CN104051449A - Optical distance sensing device and assembly method thereof - Google Patents

Abstract

The invention discloses an optical distance sensing device and an assembling method thereof, wherein the optical distance sensing device comprises: the light-emitting unit and the photosensitive unit are electrically connected with the first substrate, the light-emitting unit comprises a second substrate and a light-emitting element electrically connected with the second substrate, the photosensitive unit comprises a third substrate, an opaque upper cover and a photosensitive element electrically connected with the third substrate, the opaque upper cover is connected with the third substrate to be arranged above the photosensitive element, an opening corresponding to the photosensitive element is formed in the opaque upper cover, a light signal emitted by the light-emitting element can be emitted into the photosensitive element through the opening, and the light signal in the direction beside the photosensitive unit is shielded by the opaque upper cover.

Description

Optical distance sensing device and assembly method thereof

technical field

The present invention relates to an optical distance sensing device and an assembly method thereof, in particular to an optical distance sensing device and an assembly method thereof for board-level assembly of a plurality of semiconductor-packaged chips.

Background technique

Optoelectronic devices are widely used, among which optical sensing plays an indispensable role in many automated machinery, industrial machinery, semiconductor equipment, machine tools, etc. For example, proximity sensing (proximity sensing) passes through two optical Components, a light-emitting element, such as a light-emitting diode (LED) and a photosensitive element, use the photosensitive element to capture and process the light signal from the light-emitting element to detect whether an object exists, so that the controller can understand the presence or absence of the current mechanism , the position of the object or the number of passages, etc. In detail, a light-emitting element, such as an infrared light-emitting diode, emits a beam of infrared signals. If an object approaches within the detection range, part of the infrared signal will be reflected when it hits the object. At this time, the photosensitive element, such as : The infrared sensor can detect the reflected infrared signal. After signal conditioning, analog-to-digital conversion, and other processing processes, a microprocessor or microcontroller can apply the digitized signal for subsequent processing.

Several common assembly structures are proposed here. Firstly, as shown in FIG. 1 , the traditional optical distance sensing device 1 is composed of a light emitting unit 40 and a photosensitive unit 50 . Similar to general electronic chips, after the light-emitting element 42 and the photosensitive element 52 are cut into chips from the wafer, they also need to be mounted on the substrates 41 and 51 through the semiconductor packaging process to increase their mechanical strength. The gold wires 44, 54 construct the power connection relationship and the signal output/input connection channel, and seal the light-emitting element 42 and the photosensitive element 52 in the transparent substance 43, 53 to maintain their barrier properties from water vapor and air, so as to form The light emitting unit 40 and the photosensitive unit 50 . Afterwards, the light-emitting unit 40 and the photosensitive unit 50 are installed on the printed circuit board 10 through board-level assembly, and electrically connected to the printed circuit board 10 by soldering substances 41 and 51 to form the optical distance sensing device 1 . However, since there is no shielding element between the light-emitting unit 40 and the photosensitive unit 50, the light signal emitted by the light-emitting unit 40 does not need to pass through the path of the protective cover 30 and reflected back to the photosensitive unit 50 by the object 20 (in order to realize Indicated by line arrows), it can directly enter the photosensitive unit 50 from the side or reflect at a large angle on the protective cover 30 and enter the photosensitive unit 50 (indicated by dashed arrows). This will cause misjudgment of objects approaching due to misreading or excessive background noise, which is not a reliable design.

In order to improve the above-mentioned shortcoming of Fig. 1, the common practice at present is to install a light-shielding rubber 60 between the printed circuit board 10 and the protective cover 30, the optical distance sensing device 2 shown in Fig. 2 and the optical distance sensing device shown in Fig. 3 Measuring device 3. The difference between Fig. 2 and Fig. 3 is only that the light-emitting unit 40 and photosensitive unit 50 in Fig. 2 are directly mounted on the printed circuit board 10, while the light-emitting unit 40 and photosensitive unit 50 in Fig. 3 are mounted on a flexible printed circuit board 13 , the flexible printed circuit board 13 is installed on the printed circuit board 10 through a connection unit 14 . However, regardless of the structure shown in FIG. 2 or FIG. 3 , the light-shielding rubber 60 is directly connected to the printed circuit board 10 and the protective cover 30 between the light-emitting unit 40 and the photosensitive unit 50 and outside, so as to prevent light signals from passing through the light-emitting unit 40 and the photosensitive unit 50 to enter the photosensitive unit 50 or reflect on the protective cover 30 at a large angle to enter the photosensitive unit 50 . However, since the assembling process of the light-shielding rubber 60 can only be done manually, it cannot be integrated with the current industrial machines, and faces the problems of difficult assembly, time-consuming and high cost.

Therefore, the industry has proposed a structure that can improve the aforementioned problems. The optical distance sensing device 4 shown in FIG. Similar to the single crystal semiconductor package, the power supply connection relationship and the signal output/input connection channel are also constructed with gold wire 74 through the gold wire manufacturing process, and then the light emitting element 72 and the photosensitive element 72 are sealed in a transparent substance 77 Maintain its barrier properties with water vapor and air. However, after the gold wire process, the optical distance sensing device 4 here is further equipped with a light-shielding cover 75 to be directly connected to the substrate 71 . Two openings 76 are formed on the light-shielding cover 75, so that the light signal sent by the light-emitting element 72 can be emitted from one opening 76 and enter the photosensitive element 73 from the other opening 76. Light signal from outside. Afterwards, the polycrystalline optical distance sensing unit 70 is installed on the printed circuit board 10 by surface mount technology, and is electrically connected to the printed circuit board 10 through the solder material 17 .

If the light signal reflected from the protective cover 30 is also to be shielded, we need to change to the structure of the optical distance sensing device 5 shown in FIG. 5 for assembly. Comparing Fig. 5 with Fig. 4, a light-shielding rubber 61 is added on the light-shielding cover 75 more. However, it is conceivable that the assembling process of the light-shielding rubber 60 can only be done manually and cannot be integrated with the current industrial machines, thus facing the problems of difficult assembly, time-consuming and high cost.

Therefore, how to take into account the optical characteristics, cost and manufacturing complexity when assembling the optical distance sensing device is an urgent research topic.

Contents of the invention

An object of the present invention is to provide an optical distance sensing device and its assembly method, through the opaque upper cover installed in the photosensitive unit during semiconductor packaging, to shield optical noise and maintain good signal quality.

Another object of the present invention is to provide an optical distance sensing device and its assembly method, which can be used for semiconductor packaging with an opaque upper cover compatible with current industrial machines, thereby simplifying the assembly process and reducing the process cost.

According to the present invention, an optical distance sensing device and an assembly method thereof are provided. The optical distance sensing device includes: a first substrate on which a light emitting unit and a photosensitive unit are arranged next to the light emitting unit, the light emitting unit and the photosensitive unit They are all electrically connected to the first substrate, the light-emitting unit includes a second substrate and a light-emitting element is electrically connected to the second substrate, and the photosensitive unit includes a third substrate, an opaque upper cover, and a photosensitive element electrically connected to the third substrate. Sexual connection, the opaque upper cover is connected with the third substrate to be arranged above the photosensitive element, and an opening is formed corresponding to the photosensitive element, wherein a light signal emitted by the light emitting element can enter the photosensitive element through the opening, but beside the photosensitive unit The light signal in the side direction is blocked by the opaque cover.

According to the present invention, a method for assembling an optical distance sensing device is provided, comprising the following steps: (A) assembling a light-emitting element on a second substrate and electrically connecting the second substrate to form a light-emitting unit; (B) A photosensitive element is installed on the third substrate to be electrically connected to the third substrate, and an opaque upper cover is arranged above the photosensitive element to form a photosensitive unit, and an opening corresponding to the photosensitive element is formed in the opaque upper cover; and (C) in a The light-emitting unit and the photosensitive unit are installed on the first substrate and arranged next to the light-emitting unit, and the light-emitting unit and the photosensitive unit are electrically connected to the first substrate, so that a light signal emitted by the light-emitting element can enter the photosensitive element through the opening. The light signal in the direction beside the photosensitive unit is blocked by the opaque upper cover.

The aforementioned light-emitting unit and photosensitive unit are preferably semiconductor-packaged structures. During the semiconductor packaging process, it is more preferable to seal the light-emitting element and the photosensitive element with a transparent material to block moisture and air. The formulation of the transparent substance is not limited, and it can be a compound of a single component or a mixture of multiple compounds mixed in certain proportions, such as a mixture of plastic, hardener, catalyst, epoxy, and transparent glue. The shape of the transparent substance can also be formed by a molding process and/or other forming processes, and there is no limitation here.

The aforementioned second and third substrates are substrates used at the semiconductor packaging level, and the first substrate is used at the board-level assembly level. The first, second and third substrates can protect the components arranged thereon and enlarge the electrode size, and the types thereof are not limited here, for example, they can be ball grid array (Ball GridArray) substrate, lead frame (leadframe), Copper foil substrate, resin substrate, printed circuit board substrate, flexible printed circuit board substrate, or other types of substrates. Therefore, specific types can be selected according to the pin specifications of the light-emitting unit and photosensitive unit or the specifications of the semiconductor substrate. substrate.

The material of the opaque upper cover is not limited, and can be made of any opaque material that can block light, for example, resin, nylon, plastic, metal, liquid crystal polymer (Liquid crystalpolyester), or other opaque materials can be used, preferably It is a black opaque upper cover made of high temperature resistant material, which is not limited in the present invention. For example, PA6T, PA9T, PA66, PPA, HTN, PA46, etc. can be used for nylon, polyphenylene sulfide (PPS) resin can be used for resin, and PEK, PEEK, TPI, etc. can be used for plastic. Secondly, the opaque upper cover can optionally include other detailed structures, such as an additional front plate and at least one side wall connected to the front plate, the front plate can partially cover the upper surface of the photosensitive unit, so as to block part of the reflection from the protective cover The side wall can be connected with the third substrate through an adhesive substance on the outside of the photosensitive unit, so as to prevent the ambient light source from interfering with the photosensitive element from the outside direction. Similarly, the formulation of the aforementioned adhesive substance is not limited, but epoxy resin is preferred. The opaque cover can be made by molding, injection molding or other techniques, without limitation.

Therefore, the present invention uses an opaque upper cover that cooperates with the semiconductor packaging process to shield optical noise, improve the optical signal components reflected from close objects into the photosensitive element, so as to improve the quality of optical signals read by the optical distance sensing device, and at the same time The assembly process of the optical distance sensing device is simplified and the process cost is reduced.

Description of drawings

FIG. 1 shows a schematic cross-sectional structure diagram of a conventional optical distance sensing device.

FIG. 2 shows a schematic cross-sectional structure diagram of another conventional optical distance sensing device.

FIG. 3 shows a schematic cross-sectional structure diagram of another conventional optical distance sensing device.

FIG. 4 shows a schematic cross-sectional structure diagram of another conventional optical distance sensing device.

FIG. 5 shows a schematic cross-sectional structure diagram of another conventional optical distance sensing device.

FIG. 6 shows a schematic cross-sectional structure diagram of an optical distance sensing device according to an embodiment of the present invention.

Detailed ways

To further illustrate various embodiments, the present invention provides drawings. These drawings are part of the disclosure content of the present invention, which are mainly used to illustrate the embodiments, and can be used in conjunction with the relevant descriptions in the manual to explain the operating principles of the embodiments. With reference to these contents, those skilled in the art should understand other possible implementations and advantages of the present invention. Components in the drawings are not drawn to scale, and similar component symbols are generally used to denote similar components.

First please refer to FIG. 6 , which shows a schematic cross-sectional structure of an optical distance sensing device according to an embodiment of the present invention. Here, an optical distance sensing device 6 including a light emitting unit 40 and a photosensitive unit 57 is used as an example. However, the present invention is not limited thereto, and other combinations including more than one light emitting unit 40 or photosensitive unit 57 may also be possible. As shown in the figure, the optical distance sensing device 6 includes a first substrate 18 , a light emitting unit 40 , a photosensitive unit 57 and a protective cover 30 . The light emitting unit 40 and the photosensitive unit 57 are preferably semiconductor-packaged first, and then installed on the first substrate 18 through the soldering materials 11 and 12 in the board-level assembly process. Here, the light-emitting unit 40 illustratively includes a second substrate 41, a light-emitting element 42, a transparent substance 43, and several gold wires 44; the photosensitive unit 57 includes a third substrate 51, a photosensitive element 52, and several gold wires 54 , a transparent substance 55 and an opaque upper cover 56 .

The semiconductor packaging process of the light-emitting unit 40 is first to assemble the light-emitting element 42 on the second substrate 41. It should be noted that the type of the second substrate 41 is not limited here. For example, it can be a Ball Grid Array (Ball Grid Array) ) substrates, leadframes, copper foil substrates, resin substrates, printed circuit board substrates or other types of substrates, specific types of substrates can be selected according to the pin specifications of the light emitting elements 42 disposed thereon. The second substrate 41 can protect the light emitting element 42 disposed thereon and enlarge the electrodes of the light emitting element 42 . The process steps of assembling the light-emitting element 42 on the second substrate 41 are not limited, depending on the type of the second substrate 41. Here, the second substrate 41 is, for example, a lead frame, and the light-emitting element 42 is, for example, an infrared light emitting device cut from a wafer. Diode chips. The light-emitting element 42 can be first fixed on the second substrate 41 through a die-bonding process, and then a gold wire (wire bounding) process is performed to connect the light-emitting element 42 and the output on the second substrate 41 through the gold wire (bonding wire) 44. The electrodes (not shown in the figure) are electrically connected to achieve the electrical connection between the light-emitting element 42 and the conductor medium on the second substrate 41 , such as pins, balls, or other forms of conductor medium.

Next, the light emitting element 42 is sealed in the transparent substance 43 by a molding process. The formulation of the transparent substance 4 is not limited, and it can be a compound of a single component or a mixture of multiple compounds mixed in certain proportions, such as: a mixture of plastic, hardener, catalyst, epoxy resin, and transparent glue. After being sealed, the light-emitting element 42 can block moisture and other substances that will affect the normal operation of the light-emitting element 42 .

The semiconductor packaging process of the photosensitive unit 57 is mainly to assemble the photosensitive element 52 on the third substrate 51 to be electrically connected to the third substrate 51, and to arrange the opaque upper cover 56 above the photosensitive element 52 to form a photosensitive unit 57. The opaque upper cover An opening 563 is formed in 56 corresponding to the photosensitive element 52 . In detail, there are several variations: the first is to carry out the molding process to seal the photosensitive unit 57 in the transparent substance 55 after the semiconductor packaging process of the photosensitive unit 57 is carried out with the solid crystal and the gold wire process, and then in the second The opaque upper cover 56 is connected to the third substrate 51 through an adhesive substance (not shown) on the third substrate 51, so that the opaque upper cover 56 is disposed on the photosensitive unit 57 to shield light noise. The second is to connect the opaque upper cover 56 to the third substrate 51 via an adhesive substance (not shown) on the third substrate 51 after the semiconductor packaging process of the photosensitive unit 57 carries out the die-bonding and gold wire processes. The opaque upper cover 56 is arranged on the photosensitive unit 57 to shield light noise, and then the photosensitive unit 57 is sealed in a transparent substance 55 such as transparent glue. The third method is to seal the photosensitive unit 57 in a transparent substance 55 such as transparent glue after the semiconductor packaging process of the photosensitive unit 57 is carried out with the crystal bonding and gold wire process, and then the opaque upper cover 56 is formed by molding and placed on the on the photosensitive unit 57 to shield light noise. The fourth is to form a transparent substance 55 in the first molding process after the semiconductor packaging process of the photosensitive unit 57 is carried out with the die bonding and gold wire process, and then seal the photosensitive unit 57 in the transparent substance 55, and then pass through the second molding process. The opaque upper cover 56 formed by plastic process is disposed on the photosensitive unit 57 to shield light noise. Both the aforementioned first and fourth semiconductor encapsulation processes can form light-tunable structures in the transparent substance 55 during the molding step, such as light-concentrating lens structures or other types of structures.

The material of the opaque upper cover 56 is not limited, it can be made of any opaque material that can block light, for example, it can be made of resin, nylon, plastic, metal, liquid crystal polymer (Liquid crystalpolyester), or other opaque materials, preferably It is a black opaque upper cover made of high temperature resistant material, which is not limited in the present invention. For example, PA6T, PA9T, PA66, PPA, HTN, PA46, etc. can be used for nylon, polyphenylene sulfide (PPS) resin can be used for resin, and PEK, PEEK, TPI, etc. can be used for plastic. Here, the opaque upper cover 56 exemplarily includes a side wall 561 and a front plate 562 , and an opening 563 is formed on the edge of the front plate 562 corresponding to the photosensitive unit 57 thereunder. The side wall 561 can be connected to the third substrate 51 through an adhesive substance (not shown) on the outside of the photosensitive unit 57, so as to prevent ambient light from interfering with the photosensitive element 52 from the outside direction, and the front plate 562 can partially cover the photosensitive unit 57. The upper surface is used to block part of the light signal reflected from the protective cover 30 from entering the photosensitive unit 57 . The formulation of the adhesive substance is not limited, but epoxy resin is preferred. The opaque upper cover 56 can be made by molding, injection molding or other processes, without limitation.

It should be noted that the present embodiment does not limit the type of the third substrate 51, for example, it can be a ball grid array (Ball Grid Array) substrate, lead frame (leadframe), copper foil substrate, resin substrate, printed circuit board The substrate or other types of substrates can be selected according to the pin specification of the photosensitive element 52 disposed thereon. Afterwards, a board-level assembly process is carried out to assemble the light-emitting unit 40 and the photosensitive unit 57 on the first substrate 18 to be arranged next to the light-emitting unit 40, and to electrically connect the light-emitting unit 40 and the photosensitive unit 57 to the first substrate 18, so as to emit light. The light signal emitted by the element 40 can enter the photosensitive element 52 through the opening 563 , but the light signal in the side direction of the photosensitive unit 57 is blocked by the opaque upper cover 56 . In the board-level assembly process here, the light-emitting unit 40 and the photosensitive unit 57 are first fixed on the reserved position of the first substrate 18 with soldering materials 11 and 12. Usually, the reserved position has been equipped with corresponding pin points, so after soldering After that, the electrical connection between the light emitting unit 40 , the photosensitive unit 57 and the first substrate 18 is formed. At this time, the light-emitting unit 40 and the photosensitive unit 57 output/input electronic signals or power through the conductive medium on the first substrate 40, such as a connector or other forms of conductive medium, to perform light-emitting or photosensitive operations, so that the light-emitting element After being reflected by an object 20 located within a certain distance range, the light signal emitted by 42 can enter the photosensitive unit 57 through the opening 563 . However, the light signal emitted laterally from the light emitting element 42 and most of the light signal reflected from the protective cover 30 (indicated by a dotted line) will be shielded by the opaque upper cover 56 so as not to be detected by the photosensitive unit 57 . When the photosensitive unit 57 detects the reflected light signal, it converts the light signal into an electronic signal and outputs it to a back-end component (not shown in the figure), so as to confirm that there is an object 20 approaching.

It should be noted that the first substrate 18 is a substrate used at the board-level assembly level, which can protect the light-emitting unit 40 and the photosensitive unit 57 disposed thereon and enlarge the electrode size, and its type is not limited here. For example, it can be It is a printed circuit board substrate, a flexible printed circuit board substrate, or other types of substrates, so a specific type of substrate can be selected according to the specifications of the second substrate 41 or the third substrate 51 disposed thereon.

Therefore, the present invention uses an opaque upper cover that cooperates with the semiconductor packaging process to shield light noise, increase the light signal components reflected from the shield and enter the photosensitive element, so as to improve the quality of the signal read by the photosensitive element, and simultaneously simplify the assembly process and Reduce process cost.

The above description is based on multiple different embodiments of the present invention, wherein each feature can be implemented singly or in different combinations. Therefore, the disclosed embodiments of the present invention are specific examples to illustrate the principle of the present invention, and the present invention should not be limited to the disclosed embodiments. Furthermore, the foregoing descriptions and accompanying drawings are merely exemplary of the present invention and are not intended to limit it. Variations and combinations of other elements are possible without departing from the spirit and scope of the invention.

Description of main component symbols

1, 2, 3, 4, 5, 6 Optical distance sensing device

10 Printed Circuit Board

11, 12, 15, 16, 17 welding materials

13 Flexible printed circuit board

14 Connection unit

18 The first substrate

20 objects

30 Protective cover

40 Lighting Units

41 Second substrate

42 Light-emitting components

43 Transparent substances

44 gold thread

50, 57 photosensitive unit

51 The third substrate

52 photosensitive element

53 Transparent substances

54 gold thread

55 Transparent substances

56 opaque cover

60, 61 Shading rubber

70 Polycrystalline optical distance sensing unit

71 Substrate

72 Light-emitting components

73 photosensitive element

74 gold thread

75 shading cover

76 opening

77 Transparent substances

561 side wall

562 front panel

563 opening

Claims (16)

1. an optical distance sensing apparatus, is characterized in that:

One first substrate, other this luminescence unit of being located at of assembling one luminescence unit and a photosensitive unit on it, this luminescence unit and this photosensitive unit are all electrically connected with this first substrate, this luminescence unit comprises that a second substrate and a light-emitting component and this second substrate are electrically connected, this photosensitive unit comprises that one the 3rd substrate, an opaque upper cover and a photo-sensitive cell are connected with the 3rd electrical property of substrate, above this opaque upper cover system is connected to be arranged at this photo-sensitive cell with the 3rd substrate, wherein and be formed with an opening to should photo-sensitive cell;

Wherein, the smooth signal that this light-emitting component sends can be incident upon this photo-sensitive cell through this opening, but is covered by this opaque upper cover in this light signal system of the direction of this photosensitive unit side.

2. optical distance sensing apparatus as claimed in claim 1, wherein this opaque upper cover more forms a header board and at least one sidewall is connected with this header board, and this sidewall is connected with the 3rd substrate at the outside of this photosensitive unit one adhering substance.

3. optical distance sensing apparatus as claimed in claim 2, wherein this adhering substance is epoxy resin.

4. optical distance sensing apparatus as claimed in claim 1, wherein this opaque upper cover is a black non transparent upper cover.

5. optical distance sensing apparatus as claimed in claim 1, wherein this opaque upper cover is nylon, plastic cement, metal or liquid crystal polymer.

6. optical distance sensing apparatus as claimed in claim 1, wherein this opaque upper cover is for to make through molding.

7. optical distance sensing apparatus as claimed in claim 1, wherein this first substrate is a copper clad laminate, a lead frame, a resin substrate, a printed circuit board base board or a flexible printed circuit board base board.

8. optical distance sensing apparatus as claimed in claim 1, wherein this second substrate is a copper clad laminate, a lead frame, a resin substrate, a printed circuit board base board or a flexible printed circuit board base board.

9. optical distance sensing apparatus as claimed in claim 1, wherein the 3rd substrate is a copper clad laminate, a lead frame, a resin substrate, a printed circuit board base board or a flexible printed circuit board base board.

10. optical distance sensing apparatus as claimed in claim 1, wherein this light-emitting component and this photo-sensitive cell are all with a transparency material sealing.

11. optical distance sensing apparatus as claimed in claim 10, wherein this transparency material comprises the mixture of plastic cement, curing agent that arbitrary proportion mixes, catalyst, epoxy resin, transparent adhesive tape.

12. 1 kinds of optical distance sensing apparatus assemble methods, is characterized in that:

(A) on a second substrate, assemble a light-emitting component and this second substrate is electrically connected to form a luminescence unit;

(B) on one the 3rd substrate, assemble a photo-sensitive cell and be connected with the 3rd electrical property of substrate, and an opaque upper cover is arranged to this photo-sensitive cell top to form a photosensitive unit, in this opaque upper cover, be formed with an opening to should photo-sensitive cell; And

(C) on a first substrate, assemble other this luminescence unit of being located at of this luminescence unit and this photosensitive unit, and by this luminescence unit and this photosensitive unit and the electric connection of this first substrate, make the smooth signal that this light-emitting component sends be incident upon this photo-sensitive cell through this opening, but covered by this opaque upper cover in this light signal system of the direction of this photosensitive unit side.

13. optical distance sensing apparatus assemble methods as claimed in claim 12, wherein step (B) more comprises: make at least one sidewall of being connected with a header board of this opaque upper cover, be connected with the 3rd substrate at the outside of this photosensitive unit one adhering substance.

14. optical distance sensing apparatus assemble methods as claimed in claim 13, wherein step B) more comprise: using epoxy resin as this adhering substance, this sidewall of this opaque upper cover is connected with the 3rd substrate.

15. optical distance sensing apparatus assemble methods as claimed in claim 12, wherein step (B) more comprises: form this opaque upper cover with nylon, plastic cement, metal or liquid crystal polymer.

16. optical distance sensing apparatus assemble methods as claimed in claim 12, wherein step (B) more comprises: make this opaque upper cover with molding processing procedure.