Improved adhesion promoter system for potted electronic components, in particular for passive sonar

Abstract

The present invention relates to a polymer-encased electronic component (10), wherein the electronic component (20) has a metal surface (30) at least in places, wherein the polymer-encased electronic component (10) has a polymer matrix (40), wherein the metal surface (30) of the electronic component (20) is connected to an adhesion promoter (50) and wherein the adhesion promoter (50) comprises a compound of formula M1 2[M2F6] where M1 = H, NH4, Li, Na, K, Rb, Cs and M2 = Ti, Zr, characterised in that a phenoplast (60) is arranged between the adhesion promoter (50) and the polymer matrix (40).

Description

August 19, 2025 Improved adhesion promoter system for encapsulated electronic components, especially for passive sonar. The invention relates to a polymer-encased electronic component, for example a passive sonar with optimized lifetime and simplified manufacturing, as well as the possibility of embedding further electronic components. A fundamental distinction is made between active and passive (sonar) detection systems. While active systems, such as the ASDIC (Anti-Submarine Detection Investigation Committee) system developed during World War II, emit and receive sound waves, passive systems only receive and analyze signals emitted by the environment. The advantage of passive systems is that they do not emit their own locatable signals. However, precise spatial localization of underwater objects is more difficult using passive systems alone. Therefore, many surface and underwater vessels typically employ both passive and active sonar systems, depending on their mission profile. In known hydrophones, two hollow sphere hemispheres are joined to form a single hollow sphere. German patents DE 102 12 291 C1 and US 6,029,113 A disclose hollow sphere hemispheres made of a piezoceramic material. The hollow sphere hemispheres are oppositely polarized, and an inner and outer electrode of each hollow sphere are connected via a resistor to an inverting voltage amplifier. An exemplary hydrophone setup can also be found in German patent DE 10 2008 029 269 A1.

[0002] ,

[0007] -

[0008] and

[0018] -

[0024] , The hollow sphere itself is often further protected from external influences such as moisture and dirt by a polymer coating. This polymer coating must be specifically designed for use with a hydrophone, taking into account the speed of sound and the long-term stability of the material. August 19, 2025 The effectiveness and shielding of the polymer coating depend largely on its bond to the ceramic surface of the hollow sphere. Due to the differing material properties of the metallic surface coating of the ceramic and the polymer coating, an additional bonding agent is often required. This bonding agent (preferred definitions are also those described in "Römpp Chemie Lexikon, 9th edition, Vol. 3, p. 1704, 1995") must ensure a secure, durable, and strong bond between the metal surface on the ceramic and the polymer coating. Because of its use in a humid, potentially saline environment, which may also exhibit significant temperature and pressure fluctuations, the bonding agent must also guarantee high long-term stability of the bond with regard to chemical and mechanical stresses. For the aforementioned application, various adhesion promoters are known, e.g., "Passirex" (possibly a registered trademark), particularly those based on Cr(VI) compounds. The carcinogenic potential of Cr(VI) compounds has been known for some time. Especially during the manufacture of the hydrophone, exposure of employees to Cr(VI) compounds cannot be completely ruled out. Furthermore, a release of the Cr(VI) compound is possible in the event of damage, particularly to the hydrophone. Proper disposal is also made more complex and expensive by the presence of Cr(VI) compounds. The term Cr(VI) compounds refers to compounds of chromium in the oxidation state plus six. This includes salts, complex compounds, melts, and solutions. As part of Regulation (EC) No 1907 / 2006, the "REACH Regulation," the requirements for the use of substances that are often considered harmful to health have been significantly increased. Due to the risk assessment required in the authorization process, many compounds must be replaced with less problematic alternatives. US 6,029,113 A discloses the construction of a differential hydrophone comprising a ceramic sphere made of two piezoelectric hemispheres. The arrangement enables the August 19, 2025 Recording of acoustic signals caused by changes in water pressure and their conversion into electrical signals. DE 102 12 291 C1 discloses an underwater antenna with at least one hydrophone and a symmetrical electrical amplification circuit associated with the hydrophone. DE 10 2008 029 269 A1 discloses a hydrophone for an underwater antenna, which has two spherical hemispheres made of radially polarized piezoelectric material, assembled to form a hollow sphere, and electrodes covering the inner and outer surfaces of the hemispheres. The spherical hemispheres are attached to the underside and top surface of a support surface with their edges in a mirror-symmetrical manner. EP 0 099 643 A2 discloses a high-attenuation polymer composition comprising a segmented block copolymer of polyurethane and an elastomer. Furthermore, a towed sonar system comprising a tube made of the aforementioned polymer composition is disclosed. A plurality of hydrophones are arranged within the tube. From DE 10 2019 202 889 A1, an adhesion promoter for a piezoceramic hydrophone is known. Sonar systems are becoming increasingly complex to obtain more information and perform more sophisticated procedures. This makes it desirable to integrate electronic components, for example for data compression or data processing, directly into the sonar systems themselves, and not just the hydrophones. A critical factor here is the time between treating the metallic surface and the potting process. If the metallic surface has been pretreated accordingly, the potting must be carried out promptly to ensure the adhesion promoter is still effective. Extending this time period between pretreatment and potting would be advantageous. August 19, 2025 In addition to spherical hydrophones, other electronic components are increasingly being integrated and thus also potted. However, these typically do not have a simple spherical surface, but may have edges or even undercuts. This improves the problem of reliable surface treatment to enhance adhesion and further reduces the time between surface optimization and potting. The object of the invention is to further optimize the adhesive strength of the bond between the potting compound and the metallic surface of the electronic components, as well as their long-term durability and storage capacity. This problem is solved by the polymer-coated electronic component with the features specified in claim 1 and by the method with the features specified in claim 6. Advantageous embodiments are described in the dependent claims, the following description, and the drawing. The polymer-encapsulated electronic component according to the invention is preferably a sonar, wherein "sonar" here also includes a sonar component. Sonar systems are typically in direct contact with water, especially with saline seawater. This makes these systems inherently susceptible to corrosion. Furthermore, they are often permanently integrated into the vessels, making replacement difficult. Therefore, corrosion must be prevented. On the other hand, the separation of the surrounding polymer matrix from the sound receivers must also be prevented, as this creates a gap that impairs or even prevents sound reception. The increasing integration of additional electronic components besides the hydrophones into modern sonar systems also presents challenges due to their more complex form factor, which can be overcome according to the invention.This refers to a polymer-encapsulated electronic component, for example, a passive sonar, in which at least one electronic component, but preferably a plurality of electronic components, are bonded together in a polymer to form a single component. The electronic components are preferably hydrophones, and more preferably hydrophones and other electronic components, for example, integrated circuits. August 19, 2025 The electronic component has a metallic surface, at least in some areas. The polymer-encapsulated electronic component has a polymer matrix. This polymer matrix forms the body of the polymer-encapsulated electronic component, ensures mechanical stability, the fixed positioning of the electronic components relative to each other, and at least primarily prevents the ingress of water. The metallic surface of the electronic component is bonded to an adhesion promoter. The adhesion promoter comprises a compound of the formula (M 1 )2[(M 2 )Fe] with M 1 = H, NH4, Li, Na, K, Rb, Cs and M 2 = Ti, Zr. One advantage of this adhesion promoter is the absence of Cr(VI) compounds. According to the invention, a phenolic resin is arranged between the adhesion promoter and the polymer matrix. Phenoplasts have proven to be particularly suitable. Firstly, they can be applied in liquid form like an adhesive. It is assumed that the selection of phenolic resins as the bonding element could offer two advantages that could be responsible for the optimized service life and processability. Firstly, the phenolic resin appears to represent a very good water barrier, so that even over extended periods, water diffusing through the polymer matrix cannot reach the electronic components, thus protecting the metal surface from corrosion. This effect would also explain the longer waiting time between the surface treatment of the metal and the final embedding of, for example, a hydrophone into the polymer matrix.Furthermore, the phenolic resin appears to further improve the adhesion between the adhesion promoter itself and the polymer matrix, thus preventing delamination. While this adds an extra step to the manufacturing process, increasing production costs, it can extend the product's lifespan and reduce rejects. In a further embodiment of the invention, the polymer matrix contains polyurethanes, silicones, polyesters, polyethers, polyamides, preferably polyurethanes. August 19, 2025 In a further embodiment of the invention, the adhesion promoter contains anti-corrosion agents. This makes it possible to prevent corrosion caused by small traces of water that nevertheless penetrate to the metal through diffusion. In a further embodiment of the invention, the electronic component is a piezoceramic hydrophone and the polymer-encased electronic component is a passive sonar. The passive sonar, or electroacoustic underwater antenna, is preferably used in submerged and surface vessels. Examples of such a design, for example as a side antenna attached to the outer hull or as an electroacoustic underwater antenna, can be found in DE 10 2004 037 987 A1 in paragraph

[0013] until

[0022] , In another embodiment of the invention, the electronic component has edges or undercuts. Hydrophones are available in various geometric designs. These often have uneven surfaces and through-holes (bores), meaning the surface of the hydrophones is not comparatively simple. Furthermore, additional electronic components, such as integrated circuits, are increasingly being integrated, for example, to reduce the amount of data to be transferred. Problems can arise at edges or undercuts both during the application of the adhesion promoter and during the production of the polymer matrix. Moreover, such points are also primary weak points under mechanical stress or temperature fluctuations, where failure can occur. Therefore, the technology for manufacturing hydrophones cannot simply be transferred to other electronic components. A hydrophone, in particular a piezoceramic hydrophone, comprises at least the following elements: A first spherical hemisphere and a second spherical hemisphere are assembled to form a hollow sphere. For the purposes of this invention, the term "spherical hemisphere" preferably refers to a hemisphere with an inner cavity. Preferably, the inner cavity comprises / forms 10% to 90% of the hemisphere's volume, for example, based on a wall thickness of 0.5 mm to 4 mm, more preferably 0.8 mm to 2 mm. An exemplary hydrophone design can be found, among others, in DE 10 2008 029 269 A1, paragraph

[0018] to

[0022] , The first spherical hemisphere and the August 19, 2025. The second spherical hemisphere comprises a radially polarized, piezoelectric material, for example, lead zirconate titanate (PZT). The first and second spherical hemispheres have an outer layer. The term "outer layer" preferably includes, within the meaning of the invention, at least a partial coating of the spherical hemisphere surfaces. The term "partial" preferably includes a coating of at least 30%, more preferably at least 75%, of the spherical hemisphere (top) surfaces. To prevent a short circuit, individual sections of the spherical hemisphere surfaces of the first and second spherical hemispheres can be designed without an outer layer (coating) or with an insulating layer or element arranged between them. This preferably includes, for example, the connecting surface of the two spherical hemispheres to each other.For the purposes of the invention, the term "outer layer" preferably comprises a coating on the surface of the spherical hemisphere, particularly preferably the inner and outer shell surfaces of the respective hemisphere. The outer layer comprises silver and / or silicon compounds, or equivalently, "contains" silver and / or silicon compounds. Furthermore, a hydrophone comprises electrical contacts between the first and second spherical hemispheres. A polymer casing encloses the hollow sphere and prevents or slows down the penetration of moisture or dirt. In a further aspect, the invention relates to a method for manufacturing a polymer-coated electronic component. The method comprises the following steps: a) providing an electronic component with at least a partially metallic surface, b) applying at least to the metallic surface an adhesion promoter comprising a compound of the formula (M 1 )2[(M 2 )Fe] with M 1 = H, NH4, Li, Na, K, Rb, Cs and M 2 = Ti, Zr, c) Applying a phenolic resin to the adhesion promoter, d) Creating a polymer matrix for embedding the electronic component in a polymer-coated electronic component. August 19, 2025 The method differs from the state of the art in that not only spherical hydrophones but also any electronic components can be provided, and secondly in that step c) is additionally performed. In a further embodiment of the invention, the process is interrupted between step c) and step d). This enables the more efficient manufacturing of, in particular, larger sonar systems, in which a large number of hydrophones must be arranged and, in particular, connected to integrated electronic processing. By extending the processing time, larger and more complex, and therefore more efficient, sonar systems become possible. In a further embodiment of the invention, the application in step c) is carried out by applying a preparation, wherein the preparation comprises at least the components toluene, ethanol, phenol, and formaldehyde. In this process, phenol and formaldehyde, in particular, react to form the phenolic resin. The preparation may, for example, already contain initial reaction products of phenol and formaldehyde on the way to the formation of the phenolic resin. In a further embodiment of the invention, the application of the adhesion promoter in step b) and / or the phenolic resin in step c) is carried out by spraying, dipping and / or brushing methods. The invention further includes the use of the polymer-coated electronic component according to the invention in warships and research vessels, preferably submarines, ASW (anti-submarine warfare) helicopters, sonar buoys, frigates, destroyers, corvettes, speedboats and / or unmanned watercraft, both remotely controlled and autonomous. The polymer-coated electronic component according to the invention is explained in more detail below with reference to an embodiment shown in the drawing. Fig. 1 Example of a polymer-coated electronic component August 19, 2025 The diagram is purely schematic and not to scale. It serves only to illustrate the basic structure. Identical components have the same reference symbols. Figure 1 shows a highly simplified, schematic representation of a polymer-encased electronic component 10. For example, the polymer-encased electronic component 10 is a passive sonar. In this simplified and purely illustrative example, the polymer-encased electronic component 10 has two hydrophones 22, each consisting of two hemispheres, each with a metallic surface 30. These metallic surfaces 30 of the hydrophones 22 are connected via wires 24 to an electronic component 20, for example, an integrated circuit, whose surface has been simplified to a single metallic surface 30, as its structure is not essential here. The electronic component 20 is connected via a connection 70, for example, a sheathed cable, to other systems, such as a ship's sonar system.As is known from the prior art, metallic surfaces 30 (in the example shown, including the wires 24, which are also metallic) are coated with an adhesion promoter 50. A phenolic resin 60 is arranged between the adhesion promoter 50 and the polymer matrix 40. Reference sign 10 polymer-coated electronic component 20 electronic component 22 Hydrophone 24 wire 30 metallic surfaces 40 Polymer matrix 50 liability mediators 60 Phenoplast 70 connection

Claims

August 19, 2025 Patent claims 1. Polymer-coated electronic component (10), wherein the electronic component (20) has at least a metallic surface (30) in certain areas, wherein the polymer-coated electronic component (10) has a polymer matrix (40), wherein the metallic surface (30) of the electronic component (20) is bonded to an adhesion promoter (50), and wherein the adhesion promoter (50) is a compound of the formula (M 1 )2[(M 2 )Fe] with M 1 = H, NH4, Li, Na, K, Rb, Cs and M 2 = Ti, Zr comprising, characterized in that a phenolic resin (60) is arranged between the adhesion promoter (50) and the polymer matrix (40).

2. Polymer-coated electronic component (10) according to claim 1, characterized in that the polymer matrix (40) contains polyurethanes, silicones, polyesters, polyethers, polyamides, preferably polyurethanes.

3. Polymer-coated electronic component (10) according to one of the preceding claims, characterized in that the adhesion promoter (50) contains anti-corrosion agent.

4. Polymer-coated electronic component (10) according to one of the preceding claims, characterized in that the electronic component (10) is a piezoceramic hydrophone.

5. Polymer-coated electronic component (10) according to one of the preceding claims, characterized in that the electronic component (20) has edges or undercuts.

6. A method for producing a polymer-coated electronic component (10), the method comprising the following steps: a) providing an electronic component (20) having at least a metallic surface (30) in some areas, b) applying at least to the metallic surface (30) an adhesion promoter (50) comprising a compound of the formula (M 1 )2[(M 2)Fe] with M 1 = H, NH4, Li, Na, K, Rb, Cs and M 2 = Ti, Zr; 19.08.2025 c) Applying a phenolic resin (60) to the adhesion promoter (50), d) Creating a polymer matrix (40) for embedding the electronic component (20) in a polymer-coated electronic component (10).

7. Method according to claim 6, characterized in that the method is interrupted between step c) and step d).

8. Method according to one of claims 6 to 7, characterized in that the application in step c) is carried out by applying a preparation, wherein the preparation contains at least the components toluene, ethanol, phenol and contains formaldehyde.

9. Method according to one of claims 6 to 8, characterized in that the application of the adhesion promoter (50) in step b) and the phenolic resin (60) in step c) is carried out by spraying, dipping and / or brushing.

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