WO2003105465A1

WO2003105465A1 - Optical module and optical system

Info

Publication number: WO2003105465A1
Application number: PCT/DE2003/001866
Authority: WO
Inventors: Josef Dirmeyer; Harald Schmidt; Stephan Voltz
Original assignee: Siemens Aktiengesellschaft
Priority date: 2002-06-11
Filing date: 2003-06-05
Publication date: 2003-12-18
Also published as: DE10225919B3

Abstract

An optical module comprises a lens holder (14), inside of which a lens arrangement consisting of, for example, three lenses (16, 18, 20) is placed. Preferably, the lenses (16, 18, 20) are clearly oriented toward one another and with regard to the lens holder (14) by their geometric design thereby rendering further optical adjustment of the system unnecessary. The lens holder (14) is provided in the form of a MID (molded interconnected device) having integrated conductor paths and serves as a circuit support for a semiconductor element (12) that is mounted using flip-chip technology.

Description

description

Optical module and optical system

The invention relates to an optical module with a circuit carrier, a semiconductor element arranged on the circuit carrier by means of flip-chip technology and a lens unit for projecting electromagnetic radiation onto the semiconductor element, the lens unit comprising a lens holder and a lens arrangement.

The invention further relates to an optical system with an optical module with a circuit carrier, a semiconductor element arranged on the circuit carrier by means of flip-chip technology and a lens unit for projecting electromagnetic radiation onto the semiconductor element, the lens unit comprising a lens holder and a Includes lens assembly.

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

For applications in the interior or exterior of a vehicle, there are high requirements 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 system of the type mentioned at the outset may only 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 realizing the optical systems. With conventional means it is therefore extremely difficult to find a hermetically sealed reliable one Build unit from a camera chip (CCD or CMOS) and optics.

Furthermore, it is important for the series use of the modules and systems that they can be manufactured inexpensively; this is fundamentally contrary to the requirements mentioned.

Another problem area with the modules and systems in question is related to the fact that the modules generally work with a fixed focal length. Therefore, the distance between the camera chip and the optics must be set and fixed during production. This leads to a considerable manufacturing effort. This also poses a quality risk.

It is also problematic and cost-driving that the entire manufacturing process of the electronics and optics either has to take place in a clean room or corresponding cleaning procedures have to be carried out in order to guarantee freedom from dust and thus to meet the quality requirements.

It is also problematic that lens surfaces in optical systems tend to fog up, particularly in the case of changing temperatures and high air humidity.

In poor lighting conditions, optical modules quickly reach their functional limits.

Particularly in systems which largely have a classic design consisting of a lens and a camera chip, the camera chip being applied in a housing on a circuit carrier, it is difficult to avoid the problems mentioned and to meet the quality requirements mentioned. The lens is adjusted to the camera chip during production, which sets the focus. By means of a suitable locking option, for example by means of a screwing or gluing, the lens is fixed relative to the camera chip. With classic systems, it is also extremely difficult to provide measures against fogging. For example, passivation coatings would cause excessive deterioration in the transmission and thus the optical properties. It is also difficult to take action in low light conditions. With classic systems, additional lighting is arranged on a separate circuit board. In this way, the radiation properties of the LEDs are largely determined.

However, further developed options are known with which the problems of the prior art can be avoided in part and which meet some of the requirements mentioned. EP 1 081 944 A2 discloses a module and a system which correspond to the genera mentioned at the outset. According to the categories, it is provided that the semiconductor element is arranged on the circuit carrier using flip-chip technology and that the circuit carrier is implemented as a flexible printed circuit board. In this way, the optical module can be sealed comparatively easily, since it is no longer necessary to arrange a system board next to the optics within a hermetically sealed housing. Rather, it can be provided outside the optical module. The flip-chip technology allows the optical module to be designed to be particularly small, which is particularly desirable in the motor vehicle sector and is associated with great advantages. The flip-chip technology is also easy to automate.

However, the optical module and the optical system of the prior art still have disadvantages. For example, no special precautions have been taken to ensure the optical quality of the module with low tolerances. Rather, the arrangement according to EP 1 081 944 A2 also has to be care is taken to position the components exactly so that the optics are not impaired due to installation tolerances.

The invention is therefore based on the object of providing an optical module and an optical system, so that a reliable optical quality can be made available with simple and inexpensive installation without adjustment and, in particular, focusing, and in particular Measures against fogging and poor lighting conditions can be implemented in a simple manner.

This object is achieved with the features of the independent claims.

Advantageous embodiments of the invention are specified in the dependent claims.

The invention builds on the generic optical module in that the lens holder is a MID ("molded interconnected device") with integrated conductor tracks and that the lens holder forms the circuit carrier for the semiconductor element.

MID technology is essentially based on the use of high-temperature thermoplastics, which are metallized in a structured manner. MIDs, i.e. spatial (3-dimensional) injection molded circuit carriers, are molded parts with an integrated circuit pattern structure. In particular, reference should be made to the rationalization potential of MID structures, and the environmental compatibility that is achieved in comparison to conventional circuit carriers should also be mentioned. MIDs can be produced in various ways, for example by producing the circuit carrier by single injection molding and then by

Hot stamping a metallization takes place, which is then structured by stamping. Also after the electro-metallization. Following the metallization, be it by hot stamping or galvanically, structuring can also be created using a 3D mask or an imaging laser process. The circuit carrier can also be produced by other plastic processing methods, for example by double injection molding. The metallization and the structuring of the MID can also be carried out in an integrated manner by means of a conductor foil. The aforementioned methods for producing MIDs are only to be understood as examples of a large number of known methods from the prior art, it being possible to use MIDs produced in any way within the scope of the present invention.

MIDs specifically related to the present invention offer the possibility of using a manufacturing technology with particularly low tolerances between the semiconductor element and the lens unit.

Due to the fact that printed conductors are integrated in the lens holder implemented as MID, the semiconductor element can be soldered or glued directly onto the lens holder. This makes the construction and assembly particularly easy. Furthermore, practically no additional uncertainty with regard to the optical structure is generated by such a method. The

Tolerance chain, which is expanded in conventional structures by the thickness of an additional circuit carrier and the thickness of any stabilizing elements that may be provided, has been reduced to a measure within the scope of the present invention.

A lens arrangement with at least one lens is advantageously provided. When using only one lens, it is avoided that additional optical tolerances are caused by a complicated lens structure. However, it is particularly preferred that the lens arrangement comprises a plurality of lenses in the form of a package. 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 are in direct contact with one another. As a result, fluctuations in the lens arrangement in the Z direction, that is to say in the direction in which the lenses follow one another, are practically excluded. The tolerances only depend on the lenses themselves.

It is also particularly useful that the relative positions of the lenses to one another are determined by the geometry of the lenses 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 accordingly.

It is particularly useful that exactly one of the lenses is connected to the lens holder. Since the lenses determine their relative positions with each other, it is sufficient to connect exactly one lens to 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 dustproof 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 exactly one lens is connected to the lens holder by ultrasound, laser welding and / or adhesive methods.

It can also be provided that the lens arrangement is snapped into the lens holder. This also ensures exact positioning. It should also be emphasized that in this way a possibility of separation between the lenses and the expensive semiconductor element can be ensured. Furthermore, it can be prevented in this way that temperature expansions of the various components have a negative effect on the adjustment and in particular the focusing.

The sealing effect is provided in a particularly advantageous manner, in particular in connection with a snap assembly, 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 the

It must be ensured that no snaps are brought into the lenses; Tensions would always have a negative impact on the optical properties. In this connection it should also be mentioned that temperature expansions can be compensated for.

It can also be particularly advantageous that undesired optical effects, in particular due to the incidence of light from the side, are prevented by blackening or by using total reflection. These are examples of suitable measures.

The optical module according to the invention can be developed in a particularly advantageous manner in that a ventilation duct is provided. In this way, the sealed module can "breathe". If the optical module is to be used for larger temperature fluctuations, it can be used as prove sensible to stick a DAE film (pressure compensation element) over an opening.

To protect against environmental influences that promote the aging process, it can be provided that the semiconductor element is covered with a globtop.

In a particularly preferred embodiment of the present invention it is provided that light-emitting diodes (LEDs) are arranged in the vicinity of the radiation entry area of the lens arrangement. In this way, the optical module can work even in poor lighting conditions.

In this context, it is particularly preferred that the light-emitting diodes are arranged in a ring around the lens arrangement and that the axes of the light-emitting diodes alternately form different angles with the axis of the module. Such a mutual arrangement of the light-emitting diodes serves to achieve diffuse illumination, which leads to a uniform illumination of the objects to be optically detected.

Furthermore, it is particularly preferred that the light-emitting diodes contact the lens holder implemented as MID directly. In this way, no additional components are required to supply the LEDs with voltage.

For example, the light-emitting diodes can be contacted on the lens holder by means of SMD technology. This is a common contacting technique that can also be used in the context of this preferred embodiment.

However, it is also possible for the light-emitting diodes to be contacted on the lens holder by means of bonding technology.

In a further preferred embodiment of the present invention it is provided that the module can be heated. In this way, fogging of the lenses in the event of temperature fluctuations can be counteracted. This is supported by the lens holder implemented as a MID, since in this way electrical current can be distributed variably without additional components.

In this context, it is particularly advantageous that thermally conductive plastics are provided for heating the module. This enables controlled heating of the entire module.

It is usefully provided that the module can be connected to a rigid circuit board via a flat cable. This is a particularly cost-effective solution for connecting the module to a controller.

It can also be advantageous that a connection of the module with a rigid circuit board is integrated with the lens holder implemented as MID. In this way, the number of components required is reduced again.

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.

This optical system is developed in a particularly useful manner in that the module can be connected to a rigid circuit board via a flat cable.

Furthermore, the optical system can also be developed in a particularly advantageous manner in that a connection of the module with a rigid circuit board is integrated with the lens holder realized as an MID.

The invention is based on the finding that it is possible to have a compact, highly integrated module solution with a low level To provide dimensions that are easy to assemble and therefore particularly inexpensive. It is possible to provide various functionalities with small dimensions at the same time. The optical module and the optical system are practically maintenance-free. Particularly in the sense of saving costs, it is also not necessary to optically adjust the optical module, since this is already present due to the geometrical design of the components and because the tolerance chain is shortened to one dimension. The module is stable and of high quality, and an integrated solution of sensor and optics in a modular design is provided. The modular design means that the number of variants is reduced, which is in the sense of the common parts concept that is always sought. The modules can be easily removed from the overall system. In particular, the lenses can also be removed from the optical module in the advantageous snap-in assembly and thus separated from the expensive semiconductor. Overall, an integrated solution with sensor, optics, lighting and heating device is provided, which uses a particularly inexpensive connection between the optics module and the main board. The invention can be used particularly useful in the implementation of video systems and in the combination of video systems with radar systems in the automotive field.

The invention will now be explained by way of example with reference to the accompanying drawings using preferred embodiments.

Show it:

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

FIG. 2 shows a second perspective illustration of an optical module according to the invention; FIG. 3 shows a perspective, partially sectioned illustration of an optical module according to the invention;

Figure 4 is an exploded perspective view of an optical module according to the invention;

FIG. 5 shows a sectional view of an optical module according to the invention; and

Figure 6 is a side view of another embodiment of an optical module according to the invention.

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

Figure 1 shows a perspective view of an optical module according to the invention. In the assembled state of the optical module shown, a lens holder 14 and a flat cable 36 can be seen. A (not visible) light-sensitive semiconductor element is arranged under the globtop 26, which can also be recognized. At the opposite end of the flat cable 36, the latter is provided with soldering pads 28, so that contact between the optical module and a circuit board, for example by iron soldering using the soldering pads 28, can be established without any further electrical connection. Recesses and light-emitting diodes 38 arranged therein can be recognized on the side of the optical module opposite the globtop 26.

Figure 2 shows a second perspective view of an optical module according to the invention. The special alternating arrangement of the light-emitting diodes 38 around a lens 20 provided for the radiation entry can be seen here. FIG. 3 shows a perspective, partially sectioned illustration of an optical module according to the invention. The interior of the lens holder 14 can be seen here. For a description of this arrangement, reference is also made to FIG. 4, which shows an exploded view of the optical module according to the invention, and to FIG. 5, which shows the optical module in a sectional view. Three lenses 16, 18, 20 are inserted into the lens holder 14. The lenses are shaped such that they assume a defined position within the lens holder 14 relative to one another. Furthermore, at least one of the lenses is designed such that it interacts with the lens holder 14 and thus also assumes a defined position with respect to the lens holder 14 and ultimately with respect to the semiconductor element 12. In this way, all lenses 16, 18, 20 are adjusted with respect to the semiconductor element 12. This adjustment is not influenced by further measures, since the semiconductor element 12 is arranged directly on the lens holder 14, which acts as a substrate. For this purpose, the lens holder 14 is implemented as a MID (“molded inter-connected device”) with integrated conductor tracks. The connection between the semiconductor element 12 and the lens holder 14 takes place by means of flip-chip technology in that a solder connection is made via solder bumps 30. The connection can then be reinforced with an underfill.

Furthermore, the light-emitting diodes 38 can also be seen in FIGS. 3, 4 and 5, the mutual arrangement being clearly shown in FIG.

The semiconductor element 12 may be configured as a CMOS or CCD ^'. In addition to or in addition to the soldered connection, an adhesive connection can also be provided. An underfill can be applied for reinforcement. In order to protect the expensive semiconductor element 12 against environmental influences, a globtop 26 is provided. In order to allow ventilation of the optical module in the case of, in particular, strong temperature fluctuations, an opening for ventilation can be provided. Just- if it is possible to place an adhesive DAE (adhesive pressure compensation element) on an opening.

The fact that the lens holder 14 is designed as a MID enables not only the power supply of the light-emitting diodes 38 via integrated conductor tracks but also heating of the entire module, which can be supported in particular by the use of heat-conducting plastic.

FIG. 6 shows a further embodiment of an optical module according to the invention. In addition to the elements already mentioned in connection with the figures described above, molded metalized pins with an integrated possibility for length expansion are provided here, so that there is a further possibility of connecting the optical module to further system components, for example with a circuit board.

The invention can be summarized as follows. An optical module has a lens holder 14, in which a lens arrangement comprising, for example, three lenses 16, 18, 20 is inserted. The lenses 16, 18, 20 are preferably clearly aligned with one another and with respect to the lens holder 14 due to their geometric design, so that no further optical adjustment of the system is required. The lens holder 14 is designed as a MID (“molded interconnected device”) with integrated conductor tracks and serves as a circuit carrier for a semiconductor element (12) applied using flip-chip technology.

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.

Claims

claims

1. Optical module with

- a circuit carrier,

a semiconductor element (12) arranged on the circuit carrier by means of flip-chip technology and

a lens unit (14, 16, 18, 20) for projecting electromagnetic radiation onto the semiconductor element,

wherein the lens unit (14, 16, 18, 20) comprises a lens holder (14) and a lens arrangement (16, 18, 20),

characterized ,

that the lens holder (14) is a MID ("molded interconnected device") with integrated conductor tracks and

that the lens holder (14) forms the circuit carrier for the semiconductor element (12).

2. Optical module according to claim 1, that a lens arrangement (16, 18, 20) with at least one lens is provided.

3. The optical module as claimed in claim 2, so that the lens arrangement (16, 18, 20) comprises a plurality of lenses in the form of a package.

4. Optical module according to claim 3, characterized in that the lenses (16, 18, 20) are in direct contact with one another.

5. Optical module according to claim 3 or 4, so that the relative positions of the lenses (16, 18, 20) are determined by the geometry of the lenses themselves.

6. Optical module according to one of claims 2 to 5, d a d u r c h g e k e n n z e i c h n e t that exactly one lens (20) is connected to the lens holder (14).

7. Optical module according to claim 6, d a d u r c h g e k e n n z e i c h n e t that the exactly one lens (20) is waterproof and dustproof connected to the lens holder (14).

8. Optical module according to claim 6 or 7, so that the one lens (20) is connected to the lens holder (14) by ultrasound, laser welding and / or adhesive methods.

9. Optical module according to one of claims 7 or 8, so that the lens arrangement (16, 18, 20) is snapped into the lens holder (14).

10. The optical module according to claim 9, so that the lenses (16, 18, 20) have a hard and a soft component, the soft component being arranged on the circumference of the lenses for sealing.

11. Optical module according to one of the preceding claims, characterized in that undesired optical effects, in particular due to the incidence of light from the side, are prevented by blackening or by using total reflection.

12. Optical module according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that a ventilation channel is provided.

13. Optical module according to one of the preceding claims, that the semiconductor element (12) is sealed with a glob top (26).

14. The optical module according to one of the preceding claims, that light emitting diodes (38) are arranged in the vicinity of the radiation entry area of the lens arrangement (16, 18, 20).

15. Optical module according to claim 14, d a d u r c h g e k e n n z e i c h n e t,

that the light-emitting diodes (38) are arranged in a ring around the lens arrangement (16, 18, 20) and

- That the axes of the light-emitting diodes (38) alternately include different angles with the axis of the module.

16. Optical module according to claim 14 or 15, so that the light-emitting diodes (38) contact the lens holder (14) realized as MID directly.

17. Optical module according to claim 16, characterized in that the light-emitting diodes (38) are contacted by means of SMD technology on the lens holder (14).

18. Optical module according to claim 16, so that the light-emitting diodes (38) are contacted on the lens holder (14) by means of bonding technology.

19. Optical module according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the module is heated.

20. Optical module according to claim 19, so that heat-conducting plastics are provided for heating the module.

21. Optical module according to one of the preceding claims, that the module can be connected to a rigid circuit board via a flat cable (36).

22. Optical module according to one of the preceding claims, that a connection of the module with a rigid circuit board is integrated with the lens holder (14) realized as a MID.

23. Optical system with an optical module according to one of claims 1 to 22.

24. Optical system according to claim 23, so that the module can be connected to a rigid circuit board via a flat cable (36).

25. Optical system according to claim 23, characterized in that a connection of the module with a rigid circuit board is integrated with the lens holder (14) realized as MID.