Embodiments of the present technology relate to methods for reclaiming a memory die in a damaged semiconductor package, and forming a new memory card using the reclaimed semiconductor package.
The strong growth in demand for portable consumer electronics is driving the need for high-capacity storage devices. Non-volatile semiconductor memory devices, such as flash memory storage cards, are becoming widely used to meet the ever-growing demands on digital information storage and exchange. Their portability, versatility and rugged design, along with their high reliability and large capacity, have made such memory devices ideal for use in a wide variety of electronic devices, including for example digital cameras, digital music players, video game consoles, PDAs and cellular telephones.
Cross-sectional side, top and bottom views of a conventional semiconductor package 20 are shown in
The controller die 24 is generally smaller than the memory die 22. Accordingly, the controller die 24 is conventionally placed at the top of the memory die stack. In
Referring now to the bottom view of
In testing finished semiconductor packages, there will be some number of packages that fail due to a problem with the controller die in the package. Instead of throwing away the entire package, it is known to “reclaim” the package by electrically isolating the controller die 24 within the package and repackaging the memory die in a new semiconductor package. Today, the controller die 24 is electrically isolated from the substrate 26 by mechanically grinding off the molding compound 34 on the top of the package 20 until the wires 32 connecting the controller die 24 to the substrate 26 are exposed and severed. The grinding equipment is typically either custom designed or is a non-standard piece of semiconductor equipment used in the machining shop with very low units per hour. Regardless of the equipment, the grinding is carried out in an uncontrolled environment and does not provide adequate grinding depth control.
Mechanical grinding also introduces mechanical stresses on the memory die 22, which may crack or otherwise damage one or more of the memory die 22. The grinding also reduces the original package thickness, which weakens the package structure and complicates downstream surface mount technology (SMT) processes due to non-standard package thickness. The grinding process may also expose the passive components in the package (not shown), which have a vertical height above the substrate 26 approaching that of the controller die bond wires 32.
One aspect of the present technology is to reclaim a semiconductor package. In one embodiment, a semiconductor dicing saw blade severs the bond wires electrically connecting the controller die to the substrate. The saw blade cuts through a portion of the package surface along a first edge of the controller die to sever one set of the bond wires electrically coupling the controller die with the package substrate. The semiconductor saw blade may make a second cut through a portion of the package surface along a second edge of the controller die to sever the remaining portion of the bond wires electrically coupling the controller die with the package substrate. In an alternative embodiment, the semiconductor dicing saw may instead sever all bond wires electrically coupling the controller die with the package substrate in a single pass over the package. The semiconductor saw blade does not sever the electrical coupling between the one or more memory die and the package substrate. The exposed bond wires between the controller die and substrate are next covered with an electrically insulating material. In an alternative embodiment, a laser may be used (instead of a dicing saw blade) to cut through a portion of the package surface to sever the bond wires electrically coupling the controller die to the package substrate.
A further aspect of the present technology is to form a new semiconductor package using the reclaimed semiconductor package. In one embodiment, a reclaimed semiconductor package is affixed to the surface of a second new substrate. The reclaimed package is electrically coupled to the second substrate by surface mounting the exposed test pads of the reclaimed package to contact pads on the second substrate. The test pads of the reclaimed semiconductor package electrically couple the memory die of the reclaimed semiconductor package with the second substrate. A second controller die is also affixed to and electrically coupled with the second substrate. The second substrate, with the reclaimed semiconductor package and second controller die affixed, is encapsulated in an electrically insulating molding compound to form a finished semiconductor package.
Embodiments will now be described with reference to
As indicated in the Background section, memory cards may fail final testing for several reasons. Embodiments described hereinafter relate to novel methods for reclaiming semiconductor packages which fail due to a faulty controller die. For the purpose of describing this technology, the reclaimed semiconductor packages may come from a variety of different types of semiconductor packages such as those used for, but not limited to, secure digital cards, compact flash cards, memory sticks, universal serial bus (USB) flash drives, USB storage devices, and the like.
In step 304, it is determined whether the flash memory card (which has been sorted into the “failed” group) is lidded. If the flash memory card is lidded, the lid is removed from the flash memory card, in step 306 (a flash memory card without a lid is referred to as a “flash memory package” or “semiconductor package”). Once the lid of the flash memory card is removed (or if the flash memory card did not have a lid to begin with), the flash memory package is reclaimed, in step 308. As will be discussed in more detail later, the controller die 124 in the damaged semiconductor package 120 is electrically isolated from the substrate 126, in step 308.
Step 308 is explained in greater detail with reference to the top and edge views of
Each memory die 122 is electrically coupled to the substrate 126 by affixing bond wires 134 between the bond pads 128 on the memory die 122 and the contact pads 130. The controller die 124 is electrically coupled to the substrate 126 by affixing bond wires 132 (including wires 132a and 132b) between the bond pads 128 on the controller die 124 and the contact pads 130. The bond pads 128a are electrically coupled to the substrate 126 by affixing the bond wires 132a between the bond pads 128a and the contact pads 130. The bond pads 128b are electrically coupled to the substrate 126 by affixing the bond wires 132b between the bond pads 128b and the contact pads 130. The memory die 122, the controller die 124 and bond wires 132a, 132b and 134 are encapsulated in a molding compound 137 (
In order to isolate the controller die 124 from the substrate 126 during the reclamation process, bond wires 132a and 132b are severed (step 402,
Cutting path A and cutting path B are shown as linear paths, though they need not be in alternative embodiments. In order to cut path A into the molding compound 137, the cutting tool makes a single pass across the semiconductor package 120. In order to cut path B into the molding compound 137, the cutting tool (either the same tool as made path A or another cutting tool) then makes another pass across the semiconductor package 120. Cutting path A is generally adjacent to and parallel with the edge 124a of the memory die 124. Cutting path A is offset from the second edge 140 of the substrate 126 by a distance d2. Cutting path B is generally adjacent to and parallel with the edge 124b of the controller die 124. The cutting path B is offset from the edge 138 by a distance d1.
Cutting path A and cutting path B may be made along the entire width and length of package 120, respectively. However, it is understood that the cutting path A and/or cutting path B may be made along only a portion of the width and/or length of the package 120 with the provision that the cutting paths A and B be sufficiently long to sever all of the bond wires connecting controller die 124 to substrate 126.
In one embodiment, the cutting tool comprises a semiconductor dicing saw blade. A blade having a thickness of, by way of example only, 1.0 mm is used to cut the molding compound 137 of the semiconductor package 120 along paths A and B. Such a thin blade ensures that the bond wires 132a and 132b will be severed despite a variation in the actual position of the controller die 124 with respect to one of the reference edges 138 or 140 due to package dimensional tolerances (typically +/−0.05 mm) and die-placement accuracy (typically +/−0.02 mm). A thin saw blade also limits the chance that the passive component 129 will be cut or exposed as a result of cutting the package along path A or path B. The width or thickness of the saw blade may vary in further embodiments.
In order to increase the efficiency of cutting each semiconductor package 120, multiple semiconductor packages 120 may be mounted and aligned on a tape or sawing jig in a predetermined matrix. Thus, a single pass of the cutting tool across the tape (or jig) will cut a path into the molding compound 137 of multiple semiconductor packages 120 along, for example, path A. The same would be true for cutting multiple packages 120 along path B or path C (explained below with respect to
In an alternative embodiment, instead of a cutting blade, the cuts A, B or C may be made with a laser. A variety of lasers are known which can partially cut through molding compound 137 as described above, including for example CO2 lasers, YBO4 lasers, Argon lasers, etc. Such lasers are manufactured for example by Rofin-Sinar Technologies of Hamburg, Germany. Where the cuts A and B are made by a laser, the two cuts may be made in a single pass. That is, after severing the bond wires along a first edge of the controller die 124, the laser (or the jig holding the semiconductor package 120) may make a right angle turn so that the laser then severs the bond wires along the next adjacent edge.
The semiconductor package 120 may be cut along paths A and B in any order (e.g., path A first, then path B, or vice versa). Moreover, while die bond pads 128 are shown along only two edges, it is understood that any number of cuts may be used as described above to sever any and all bond wires from controller die bond pads whether those die bond pads are distributed along one, two, three or all four sides of the controller die 124. Furthermore, in high density applications, it is also known to redistribute some of the controller bond wires onto a second, dummy die using an RDL process. The redistributed electrical connections coupling the controller die to the substrate may also be severed with cuts as described above.
After the cutting tool has severed the bond wires 132a and 132b (either by cutting the molding compound 137 along path C or paths A and B), the controller die 124 is electrically isolated from the substrate 126. Referring again to the flowcharts of
As explained below, the reclaimed semiconductor package is mounted on a substrate and then encapsulated. As such, in an alternative embodiment, it is conceivable that step 404 of sealing the cutting paths with an insulating material be omitted.
In step 310, the reclaimed flash memory package is subjected to an external visual inspection. After the flash memory package passes the external visual inspection, the memory die in the flash memory package is tested, in step 312. The memory die are tested to verify the integrity of the electrical connections between the memory die and the substrate (e.g., verify that the bond wires 134 between the memory die 122 and the substrate 126 were not severed during the reclaim process in step 308). In some applications, memory packages include only memory die and no controller die. Upon completion of step 310, the reclaimed semiconductor package 120 described above may then be used for such applications.
For memory card applications including both memory die and a controller die, the reclaimed package 120 may be coupled with a new controller die on a new substrate and encapsulated. Such a memory card is now explained with reference to
Referring now to the flowchart of
Step 314 is explained in greater detail in the flowchart of
It is understood that the number and configuration of test pads 148 and contact pads 108 is by way of example only, and each may vary in alternative embodiments. Moreover, there is no requirement that all test pads 148 be electrically connected to a contact pad 108. Substrate 102 may further include a conductance pattern defining electrical traces 110 (only some examples of which are shown) for transferring signals to and from the contact pads 108.
After the reclaimed semiconductor package 120 and the second controller die 116 are mounted to the second substrate 102, the reclaimed semiconductor package 120 and second controller die 116 are encapsulated within an electrically insulating molding compound 162 in step 316. The second substrate 102, with the reclaimed semiconductor package 130 and second controller die 116 affixed and encapsulated, comprises a new semiconductor package 150 as shown in
In step 318, the new semiconductor package 150 may be lidded. The new flash memory card (package plus lid) may be electrically tested in step 320. Assuming the new flash memory card passes the test, the new flash memory card may be labeled in step 322 with the card and/or brand name and an identification number for the card. A final visual inspection may be conducted to check for scratches and discoloration in step 324. If the new flash memory card passes the inspection, the new flash memory card may then be shipped in step 328 to a supplier such as an original equipment manufacturer, retail store and the like for use with a third-party host device (e.g., digital camera).
The foregoing detailed description of the inventive system has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the inventive system to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. The described embodiments were chosen in order to best explain the principles of the inventive system and its practical application to thereby enable others skilled in the art to best utilize the inventive system in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the inventive system be defined by the claims appended hereto.
Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.
Number | Name | Date | Kind |
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6002178 | Lin | Dec 1999 | A |
6249052 | Lin | Jun 2001 | B1 |
7569923 | Meir | Aug 2009 | B2 |
Number | Date | Country | |
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20090325321 A1 | Dec 2009 | US |