Abstract:
An automatic decapsulation system for a device is disclosed. The system comprises an etch plate, an etch head, a sheet coupled to the etch head, a rubber gasket disposed between the etch head and the sheet, and an integrated spacer and protection plate for securing the device without damaging the backside of the device during decapsulation. In one embodiment of the present invention, the integrated spacer and protection plate is adjustable to accommodate devices of varying sizes.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention is related to the following co-pending U.S. Applications: Automatic Decapsulation System Utilizing An Acid Resistant, High Heat Endurance and Flexible Sheet and a Method of Use, Ser. No. 09/551,300, filed on Apr. 18, 2000, and assigned to the assignee of the present invention; and Automatic Decapsulation System Utilizing An Acid Resistant, High Heat Endurance and Flexible Sheet Coupled to a Rubber Gasket and a Method of Use, Ser. No. 09/680,558 now U.S. Pat. No. 6,409 878 filed on Oct. 5, 2000, and assigned to the assignee of the present invention. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to automatic decapsulators and more particularly to the device protection unit utilized in such decapsulators. 
     BACKGROUND OF THE INVENTION 
     Automatic decapsulators are used to expose the die in any plastic package or device by etching away the die&#39;s plastic covering. Either fuming sulfuric, fuming nitric, or mixed fuming nitric and sulfuric acids may be used as an etchant. Decapsulation is a fast and safe process that produces a clean, uncorroded die surface. When fuming nitric acid is used as the etchant, there is little or no damage to the die surface or bond pads. Fuming sulfuric acid is normally used at an elevated temperature to remove the plastics that are not compatible with fuming nitric acid. The etching process is performed under pressure in an inert atmosphere to reduce metal oxidation and to reduce the production of harmful fumes. 
     FIG. 1 a  illustrates a side view of a typical system for automatic decapsulation of a device. The system  10  includes a safety cover  11  which is coupled to an etch plate  13 . The system  10  also includes a positioning fixture  12  coupled to the etch plate  13  which is typically metal and is aligned with a package  16  and a gasket  14 , typically made of rubber. The gasket  14  is positioned under the device  16  with an etch window in the gasket&#39;s center. During decapsulation, the device holder  20  presses down on the device  16 , which presses down upon the rubber gasket  14 , creating a tight seal with the etch head  18 . The etchant is then provided by the etch head  18  through the etch window to the device  16 . 
     For many current plastic packages, such as plastic ball grid array (PBGA) or fine ball grid array (FBGA) packages, solder balls are disposed on the backside of the package, i.e., on the face opposite to that exposed to the etchant. Decapsulating such packages is a challenge because the decapsulation temperature exceeds the melting point of the solder balls, and the solder balls can be deformed by the device holder. Moreover, some packages, like FBGA packages, can be as small as 5 mm on each side, thereby presenting alignment problems. 
     Co-pending U.S. patent application Ser. No. 09/680,558 entitled, “Automatic Decapsulation System Utilizing An Acid Resistant, High Heat Endurance and Flexible Sheet Coupled to a Rubber Gasket and Method of Use,” filed on Oct. 5, 2000, and assigned to the assignee of the present invention, addresses some of the challenges faced when decapsulating ball grid array packages. According to one embodiment of the co-pending patent application, a spacer and a protection plate are disposed between the device and the device holder so that the device holder does not come in direct contact with the backside of the device. The spacer makes contact with the backside of the device only in areas without solder balls. Accordingly, the spacer prevents the protection plate from deforming the solder balls during decapsulation. 
     FIG. 2 a  illustrates a side view of the automatic decapsulation system  100  in accordance with the above-referenced co-pending application. The system  100  is similar to the system  10  of FIG. 1, and includes a safety cover  11 ′ which is coupled to an etch plate  13 ′. As is seen, a spacer  108  is inserted between the backside of the package  110  and the protection plate  106 . A rubber gasket  104  is placed between a gasket plate  102  and a head etch  18 ′. The spacer  108  is preferably made of a TEFLON sheet having a thickness of at least the height of the solder balls. TEFLON® is well known in the art. The generic term for TEFLON is polytetrafluoroethylene (PTFE). FIG. 2 b  illustrates a top view of the backside of the device  110  with the spacer  108  in accordance with the present embodiment. As is shown, a window is cut out of a sheet (not shown) to form the spacer  108 , which surrounds and protects the solder balls. Accordingly, when the protection plate  106  is placed on top of the spacer  108 , the plate  106  does not come in contact with the backside of the device  110 , and the solder balls are protected from being crushed. 
     Although the above-described system in the co-pending patent application functions for its intended purpose, one of ordinary skill in the art will readily recognize that it would be desirable to improve the way in which the backside of the device is protected. For instance, it would be desirable to simplify the placement of the spacer, such that alignment with a very small device, such as a FBGA package, is accomplished with relative ease. It also would be desirable to devise a system in which the protection plate is easily put in place and kept in place during decapsulation. In addition, it would be desirable to reduce the cost and labor associated with manufacturing different spacers having different sizes to match the various package sizes. 
     Accordingly, what is needed is a system and method to overcome the above-identified problems. The system and method should be cost effective and easy to implement with existing processes and equipment. The present invention addresses such a need. 
     SUMMARY OF THE INVENTION 
     An automatic decapsulation system for a device is disclosed. The system comprises an etch plate, an etch head, a sheet coupled to the etch head, a rubber gasket disposed between the etch head and the sheet, and an integrated spacer and protection plate for securing the device without damaging the backside of the device during decapsulation. In one embodiment of the present invention, the integrated spacer and protection plate is adjustable to accommodate devices of varying sizes. 
     The integrated spacer and protection plate of the present invention automatically aligns the spacer with the device, thereby reducing the amount of time taken to otherwise align the spacer. In addition, because the spacer and protection plate are integrated, the protection plate is put in place and kept in place automatically. In a preferred embodiment, the integrated spacer and protection plate is manufactured from a TEFLON sheet, thereby providing a highly durable and cost efficient solution. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a side view of a conventional system for autodecapsulation. 
     FIG. 2 a  illustrates a side view of the decapsulation system in accordance with the co-pending application. 
     FIG. 2 b  illustrates a top view of the backside of the device and spacer in accordance with the co-pending application. 
     FIG. 3 is a side view of the decapsulation system in accordance with the first preferred embodiment of the present invention. 
     FIG. 4 a  illustrates a top view of the integrated spacer and protection plate in accordance with the first preferred embodiment of the present invention. 
     FIG. 4 b  illustrates a side view of the integrated spacer and protection plate in accordance with the first preferred embodiment of the present invention. 
     FIG. 5 is a side view of the decapsulation system in accordance with the second preferred embodiment of the present invention. 
     FIG. 6 a  illustrates a top view of the integrated spacer and protection plate in accordance with the second preferred embodiment of the present invention. 
     FIGS. 6 b  and  6   c  illustrate cross sectional views of the integrated spacer and protection plate in accordance with the second preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     The present invention relates generally to automatic decapsulators and more particularly to the device protection unit utilized in such decapsulators. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein. 
     The present invention utilizes an integrated spacer and protection plate. The integrated spacer and protection plate is designed to be placed over the gasket for easy alignment. The integrated spacer and protection plate sits on the edge of the device and includes an area located over the device, which serves to protect any elements that may be situated on the backside of the device. During decapsulation, the device holder clamps down on the integrated spacer and protection plate, which in turn secures the device to the etch head. 
     The present invention will be described in accordance with two preferred embodiments. The present invention, however, is not limited to the described embodiments, and one skilled in the art would appreciate that different embodiments could exist which incorporate an integrated spacer and protection plate. Those embodiments would certainly fall within the spirit and scope of the present invention. 
     First Preferred Embodiment 
     FIG. 3 illustrates a side view of the decapsulation system  200  in accordance with the first preferred embodiment of the present invention. The integrated spacer and protection plate  202  replaces the spacer  108  and protection plate  106  (FIG. 2 a ) utilized in the decapsulation system  100 . A rubber gasket  104 ′ is placed between a gasket plate  102 ′ and a head etch  18 ″. To simplify alignment, the integrated spacer and protection plate  202  is preferably similar in size to the gasket plate  102 ′. In one preferred embodiment, alignment is ensured by lining up holes  112 ′ in the integrated spacer and protection plate  202  and the gasket plate  102 ′ such that fixture pins (not shown) can be inserted through the holes  112 ′ into the etch plate  13 ″. 
     As is shown, the integrated spacer and protection plate  202  fits onto the package  110 ′ and forms a cap over the solder balls. During decapsulation, the device holder  20 ″ applies pressure down onto the integrated spacer and protection plate  202 , which in turn presses the package  110 ′ into the gasket  102 ′, thereby creating a seal between the package  110 ′ and the head  18 ″. 
     FIGS. 4 a  and  4   b  illustrate the top and side views, respectively, of the integrated spacer and protection plate  202  in accordance with the first embodiment of the present invention. As is shown in FIG. 4 b , a multi-tiered trench is machined into the bottom surface of the plate  202 . The first tier  203  is for holding the package  110 ′ (FIG. 3) in place. The shape and size of the first tier  203  is substantially the same shape and size of the package  110 ′. The first tier&#39;s  203  height is preferably less than the package  110 ′ standoff height when the package  110 ′ is sitting on the TEFLON/Rubber gasket plate  102 ′ (FIG.  3 ). As such, the plate  202  sits on the edge of the package  110 ′, as opposed to sitting on the gasket plate  102 ′. 
     Referring back to FIGS. 4 a  and  4   b , a second tier  204  is formed above the first tier  203 . The second tier  204  is similar in shape, but smaller in size to the first tier  203 . Preferably, the second tier  204  is 0.5 mm smaller on each side than the first tier  203 . A rim  206  created between the first  203  and second  204  tiers acts as a spacer, making direct contact around the package  110 ′ edges where no solder balls exist. The second tier  204  forms a cap  205  over the solder balls (not shown) and prevents them from being deformed during decapsulation. The height of the second tier  204  is preferably at least twice the height of the solder balls. So, for example, for small packages (FBGA), the height of the solder balls can range from 0.15 mm to 0.30 mm, and therefore, the height of the second tier  204  should preferably be at least 0.60 mm. 
     The integrated spacer and protection plate  202  according to the first embodiment of the present invention is preferably made from TEFLON or stainless steel. As mentioned above, the cap  205  is utilized as a protection plate, where the device holder  20 ″ will apply pressure in order to seal the package  110 ′ to the etch head  18 ″ for decapsulation. Because TEFLON becomes somewhat pliable at decapsulation temperatures, the thickness must be sufficient to enable the cap  205  to withstand the pressure exerted by the device holder  20 ″ without deforming. Accordingly, the thickness of the integrated spacer and protection plate  202  made from TEFLON is at least approximately 0.125 inches. 
     As is seen in FIG. 3, the package  110 ′ sits in the gasket plate  102 ′ and the integrated spacer and protection plate  202  fits directly over the package  110 ′, such that the package  110 ′ fits within the first tier  203  and contacts the rim  206 . Because the spacer and protection plate are integrated, these elements are automatically aligned over the package  110 ′ when the integrated spacer and protection plate  202  is set in place. Accordingly, what was once a tedious and time consuming task of placing a spacer and protection plate on top of a tiny device, now becomes a simple task that can be performed with relative ease. 
     Second Preferred Embodiment 
     A second preferred embodiment of the present invention is directed to an integrated spacer and protection plate, which is adaptable to packages having different sizes. Accordingly, the second preferred embodiment of the present could be used for a variety of devices without the need for customization. 
     FIG. 5 illustrates a cross sectional view of the side of the decapsulation system  300  in accordance with the second preferred embodiment of the present invention. Like the first preferred embodiment, the integrated spacer and protection plate  302  replaces the spacer  108  and protection plate  106  (FIG. 2 a ) utilized in the decapsulation system  100 . A rubber gasket  104 ″ is placed between a gasket plate  102 ″ and a head etch  18 ′″. To simplify alignment, fixture pins  112 ″ extend through the gasket plate  102 ″ and the integrated spacer and protection plate  302 . 
     As is shown, the integrated spacer and protection plate  302  fits onto the package  110 ″ and forms a cap over the solder balls. During decapsulation, the device holder  20 ′″ applies pressure down onto the integrated spacer and protection plate  302 , which in turn presses the package  110 ″ into the gasket plate  102 ″, thereby creating a seal between the package  110 ″ and the etch head  18 ′″. 
     FIGS. 6 a ,  6   b  and  6   c  illustrate top and cross sectional views of the integrated spacer and protection plate  302  in accordance with the second preferred embodiment of the present invention. As is shown in FIG. 6 b , the integrated spacer and protection plate  302  is a plate  304  that includes a plurality of bars ( 303 ,  303   a ) therein. The bars ( 303 ,  303   a  . . . ) slide horizontally along the length of the plate  304 . As is seen in FIGS. 6 a  and  6   b , a step  310  is formed on each bar ( 303 ,  303   a ) at an end facing the middle line of the plate  304 . In FIG. 6 a , a slot  306  is provided in each bar ( 303   a ,  303  into which the fixture pins  112 ″ (FIG. 5) can be inserted for alignment purposes. 
     As is seen in FIG. 6 c , each bar ( 303 ) slides along a notched slot formed within the plate  304 . FIG. 6 b  shows that, in one embodiment, a first and a second bar ( 303 ,  303   a ) share the notched slot. When the first and second bars ( 303 ,  303   a ) are moved toward or away from the middle line of the plate  304 , the opening created between the bars ( 303 ,  303   a ) contracts or expands. 
     Because the step  310  is provided on the bars ( 303 ,  303   a ), a first  308  and a second  309  opening is formed by the bars ( 303 ,  303   a ), as is seen in FIG. 6 b . The first and second bars ( 303 ,  303   a ) are adjusted by sliding them toward or away from one another so that the first opening  308  is substantially the same size as a side of the package  110 ″. The first opening  308  holds the package  110 ″ in place. The height of the first opening  308  is preferably less than the package  110 ″ standoff height when the package  110 ″ is sitting on the TEFLON/Rubber gasket plate  102 ″ (FIG.  5 ). Referring back to FIG. 6 b , the step  310  created between the first  308  and second  309  openings acts as a spacer, making direct contact with the package  110 ″ edge where no solder balls exist. The width of the step  310  is preferably 0.5 mm. The height of the second opening  309  is preferably at least twice the height of the solder balls. 
     Once the first  308  opening is adjusted to fit the package  110 ″, the bars ( 303   a ,  303 ) are set in place by a plurality of pins  305  screwed down from the top of the plate  304 . Referring back to FIG. 5, when the integrated spacer and protection plate  302  is put in place, the package  110 ″ fits into the first opening  308  of the integrated spacer and protection plate  302  and the package  110 ″ makes contact via the step  310 . The solder balls are protected within the second opening  309 , while the device holder  20 ′″ applies pressure to the integrated spacer and protection plate  302  to secure and seal the package  110 ″. 
     For today&#39;s FBGAs, the package size is far from standardized. In fact, packages can come in 30-40 different sizes. By being able to adjust the size of the first  308  opening, the integrated spacer and protection plate  302  can be used for a variety of packages having different sizes. This embodiment of the present invention also incorporates the positive attributes of the first preferred embodiment of the present invention, that is, easy alignment, cost effectiveness, and durability. 
     Although the present invention has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiments and those variations would be within the spirit and scope of the present invention. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.