Abstract:
Disclosed herein is a light modulator module package, which is advantageous because a size of the module package is minimized and heat is efficiently dispersed while the optical properties of a light modulator device are maintained.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates, generally, to a light modulator module package, and more particularly, to a light modulator module package, which has a minimal size and efficiently disperses heat, while maintaining the optical properties of a light modulator device.  
         [0003]     2. Description of the Related Art  
         [0004]     Recently, micro-machining techniques for fabricating micro-optical components, such as micro-mirrors, micro-lenses or switches, micro-optical sensors, micro-biochips, and-micro-wireless communication devices, using a process of manufacturing a semiconductor device, have been developed. MEMS (Micro-Electro-Mechanical Systems), concerning the micro-machining techniques, and the devices and systems fabricated by such techniques, are regarded as rapidly growing technologies in a broad range of commercial applications.  
         [0005]     In particular, the micro-mirror has been commercially applied to large image displays, optical signal distributors, bar-code scanners, or optical signal decay units, or research for commercialization thereof is under study.  
         [0006]      FIG. 1  is a perspective view showing a conventional grating light modulator using electrostatic force, which is disclosed in U.S. Pat. No. 5,311,360.  
         [0007]     As shown in  FIG. 1 , a light modulator  10  disclosed in U.S. Pat. No. 5,311,360 has a plurality of equally spaced-apart deformable grating elements  18 , each of which includes a light-reflective planar surface and is suspended above a silicon substrate  16 . Further, an insulating layer  11  is deposited on the substrate  16 , after which a sacrificial silicon dioxide layer  12  is deposited.  
         [0008]     The silicon dioxide layer  12  is partially etched in such a way that the grating elements  18  are supported on the silicon dioxide layer  12  by a nitride frame  20 .  
         [0009]     To modulate light having a single wavelength of λ 0 , the modulator  10  is designed so that the thicknesses of the grating elements  18  and the silicon dioxide layer  12  total one quarter of λ 0 .  
         [0010]     The grating amplitude of the modulator  10 , which is defined by a vertical distance d between the reflective surfaces of the grating elements  18  and the reflective surface of the substrate  16 , is controlled by applying the voltage between the grating elements  18  and the substrate  16 .  
         [0011]     However, since the light modulator disclosed in U.S. Pat. No. 5,311,360 uses electrostatic force for position control of the micro-mirror, the switching voltage is relatively high (about 3 V) and the relationship between the applied voltage and the displacement is not linear, therefore resulting in unreliable light control.  
         [0012]     To overcome the above problems, thin-film piezoelectric light modulators have been proposed.  
         [0013]     In this regard, a conventional diffractive thin-film piezoelectric light modulator is shown in  FIG. 2 .  
         [0014]     As shown in  FIG. 2 , the conventional diffractive thin-film piezoelectric light modulator  100  includes a silicon substrate  101  having a depressed portion, an etching prevention layer  102  formed on the silicon substrate  101 , a lower support  111  having both ends of a bottom surface thereof attached to the silicon substrate  101  on both sides of the depressed portion of the substrate  101  to cover the depressed portion of the substrate  101 , lower electrode layers  112  and  112 ′ formed on both sides of the lower support  111 , piezoelectric material layers  113  and  113 ′ formed on the lower electrode layers  112  and  112 ′, upper electrode layers  114  and  114 ′ formed on the piezoelectric material layers  113  and  113 ′, and a micro mirror  115  formed at a central position on the lower support  111 .  
         [0015]     As such, it is preferable that such a conventional diffractive thin-film piezoelectric light modulator  100  be modularized to be commercially available. For modularization, various characteristics should be considered.  
         [0016]     Generally, in the conventional diffractive thin-film piezoelectric light modulator  100 , a drive integrated circuit is manufactured on another substrate and then modularized in hybrid form, rather than being integrated on the same die, resulting in high yields and low fabrication costs. Thus, the light modulator has been preferably manufactured in hybrid form.  
         [0017]     However, since the conventional diffractive thin-film piezoelectric light modulator  100  uses light, it cannot utilize the common modularization structure and process unchanged, unlike general devices, and also, it requires specialized components.  
         [0018]     In addition, the conventional diffractive thin-film piezoelectric light modulator  100  is disadvantageous because its active device has very low resistance to moisture due to structural properties, and hence, needs to be sealed from the exterior. Further, to stabilize operating properties and increase the lifetime of the device, the diffractive thin-film piezoelectric light modulator  100  should be designed to efficiently disperse heat generated when operating the device and irradiating light.  
       SUMMARY OF THE INVENTION  
       [0019]     Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide a light modulator module package, which is advantageous because it has minimal size and efficient heat dispersal while maintaining the optical properties of a light modulator device.  
         [0020]     In order to accomplish the above object, the present invention provides and light modulator module package, which comprises a printed circuit board (PCB) having an inner circuit and a hole to receive an incident beam of light□ a light transmissive lid attached to the upper surface of the PCB□ a light modulator device formed on the light transmissive lid to correspond to the position of the hole in the PCB so as to modulate the incident beam of light passing through the hole in the PCB to be emitted as diffracted lights□ one or more drive integrated circuits formed around the light modulator device to supply a driving voltage to the light modulator device, in response to an externally input control signal□ a connector formed on one side of the PCB to supply the externally input control signal to the drive integrated circuits□ and a molded part to enclose the PCB and the light transmissive lid to hold the PCB and the light transmissive lid.  
         [0021]     In addition, the module package further comprises a heat spreader formed on the light modulator device and the drive integrated circuits to disperse heat.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0023]      FIG. 1  is a perspective view showing a conventional grating light modulator using electrostatic force□ 
         [0024]      FIG. 2  is a sectional view showing a conventional diffractive thin-film piezoelectric light modulator□ 
         [0025]      FIG. 3  is an exploded perspective view showing a light modulator module package, according to a first embodiment of the present invention□ 
         [0026]      FIG. 4  is a sectional view showing the light modulator module package, according to the first embodiment of the present invention□ 
         [0027]      FIG. 5  is a flow chart showing a process of fabricating the light modulator module package, according to the first embodiment of the present invention□ 
         [0028]      FIGS. 6   a  to  6   f  are sectional views sequentially showing the process of fabricating the light modulator module package of  FIG. 5 □ and  
         [0029]      FIG. 7  is a sectional view showing a light modulator module package, according to a second embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]     Hereinafter, a detailed description will be given of a light modulator module package according to the present invention, with reference to the appended drawings.  
         [0031]      FIG. 3  is an exploded perspective view showing a light modulator module package, according to a first embodiment of the present invention, and  FIG. 4  is a sectional view showing the light modulator module package, according to the first embodiment of the present invention.  
         [0032]     As shown in  FIGS. 3 and 4 , a light modulator module package  200 , according to the first embodiment of the present invention, includes a PCB  210 , a light transmissive lid  220 , a light modulator device  230 , drive integrated circuits  240   a ,  240   b,    240   c  and  240   d,  a heat spreader  250 , a connector  260  and a molded part  270 .  
         [0033]     The PCB  210  has a hole located such that an incident beam of light is radiated on the light modulator device  230 . Also, the PCB  210  has an inner circuit to supply a control signal, which is input through the connector  260  from an external control circuit, to the drive integrated circuits  240   a,    240   b,    240   c  and  240   d.  The PCB  210  is bonded to the drive integrated circuits  240   a,    240   b,    240   c  and  240   d by means of wires to achieve electrical connection therebetween.    
         [0034]     The light transmissive lid  220  is attached to an upper surface of the PCB  210 , and is preferably formed of a light transmissive material of high quality to effectively transmit the incident beam of light.  
         [0035]     Further, the upper surface of the light transmissive lid  220 , which is opposite the surface thereof attached to the PCB  210 , is coated with an absorbent film or a scattering film so as to prevent irregular reflection of the incident beam of light from the upper surface of the light transmissive lid  220  by absorbing or scattering the incident beam of light. In addition, to decrease undesired radiation and reflectivity, a non-reflective film may be provided on either surface or both surfaces of the light transmissive lid  220 . As such, the absorbent film or the scattering film is formed of black metal.  
         [0036]     The light modulator device  230  is formed on the light transmissive lid  220  to correspond to the position of the hole in the PCB  210 , and thus, it functions to modulate the incident beam of light passing through the hole in the PCB  210  to be emitted as diffracted light.  
         [0037]     The light modulator device  230  is connected to the central portion on one surface of the light transmissive lid  220  through a flip chip, and has a rectangular cross-section which is relatively long in one direction.  
         [0038]     The light modulator device  230  is sealed from the exterior using an adhesive, and is electrically connected by the wires provided along the surface of the light transmissive lid  220 .  
         [0039]     The drive integrated circuits  240   a,    240   b,    240   c  and  240   d  are connected around the light modulator device  230  attached to the upper surface of the light transmissive lid  220  through flip chips, and function to supply the driving voltage to the light modulator device  230 , in response to the externally input control signal.  
         [0040]     The drive integrated circuits  240   a,    240   b,    240   c  and  240   d  have rectangular cross-sections smaller than the light modulator device  230 . The number of integrated circuits may be increased or decreased, if required.  
         [0041]     The heat spreader  250  is provided to disperse the heat. generated by the light modulator device  230  and the drive integrated circuits  240   a,    240   b,    240   c  and  240   d.  The heat spreader  250  is formed of metal having high heat dispersal efficiency.  
         [0042]     As shown in  FIG. 4 , the drive integrated circuits  240   a,    240   b,    240   c  and  240   d  are formed to be higher than the light modulator device  230 . Thus, the heat spreader  250 , which serves to disperse the heat generated by the light modulator device  230  and the drive integrated circuits  240   a,    240   b,    240   c  and  240   d,  has a protrusion corresponding to the height of the light modulator device  230 . In addition, the surface of the heat spreader  250 , which is in contact with the light modulator device  230  and the drive integrated circuits  240   a,    240   b,    240   c  and  240   d,  must be formed to be smooth to assure a secure adhesion therebetween.  
         [0043]     The connector  260  is formed on one side of the PCB  210  to supply the externally input control signal to the drive integrated circuits  240   a,    240   b,    240   c  and  240   d,  and is attached to the upper surface of the PCB  210  using an adhesive.  
         [0044]     In a preferred embodiment, one side end of the connector  260  protrudes slightly from the side end of the PCB  210 .  
         [0045]     The molded part  270  encloses the PCB  210 , the light transmissive lid  220  on which the light modulator device  230  and the drive integrated circuits  240   a,    240   b,    240   c  and  240   d  are formed, and the heat spreader  250 , so as to firmly hold them and protect them from external impacts.  
         [0046]      FIG. 5  is a flow chart showing a process of fabricating the light modulator module package, according to the first embodiment of the present invention.  FIGS. 6   a  to  6   f  are sectional views sequentially showing the process of fabricating the light modulator module package of  FIG. 5 .  
         [0047]     As shown in  FIG. 5 , the process of fabricating the light modulator module package  200 , according to the first embodiment of the present invention, includes attaching the connector  260  to the upper surface of the PCB  210  (S 110 ), attaching the light modulator device  230  and the drive integrated circuits  240   a,    240   b,    240   c  and  240   d  to the upper surface of the light transmissive lid  220  (S 120 ), preparing the heat spreader  250  (S 130 ), laminating the light transmissive lid  220  on the PCB  210  and conducting wire bonding (S 140 ), attaching the heat spreader  250  to the upper surfaces of the light modulator device  230  and the drive integrated circuits  240   a,    240   b,    240   c  and  240   d  (S 150 ), and forming the molded part  270  to fabricate a light modulator module package  200  (S 160 ).  
         [0048]     Although the attaching of the connector  260  to the upper surface of the PCB  210  (S 110 ), the attaching of the light modulator device  230  and the drive integrated circuits  240   a,  240     b,    240   c  and  240   d  to the upper surface of the light transmissive lid  220  (S 120 ), and the preparing of the heat. spreader  250  (S 130 ) may be sequentially performed, it is preferable that they be simultaneously performed in parallel to reduce the total processing time.  
         [0049]     Specifically, in  FIG. 6   a,  the PCB  210  having an inner circuit is prepared, one side of which has the connector  260  attached (S 110 ).  
         [0050]     In  FIG. 6   b,  the light transmissive lid  220 , which is coated with the absorbent film, the scattering film or the non-reflective film, is prepared, and the light modulator device  230  is attached to the central portion on the coated surface of the light transmissive lid  220 , and a plurality of drive integrated circuits  240   a,    240   b,    240   c  and  240   d  is attached around the light modulator device  230  (S 120 ).  
         [0051]     In  FIG. 6   c,  the heat spreader  250 , which has a protrusion corresponding to the height of the light modulator device  230 , is prepared (S 130 ).  
         [0052]     In  FIG. 6   d,  the lower surface of the light transmissive lid  220 , which does not have the light modulator device  230  and the drive integrated circuits  240   a,    240   b,    240   c  and  240   d,  is attached to the upper surface of the PCB  210 , and then the signal lines of the drive integrated circuits  240   a,    240   b,    240   c  and  240   d  are bonded to the signal line of the PCB  210  by the wires (S 140 ).  
         [0053]     In  FIG. 6   e,  the heat spreader  250  is attached to the upper surfaces of the light modulator device  230  and the drive integrated circuits  240   a,    240   b,    240   c  and  240   d  (S 150 ).  
         [0054]     In  FIG. 6   f,  the molded part  270  is formed so that the PCB  210 , the light transmissive lid  220  on which the light modulator device  230  and the drive integrated circuits  240   a,    240   b,    240   c  and  240   d  are formed, and the heat spreader  250  are securely held and protected from external impacts, thus obtaining a desired light modulator module package  200  (S 160 ).  
         [0055]     Turning now to  FIG. 7 , there is a sectional view showing a light modulator module package, according to a second embodiment of the present invention.  
         [0056]     As shown in  FIG. 7 , a light modulator module package  300 , according to the second embodiment, includes a PCB  310 , a light transmissive lid  320 , a light modulator device  330 , drive integrated circuits  340   a  and  340   b,  a heat spreader  350 , a connector  360  and a molded part  370 .  
         [0057]     Compared to the light modulator module package  200  shown in  FIGS. 3 and 4 , the light modulator module package  300  shown in  FIG. 7  is structured in such a way that the light modulator device  330  and the drive integrated circuits  340   a  and  340   b  are formed to have the same height, and thus, the entire adhesion surface of the heat spreader  350  is flat.  
         [0058]     Therefore, the process of fabricating the light modulator module package  300  shown in  FIG. 7  does not require the shaping of the heat spreader  350  to correspond to the heights of the light modulator device  330  and the drive integrated circuits  340   a  and  340   b.  Thereby, the fabrication process of the above module package  300  is simplified, and fabrication costs thereof decrease.  
         [0059]     As described above, the present invention provides a light modulator module package which is light, slim, short and small.  
         [0060]     The light modulator module package of the present invention is advantageous because heat generated by the light modulator device and the drive integrated circuits is effectively dispersed through the heat spreader.  
         [0061]     The light modulator module package of the present invention is advantageous because the optical properties of the light modulator device are not reduced when the module package is fabricated.  
         [0062]     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.