Memory cube and its manufacturing process

The present invention relates to a memory cube and method of manufacturing.

The invention relates to the field of integrated circuits, and more specifically cubic housings of integrated circuits. Such devices allow to include a large number of separate components integrated in a low volume ensuring easy connection of integrated components.

US-A-4,521,921 describes an electronic module for high density formed by bonding to the epoxy adhesive of chips to form a stack; each chips is provided on one face of conductors deposited during process manufacturing of the chip, the wire ends on one side of the chip forming connection terminals. This document is primarily raises the problem of connecting the chip terminals on one side of stacking perpendicular to the plane of the chip, ie on the contact plane, and To this end, to make an attack on the side of the stack, the depositing an insulating material and removing part of the insulating material to discover the ends of the chip terminals.

US Patent 5,563,086 describes the structure and manufacturing a memory cube integrated to obtain a high density component. It is proposed in this paper stacked memories, in an example of the memory 16 megabytes, arranging between two neighboring parties' submissions metal transfer, insulation layers and an adhesive layer for fixing the memories.

3D + company offers cubes memories formed a set 64 megabytes of memory, in TSOP packages (thin small outline package). The manufacture of these cubes is made through the following process. Each of the memories is first fixed on film and wired on the film. After wiring, each memory is tested on the film. The individual films are stacked and the stack is assembled with the leadframe. The assembly is introduced into a mold; the resin is injected into the mold. After demoulding, the memory cube is machined on at least one side perpendicular to the plane memories, and metallic and engraved by laser so to recover the interconnection between components. On his lateral surfaces of the finished component, see the section of films used for the positioning of memories. 1 shows a sectional view schematic of such a memory cube. It shows a set of memories TSOP 64 megabyte 1 to 9; each memory is wired on a film 11 to 19. The assembly is molded in a resin 20, which exceed the leadframes ends 22 and 23. The line 25 indicates the area of cutting the memory cube which is adjacent to the ends of the films.

This process has the disadvantage of requiring a wiring different memories and a subsequent test wiring. In addition, it allows get as memories of a cubic well above the thickness sum of the thicknesses of the housings of the various assembled components.

The invention proposes a solution which overcomes this drawback. She permits to simplify and shorten the memory cube manufacturing cycle; in Furthermore, it allows for more compact components.

More specifically, the invention provides a method of manufacturing a memory cube, including<ul><li>stacking a plurality of memories and connectivity elements in a mold ensuring their relative positioning;</li><li>molding memories and connection elements in the resin inside the mold.</li></ul>

Advantageously, the memories are stacked directly on top of each others.

In another implementation, the method comprises a step bonding memory directly on each other before they stack in the mold.

Preferably, the connection elements include a gate connection.

One can also provide a step of demoulding the molded assembly, an abrasion step to one side of the molded assembly parallel to the plane of memories, a metallization step of the abraded surface, and a step of etching the metallized side.

The memories may have TSOP packages.

The invention also provides a memory cube, comprising a plurality of memories stacked directly on each other, and elements of connectors, molded in resin.

In one embodiment, adjacent memories have Cases bonded directly to each other.

The memories advantageously have TSOP packages.

In one embodiment, the connection elements include a leadframe.

Other features and advantages of the invention will become apparent to the reading of the following description of embodiments of the invention, given by way of example and with reference to the accompanying drawings which show:<ul><li>Figure 1 a schematic section of a memory cube pursuant to Art prior;</li><li>2 shows a schematic cross section of a memory cube of the invention;</li><li>3, a cross-sectional view of a memory cube mold according to the invention;</li><li>4 is a cross-sectional view of a memory cube mold according to the invention in a plane perpendicular to that of Figure 3.</li></ul>

The invention is based on the surprising finding that the films used as intermediate carrier in the memory cubes are useless; at Contrary to popular belief, the invention proposes to stack directly remembered for manufacturing the memory cube. It offers further use of the mold itself to ensure the relative positioning of the memories eet lead frames before the injection or pouring of the resin.

Figure 2 shows a schematic cross section of a memory cube according to the invention. This memory cube includes a plurality of memories 31 39, for example memories in boxes TSOP, which are stacked directly on each other, and which are molded in a resin; the cube includes connection elements, typically a grid 41 connection partially molded in resin.

The memory cube 2 is manufactured as follows. stacking in a mold a plurality of memories, for example memories having a TSOP package. The shape and size of the mold are chosen so to ensure the accurate relative positioning of memories and elements of connections. For example, a set of about 100 mm between the housings and connection elements and the mold positioning means is kind to provide an acceptable result.

Figure 3 shows a cross sectional view of a mold for cube memory of the invention. This one includes two elongated shoulders 50 and 51 located on sidewalls 52 and 53 opposite the mold, parallel the bottom 54 of the mold, near the bottom; in this case, the pin located on both sides of the first housing TSOP introduced into the mold come lean against the shoulders. The shoulders thus provide a precise positioning of a least one housing in the bottom of the mold, in a plane direction of the housing. Is shown in phantom interrupted in FIG TSOP a housing 55 disposed in the mold.

4 shows a cross-sectional view of the mold of Figure 3, in a plane orthogonal. It shows that to maintain a housing TSOP in the plane of the housing, it is also possible shoulders 56 and 57, the side walls of the mold and perpendicular to the mold, which come to bear against the pins of the package, so as to prevent or restrict any movement of Enclosure in his plan. This is to ensure a easy positioning of the TSOP arranged the mold, in all directions.

The following boxes can be arranged in the same way in mold. They can also be glued on to each directly screening the other, the assembly then being introduced directly into the mold.

Once the different housings are introduced into the mold, features in the mold the connection elements, typically a gate connection (or "lead frame" in English) to be later connected to pins of the memories. The leadframe is then held in position relative to the housings TSOP through cover mold.

We then proceeded to the molding of the assembly, by injection into inside the mold with a resin. The resin is typically a resin vector such as an epoxy resin, which is a typical use in this such applications. The injection of such a resin in the mold alters not the relative position of different memories. The amount of resin necessary is less than that required in the systems of the prior art, due to the size of the mold.

After shooting resin is unmolded together; the line 44 in Figure 2 shows the shape of the assembly after release; as can be seen, memories pin ends flush with the edge of the resin. he turns out surprisingly that the small amount of resin corresponding enough to ensure a satisfactory mechanical assembly of memories.

This is followed by cutting or abrasion of the cube; as seen in Figure 2, you only in this step to remove the faces of the cube a very low amount of material to make the flush Pin sections memories. In Figure 2, the line 46 indicates the boundary Memory cube after the step of cutting or abrasion. We proceed then in a manner known per se to the metallization of the abraded surface, and its etching to connect pins briefs to the leadframe.

The method of the invention avoids the steps of attaching and wiring memories on film. It simplifies the manufacture of cubes memory, and makes it more safe, insofar as it avoids possible disconnections among the memories and the film during molding. Furthermore, it allows to obtain a cube whose width and length are very near housing those memories; the thickness of the cube is of the order of the sum briefs thicknesses.

Of course, the present invention is not limited to the examples and described and shown embodiments, but is capable of many variants to the skilled artisan. Thus, the invention has been described with reference to memory; it applies to other types of components that such memories have identical shapes and adapted to be stacked. It applies not only to TSOP housings, but also to other types of housings side pins.