WO2017001888A1

WO2017001888A1 - Conductive polymeric housing for electronic component

Info

Publication number: WO2017001888A1
Application number: PCT/IB2015/054879
Authority: WO
Inventors: Ricardo Manuel DUARTE FREITAS; Ricardo FIGUEIRÊDO DE SÁ; Marta Virgínia PINTO GOMES; Ana Filipa GONÇALVES DA COSTA CARNEIRO; Alexandre Manuel DA COSTA PITÃES; Nuno Miguel PORTELINHA GONÇALVES; Agnieszka Elżbieta ŻMIJEWSKA ROCHA; Carla Alexandra FARIA LOUREIRO SIMÕES; Ricardo Emanuel RIBEIRO CAMPOS; Luís Carlos NETO MARTINS; Rui Nuno FERREIRA PINTO; Pedro Miguel SOUSA BERNARDO; Carlos Jorge MARQUES RIBEIRO; António José VILELA PONTES; José Ernesto DO PAÇO VIANA
Original assignee: Bosch Car Multimedia Portugal, S.A.; Universidade Do Minho
Priority date: 2015-06-29
Filing date: 2015-06-29
Publication date: 2017-01-05
Also published as: CN209120583U

Abstract

Conductive polymeric housing for an electronic component comprising a base shell for mating with a cover shell for obtaining a closed housing, wherein both said shells are conductive polymeric and each shell comprises a plurality of teeth positioned on one or more of the shell sidewalls, said teeth being substantially coplanar with the sidewall in which they are positioned, said teeth comprising laterally interspersed spaces for receiving the teeth of the other shell, all said teeth being integrally formed with the respective shell by injection moulding, such that each tooth is laterally compressed against a mating tooth or mating teeth of the other shell when the housing is closed.

Description

CONDUCTIVE POLYMERIC HOUSING FOR ELECTRONIC COMPONENT Technical field

[0001] The present disclosure relates to the housing of electronic devices, in particular the manufacture of housings intended to enclose an electronic component or components used in the automotive industry, in particular to ensure EMC - electromagnetic compatibility, and immunity from EMI - electromagnetic interference and ESD - electrostatic discharge. Further in particular, it is described a polymeric housing that may enclose any kind of electronic components, for example a media centre, a digital disc player, a radio, a display or a computer. This disclosure can be applied in any kind of industry that needs housings for electronic components, such as automotive applications.

Background Art

[0002] The present disclosure relates to housings for electronic devices, in particular housings intended to enclose an electronic component or components used in the automotive industry.

[0003] Traditional approaches resort to metallic materials (US 5,256,833) that must present foldings and openings specifically conceived for such a purpose (US 8,541,696 B2, WO 2014/145594 Al and US 2007/0297160 Al, both focused on EMC shielding).

[0004] Alternatives include the usage of other materials (such as polymers) with an added electrically-conductive EMI shielding layer (for example, sprayed - US 6,763,576 B2 or overmoulded or coupled on top - US 6,807,731 B2) or the overmoulding of an electrically conductive wire mesh screen (US 2014/0347831 Al) or wire (US 6,137,050) or the use of other conductive inserts (US 4,880,679). Other options include an electrically conductive polymer (US 2007/0297160, US 2012/0285738).

[0005] As the Shielding Effectiveness (SE) is measured in dB (represented in a logarithmic scale), the requirements for higher shielding levels represents exponential decrease in maximum allowable openings. High SE requirements result in very small acceptable openings. This leads to the use of gaskets or similar additional components to ensure for proper closing (US2477267 A, US 3783173 A, US7402761 B2, US 6,355,878 Bl, US 7,889,515 B2 - conductive gaskets - US 7,078,614 Bl, US 7,527,506 B2 - metal springs or WO 2008/153917 Al, US 5,265,833 - solutions including several alternatives). Alternative geometries are also described in order allow for competent closing - US 5,565,656. In the case of polymers (in particular US 2007/0297160), the characteristic shape flexibility of polymers lead to a configuration of the edges developed in order to ensure maximum contact between parts of the casing and, thus, a good conduction while reducing or eliminating the need of gaskets or other alternatives.

[0006] A chassis that assumes the function of assuring ESD immunity is particularly in need of a proper contact between PCB and casing (US 4,494,651). The high variability in terms of PCB thickness results in the use of flexible conductive elements with this purpose (US 8,472,203 B2).

[0007] It can be seen that the vast majority of the solutions presented require additional elements, either metallic or polymeric, to allow for proper sealing and electrical conduction amongst different parts of the casing (essential to EMI, EMC and ESD immunity). The main reason for the need of these components is the high variability in PCB thickness. This adds parts, costs and processes to the manufacturing of such components. Also, the usage of metallic components has an impact in weight (either when directly changing the material in a given geometry or when considering that polymers have the potential to be produced in much more optimized structures).

[0008] These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure. General Description

[0009] The present disclosure describes a polymeric housing that not only provides the obvious functions, such as mechanic support and dust and water protection, but is also able to provide electromagnetic compatibility (EMC), electromagnetic interference immunity (EMI) and electrostatic discharge (ESD) immunity. These properties ensure that the device will not be affected by electromagnetic (EM) radiations emitted by surrounding components - EMI-, that the radiations that it emits will not affect surrounding components - EMC - and that, in the case of a electrostatic discharge - ESD -, the current will be conducted to the chassis and not to the PCB, thus avoiding an overload of components that could become damaged.

[0010] To ensure that these functions are properly implemented the disclosure ensures:

Adequate surface and volume conductivity;

Adequate geometry to ensure efficient electromagnetic blockage;

Adequate contact between PCB and casing.

[0011] The present disclosure comprises a polymeric housing of a given thickness to enclose electronic components like a mediacenter used in the automotive industry (Fig. 1). More specifically it comprises a housing that encloses a media centre that it can be applied to, not only, but including, passenger cars. An embodiment of the solution here presented is composed exclusively of one polymeric component, preferably an electrically conducting polymer, able to provide such functions (EMC, EMI and ESD immunity) without the need of additional conductive sealing components.

[0012] The material might be an intrinsically conducting polymer (ICP) or a non-ICP, as far as it contains electrically conductive fillers. The non-ICP materials work as a matrix and might be, for example, PP, PC, PA, PBT, ABS, PC/ABS, PET and PS amongst other thermoplastics. The conductive fillers need, obviously, to be electrically conductive materials. These might be, for example, carbon fibres, coated carbon fibres, carbon black, steel fibres, and stainless steel fibres, amongst others. Mechanical and electrical properties will be a direct consequence of the composition of these materials and the processing conditions.

[0013] The mechanical properties of the polymer, such as stiffness, are relevant in that: being too low the material will deform too easily and will not achieve proper compression of the electronic components and closing forces; being too high the material will hardly deform at all and will not achieve contact compression effects; being this selection of adequate polymeric materials regarding these properties within the normal and usual duties of the skilled person in this field.

[0014] The housing may present, or not, holes to ensure adequate ventilation and heat removal (2). This solution is able to be produced in a single production step, e.g. by injection moulding, by the end of which it is possible to obtain a polymeric part able to effectively protect both an electronic component and the surrounding ones. This implies a reduction in the number of parts and process steps and has a potential for weight, cost and environmental impact reduction.

[0015] The disclosure describes a conductive polymeric housing for an electronic component comprising a base shell for mating with a cover shell for obtaining a closed housing, wherein both said shells are conductive polymeric and each comprises a plurality of teeth positioned on one or more of the shell sidewalls, said teeth being substantially coplanar with the sidewall in which they are positioned, said teeth comprising laterally interspersed spaces for receiving the teeth of the other shell, said teeth being integrally formed with the respective shell by injection moulding, such that each tooth is laterally compressed against a mating tooth or mating teeth of the other shell when the housing is closed.

[0016] In an embodiment, said teeth are integrally formed such that each tooth of the base shell is laterally compressed against two mating teeth of the cover shell when the housing is closed. [0017] In an embodiment, each said tooth has two lateral angled surfaces such that the tooth lateral angled surfaces are compressed against the lateral angled surfaces of the two mating teeth of the other shell when the housing is closed.

[0018] In an embodiment, each said angled surface has an angle, in respect to the perpendicular of the closure plane of the housing, larger than 0° and smaller than to 45°. An angle of 0° results in a constant interference regardless of the PCB's thickness. Angles of 45° or higher have an increase of the interference equal to the PCB's thickness reduction. Angles between 0° and 45° have an interference increase lower than the PCB's thickness reduction. This relation is lower for lower angles. If a smaller interference/thickness reduction relation is desired, angles up to 10° perform better. Angles between 10° and 45° will have a higher interference/thickness reduction relation. In an embodiment, each said tooth has the shape of a triangle which is truncated distal to the closure plane of the housing.

[0019] In an embodiment, each said tooth has the shape of a trapezoid with its parallel sides being parallel to the closure plane of the housing, with the smaller of those parallel sides being distal from the closure plane, and the larger of those parallel sides being proximal from the closure plane.

[0020] In an embodiment, the conductive polymeric housing comprises said cover shell.

[0021] In an embodiment, the conductive polymeric housing comprises a planar sidewall, ensuring that, regardless of the PCB's thickness, the housing will present minimal openings, the planar sidewall being coplanar with said teeth and extending from the base of the teeth to part of the extent of the teeth, but not extending to the full extent of the teeth, said planar sidewall being integrally formed with the respective shell by injection moulding. This has advantages namely in avoiding openings that may allow dust, liquids or particles to enter the housing. This has advantages namely in avoiding openings that may create EMC or EMI issues.

[0022] In an embodiment, the conductive polymeric housing comprises a hinge arranged between the base shell and the cover shell. [0023] In an embodiment, the electronic component is a PCB.

[0024] In an embodiment, the conductive polymeric housing comprises one or more electrical contact protrusions for making electrical contact with the PCB, said protrusion being integrally formed with the respective shell by injection moulding.

[0025] In an embodiment, the electrical contact protrusions are wall-shaped.

[0026] In an embodiment, the conductive polymeric housing comprises one or more support protrusions for physically supporting the PCB, said protrusion being integrally formed with the respective shell by injection moulding.

[0027] In an embodiment, the electrical contact protrusions of one said shells protrude more than the support protrusions of the same shell by a predetermined amount for reinforcing the electrical contact between the electrical contact protrusions and the PCB.

[0028] In an embodiment, the conductive polymeric housing comprises one or more ventilation holes.

Brief Description of the Drawings

[0029] The following figures provide preferred embodiments for illustrating the description and should not be seen as limiting the scope of invention.

[0030] Figure 1: Schematic representation of a general depiction of a whole device box having a housing according to an embodiment the disclosure.

[0031] Figure 2: Schematic representation of the side view of an open box with detailed display of height dimensions and different between screwing zone and discharge zone having a housing according to an embodiment the disclosure.

[0032] Figure 3: Schematic representation of the side view of an open box with detailed display of joining teeth and its configuration of a housing according to an embodiment the disclosure. Detailed Description

[0033] The developed polymeric housing according to embodiments of the disclosure is able to effectively provide both EMC and EMI. The two shells that compose the box are connected through a live hinge, a hinge, other connection configuration or not connected thus making the box composed of two or more separate components. This disclosure allows for a competent connection between the components without the use of any kind of gasket or additional part to ensure the connectivity between shells.

[0034] To ensure the adequate connectivity between the two shells, the developed device makes use of a specially designed joining mechanism that reduces the gap dimensions, resulting in an efficient joint.

[0035] In order to reduce the length of the joining gaps, a structure of alternate teeth (3) has been placed along the length of the joining area. In particular, the teeth may have the shape of a truncated triangle or a trapezoid with its parallel sides being parallel to the closure plane of the housing, with the smaller of those parallel sides being distal from the closure plane, and the larger of those parallel sides being proximal from the closure plane.

[0036] These teeth close in a manner that each teeth is compressed against the two adjacent ones of the other half of the housing, in particular compressing laterally against the two adjacent ones of the other half of the housing, keeping the PCB free of stress from the joining forces.

[0037] In particular, each of the lateral sides of the trapezoid is for mating with the two opposing interspersed teeth.

[0038] Said teeth have a given periodicity, being this periodicity subject of adaptation to the needs of the system, according to the dimensions, characteristics of the material and shielding effectiveness (SE) needs. The teeth have angled sides (angle a in Fig. 3) in respect to the perpendicular of the closure plane of the housing, being a comprised in an interval between 0° and 45° in reference to the plane normal to the closing surface. [0039] If the angle (a) is lower than 0° then the inclination is reversed and the lateral sides of opposing teeth will not fit. If the angle (a) is higher than 45° then there is no advantage in the adoption of this approach since the increase in the interference after the initial contact between the angled sides of the teeth is the same as the PCB's thickness reduction.

[0040] The teeth may be reinforced by a sidewall coplanar with said teeth. The sidewalls from the two housing shells maybe calculated such that the sidewalls of both shells are aligned along the same plane. Preferably, the sidewall should not touch when the housing is closed by coupling the housing shells, because the absorption of movement by the compression of the teeth will no longer be possible. After the sidewalls touch, the mating movement of the shells is blocked.

[0041] This geometric configuration allows for an adequate closing of the box regardless of the PCB thickness (as far as the dimensions remain within the tolerance) that reflects in an efficient contact between the two parts. This contact is relevant for the ESD and EMI functions of the casing.

[0042] The teeth design can vary in size (width, thickness, height) and in angle (a). Larger angles will represent a larger interference growth with PCB thickness reduction. Consider a nominal PCB thickness of n and that the thickness ranges between n-t and n+t, being t the PCB thickness tolerance. For the maximum PCB thickness there will be an interference i₀. As the thickness varies (decreases) the interference increases. The maximum interference is achieved for minimum PCB thickness. At this point the interference is i₀+2t.tan(a). From this expression it is possible to assess that lower angles lead to lower interference increase.

[0043] Together with the characteristics of the material used and clamping force, this angle can be adjusted so that the fluctuations of the enclosed PCB can be absorbed by the compression of said teeth, without adding any stress to the PCB. In one arrangement, an angle of 10^ was used, in a way that for a closing (vertical movement of 0.5 mm, the teeth will only compress against each other 0.1 mm). For a PCB, of nominal thickness (i.e. 1.6 mm ± 0.2 mm, which means 1.4 - 1.8 mm), the teeth will be compressed 0.1 mm. For the thinnest PCB (within tolerances) said teeth will be compressed 0.15 mm and for the thickest PCB compression will be of 0.05 mm. This ensures that even though PCB can vary 0.4 mm, compression variations will be less than 0.1 mm and contact between the two shells is always ensured. Therefore, both EMC and EMI is also ensured for the contact between the two shells is guaranteed.

[0044] The closing adjustment that the described mechanism provides, also ensures that a direct contact between housing and PCB is complete. With prior solutions, the housing has a defined closing point, which would result in poor contact between housing and PCB, for the thinnest PCBs. On the other hand, over dimensioning that would ensure a good grounding effect thus providing a good ESD, would result in excess stress to the PCB, compromising its mechanical integrity.

[0045] Because the housing shells have a range of good closing points, the two shells can always adjust to all ranges of PCB, within given tolerances. The developed mechanism uses a given difference (x) between the contact points from the screwing zones (4) and the contact points used for electrical discharge (1). In this manner, when a given torque is applied to said screws, the pressure of the housing to the PCB in the screwing areas is constant, as is the pressure of the housing in the discharge areas. Such difference can be adjusted according to the characteristics of used material, so that the additional pressure given by the height difference is not excessive according to the PCB characteristics.

[0046] The electrical contacts between housing shell and PCB can be protrusions from the same material and integral to the shell. Such protrusions can be embossments, pillars, cone-shaped, pyramid-shaped, among others.

[0047] Such contact protrusion can also be wall-shaped, i.e. a thin long linear protrusion presenting a long linear contact surface for contacting with the PCB. Thus the area of contact has also been maximized to the total area of the upper surface of contact wall (1), as to ensure a good level of electrical conductivity is achieved.

[0048] The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0049] The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof.

[0050] The above described embodiments are combinable.

[0051] The following claims further set out particular embodiments of the disclosure.

Claims

C L A I M S

1. Conductive polymeric housing for an electronic component comprising a base shell for mating with a cover shell for obtaining a closed housing,

wherein both said shells are conductive polymeric and each shell comprises a plurality of teeth positioned on one or more of the shell sidewalls, said teeth being substantially coplanar with the sidewall in which they are positioned,

said teeth comprising laterally interspersed spaces for receiving the teeth of the other shell,

said teeth being integrally formed with the respective shell by injection moulding, such that each tooth is laterally compressed against a mating tooth or mating teeth of the other shell when the housing is closed.

2. Conductive polymeric housing according to the previous claim, said teeth being integrally formed such that each tooth of the base shell is laterally compressed against two mating teeth of the cover shell when the housing is closed.

3. Conductive polymeric housing according to the previous claims wherein each said tooth has two lateral angled surfaces such that the tooth lateral angled surfaces are compressed against the lateral angled surfaces of the two mating teeth of the other shell when the housing is closed.

4. Conductive polymeric housing according to the previous claim, wherein each said angled surface has an angle, in respect to the perpendicular of the closure plane of the housing, larger than 0° and smaller or equal to 45°, in particular substantially 10° or less, further in particular substantially 10°.

5. Conductive polymeric housing according to any of the previous claims wherein the tooth has the shape of a triangle which is truncated distal to the closure plane of the housing.

6. Conductive polymeric housing according to any of the previous claims wherein the tooth has the shape of a trapezoid with its parallel sides being parallel to the closure plane of the housing, with the smaller of those parallel sides being distal from the closure plane, and the larger of those parallel sides being proximal from the closure plane.

7. Conductive polymeric housing according to any of the previous claims comprising said cover shell.

8. Conductive polymeric housing according to any of the previous claims comprising a planar sidewall, the planar sidewall being coplanar with said teeth and extending from the base of the teeth to part of the extent of the teeth, but not extending to the full extent of the teeth,

said planar sidewall being integrally formed with the respective shell by injection moulding.

9. Conductive polymeric housing according to any of the previous claims comprising a hinge, or a live hinge, arranged between the base shell and the cover shell.

10. Conductive polymeric housing according to any of the previous claims wherein the electronic component is a PCB.

11. Conductive polymeric housing according to the previous claim, comprising one or more electrical contact protrusions for making electrical contact with the PCB, said protrusion being integrally formed with the respective shell by injection moulding.

12. Conductive polymeric housing according to the previous claim wherein the electrical contact protrusions are wall-shaped.

13. Conductive polymeric housing according to any of the claims 10 - 12, comprising one or more support protrusions for physically supporting the PCB, said protrusion being integrally formed with the respective shell by injection moulding.

14. Conductive polymeric housing according to claims 11 or 12 and according to claim 13, wherein the electrical contact protrusions of one said shells protrude more than the support protrusions of the same shell by a predetermined amount for reinforcing the electrical contact between the electrical contact protrusions and the PCB.

15. Conductive polymeric housing according to any of the previous claims comprising one or more ventilation holes.

16. Conductive polymeric housing according to any of the previous claims wherein the conductive polymeric shell is made of a intrinsically conducting polymer, or a non- intrinsically conducting polymer selected from the list of PP, PC, PA, PBT, ABS, PC/ABS, PET or PS, combined with one or more conductive filler materials such as carbon fibres, coated carbon fibres, carbon black, steel fibres, or stainless steel fibres.