Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With contact or lead
Reexamination Certificate
2001-03-23
2003-02-18
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With contact or lead
C257S678000, C257S680000, C257S690000, C257S697000, C257S738000, C257S778000
Reexamination Certificate
active
06521988
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a device for packaging electronic components and to a method for packaging electronic components.
One way of packaging electronic components is known as the BGA (ball grid array) housing. The device for packaging electronic components in BGA housings has a mounting frame, which frames and retains a plastic intermediate substrate. The plastic intermediate substrate has a plurality of contact bumps with connected conductor tracks that lead to a plurality of semiconductor positions inside the associated mounting frame. At these semiconductor chip positions, semiconductor chips are mounted, whose contact faces are connected to the conductor tracks of the plastic intermediate substrate. At the same time, plastic spacers or spacing layers assure that the semiconductor chips are retained on the plastic intermediate substrate at the semiconductor chip positions. To that end, the spacers or spacing layers, which comprise a silicone composition, can be coated with adhesive.
For packaging the plurality of semiconductor chips with a plastic casting composition, this composition is potted in order to filled up the interstices among the semiconductor chips and to fill the voids between the semiconductor chips and the plastic intermediate substrate as well as the mounting frame. After that, the plastic intermediate substrate is sawn apart in the region of the plastic casting composition between the semiconductor chips, and the packaging of the electronic components is thus completed.
In the cutting operation, the saw blade is guided through the plastic casting composition, which essentially comprises silicone composition. In this cutting method, sticky deposits of sawing residues occur, such as silicone beads, and hence these deposits are removed mechanically in a further cleaning process. Such a cleaning process is cost-intensive and complicated. Moreover, without this mechanical cleaning process, the external dimensions and external shape of the housing remain undefined. In addition, in subsequent production steps, the sawing residues can drop off and contaminate devices downstream, such as testing pedestals. Furthermore, it has been found that a housing whose contact bump arrangement on the plastic intermediate substrate is substantially larger in its area than the semiconductor chip itself is extremely mechanically unstable, since the plastic intermediate substrate with the contact bumps typically comprises a flexible, metal-coated polyamide. Stabilizing the extremely unstable outer edge that protrudes past the semiconductor chip dimensions has been feasible until now, for this housing type, only by complicatedly applying individual housing frames, by a time-consuming and expensive method that demands increased precision.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to disclose a device for packaging electronic components and a method for packaging such components that overcomes the above disadvantages when BGA housings on a plastic intermediate substrate are separated into individual components and that allows sawing in which no sticky deposits of sawing residues whatever can occur.
According to the invention, in addition to the semiconductor chips, a plastic grid is disposed on the plastic intermediate substrate, which grid surrounds each semiconductor chip in framelike fashion and which is provided for packaging the plurality of semiconductor chips with a plastic casting composition between semiconductor chips and the plastic grid. A device equipped in this way has the advantage that in the sawing process, the thermoplastic plastic casting composition no longer comes into contact with the saw blade and thus sticky residues or deposits, such as silicone beads if the potting composition comprises silicone, can form; instead, for cutting apart the device for packaging electronic components into individual electronic components, the saw blade can be guided through the plastic grid, so that it has no contact with the plastic casting composition whatever at the cut faces.
By the disposition of a plastic grid in a conventional mounting frame, so that the otherwise usual plastic casting composition is in part replaced by the plastic grid, on the one hand a considerable amount of plastic casting composition can be saved, and on the other, the previous devices for packaging electronic components can continue to be used without restriction.
Furthermore, with the device of the invention, time-consuming and expensive housing mounting with stabilizing individual frames is avoided, because these individual frames are created directly as the plastic grid is cut apart.
In a further preferred embodiment of the device for packaging electronic components, a mounting frame with a single large area opening for a plurality of semiconductor chip positions on the plastic intermediate substrate is replaced by a novel mounting frame, improved according to the invention, which has a plurality of individual openings that correspond in shape and size to the electronic components to be formed, so that in this embodiment of the invention, there is no need to produce and mount a plastic grid before the potting with a plastic casting composition is done.
The plastic intermediate substrate with its plurality of semiconductor chip positions can still be used as before for the improved mounting frame of the invention as well. This has the advantage that the design or construction of the plastic intermediate substrate with the semiconductor chip positions and the semiconductor chips disposed thereon, and their connections with the contact bumps via conductor tracks of the plastic intermediate substrate, can all be kept entirely as is. The advantage over a device with a single large-area opening is that when the plurality of electronic components are separated into individual BGA housings, the saw blades need no longer be guided through a plastic casting composition but instead are guided entirely within the material comprising the mounting frame. Thus with this version as well, the formation of sticky deposits in the cutting operation is averted.
In a preferred embodiment, the plastic casting composition is a thermoplastic silicone composition. This has the advantage that the differing thermal expansion behavior of the inner semiconductor chip and the outer plastic grid can be compensated for by the thermoplastic silicone composition, so that no stresses whatever are exerted on the protective frame, created from the plastic grid, or on the semiconductor chip located in the interior of the protective frame.
In a further preferred embodiment, the mounting frame comprises a dimensionally stable plastic. This has the advantage that the typically relatively flexible plastic intermediate substrate, by being glued to the mounting frame, offers a relatively stable device for packaging electronic components. The dimensionally stable plastic can preferably comprise polyethylene, polypropylene, polyamides or polycarbonates, polyvinyl chloride, or polytetrafluoroethylene, with suitable fillers.
In a further preferred embodiment, the mounting frame can also be made from a duroplastic, such as an epoxy resin or other two component plastics. Such plastics have the advantage that particularly in the sawing process, they do not form any thermoplastic, sticky residues or deposits but instead can be machined.
In a further preferred embodiment, the mounting frame and the plastic grid can be made from the same material, so that in the sawing operation, the same peripheral and starting conditions and the same sawing rates can be attained. In the preferred embodiment of the invention in which the mounting frame and the plastic grid are a one-piece, integral component, with openings for each semiconductor chip, as noted above, the mounting frame and the plastic grid are made from the very outset from the same material.
In another preferred embodiment of the invention, the semiconductor chip positions are disposed in rows and columns on the p
Hauser Christian
Pohl Jens
Winderl Johann
Greenberg Laurence A.
Infineon - Technologies AG
Locher Ralph E.
Nelms David
Stemer Werner H.
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