Abstract:
A device structure with preformed ring includes a sensor chip and a ring disposed and surrounded on periphery of sensitive area of an active surface thereof. The device structure with preformed ring may batchly bind and electrically connect to a carrier by a way of two-dimension array, and then a packaging process is performed. During the packaging process, the top portion of the ring can be used to against the inner side of a packaging mold, so as to stop the packaging material covering the device at outside of the ring and stick with the ring. Therefore, an opening is formed on the sensitive area surface of the device. Depending on the ring, the extra process for eliminating the packaging material on the sensitive area surface can be avoided in the conventional process.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 096119341 filed in Taiwan, R.O.C. on May 30, 2007, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a device structure and the process thereof and more particularly to a device structure and the process thereof which forms a ring on the sensitive area of the sensor chip in order to bind to the sealant, and forms an opening in the ring. 
         [0004]    2. Related Art 
         [0005]    Lately, certain consumer electronic goods such as a watch manometer or a cell phone can be very successful by integrating a manometer therein. Therefore, based on the increase demand of the forgoing applications, how to provide a low cost manometer module and a small size of manometer module becomes a concern in this manometer module assembly business, since the pressure sensor is where the main cost of the assembly will be. According to the present technology, the design of a pressure sensor assembly is primarily following a two step process, where a preformed lead pin frame process is followed by an exterior cover process. The differences between those related patents involve the structure of the preformed lead frame, the location of the test pressure source conducting hole or the location of the reference atmosphere pressure hole. The prior patents, such as U.S. Pat. Nos. 5,852,320, 4,655,083, 5,465,626, 6,066,882, 4,563,697 and 5,209,120 are mainly focus on the use of a single unit process to perform the assembly of the relative pressure sensitive module. As to the structure of the preformed lead frame, they are mainly using a TO-can plastic frame with an outer lead metal. And regarding to the lead welding structure of the electric interface of the pressure sensitive module, there are two kinds of processes: one is through hole and the other is surface mount technology (SMT). 
         [0006]    In addition, more and more pressure sensor modules are introducing a one dimensional batch process, where uses a bulk substrate with a matured one body mold to increase the throughput of the pressure module. The bulk substrate often is a printed electric board (PCB) or a lead-frame. Basically, the molding process in nature has an inherent property of mass production which has an advantage in cost reduction, so it is widely accepted by the major assembly manufacturers that it is an efficient process for cost down. However, in order to fulfill the special need when design a chip sensor of a pressure sensitive module, the sensor chip, the test pressure source conducting hole and the reference atmosphere pressure hole must to be processed or to be released before or after the molding process. There are three kinds of processes to do it. The first one is occupying the location of the via with a inserted bump mold in advance before the injection forming process of the molding is performed, and then after the mold is filled with the liquid plastic and becomes solid, the inserted object which is in the mold will be separated along with the mold removing process. So, the via hole will be formed naturally. The process is shown in U.S. Pat. No. 5,897,338. 
         [0007]    Another process is so-called process to release method, which is using the etching process after the whole sensor module is molding and formed to etching out the material of the unnecessary part of the area which is designed for the hole till the sensor chip or the protection layer above is exposed. As a result, the via space for the sensor chip is released. The related patents can refer to U.S. Pat. No. 4,823,605 and the U.S. Pat. No. 6,379,988.  FIG. 1A  shows the micro-electro-mechanical pressure sensitive device 10 of the U.S. Pat. No. 6,379,988. In the figure, in order to protect the micro-sensor or the actuator above the micro-electro-mechanical sensor  11 , before the molding process of the micro-electro-mechanical sensor  11 , a sacrificed protection layer  13  will be in advance covered on the micro-electro-mechanical sensor  11  and will be embedded in the molding material  14  after the molding process. Consequently, there must be a window to be opened above the micro-sensor or the actuator  12 . The window opening process is shown in  FIG. 1B  and  FIG. 1C , where there are two different strong acids used for spray etching. In one process, a first pad  15  is formed on the molding material  14  to define the area to be etched. Then, a first strong acid  16  is sprayed for a certain amount of time to allow the molding material  14  which is exposed to the first strong acid  16  to be able to be removed to expose the sacrificed protection layer  13 . After that, a second pad  17  is used to cover the first opening area of the molding material, and a second strong acid  18  is used for spray etching for a certain amount of time to remove the sacrificed protection layer  13 . So the micro-sensor or the actuator  12  of the micro-electro-mechanical sensor device  11  will be released and exposed to the air. 
         [0008]    The other process is a mix, which utilizes the two-step preformed lead frame process and the one-dimensional batch process. The exterior cover process is used to form the sensitive via hole of the sensor chip while the whole sensor module is formed by one body molding. That is, the sensor chip after formed by the one body molding process is binding to the saved space of the formed module and the exterior cover which has a saved via hole will then assemble to the sensor module body. The related patents are U.S. Pat. Nos. 6,927,482 and 6,401,545. 
         [0009]    To summarize the forgoing processes, the single unit process method may have the throughput problem, which on the other hand may make a high cost preformed lead plastic substrate device even more costly. Therefore, from a view of upstream and downstream manufacturers, it is very difficult to reduce the overall cost of the assembly. Thus, a new package model is probably a possible and necessary way to solve this problem. In addition, the through hole and the metal lead frame processes need more foot print area than the regular base area of the manometer module, which will put a limitation to the reduction of the size of the whole module. 
       SUMMARY 
       [0010]    The present invention is to provide a device structure with preformed ring and the process thereof, so an opening can be naturally formed above the sensitive area while the sensor chip is packaging. 
         [0011]    The device structure of the present invention with preformed ring includes: a sensor chip and a ring. The sensor chip has an active area and a back. The active area has a sensitive area and a plurality of pads. The ring is disposed on the active area of the sensor chip and surrounding the periphery of the sensitive area. 
         [0012]    The back in the foregoing embodiment further includes a cave and can be covered by a supporting structure layer which has a hole. 
         [0013]    The foregoing embodiment can apply to a sensor chip packaging and can further include binding and electric coupling the foregoing device structure to a carrier, where when sealing, the top of the ring will be against the top inner face of the mold to make the sealant only surround and combine outside the ring, so the interior of the ring can naturally form a space for the sensitive area of the sensor chip. 
         [0014]    The ring of the foregoing embodiment can be formed by a thick film process, such as a stencil printing, a spin-coating, a plastic film hot pressing and so on. 
         [0015]    The invention may have the following effect. The device structure can be batch formed by using a wafer, and when applied to the sensor chip packaging, a two dimensional batch processing can be applied in order to bind the sensor chip to the carrier and then sealed at once. So as a result, the process can be simplified and the device structure needs not to be removed after sealing, and the hollow area inside of the ring will be the future via hole for the sensor chip. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The present invention will become more fully understood from the detailed description given below, which is for illustration only and thus is not limitative of the present invention, wherein: 
           [0017]      FIG. 1A ,  FIG. 1B  and  FIG. 1C  show a diagram flowchart of a prior manufacturing method of an opening of the sensitive area of the micro-electro-mechanical sensor device; 
           [0018]      FIG. 2A  is a diagram showing a cross section view of the sensor chip according to the invention; 
           [0019]      FIG. 2B  is a diagram showing a cross section view of an illustrative embodiment of via hole of the device structure according to the invention; 
           [0020]      FIG. 2C  is a diagram showing a cross section view of an illustrative embodiment of the device structure where the back has a cave according to the invention; 
           [0021]      FIG. 2D  is a diagram showing a cross section view of an illustrative embodiment of the device structure where the back has a cave and a supporting plate with a hole according to the invention; 
           [0022]      FIG. 2E  shows a vertical view of the  FIG. 2D ; 
           [0023]      FIG. 3A  is a diagram showing a cross section view of the sensor chip package according to the invention; 
           [0024]      FIG. 3B  is a diagram showing a cross section view of an illustrative embodiment of the sensor chip package where the back of the sensor chip has a cave according to the invention; 
           [0025]      FIG. 3C  is a diagram showing a cross section view of an illustrative embodiment of the sensor chip package where the back of the sensor chip has a cave and the carrier has a via hole according to the invention; 
           [0026]      FIGS. 4A to 4C  show the cross views of an illustrative embodiment of the invention which applies to the substrate; 
           [0027]      FIGS. 5A to 5C  show the cross views of an illustrative embodiment of the invention which applies to the lead frame; 
           [0028]      FIG. 6  is a diagram showing the cross view of the invention which applies to the three-dimensional subsystem sensor system; 
           [0029]      FIG. 7  is a diagram showing the cross view of the invention with added dust proof mechanism; 
           [0030]      FIG. 8  is a diagram showing the cross view of the invention with added light filter/light condensing mechanism; 
           [0031]      FIGS. 9A to 9D  are the flowcharts showing the process of manufacturing the sensor chip package with preformed ring; 
           [0032]      FIG. 9E  shows the flowchart of the process of manufacturing the cave of the sensor chip package with preformed ring; 
           [0033]      FIG. 9F  shows the flowchart of the process of manufacturing the opening and the supporting structure layer of the sensor chip package with preformed ring; and 
           [0034]      FIGS. 10A to 10E  are the flowcharts showing the process of manufacturing the sensor module with preformed ring. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]      FIG. 2A  and  FIG. 2D  show the device structure with preformed ring according to the invention, which includes a sensor chip  21  and a ring  30 . The sensor chip  21  has an active surface  211  and a back  212 . The active surface  211  has a sensitive area  2111  and a plurality of pads  2112 . The ring  30  is disposed on the active surface  211  of the sensor chip  21  and surrounding the periphery  21111  of the sensitive area  21111  and has a hollow interior area  32 . 
         [0036]      FIG. 2B  is a cross section view of an embodiment of the via hole of the device structure according to the invention. The bottom of the pad  2112  of the device structure  20   a  can further include an electric conductive hole  2124  which penetrates through to the back  212 . On the back  212  where corresponds to the electric conductive hole  2124  is disposed a bottom pad  2125 , which connects to the electric conductive hole  2125  through a metal wire. 
         [0037]    In  FIG. 2C  and  FIG. 2D , the foregoing embodiment can also have a cave  2121  on the back  212  of the sensor chip  21  to form the device structure  20   c . Because forming a cave  2121  on the back will reduce the chip&#39;s rigidity, a supporting structure layer  2122  can be further formed on the back  212 , which will constitute the device structure  20   d . The supporting structure layer  2122  includes a hole  2123  which corresponds to the cave  2121 . The structure layer  2122  also can cover the back  212  in order to increase the rigidity of the structure. 
         [0038]    In  FIG. 3A , the embodiment of the sensor chip package  40  according to the invention is binding and electric coupling the foregoing device structure  20  to an upper surface  411  of a carrier  41  and forming an encapsulation  50  which covers the device structure  20  and the upper surface  411  of the carrier  41 . 
         [0039]      FIG. 3B  shows the embodiment of the sensor chip package  40   a  where the device structure  20   a  is binding and electric coupling to an upper surface  411  of a carrier  41 . 
         [0040]      FIG. 3C  is similar to the embodiment in  FIG. 3B , where the carrier  41  can further have a via hole  412  which corresponds to the cave  2121  so that via hole  412  can interconnect with the cave  2121 , which constitutes a sensor chip package  40   b  embodiment. 
         [0041]    In the foregoing embodiment of sensor chip package  40   b , the device structure  20   a  also can apply to the device structure  20   b  which has a supporting structure layer  2122 . 
         [0042]    The forgoing sensor chip packages  40 ,  40   a  and  40   b  can apply to structures with different function in order to form different kinds of sensor modules. 
         [0043]    In  FIG. 4A , the sensor module A embodiment is using the sensor chip package  40   b  (or the embodiment which has a supporting structure layer  2122 ), and the top of the packing sealant  51  is above the top of the ring  30  to form a cave a 1  space above the top of the ring  30 . 
         [0044]    In  FIG. 4B , the sensor module B is using the sensor chip package  40   b  (or the embodiment which has a supporting structure layer  2122 ), and is embedding an O-ring b 1  in the encapsulation  50 . 
         [0045]    In  FIG. 4C , the sensor module C is using the sensor chip package  40   b  (or the embodiment which has a supporting structure layer  2122 ) and is forming a guide tube c 1  on the encapsulation  50  to form an external connecting guide. In the foregoing sensor module A, B and C, the carrier  41  can be one with the via hole  412  or an solid object without the via hole  412 . Certainly, when the carrier doesn&#39;t have the via hole  412 , the device structure  40   b  need not to have the supporting structure layer  2122 . 
         [0046]    In  FIG. 5A , the sensor module D is using the device structure  20   c  (or the device structure  20   b ) to bind and electric connect to a lead frame  41   a  and forming an encapsulation  50 . The lead frame  41   a  can have different types, such as the sensor module E embodiment in  FIG. 5B  or the sensor module F embodiment in  FIG. 5C . 
         [0047]    In the foregoing sensor module embodiments D, E and F, the lead frame  41   a  can be one with the via hole  412  or an solid object without the via hole  412 . When the lead frame  41   a  doesn&#39;t have the via hole  412 , the device structure  20   b  can be used. 
         [0048]    In  FIG. 6 , the sensor module G embodiment is using the sensor chip package  40   b  (or the embodiment which has the supporting structure layer  2122 ) to bind and electric connect to an application specific integrated circuit (ASIC) device g 1 . The ASIC device g 1  is also electric coupled to a carrier  41 , and an encapsulation  50  is covering the carrier  41 , the ASIC device g 1 , and the sensor chip package  40   b  (or the embodiment which has the supporting structure layer  2122 ). 
         [0049]    In  FIG. 7 , the sensor module H embodiment is using the sensor chip package  40   b  with the preformed ring  30  (or the embodiment which has the supporting structure layer  2122 ) where there is a dust-proof mechanism included on top of the ring  30 , which can be a dust-proof filter such as a plastic weave, a paper weave, a fiber weave or a metal net to keep the good performance of the sensor chip package  40   b  (or the embodiment which has the supporting structure layer  2122 ). 
         [0050]    In  FIG. 8 , the sensor module I embodiment is using the sensor chip package  40   b  with the performed ring  30  (or the embodiment which has the supporting structure layer  2122 ) where there is a light filter or light condensing mechanism added to the top of the ring  30 , which can be a light polarized plate, a light filter plate or a light condensing plate to corporate with the sensor chip package  40   b  (or the embodiment which has the supporting structure layer). 
         [0051]      FIGS. 9A to 9D  show a cross section view of the flowchart based on the invention. The steps include: provide a sensor wafer  201 , which has a surface  202 , and a plurality of sensor chips  21 , the sensor chip  21  has an active surface  211  and a back  212 , and the active surface  211  has sensitive area  2111  (step S 10 ); form a dike layer  301  on the surface of the sensor wafer  201  (step S 11 ); pattern the dike layer  301  to form a hollow interior area  32  which is surrounded by skirts  31 , where together with the sensitive area  2111  of the sensor chip  21  and the periphery  21111  of the pad  2112  will define the ring  30  (step S 12 ); dice the sensor wafer  201  to form a plurality of device structure  20  with preformed ring  30  (step S 13 ). 
         [0052]    In  FIG. 9E , a step of forming a cave  2121  on the back  212  of each sensor chip  21  (step S 12   a ) is further included before the step of dicing (step S 13 ) and after the step of forming the dike layer  301  (step S 12 ). In addition, as shown in  FIG. 9F , a step of forming a supporting structure layer  2122  which should be made of a strong material on the back of each sensor chip  21 , and a via hole  2123  on the location which corresponds to the cave  2121  is further included. 
         [0053]      FIGS. 10A to 10E  show a cross section view of the flow chart based on the invention. The steps include: provide at least one device structure  20   a  with preformed ring (step S 20 ); bind a device structure  20   b  on an upper surface of a carrier  41 , where the upper surface of the carrier has a plurality of pads (step S 21 ); electric connect the device structure  20   b  to the pad on the upper surface of the carrier  41  (step S 22 ); place the device structure  20   b  and the carrier  41  in a packaging mold  60 , where the upper mold  60   a  is tightly against the top of the ring  30  to make sure that the sealant  51  will only surround the skirts  31  of the ring  30  and will not flow into the interior area  32  of the ring, where if possible, the lower mold  60   b  can be against the lower surface of the carrier  41  (step S 23 ), and certainly, if the carrier  41  is a lead frame  41   a , the lower mold  60   b  of the packaging mold  60  need not to be against the lower surface; inject the sealant  51  into the packaging mold  60  to form an encapsulation  50 , where the sealant  51  of the package  40  surrounds the periphery of the ring  30  to form an opening space within the interior area  32  (step S 24 ); dice the encapsulation  50  to form a plurality of sensor chip packages  40   a  (step S 25 ). 
         [0054]    In addition, before the carrier  41  is provided, a via hole  412  can be in advance formed on the carrier  41  in order to be fit for the specific application of the sensor chip package  40   a.    
         [0055]    While the illustrative embodiments of the invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments, which do not depart from the spirit and scope of the invention