LCOS module and forming method thereof

Abstract

The invention provides an LCOS (Liquid Crystal On Silicon) module and a forming method thereof. The LCOS module comprises an LCOS structure, a substrate, a cofferdam and top cover glass, the base, the cofferdam and the top cover glass define a sealed cavity; the LCOS structure is arranged in the sealed cavity, and the bottom of the LCOS structure is arranged on the substrate; the LCOS structure comprises an LCOS substrate, a glass substrate, a liquid crystal layer and frame glue, wherein the LCOS substrate and the glass substrate are oppositely arranged; the liquid crystal layer is located between the LCOS substrate and the glass substrate; the frame glue is used for attaching the LCOS substrate and the glass substrate, and the liquid crystal layer is surrounded by the frame glue. The LCOS structure is sealed for the first time through frame glue, a sealed cavity is defined by the base, the cofferdam and the top cover glass for secondary sealing, and permeation of water vapor is improved; the reliability of the LCOS module is improved, and the reflectivity of an LCOS product is not affected.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuit manufacturing, and in particular relates to an LCOS module and a forming method thereof. Background Art

[0002] The LCOS (Liquid Crystal on Silicon) structure is a new type of reflective projection display device that uses semiconductor silicon technology to control liquid crystals to project color images. The LCOS structure not only boasts high light efficiency, a compact size, a high aperture ratio, and mature manufacturing technology, but also easily achieves high resolution and full color expression.

[0003] The LCOS structure consists of a silicon substrate and a glass substrate positioned opposite each other, along with a sealant connecting the two substrates. Liquid crystal is filled in the sealant between the two substrates, relying solely on the sealant to provide a seal and prevent moisture penetration. During high-temperature and high-humidity reliability testing, the LCOS structure may experience reliability issues due to moisture penetrating the liquid crystal. Summary of the Invention

[0004] The purpose of the present invention is to provide an LCOS module, in which the LCOS structure is sealed once by frame glue and is sealed twice by a base, a cofferdam and a top cover glass to form a sealed cavity, thereby improving the permeability of water vapor; while improving the reliability of the LCOS module, the reflectivity of the LCOS product is not affected.

[0005] The present invention provides an LCOS module, comprising:

[0006] An LCOS structure, a substrate, a cofferdam, and a top cover glass; the substrate, the cofferdam, and the top cover glass enclose a sealed cavity; the LCOS structure is disposed in the sealed cavity, and the bottom of the LCOS structure is disposed on the substrate;

[0007] The LCOS structure includes: an LCOS substrate and a glass substrate arranged opposite to each other, a liquid crystal layer and a frame glue; the liquid crystal layer is located between the LCOS substrate and the glass substrate; the frame glue is used to bond the LCOS substrate and the glass substrate, and the frame glue surrounds the liquid crystal layer.

[0008] Furthermore, a light shielding layer is provided in a peripheral area of a surface of the glass substrate away from the liquid crystal layer, and an optical structural adhesive is provided between the top surface of the glass substrate and the bottom surface of the top cover glass.

[0009] Furthermore, an anti-reflection coating is provided on a surface of the top cover glass away from the glass substrate.

[0010] Furthermore, the cavity area outside the LCOS structure in the sealed cavity is filled with inert gas or glue.

[0011] Furthermore, the base and the cofferdam are an integral structure or a separate structure.

[0012] Furthermore, the material of the substrate includes: any one of ceramics, organic substrates or reinforced steel sheets.

[0013] Furthermore, a first flexible circuit board is provided on a surface of the base close to the LCOS substrate, and the pads on the LCOS substrate are electrically connected to the pads on the first flexible circuit board via a first wire.

[0014] Furthermore, the material of the base includes: reinforcing steel sheets; the LCOS substrate is bonded to the base by a soft structural adhesive; the cofferdam includes a connected horizontal cofferdam portion and a vertical cofferdam portion, a second flexible circuit board is provided on the upper surface of the horizontal cofferdam portion, and the solder pads on the LCOS substrate are electrically connected to the solder pads on the second flexible circuit board through a first wire.

[0015] The present invention also provides a method for forming an LCOS module, comprising:

[0016] S1. Providing a substrate, on which a cofferdam is arranged;

[0017] S2. Adhere an LCOS structure to the surface of the substrate located within the cofferdam; the LCOS structure includes an LCOS substrate and a glass substrate disposed opposite to each other, a liquid crystal layer, and a sealant; the liquid crystal layer is located between the LCOS substrate and the glass substrate; the sealant is used to adhere the LCOS substrate and the glass substrate, and the sealant surrounds the liquid crystal layer;

[0018] S3. Bonding the top cover glass to the cofferdam to form a sealed cavity; the LCOS structure is disposed in the sealed cavity.

[0019] Furthermore, after step S2 and before step S3, the method further includes: coating an optical structural adhesive on the surface of the glass substrate; after step S3, bonding the glass substrate and the top cover glass with the optical structural adhesive.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention provides an LCOS module and a method for forming the same, comprising: an LCOS structure, a substrate, a cofferdam, and a cover glass; the substrate, the cofferdam, and the cover glass enclose a sealed cavity; the LCOS structure is disposed within the sealed cavity, with the bottom of the LCOS structure disposed on the substrate; the LCOS structure comprises: an LCOS substrate and a glass substrate disposed opposite each other, a liquid crystal layer, and a sealant; the liquid crystal layer is located between the LCOS substrate and the glass substrate; the sealant is used to bond the LCOS substrate to the glass substrate and surround the liquid crystal layer. The LCOS structure is sealed primarily with the sealant, and then sealed again with the substrate, the cofferdam, and the cover glass enclosing the sealed cavity, thereby improving water vapor permeability. This improves the reliability of the LCOS module while maintaining the reflectivity of the LCOS product. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 2 is a cross-sectional diagram of a first example of an LCOS module according to an embodiment of the present invention.

[0023] Figure 2 FIG. 1 is a schematic top view of a first example of an LCOS module according to an embodiment of the present invention.

[0024] Figure 3 FIG. 4 is a schematic cross-sectional view of a second example of an LCOS module according to an embodiment of the present invention.

[0025] Figure 4 FIG. 4 is a schematic cross-sectional view of a third example of an LCOS module according to an embodiment of the present invention.

[0026] Figure 5 Schematic diagram of the process of forming an LCOS module according to an embodiment of the present invention.

[0027] Figures 6 to 9 Schematic diagram of the steps of the method for forming an LCOS module according to an embodiment of the present invention.

[0028] The accompanying drawings are numerals as follows:

[0029] 11, 12, 13-substrate; 21, 22, 23-dam; 31-LCOS substrate; 32-liquid crystal layer; 33-frame glue; 34-glass substrate; 35-optical structural glue; 36-light-shielding layer; 37-first conductive wire; 38-soft structural glue; 39-second conductive wire; 40-top cover glass; 41-conductive glue; 42-adhesive glue; 50-first flexible circuit board; 51-flexible circuit board; 52-second flexible circuit board. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are in a very simplified form and are not to exact scale, and are only used for the purpose of conveniently and clearly illustrating the embodiments of the present invention.

[0031] For ease of description, some embodiments of the present application may use spatially relative terms such as "above," "below," "top," "below," etc. to describe the relationship between one element or component and another (or other) elements or components as shown in the various figures of the embodiments. It should be understood that, in addition to the orientations described in the figures, the spatially relative terms are also intended to include different orientations of the device in use or operation. For example, if the device in the figures is turned over, the elements or components described as being "below" or "beneath" other elements or components will subsequently be positioned as being "above" or "above" other elements or components. The terms "first," "second," etc., hereinafter, are used to distinguish between similar elements and are not necessarily used to describe a specific order or chronological sequence. It is to be understood that, where appropriate, these terms used in this manner are interchangeable.

[0032] Figure 1 2 is a cross-sectional diagram of a first example of an LCOS module according to an embodiment of the present invention. Figure 2 FIG. 1 is a schematic top view of a first example of an LCOS module according to an embodiment of the present invention.

[0033] An embodiment of the present invention provides an LCOS module, such as Figure 1 and Figure 2 Shown, including:

[0034] The LCOS structure, substrate 11, cofferdam 21 and top cover glass 40; the substrate 11, cofferdam 21 and top cover glass 40 enclose a sealed cavity; the LCOS structure is disposed in the sealed cavity, and the bottom of the LCOS structure is disposed on the substrate 11;

[0035] The LCOS structure includes: an LCOS substrate 31 and a glass substrate 34 arranged opposite to each other, a liquid crystal layer 32 and a sealant 33; the liquid crystal layer 32 is located between the LCOS substrate 31 and the glass substrate 34; the sealant 33 is used to bond the LCOS substrate 31 and the glass substrate 34, and the sealant 33 surrounds the liquid crystal layer 32.

[0036] Specifically, a light shielding layer 36 is provided around the peripheral area of the side of the glass substrate 34 facing away from the liquid crystal layer 32. This layer prevents stray light from entering the non-photosensitive area, thereby preventing it from affecting the performance of the liquid crystal layer 32 and the LCOS substrate 31. The material of the light shielding layer 36 may include at least one of black photoresist, plastic, metal, and black paint. For example, the material of the light shielding layer 36 is black photoresist, a material that is photosensitive and opaque after curing. The black photoresist is exposed to a predetermined size. In this embodiment, the light shielding layer 36 can be formed using an exposure process, which is simple and easy to control, and the shape and size of the light shielding layer 36 can be very precise. Of course, the material of the light shielding layer 36 is not limited to black photoresist; it can also be made of plastic or metal, which provides greater wear resistance and stability. The material of the light shielding layer 36 can also be black paint, which can be applied through a spraying and baking process. The process for forming the light shielding layer 36 is not limited to exposure; it can also be coating or sputtering.

[0037] An optical structural adhesive 35 is disposed between the top surface of the glass substrate 34 and the bottom surface of the top cover glass 40, improving the reliability of the LCOS module without affecting the reflectivity of the LCOS structure. The design of the top cover glass 40 and the optical structural adhesive 35 not only addresses the problem of water vapor intrusion through secondary sealing, but also avoids light loss (reflectivity) through the optical structural design. The optical structural adhesive 35 has a certain refractive index, minimizing the optical performance loss of the LCOS module caused by the addition of the top cover glass 40. The optical structural adhesive 35 may include adhesive and highly reflective fillers added to the adhesive. The highly reflective fillers may include nano-sized titanium dioxide, aluminum oxide, or zinc oxide. The optical structural adhesive 35 scatters light and improves reflectivity. The display industry's viewing angle testing requirements use the ratio of the brightness in the full white (L255) state to the full black (L0) state as the viewing angle, which can also be expressed as a contrast ratio (CR). The optical structural adhesive 35 bonds the glass substrate 34 and the top cover glass 40, addressing the loss of CR and reflectivity.

[0038] The cover glass 40 can also be coated with an antireflective coating (not shown) on the side facing away from the glass substrate 34 to increase light transmittance. The optical structural adhesive 35, with a suitable refractive index, and the antireflective coating on the top surface of the glass substrate 34 minimize optical performance loss, with a theoretical loss of less than 3%. Optical performance verification data for the optical structural adhesive 35 shows no optical performance degradation.

[0039] The cavity area outside the LCOS structure within the sealed cavity is filled with an inert gas or glue. The cover glass 40 provides a secondary seal between the LCOS substrate 31 (silicon-based chip) and the liquid crystal layer 32. By filling the cavity with inert gas, the impact of moisture on the reliability of the LCOS structure is further reduced, meeting the requirements for in-vehicle reliability and moisture protection. The substrate can be made of ceramic or organic substrates. The substrate and cofferdam can be integrated or separate.

[0040] Figure 1 2 is a cross-sectional diagram of a first example of an LCOS module according to an embodiment of the present invention. Figure 1 In the first example of the LCOS module shown, the base 11 and the dam 21 are separate structures. A first flexible printed circuit board 50 is provided on the side of the base 11 near the LCOS substrate 31. The pads on the LCOS substrate 31 are electrically connected to the pads on the first flexible printed circuit board 50 via first conductive wires 37. These conductive wires can be made of gold, aluminum, copper, or other suitable materials.

[0041] Figure 3 FIG. 4 is a schematic cross-sectional view of a second example of an LCOS module according to an embodiment of the present invention. Figure 3 In the second example of the LCOS module shown, the base 12 and the cofferdam 22 are an integral structure. A flexible circuit board 51 is provided on the surface of the base 12 close to the LCOS substrate 31. The pads on the LCOS substrate 31 are electrically connected to the pads of the flexible circuit board 51 through a first wire 37. The first wire 37 can be a gold wire, an aluminum wire or a copper wire or other suitable materials. The LCOS module of the second example has been tested and verified to pass the reliability test of high temperature and high humidity, as well as the high and low temperature cycle test. An optical structural adhesive 35 with a suitable refractive index and an anti-reflection coating (not shown) on the upper surface of the top cover glass 40 are selected to achieve as little optical performance loss as possible, with a theoretical loss of <3%.

[0042] Figure 4 FIG. 4 is a schematic cross-sectional view of a third example of an LCOS module according to an embodiment of the present invention. Figure 4 In the third example of the LCOS module shown, the base 13 and the cofferdam 23 are separate structures. The material of the base 13 includes, for example, a reinforcing steel sheet. The LCOS substrate 31 is bonded to the base by a soft structural adhesive 38; the cofferdam 23 includes a connected horizontal cofferdam portion and a vertical cofferdam portion, and a second flexible circuit board 52 is provided on the upper surface of the horizontal cofferdam portion. The pads on the LCOS substrate 31 and the pads on the second flexible circuit board 52 are electrically connected through a first wire and assembled by hot pressing or soldering. A flexible circuit board (FPC for short) is a highly reliable and extremely flexible printed circuit board made of polyimide or polyester film as a base material. During use, since the rigidity and load-bearing capacity of the flexible circuit board are poor and it is easy to be damaged, some flexible circuit boards can be fitted with reinforcing steel sheets at relevant positions to increase the strength.

[0043] In the third example LCOS module, the overall packaging concept remains unchanged. Instead of a ceramic substrate, the base 13 uses a reinforced steel sheet to reduce costs. A soft structural adhesive 38 is used to address the deformation stress generated by the reinforced steel sheet. The cofferdam 23 is integrally formed, and an organic substrate can be used instead of ceramic to further reduce costs. The second flexible circuit board 52 and the base 13 (e.g., a reinforced steel sheet) form a rigid-flexible board. The LCOS substrate 31 is directly mounted on the reinforced steel sheet, and the top cover glass 40 is used to seal it. This improves the reliability of the LCOS module under high temperature and high humidity conditions while reducing costs.

[0044] The present invention also provides a method for forming an LCOS module, such as Figure 5 Shown, including:

[0045] Step S1, providing a substrate, and setting a cofferdam on the substrate;

[0046] Step S2: bonding an LCOS structure to the surface of the substrate within the cofferdam; the LCOS structure includes an LCOS substrate and a glass substrate disposed opposite each other, a liquid crystal layer, and a sealant; the liquid crystal layer is located between the LCOS substrate and the glass substrate; the sealant is used to bond the LCOS substrate and the glass substrate, and the sealant surrounds the liquid crystal layer;

[0047] Step S3: Bond the top cover glass to the cofferdam to form a sealed cavity; and arrange the LCOS structure in the sealed cavity.

[0048] After step S2 and before step S3, the method further includes: coating an optical structural adhesive on the surface of the glass substrate; after step S3, bonding the glass substrate and the top cover glass with the optical structural adhesive.

[0049] Specifically, the following Figures 6 to 9 The third example is used as an example for explanation.

[0050] Step S1: Figure 6 As shown, a base 13 is provided, and a cofferdam 23 is disposed on the base 13. In this example, the base 13 and the cofferdam 23 are separate structures. The base 13 may be made of, for example, reinforcing steel sheets. The cofferdam 23 includes a connected horizontal cofferdam portion and a vertical cofferdam portion. A second flexible circuit board 52 is disposed on one side of the upper surface of the horizontal cofferdam portion, and a second conductive wire 39 is disposed on the other side of the upper surface of the horizontal cofferdam portion. A soft structural adhesive 38 is applied to the upper surface of the base 13.

[0051] Step S2: Figure 7As shown, an LCOS structure is bonded to the surface of substrate 13 within cofferdam 23; substrate 13 and LCOS structure are bonded via soft structural adhesive 38. The LCOS structure includes an LCOS substrate 31 and a glass substrate 34 positioned opposite each other, a liquid crystal layer 32, and a sealant 33. Liquid crystal layer 32 is positioned between LCOS substrate 31 and glass substrate 34; sealant 33 is used to bond LCOS substrate 31 and glass substrate 34 together, and sealant 33 surrounds liquid crystal layer 32. By pressure-bonding first conductive wires 37, pads on LCOS substrate 31 are electrically connected to pads on second flexible circuit board 52 via first conductive wires 37. Pads on the lower surface of glass substrate 34 can be electrically connected to second conductive wires 39 via conductive adhesive 41.

[0052] Step S3: Figure 8 and Figure 9 As shown, the cover glass 40 is bonded to the cofferdam 23 to form a sealed cavity; the LCOS structure is disposed within the sealed cavity. Specifically, adhesive 42 is applied to the surface of the cofferdam 23, and optical structural adhesive 35 is applied to the surface of the glass substrate 34. While the edge of the cover glass 40 is bonded to the cofferdam 23 by adhesive 42, the optical structural adhesive 35 bonds the center area between the glass substrate 34 and the cover glass 40.

[0053] The material of the substrate 13 includes, for example, reinforcing steel sheets. During use, flexible circuit boards (FPCs) are easily damaged due to their poor rigidity and load-bearing capacity. Therefore, some flexible circuit boards can be fitted with reinforcing steel sheets at relevant positions to increase their strength. The substrate 13, the second flexible circuit board 52, and the cofferdam 23 constitute a circuit board with a cavity structure. The present invention mounts an LCOS substrate 31 (silicon-based chip) in the circuit board with a cavity structure, and the sealing design of the top cover glass 40 forms a secondary seal for the LCOS substrate 31 (silicon-based chip) and the liquid crystal layer 32, reducing the impact of water vapor on the reliability of the LCOS structure. The present invention improves the reliability of the LCOS module (LCOS product package) under high temperature and high humidity conditions. The present invention can implement the process using existing equipment without affecting brightness, has high product reliability, and can select a variety of materials.

[0054] In summary, the present invention provides an LCOS module and a method for forming the same, comprising: an LCOS structure, a substrate, a cofferdam, and a cover glass; the substrate, cofferdam, and cover glass enclose a sealed cavity; the LCOS structure is disposed within the sealed cavity, with the bottom of the LCOS structure disposed on the substrate; the LCOS structure comprises: an LCOS substrate and a glass substrate disposed opposite each other, a liquid crystal layer, and a sealant; the liquid crystal layer is disposed between the LCOS substrate and the glass substrate; the sealant is used to bond the LCOS substrate and the glass substrate, and the sealant surrounds the liquid crystal layer. The LCOS structure is sealed primarily with the sealant, and then secondary sealed with the substrate, cofferdam, and cover glass enclosing the sealed cavity, thereby improving moisture permeability. This improves the reliability of the LCOS module while maintaining the reflectivity of the LCOS product.

[0055] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. The methods disclosed in the embodiments are described briefly because they correspond to the devices disclosed in the embodiments. For relevant details, refer to the method description.

[0056] The above description is only a description of the preferred embodiment of the present invention, and does not limit the scope of the rights of the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. An LCOS module, characterized in that: include: LCOS structure, substrate, cofferdam and cover glass; the substrate, the cofferdam and the cover glass enclose a sealed cavity; The LCOS structure is disposed in the sealed cavity, and the bottom of the LCOS structure is disposed on the substrate; The LCOS structure includes: an LCOS substrate and a glass substrate arranged opposite to each other, a liquid crystal layer and a frame glue; the liquid crystal layer is located between the LCOS substrate and the glass substrate; the frame glue is used to bond the LCOS substrate and the glass substrate, and the frame glue surrounds the liquid crystal layer.

2. The LCOS module according to claim 1, wherein: A light shielding layer is provided in a peripheral area of a surface of the glass substrate on a side away from the liquid crystal layer, and an optical structural adhesive is provided between the top surface of the glass substrate and the bottom surface of the top cover glass.

3. The LCOS module according to claim 1, wherein: An anti-reflection coating is provided on a surface of the top cover glass away from the glass substrate.

4. The LCOS module according to claim 1, wherein: The cavity area outside the LCOS structure in the sealed cavity is filled with inert gas or glue.

5. The LCOS module according to claim 1, wherein: The base and the cofferdam are an integral structure or a separate structure.

6. The LCOS module according to claim 1, wherein: The material of the substrate includes: any one of ceramic, organic substrate or reinforcing steel sheet.

7. The LCOS module according to claim 1, wherein: A first flexible circuit board is provided on a surface of the base close to the LCOS substrate, and the pads on the LCOS substrate are electrically connected to the pads on the first flexible circuit board through a first wire.

8. The LCOS module according to claim 1, wherein: The material of the base includes: reinforcing steel sheet; the LCOS substrate is bonded to the base by soft structural adhesive; the cofferdam includes a connected cofferdam horizontal part and a cofferdam vertical part, and a second flexible circuit board is provided on the upper surface of the cofferdam horizontal part, and the solder pad on the LCOS substrate is electrically connected to the solder pad on the second flexible circuit board through a first wire.

9. A method for forming an LCOS module, characterized in that: include: S1. Providing a substrate, on which a cofferdam is arranged; S2, bonding an LCOS structure on the surface of the substrate within the cofferdam; The LCOS structure includes: an LCOS substrate and a glass substrate arranged opposite to each other, a liquid crystal layer and a sealant; the liquid crystal layer is located between the LCOS substrate and the glass substrate; the sealant is used to bond the LCOS substrate and the glass substrate, and the sealant surrounds the liquid crystal layer; S3. Bonding the top cover glass to the cofferdam to form a sealed cavity; the LCOS structure is disposed in the sealed cavity.

10. The method for forming an LCOS module according to claim 9, wherein: After step S2 and before step S3, the method further includes: coating an optical structural adhesive on the surface of the glass substrate; after step S3, bonding the glass substrate and the top cover glass with the optical structural adhesive.

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