EP1665392A1

EP1665392A1 - Optical module and optical system

Info

Publication number: EP1665392A1
Application number: EP04787186A
Authority: EP
Inventors: Danut Bogdan; Josef Dirmeyer; Henryk Frenzel; Harald Schmidt
Original assignee: Siemens AG
Current assignee: Continental Automotive GmbH
Priority date: 2003-09-26
Filing date: 2004-09-22
Publication date: 2006-06-07
Also published as: US20060239632A1; WO2005031879A1; US7570439B2

Abstract

The invention relates to an optical module comprising: a circuit support (10); a cased semiconductor element (12) placed on the circuit support (10), and; a lens unit (14; 16, 18, 20; 21) for projecting electromagnetic radiation onto the semiconductor element (12). The lens unit preferably comprises a lens arrangement consisting of, for example, three lenses (16, 18, 20) and of a diaphragm (21). The lenses (16, 18, 20), optionally together with the diaphragm (21), are aligned in a well-defined manner due to their geometric design so that no additional optical adjustment is necessary. According to the invention, the lenses (16, 18, 20; 21) are held in a type of lens holder (14) that is an integral component of the case (13) of the semiconductor element (12).

Description

description

Optical module and optical system

The invention relates to an optical module with a circuit carrier, a packaged semiconductor element arranged on the circuit carrier and a lens unit for projecting electromagnetic radiation onto the semiconductor element.

The invention further relates to an optical system with an optical module designed in this way.

Generic optical modules and systems are used in particular in automotive engineering.

It is possible to work with electromagnetic radiation from different frequency ranges, being cumulative of the visible light, with which typically applications in the exterior of a motor vehicle such as lane departure warning

(LD), Blind Spot Detection (BSD) or Rear View Cameras work, in particular infrared radiation that is invisible to humans is preferred for applications in the interior of a motor vehicle such as Out of Position Detection (OOP) or for additional external lighting of a night vision system.

Applications in the interior or exterior of a vehicle are subject to high demands due to external influences such as temperature, humidity, pollution and vibration. The typical lifespan for systems in the vehicle is 10 to 15 years, whereby only extremely low failure rates are tolerated, so that the components of an optical one Systems of the type mentioned at the beginning are only allowed to show very slow aging.

Since the installation space of optical modules or optical systems is very limited in many cases, there are additional difficulties in the implementation of the optical systems. With conventional means, it is extremely difficult to build a hermetically sealed, reliable unit from a camera chip (CCD or CMOS sensor) and optics.

In order to achieve sufficient image sharpness for a camera system consisting of an image sensor (currently CCD or CMOS) and a lens system, the components sensor and optics must be geometrically very precisely coordinated. The tolerance range for the distance from the camera chip to the optics in the z-axis is usually in the range of a few hundredths of a millimeter in order to achieve an optimally sharp image for a certain depth of field. This is particularly problematic for so-called fixed focus systems, since these may have little tolerance during manufacture. An offset from the camera chip to the optics in the x or y axis additionally has the consequence that the optical system may "squint", i.e. the image is cut off at one edge (horizontal or vertical) because the offset means that there are no more pixels here and had to be provided as a precaution.

Another problem is the so-called "tilt", ie tilting of the camera chip around the x or y axis, which has the consequence that the image has a blurring gradient in the horizontal or vertical direction. In addition, there can also be a "rotation", ie a rotation about the z axis from the camera chip to the optics. Almost all camera systems previously on the market that are supplied with a fixed focus setting require an additional adjustment step during production, in which the distance from the camera chip to the optics is set along the z-axis and fixed at this value. This is done, for example, by means of a thread and a corresponding locking screw or an adhesive connection. An adjustment step may also be necessary for the xy offset or, if this does not take place, a correspondingly larger sensor can be provided which compensates for the tolerances by adding more pixels. It is also known to use software to calculate or calibrate the "rotation". Since otherwise sharp image information is available, the pixels only have to be reassigned in a type of "calibration process". However, there may be no more information at the edges or corners because they have been cut off. A purely mechanical reduction of "tilt" and "rotation" between the chip and the optics can usually only be achieved in conventional systems through high-precision manufacturing and

Assembly or by comparing the components.

Cameras for specific low cost applications such as Automotive, industry, digital cameras, cell phones, toys etc., however, should be possible from cost and quality assurance aspects without any adjustment processes between the optics and the camera chip, i.e. without adjusting the focus to the optical surface of the CMOS or CCD sensor. This is fundamentally contrary to the requirements mentioned.

One possibility to develop a focus-free system is to reduce the sum of the possible tolerances and elements, so that the module or system can be designed without adjustment. works at least in a certain distance and temperature range. When using the invention, for example in the context of an occupant protection system of a motor vehicle, to which the present invention is not restricted, it should be possible to guarantee sharp images at distances of, for example, 15 cm to 130 cm and at temperatures of, for example, -40 ° C. to + 105 ° C. , This is all the more realizable, the fewer elements are included in the tolerance chain. In the case of packaged semiconductor elements, the necessary solder and possibly adhesive connections or the like between the chip and the circuit carrier have a large proportion in the tolerance chain.

When using only one lens, it is avoided that additional optical tolerances are caused by a complicated lens structure. The lens holder itself, which preferably consists of plastic, can be connected to the lens arrangement in various ways, so that an exact optical alignment of the lens arrangement and the semiconductor element with respect to the lens holder or the lens arrangement can always be ensured.

Nevertheless, in systems which largely have a classic design consisting of a lens and camera chip, the camera chip or the semiconductor element being mounted in a housing on a suitable circuit carrier, it is difficult to avoid the problems mentioned in their entirety and at the same time to avoid the problems mentioned To meet quality requirements. In the case of packaged semiconductor chips, only special measures against external light radiation or other environmental influences are to be taken from the front, since the chip housing offers sufficient protection from behind, for example for the silicon which is transparent to IR radiation. However, the lens itself needs to be adjusted to the camera chip and have a defined focus. This is currently done by means of tolerance-related fixing options, for example by screwing, gluing or the like, by means of which the lens is fixed on the circuit carrier relative to the camera chip.

The invention has for its object to provide an optical module and an optical system with a semiconductor element arranged on a circuit carrier, in which the possible tolerance chain is minimized as much as possible, so that reliable optical quality without adjustment is possible with simple and inexpensive installation. and in particular focusing effort can be made available and is maintained over the life of the module or system. In addition, necessary measures against external light radiation or other environmental influences from the front should be avoided as far as possible.

This task is solved with the features of the independent patent claims. Advantageous embodiments of the invention, which can be used individually or in combination with one another, are specified in the dependent claims.

The invention is based on the generic optical module in that the lens unit for projecting electromagnetic radiation onto the semiconductor element comprises a type of lens holder which is an integral part of the housing of the semiconductor element. This can be easily achieved, especially when using injection-molded plastic housings, since in addition to the actual housing shape, the edge area in particular can be designed in almost any way, in particular with a holding area for a lens arrangement with a defined focus on the chip. In this way First, a housed chip can be manufactured as a standard SMD (= Surface Mounted Device) component, which already has a holder for the later assembly of the optics. For the first time, the tolerance range that is available for focusing is only dependent on the lens arrangement itself. In addition, the proposed solution has the advantage that the incident light from the side is completely eliminated by the integrative design of the lens holder and chip housing.

In a preferred embodiment of the invention, the area holding the lenses is formed in one piece with the housing, for example from a thermosetting material.

Alternatively, the area holding the lenses is preferred, e.g. after a two-component injection molding process, molded onto the housing. This advantageously makes it possible to selectively use different plastics. For example, it has proven useful to form the area holding the lenses from a thermoplastic material and the housing of the semiconductor housing from a thermosetting material.

The major difference between heat deformable thermoplastics and heat non-deformable thermosets is due to the behavior of the respective plastic during shaping. When a thermoplastic is heated and pressed into a mold, there is no chemical reaction. After the plastic has cooled down in the mold and has hardened, it could be brought back into another shape by heating it again without the characteristics of the plastic changing noticeably. This property can also be advantageous for the connections described below. can be used by at least one lens with the area holding it.

Thermosets, on the other hand, change chemically as they are brought into their final form. They react with polycondensation and network to form a spatial grid. This hardening by changing the structure of the molecule is advantageous, in particular with regard to fixing the lead frame of a semiconductor component, and is irreversible: once a thermoset has been molded, it can no longer be changed. Thermosets include e.g. Phenolic resins, melamines and the urea resins.

A lens arrangement with a plurality of lenses and possibly at least one diaphragm in the form of a packet is preferably provided. The optical quality can be improved by a lens with a plurality of lenses, which is also possible within the scope of the present invention, in particular since it is possible to work with small tolerances. In this context, it is also particularly advantageous that the lenses and possibly the

Faceplate are in direct contact with each other. As a result, fluctuations in the lens arrangement in the Z direction, that is, in the direction in which the lenses follow one another, are practically excluded. The tolerances are only dependent on the lens arrangement itself. It is also particularly useful that the relative positions of the lenses to one another are determined by the geometry of the lenses and, if necessary, diaphragms themselves. The arrangement of the lenses can also be determined in the XY direction by the lenses themselves, namely by designing contact surfaces of the lenses or diaphragms accordingly. It is particularly useful that exactly one of the lenses or apertures is in direct contact with the lens holder. Since the lenses determine their relative positions with one another, it is sufficient to fix exactly one lens or diaphragm with the lens holder. In this way, the entire lens arrangement is aligned with respect to the semiconductor element, as a result of which the advantageous optical quality can ultimately be ensured. In this context, it is particularly advantageous that the exactly one lens is connected to the lens holder in a watertight and dust-tight manner. For this purpose, the foremost lens is advantageously selected as the lens which interacts with the lens holder for sealing. This can be done, for example, in such a way that the exactly one lens is connected to the lens holder by ultrasound, laser welding and / or adhesive methods; if necessary, alternatively or cumulatively using screws and / or putty.

It can also be provided that the lens arrangement is snapped into the area holding the lenses by means of latching means. This also ensures exact positioning. It should also be emphasized that this makes it easier to separate the lenses from the other components, in particular the expensive semiconductor element. The sealing effect is provided in a particularly advantageous manner, in particular in connection with snap mounting, in that the lenses have a hard and a soft component, the soft component being arranged on the circumference of the lenses for sealing. The soft component also supports the general requirement that when snapping be careful not to introduce any tension into the lenses; Tensions would always have a negative impact on the optical properties. As an alternative to an adhesive or welded connection or a snap assembly, a specially designed holding element (molded ring) can be provided for fixing the lens arrangement in the area holding the lenses.

The holding element preferably has a hard and at least partially a permanently elastic component. A permanently elastic component, which is preferably circumferentially formed, can at the same time serve, in particular, to seal the lens arrangement against moisture and dirt - in addition to its own compensation function for any mechanical and / or thermal stresses that may occur. The permanently elastic component is preferably formed on the circumference adjacent to the lens. In the area of the harder component, the holding element is arranged on the area holding the lenses, for example ultrasonically or laser-welded, glued, riveted, molded on or by means of another similarly easily automated connection method. Screw and snap connections are also conceivable. The hard component of the retaining ring preferably contains a thermoplastic material. Accordingly, a permanently elastic component that preferably contains thermoplastic elastomers (TPE) or silicone or the like has proven itself. In order to provide a uniform and easy-to-use component, the permanently elastic component is preferred, e.g. after one

Two-component injection molding molded onto the hard component or vice versa.

It can furthermore be particularly advantageous that undesired optical effects, in particular due to the incidence of light from the side, by blackening and / or matting or by using total reflection, are prevented by adding appropriate pigments to the region holding the lenses. given are. These are examples of suitable measures.

The invention also consists in an optical system with an optical module of the type mentioned above. In this way, the advantages of the optical module also come into play in the context of an overall system.

The invention is based on the knowledge that by designing a chip housing with an integrated area holding the lenses before mounting the lenses, a chip can be fitted using SMD technology and a camera module can be built up with mounting the lenses, in which any mechanical focus adjustment is dispensed with can be. This means that the module can be manufactured fully automatically, which has the advantage of reducing the manufacturing and assembly costs for large numbers of pieces. Furthermore, the optical module can be developed without moving parts such as threads or fixing screws, which leads to greater reliability. Due to the small tolerances of the structure in the x and y axes, the chip surface does not have to be unnecessarily large, which makes the camera chip cheaper. The construction of such a module can be made relatively compact, which has the advantage that the camera module can also be used in applications where space is limited. Finally, the integrative structure also advantageously offers protection against extraneous light radiation.

The invention can be used particularly useful in the implementation of video systems, possibly in combination with radar systems, ultrasound systems or the like in the motor vehicle sector. The invention will now be explained by way of example with reference to the accompanying drawings based on preferred embodiments.

They show schematically:

1 shows the perspective view of an optical module according to the invention; and

Fig. 2 shows the module of Fig. 1 in a sectional view along the line A-A.

In the following description of the preferred embodiments of the present invention, identical reference symbols designate identical or comparable components.

1 shows the perspective view of an optical module according to the invention with a circuit carrier 10; an SMD-housed semiconductor element 12 arranged on the circuit carrier 10; and a lens unit 14; 16, 18, 20; 21 for projecting electromagnetic radiation onto the semiconductor element 12.

Fig. 2 shows the module of Fig. 1 in a sectional view along a section line A-A.

According to the invention, the lens unit comprises a lens holder 14, which is an integral part of the housing 13 of the semiconductor element 12. In the present exemplary embodiment, the area 14 holding the lenses is preferably formed in one piece with the housing 13, for example from one Typical duoplastic material for chip housings, which is advantageously particularly suitable for a snap, screw and / or snap connection between a lens 20 held in the area 14 and the area 14. Alternatively, a molded connection of the lens arrangement 16, 18, 20; 21 holding area 14 with the housing 13 conceivable.

The semiconductor element 12 can, according to the current technology, e.g. be designed as CMOS or CCD. The connection between the housed semiconductor element 12 and the circuit carrier 10 takes place via so-called leadframes 30, which are contacted via gold wires 28 with bond points (not shown) formed on the semiconductor chip 12. To protect the solder joint between leadframe 30 and circuit carrier 10 from a broken contact, e.g. due to mechanical reasons

Voltages, the housing 13 of the chip 12 is preferably additionally glued to the circuit carrier 10. So-called SMD adhesives or the like are suitable for this.

The circuit carrier 10 itself is preferably designed as a rigid PCB. This 10 can be electrically connected to other rigid circuit boards (not shown) via a flat cable. Such a separate electrical connection can advantageously be omitted if a flexible printed circuit board is used as the circuit carrier 10, which at the same time serves for the electrical coupling (for example by means of a plumb bob) (not shown). In terms of angle and position etc., these so-called rigid-flex systems are a particularly flexible solution for connecting the circuit carrier 10 or the module to a controller or circuit board (not shown). In the area 14 of the chip housing 13 holding the lenses, three lenses 16, 18, 20 and a diaphragm 21 are preferably used for applications in a vehicle interior. The lenses 16, 18, 20, like the diaphragm 21, are shaped such that they assume a defined position relative to one another within the region 14 of the housing 13 that holds the lenses. Furthermore, at least one of the lenses 16 is designed in such a way that it interacts with the region 14 holding the lenses in such a way that this 16 assumes a defined position relative to a surface 34 of the semiconductor element 12 that is sensitive to electromagnetic radiation. In addition, at least one lens 20 is connected to the holder 14 in a watertight and dustproof manner, for example via latching means 32. In this way, all lenses 16, 18, 20 and, if necessary, diaphragms 21 are adjusted with respect to the semiconductor element 12. This adjustment is not influenced by further measures, since the lenses 16, 18, 20; 21 holding area 14 is directly part of the semiconductor house 13.

By designing a chip housing 13 with an integrated one, the lenses 16; 18, 20; 21 holding area 14 the construction of a camera module, in which prior to assembly of the lenses 16, 18, 20; 21 a chip 12, 13 can be fitted with SMD technology and during the assembly of the lenses 16, 18, 20; 21 any mechanical focus adjustment can be dispensed with. This means that the module can be manufactured fully automatically, which has the advantage that the production and assembly costs are lower when there are large numbers of pieces. Furthermore, the module can be developed without moving parts such as threads or fixing screws, resulting in a higher one

Reliability leads. Due to the low tolerances of the structure 13; 14; 16, 18, 20; 21 also in the x and y axes, the chip surface 34 does not have to be unnecessarily large, which is the camera chip 12 makes cheaper. The structure of such a module can be made very compact, which has the advantage that the camera module can also be used in applications with limited space. Furthermore, the structure offers the possibility of designing a hermetically sealed module that is well protected against environmental influences such as moisture, dust or the like.

The features of the invention disclosed in the above description, in the drawings and in the claims can be essential for realizing the invention both individually and in any combination. It is particularly suitable for applications in the interior and / or exterior of a motor vehicle.

Claims

claims

1. Optical module with a circuit carrier (10); - A housed semiconductor element (12) arranged on the circuit carrier (10); and - a lens unit (14; 16, 18, 20; 21) for projecting electromagnetic radiation onto the semiconductor element (12); That is, the lens unit comprises an area (14) holding the lenses (16, 18, 20; 21), which is an integral part of the housing (13) of the semiconductor element (12).

2. Optical module according to claim 1, so that the region (14) holding the lenses (16, 18, 20; 21) holding the lenses (16, 18, 20; 21) is formed in one piece with the housing (13), preferably from a thermosetting material.

Optical module according to claim 1, so that the area (14) holding the lenses (16, 18, 20; 21), e.g. after a two-component injection molding process, is molded onto the housing (13).

4. The optical module as claimed in claim 3, so that the region (14) holding the lenses (16, 18, 20; 21) holding the lenses (16, 18, 20; 21) contains thermoplastic material and the housing (13) contains thermosetting material.

Optical module according to one of the preceding claims, characterized in that the lens unit (14; 16, 18, 20; 21) comprises a plurality of lenses in the form of a package, the lenses (16, 18, 20) and possibly at least one diaphragm (21 ) are preferably in direct contact with one another, and the relative positions of the lenses (16, 18, 20) and possibly the diaphragm (21) with respect to one another are preferably determined by the geometry of the lenses or diaphragm itself.

6. Optical module according to one of claims 1 to 5, characterized in that exactly one (20) of the lenses (16, 18, 20; 21) with the lens holder (14), preferably waterproof and dustproof, are in direct contact, the exactly one lens (20) is preferably fixed to the lens holder (14) by ultrasound, laser welding and / or adhesive methods.

7. Optical module according to one of claims 1 to 5, characterized in that the lenses (16, 18, 20; 21) is snapped into the lens holder (14) via latching means (32), the purpose of forming water and dust permeability Lenses (16, 18, 20) or diaphragm (21) preferably have a hard and a soft component, and wherein the soft component is designed for sealing on the circumference of the lenses (16, 18, 20; 21).

8. Optical module according to one of claims 1 to 5, characterized in that the lenses (16, 18, 20; 21) by means of a holding element in the region (14) of the lens holding the lens. housing (13), the holding element preferably having a hard and a permanently elastic component, which is designed for sealing and stress compensation on the periphery of the lens (20), and wherein the holding element with its hard component by ultrasound, laser welding and / or an adhesive or riveting process or by means of a snap or screw connection to the area (14) holding the lenses (16, 18, 20; 21).

9. Optical module according to one of the preceding claims, characterized in that the lenses (16, 18, 20; 21) holding area (14) pigments are added, which lead to blackening and / or matting or to total reflection, which prevents unwanted optical effects, especially due to the incidence of light from the side.

10. Optical system with an optical module according to one of the preceding claims.