductive material (eg, conductive ink) to produce, for example, precisely contoured tracks for a printed circuit board.

[0005] US 2012 / 055013 A1 relates to laser ablation of selected areas in order to generate antennas, for example by depositing silver ink into the ablated areas.

[0006] When inkjet printing conductive ink on the surface of a 3D electronic component (such as, for example, a SIP module), the ink tends to flow downward on an inclined or vertical surface due to gravity. This problem can be alleviated by applying only a thin layer at a time, and repeating the printing process several times in order to achieve a sufficient layer thickness. However, the edges of the printed layers are often not precisely defined. Instead, they exhibit a wavy shape, as a result of which the ink layer cannot be printed near the conductive parts of the 3D electronic component. In order to prevent electrical short circuits, safety margins must be observed. In addition, printing on surfaces that are not parallel to the print head plane of the inkjet printer also leads to imprecise and wavy print edges.

[0007] The object of the present invention is to provide a method for depositing a conductive layer on a surface of a 3D electronic component (such as, for example, a SIP) which mitigates or overcomes the disadvantages of prior art methods. In particular, the object of the present invention is to improve the sharpness of the edges of the deposited conductive layer, in particular when the layer is deposited by an inkjet printer or sprayer.

[0008] These objects are solved by the subject-matter of independent claims 1 and 10. Optional and preferred features of the invention are subject-matter of the dependent claims.

[0009] The present invention is generally suitable for depositing any kind of conductive layer (or conductive printed pattern) on a 3D electronic component. The conductive layer can be any kind of layer. When applied, the layer preferably implements an EMI shielding function for electromagnetic interference (EMI) caused by electromagnetic induction or electromagnetic radiation emitted from electronic devices within the 3D electronic component or from external sources. However, the layer can also preferably be formed so that it performs the function of an antenna in an antenna in package (AIP).

[0010] The conductive layer may consist of a conductive ink, which is a type of ink that produces conductive properties when printed and preferably cured. Examples of such types of inks are silver, gold, titanium, bismuth, nickel, chromium or copper inks or inks containing silver, gold, titanium, bismuth, nickel, chromium or copper, preferably inks containing metal organic decomposition (MOD) compounds, also called MOD inks. The conductive ink may also be of a type that contains conductive particles (e.g., silver, gold, titanium, bismuth, nickel, chromium or copper particles).

[0011] In order for the conductive ink to function as, for example, an EMI shield, it must be printed so that the conductive ink forms a continuous layer on at least a portion of the exposed surface of the 3D electronic component, with gaps no greater than a quarter wavelength of the frequency of the external or internal electromagnetic radiation to be blocked.

[0012] The conductive layer may also include a non-conductive layer, such as a protective layer, which protects the conductive layer underlying the protective layer from damage and / or other adverse environmental influences, such as excessive heat and corrosion-inducing species, for example, oxygen.

[0013] Using the method according to the invention, the conductive layer can be deposited only on certain parts of the 3D electronic component or on the entire exposed surface, and the layer thickness can be selectively manipulated so that it varies or is highly consistent and uniform over the entire deposited part of the exposed surface of the 3D electronic component. The final layer thickness, of course depending on the absolute thickness value, can be achieved in one or several subsequent deposition steps. Thus, an efficient conductive layer can be achieved, which has properties that can be particularly adapted to the needs and requirements of the user.

[0014] In the method of the present invention, SIP is preferably used. However, generally speaking, any 3D electronic component that needs to be at least partially covered by a conductive layer can be used in the method of the present invention, such as, for example, AIP. For example, the shape of the 3D electronic component can be a cube or a cuboid.

[0015] The invention can in principle be used in any digital printing process, preferably a digital inkjet printing process, by which conductive and non-conductive coatings (layers, printed patterns) can be deposited with selectively adjustable thickness, high structural consistency and uniformity and high throughput.

[0016] Inkjet printers are generally known and can have different settings that are particularly suitable for user requirements. The method of the present invention is preferably carried out using an inkjet printer with one or more print heads. Each print head has a plurality of print nozzles arranged in a print nozzle plane. The print width of the print head used in the method of the present invention can be selected according to the size of the 3D electronic component, for example 30.5 cm (12 inches) and larger.

[0017] Once the printed conductive layer is cured, a functional layer is obtained, which preferably exhibits an EMI shielding function. For example, curing can be done by using UV light. Other curing means are also conceivable, such as oven curing, IR radiation or plasma. Prior to the printing process, the surface of the 3D electronic component can undergo a pretreatment process for cleaning purposes, for example by using plasma.

[0018] After each printing step or a predetermined number of printing steps, the conductive layer can be cured. If an ink is used that requires crosslinking, the crosslinked ink can further undergo a chemical reduction step, as a result of which the metal in the form of nanoparticles will precipitate. Any solvent will evaporate and the printed ink will be sintered. The curing step is understood to include all these chemical processes that occur in a specific type of ink.

[0019] A first aspect of the present invention relates to a method for depositing a conductive layer on a surface of a three-dimensional (3D) electronic component, the three-dimensional electronic component comprising at least one electronic device embedded in a solid polymer material. The method of the present invention comprises the following steps: (i) providing a 3D electronic component; (ii) forming at least one flow barrier in the surface of the solid polymer material of the 3D electronic component; and (iii) depositing a conductive layer on at least a portion of the surface of the solid polymer material, such that the conductive layer is at least partially bounded by the at least one flow barrier.

[0020] Preferably, when the 3D electronic component is placed on a horizontal surface, at least one flow barrier is formed on a non-horizontal and / or non-planar surface, preferably a vertical surface, of the solid polymer material.

[0021] More preferably, the at least one flow barrier is a continuous annular flow barrier extending completely around the solid polymer material.

[0022] It is advantageous if at least one flow barrier is a depression.

[0023] According to a preferred embodiment of the invention, the at least one recess is formed by laser ablation or sawing or milling or embossing.

[0024] Preferably, the at least one recess has a depth in the range of 5 μm to 50 μm, and a width and a depth in the range of 5 μm to 50 μm.

[0025] More preferably, the method further comprises the step of laser marking the 3D electronic component, wherein the laser used for laser marking the 3D electronic component is also used to form the at least one recess.

[0026] Still more preferably, the step of depositing the conductive layer is performed by inkjet printing or spraying.

[0027] It is advantageous if the conductive layer is an electromagnetic interference shield covering at least one electronic device, and wherein the conductive layer is printed using conductive ink.

[0028] A second aspect of the present invention relates to a three-dimensional (3D) electronic component comprising at least one electronic device embedded in a solid polymer material, wherein the 3D electronic component comprises at least one flow barrier in a surface of the solid polymer material, and wherein a conductive layer is disposed on at least a portion of the surface of the solid polymer material such that the conductive layer is at least partially defined by the at least one flow barrier.

[0029] When the 3D electronic component is placed on a horizontal surface, it is preferred if at least one flow barrier is arranged on a non-horizontal and / or non-planar surface, preferably a vertical surface, of the solid polymer material.

[0030] It is even more preferred if the at least one flow barrier is a continuous annular flow barrier extending completely around the solid polymer material.

[0031] Advantageously, at least one flow barrier is formed as a depression.

[0032] Even more advantageously, the at least one recess has a depth in the range of 5 μm to 50 μm and a width in the range of 5 μm to 50 μm.

[0033] According to a preferred embodiment of the present invention, the layer thickness of the electrically conductive layer is in the range of 0.0001 μm to 100 μm, preferably in the range of 1 μm to 4 μm.

[0034] Preferably, the conductive layer is an electromagnetic interference shield covering at least one electronic device, and wherein the conductive layer comprises a conductive ink, preferably comprising or consisting of silver, gold, titanium, bismuth, nickel, chromium or copper.

[0035] Even more preferably, in the method of the first aspect of the invention or in the 3D electronic component of the second aspect of the invention, the 3D electronic component is a system-in-package (SIP) or an antenna-in-package (AIP), and the solid polymer material is a molding compound.

[0036] The above-described features of the first and second aspects of the present invention may be combined in any manner, and the present invention is therefore not limited to the combination of features described below with reference to preferred embodiments of the present invention.

[0037] The present invention will now be described by way of example using the accompanying drawings. The accompanying drawings are for illustrative purposes and are only used to provide exemplary embodiments of the present invention. The accompanying drawings do not limit the present invention in any way, but merely represent preferred embodiments of the present invention.

[0038] Figure 1 A conventional standard package (SIP) is shown;

[0039] Figure 2 A SIP according to a preferred embodiment of the present invention is shown;

[0040] Figure 3 Another SIP according to another preferred embodiment of the present invention is shown; and

[0041] Figure 4 A further SIP according to yet another preferred embodiment of the present invention is shown.

[0042] Again, the present invention is applicable to any kind of 3D electronic assembly having at least one electronic device embedded or encapsulated in a polymer material, although the following description and in Figures 1 to 4 The preferred embodiment shown in FIG. 1 is related to a standard package (SIP).

[0043] In the following description and in Figures 1 to 4 In the drawings, the same reference numerals refer to identical or technically similar parts in all embodiments.

[0044] Figure 1An exemplary conventional SIP 1 is shown, which includes a plurality of electronic devices 3, such as integrated circuits, positioned on a substrate 2. The substrate 2 imparts sufficient rigidity to the SIP 1. The electronic devices 3 are embedded in a polymer molding compound 4 (such as epoxy resin). In order to electromagnetically shield the electronic devices 3 from electromagnetic interference (EMI) caused by electromagnetic induction or electromagnetic radiation, a conductive layer (printed pattern) 5 is applied to a selective portion of the surface of the polymer molding compound 4. Figure 1 In the example shown, the conductive layer 5 is deposited over the entire top surface and at portions on both side walls of the more or less cubic-shaped polymer molding compound 4 .

[0045] The conductive layer is usually preferably printed on the polymer molding compound using an inkjet printer. Since high viscosity inks are difficult to process by inkjet printing, low viscosity inks are the first choice for the conductive layer. Due to gravity, low viscosity inks tend to flow downward due to gravity, thus producing inconsistent, imprecise and wavy edges of the conductive layer. Due to the wavy (fuzzy) edges, the layer thickness of the conductive layer varies. In particular, the layer thickness near the edge on the sidewall tends to be smaller than the layer thickness elsewhere, as a result of which EMI shielding is poor in those areas where the layer thickness is thinner. If several layers of ink are printed, the thickness deviation of the wavy (fuzzy) edges tends to become larger.

[0046] To alleviate or even eliminate this problem, Figure 2 FIG. 1 shows a SIP 10A according to a preferred embodiment of the present invention. Figure 1 As shown, a plurality of electronic devices 14 are positioned on a substrate 12 and embedded in a polymer molding compound 16. A conductive (functional) layer 20A is deposited on the top surface of the polymer molding compound 16 and on portions at the sidewalls of the polymer molding compound 16. In order to improve the edge definition of the conductive layer at the sidewalls, a recess 18 is formed on a portion or all of the vertical sidewalls, which serves as a flow barrier for the ink. The recess 18 may preferably extend continuously around the circumference of the polymer molding compound 16, i.e. without any interruption or gap. The wet ink may flow into the recess 18 and may accumulate therein until the ink has been sufficiently solidified, from which point the ink may no longer flow downward due to gravity, thereby producing a precise and clear edge of the conductive layer 20A. It should be noted that, depending on the type of ink, the thickness of the layer to be printed, and other processing parameters, the wet ink may not flow into the recess, but stop shortly before reaching the bottom of the recess. In this case, the edge definition will also be improved. Figure 2 Also shown is a print head 30 of an inkjet printer having a plurality of print nozzles (not shown) positioned in a print nozzle plane 32 .

[0047] Figure 3 Another SIP 10B according to another preferred embodiment of the present invention is shown. Figure 2 The SIP 10A is different in that the conductive layer 20B is deposited only on a portion of the upper surface of the polymer molded material 16. Likewise, a recess 18 is formed at one vertical sidewall, preferably three vertical sidewalls of the polymer molded material 16, and another recess 18 is formed on the top surface of the polymer molded material 16 to prevent ink from flowing into the area on the top surface of the molded material 16 that is not covered by the ink. The recess 18 at the sidewall may preferably extend continuously along all three sidewalls of the polymer molded material 16. However, it may also extend along only one sidewall of the polymer molded material 16, so that the three sidewalls of the cubic polymer molded material 16 have no recess 18.

[0048] refer to Figure 4 , shows a SIP 10C having a dome-shaped polymer molding compound 16. A conductive layer 20C is printed on the non-planar top surface of the dome-shaped molding compound 16 using conductive ink. The conductive layer 20C is defined by a recess 18 disposed near the bottom of the dome-shaped molding compound 16 near the substrate 12. The recess 18 prevents ink from flowing into areas not covered by the ink. The recess 18 may preferably extend continuously around the circumference of the dome-shaped polymer molding compound 16, i.e., without any gaps.

[0049] Generally speaking, at least one (i.e., one or more) flow barriers 18 may be formed in the polymer molding compound 16 at selected locations. The at least one flow barrier may be a recess 18 or a platform (shoulder) not shown, both of which may be structured to prevent ink from flowing into areas not covered by ink. The at least one recess 18 may preferably have the form of a groove having a planar bottom and two side walls extending vertically from the bottom. The depth of the at least one recess may be in the range of 5 μm to 50 μm, and the width of the at least one recess 18 may be in the range of 5 μm to 50 μm. The depth and / or width of the at least one recess 18 may vary along its length. The present invention is not limited to a specific shape of the recess 18. On the contrary, it is contemplated that the recess 18 may have any shape, such as symmetrical and asymmetrical shapes in a vertical or horizontal cross section. For example, the recess 18 may be arc-shaped, semicircular, polygonal, or V-shaped. At least one recess 18 may be continuous in that it is annular with no gaps therebetween and no free ends. The at least one recess 18 may extend all the way around the circumference of the polymer molding compound 16 .

[0050] In all preferred embodiments of the present invention, the conductive layer 20A, 20B, 20C is at least partially bounded by at least one recess 18. In this context, bounding can be interpreted such that, seen in the flow direction of the ink, the upstream edge defines the edge of the conductive layer 20A, 20B, 20C. Thus, the edge definition of the conductive layer 20A, 20B, 20C is improved, regardless of whether the ink completely fills or even only partially fills the at least one recess 18. The at least one recess 18 can be formed, for example, by laser ablation, sawing, milling and embossing.

[0051] Preferably, at least one recess 18 can be formed by the same laser used to mark the 3D electronic component. For this purpose, an infrared laser with an emission wavelength of 1064 nm can be used. However, other types of lasers can also be used for this purpose, such as a green laser with an emission wavelength of 532 nm. When using an infrared laser, for example, the scanning speed of the laser can be 350 mm / s to 1350 mm / s, the frequency can be 10 Hz to 200 Hz, and the power of the infrared laser can be in the range of 20 mW to 100 W.

[0052] Low viscosity conductive ink on non-horizontal walls flows downward due to gravity. According to the invention, the flow of ink is stopped by the recesses before solidification to produce sharp and well defined edges. The recesses can be partially or completely filled with ink, resulting in a higher layer thickness in the recesses than outside the recesses. Ideally, the ink does not flow through the recesses, as a result of which the printed edges of the ink are relatively sharp and the ripples present in the prior art are reduced.

[0053] In the prior art, without forming a recessed portion in the polymer molding compound, the edge of the conductive layer may change by 150 μm, while with the present invention, with forming a recessed portion at a selected portion of the polymer molding compound, the edge of the conductive layer may change by only 50 μm after curing. Due to this reduced waviness of the edge, a more uniform layer thickness can be achieved across the entire conductive layer.

[0054] The waviness may be measured using a suitable imaging technique, such as a microscope or an automated optical inspection (AOI) system. For example, the average waviness may be determined by measuring the distance between the peaks and troughs of the wavy edge of the conductive layer relative to a reference position (preferably, a printer setting where the edge should ideally be located), and averaging the measurements for a plurality of printed 3D electronic components (e.g., 400) to obtain an average value of the waviness of the printed edge of the conductive layer. An average value may also be obtained for each surface of the polymer molding compound, for example, four average values ​​may be obtained for a cubic polymer molding compound.

[0055] The thickness of the conductive layer is preferably in the range of 0.0001 μm to 100 μm, more preferably in the range of 0.001 μm to 50 μm, still more preferably in the range of 0.1 μm to 5 μm, and even more preferably in the range of 1 μm to 4 μm.

[0056] Although SIP has been described as follows Figures 2 to 4 The preferred embodiment of the invention is shown, but the invention can also be applied to AIPs. The antenna, preferably meandering on the dome-shaped surface of the polymer encapsulant of the AIP, can be formed with a precise antenna edge by creating two spaced-apart recesses defining a raised polymer pile therebetween. The adjacent (inwardly located) edges of the two recesses then define the width of the antenna. The edge definition of the antenna is critical in terms of the frequency accuracy of the antenna.

Claims

1. A method for depositing a conductive layer on a surface of a three-dimensional (3D) electronic component (10A, 10B, 10C), the three-dimensional electronic component comprising at least one electronic device (14) embedded in a solid polymer material (16), the method comprising the following steps: -Providing 3D electronic components (10A, 10B, 10C); - forming at least one flow barrier (18) in the surface of the solid polymer material (16) of the 3D electronic component (10A, 10B, 10C); - depositing a conductive layer (20A, 20B, 20C) on at least a portion of the surface of the solid polymer material (16) such that the conductive layer (20A, 20B, 20C) 20C) is at least partially defined by the at least one flow barrier (18).

2. The method according to claim 1, wherein when the 3D electronic component (10A, 10B, 10C) is placed on a horizontal surface, the at least one flow barrier (18) is formed on a non-horizontal and / or non-planar surface, preferably a vertical surface, of the solid polymer material (16).

3. A method according to claim 1 or 2, wherein the at least one flow barrier (18) is a continuous annular flow barrier (18) extending completely around the solid polymer material (16).

4. The method according to any of the preceding claims, wherein the at least one flow barrier is a recess (18).

5. The method according to claim 4, wherein the at least one recess (18) is formed by laser ablation or sawing or milling or embossing.

6. The method according to any one of claims 4 or 5, wherein the at least one recess (18) has a depth in the range of 5 μm to 50 μm and a width in the range of 5 μm to 50 μm.

7. The method according to any one of claims 4 to 6, further comprising the step of laser marking the 3D electronic component (10A, 10B, 10C), wherein the laser used for laser marking the 3D electronic component (10A, 10B, 10C) is also used to form the at least one recess (18).

8. A method according to any one of the preceding claims, wherein the step of depositing the conductive layer is performed by inkjet printing or spraying.

9. The method according to any one of the preceding claims, wherein the conductive layer (20A, 20B, 20C) is an electromagnetic interference shield (20A, 20B, 20C) covering the at least one electronic device (14), and wherein the conductive layer (20A, 20B, 20C) is printed using conductive ink.

10. A three-dimensional (3D) electronic component (10A, 10B, 10C) comprising at least one electronic device (14) embedded in a solid polymer material (16), wherein the 3D electronic component (10A, 10B, 10C) comprises at least one flow barrier (18) in a surface of the solid polymer material (16), and wherein a conductive layer (20A, 20B, 20C) is disposed on at least a portion of the surface of the solid polymer material (16) such that the conductive layer (20A, 20B, 20C) is at least partially defined by the at least one flow barrier (18).

11. A 3D electronic component (10A, 10B, 10C) according to claim 10, wherein when the 3D electronic component (10A, 10B, 10C) is placed on a horizontal surface, the at least one flow barrier (18) is arranged on a non-horizontal and / or non-planar surface of the solid polymer material (16), preferably a vertical surface.

12. The 3D electronic component (10A, 10B, 10C) according to claim 10 or 11, wherein the at least one flow barrier (18) is a continuous annular flow barrier (18) extending completely around the solid polymer material moulding (16).

13. The 3D electronic component (10A, 10B, 10C), wherein the at least one flow barrier (18) is formed as a recess (18).

14. The 3D electronic component (10A, 10B, 10C) according to claim 13, wherein the at least one recess (18) has a depth in the range of 5 μm to 50 μm and a width in the range of 5 μm to 50 μm.

15. The 3D electronic component (10A, 10B, 10C), wherein the layer thickness of the conductive layer (20A, 20B, 20C) is in the range of 0.0001 μm to 100 μm, preferably in the range of 1 μm to 4 μm.

16. The 3D electronic component (10A, 10B, 10C), wherein the conductive layer (20A, 20B, 20C) is an electromagnetic interference shield (20A, 20B, 20C) covering the at least one electronic device (14), and wherein the conductive layer (20A, 20B, 20C) comprises conductive ink.

17. The method according to any one of claims 1 to 9 or the 3D electronic component according to any one of claims 10 to 16, wherein the 3D electronic component is a system-in-package (SIP) or an antenna-in-package (AIP), and the solid polymer material is a molding compound.

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