Electrical resistors – Resistance value responsive to a condition – Fluid- or gas pressure-actuated
Reexamination Certificate
1998-11-02
2001-11-06
Easthom, Karl D. (Department: 2832)
Electrical resistors
Resistance value responsive to a condition
Fluid- or gas pressure-actuated
C338S042000, C257S419000, C257S417000, C073S715000
Reexamination Certificate
active
06313729
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is directed to a semiconductor component formed of a chip carrier having a chip carrier surface on which a semiconductor chip is provided and wherein a pressure sensor is provided above the semiconductor chip.
Such a semiconductor component in the form of a pressure sensor has been disclosed in JP-A-7113706. This has a protective cap provided with an opening that is firmly glued to the chip carrier. A positive connection between chip carrier and protective cap insures a temporary arresting of the protective cap until the adhesive has set.
Another semiconductor pressure sensor with a fitting durably connected to the chip carrier has been disclosed in EP-A-0 497 534. After a snap-in connection, the fitting and the chip carrier exert an adequately high pressure on two elastomeric seals and the chip situated therebetween in order to assure a pressure-tight connection of the two component parts.
For measuring pressures, the medium to be measured must be brought to the sensor or, the pressure prevailing in the medium must be transmitted to the sensor. For this purpose, the pressure sensor is arranged in a component housing open at one side, so that the sensitive chip surface of the pressure sensor can proceed into direct contact with the medium to be measured. There is the disadvantage given this arrangement that the chemicals being employed during the assembly process of the semiconductor component open at one side can proceed to the sensitive chip surface of the pressure sensor, this resulting in the risk of corrosion at the component being accelerated or the component being completely destroyed. Processes upon utilization of chemicals that can result in a contamination of the component with aggressive ions, for example what are referred to as deflash processes or voltaic processes immediately after the fastening of the pressure sensor chip on the chip carrier are thereby especially critical. In a deflash process, the casting compound residues or, burrs that have remained after the plastic casting of the chip carrier are usually removed given employment of a high-pressure water jet. In the voltaic process to be implemented thereafter, the electrode terminals projecting from the housing are provided with a solderable cover coat by lead plating in order to enable a good fastening of the semiconductor component on the equipping surface of a printed circuit board.
SUMMARY OF THE INVENTION
The invention is based on the object of making available a semiconductor component with a semiconductor pressure sensor comprising a sensitive chip surface, particularly for mounting on the equipping surface of a printed circuit board, whereby the semiconductor component preferably comprises a housing open at one side with a chip carrier, said semiconductor component being designed such that a destruction of the sensitive chip surface of the pressure sensor can be avoided in processes wherein harmful chemicals are utilized.
This object is achieved by a semiconductor component comprising a chip carrier having an approximately planar chip carrier surface on which a semiconductor chip is provided. A pressure sensor is also secured above the semiconductor chip. Electrical terminals penetrate the chip carrier and electrically connect to the semiconductor chip. The protective cap overlaps the chip carrier as said pressure sensor. The protective cap comprises a retainer portion for a positive mechanical connection to a supporting structure of the chip carrier such that when the protective cap is put in place onto the chip carrier the retainer portion and the supporting structure proceed into engagement with one another. The protective cap is removable from the chip carrier. The chip carrier has a lower part on which the semiconductor chip is supported and also has lateral parts arranged at sides of the lower part that form laterally terminating housing walls of a housing for the pressure sensor, the supporting structure for the chip carrier being provided on upper edge regions of the walls, and the outside circumference of the walls having a circumferential abutment surface for supporting the retainer portion of the protective cap.
The invention proposes that the chip carrier open at one side be closed with a protective cap during the implementation of the critical assembly processes. The protective cap can also be simultaneously employed as transport protection, whereby a removal of the protective cap only occurs after the mounting of the semiconductor component or before the use of the component as a pressure sensor.
It is provided in the preferred embodiment of the invention that the protective cap is designed removable. The protective cap thereby comprises a retainer portion for a positive mechanical connection to a supporting structure of the chip carrier such that, when the protective cap is put in place on the chip carrier, the retainer portion and the structure unit engage with one another in alternating fashion. In conformity with the principle of the invention, the chip carrier is designed such that the outside circumference of the supporting structure of the chip carrier has a circumferential abutment surface that supports the retainer portion of the protective cap.
For the purpose of a an automatically implemented fixing of chip carrier and protective cap, it can thereby also be provided that the retainer portion of the protective cap is provided with a resilient projection that is allocated with a catch provided in the supporting structure of the chip carrier for the automatic fixing of the protective cap and the chip carrier in a mounting position.
The protective cap is preferably fabricated as an independently designed component part, particularly of plastic material, and can be repeatedly employed for covering the pressure sensor.
It can be provided in another advantageous embodiment of the invention that the chip carrier and the protective cap is produced of a plastic material that is resistant to the chemicals utilized in the assembly of the component.
It can be provided in another preferred embodiment that the protective cap—after the semiconductor component is put in use—is replaced by a fitting for the variable coupling of a feeder containing the medium to be measured. One thus succeeds in making a flexible mounting design available with which basically arbitrary forms of hose or plug connections can be offered for the connection to the pressure sensor, a broad spectrum of customer wishes being thus capable of being satisfied. A delivery of the medium to be measured to the sensor or, a transmission of the pressure prevailing in the medium to the sensor can be assured with a plug coupling—which is simple and cost-beneficial to manufacture—of the fitting replacing the protective cap. Thus the inclusion of outside air is precluded by the positive, play-free mechanical connection between the medium to be measured and the sensor and, therefore, an error-free pressure measurement can be implemented.
In an especially preferred way, the invention is directed to a semiconductor component for a surface mounting on the equipping surface of a printed circuit board. Given this type of mounting, the component terminals are no longer plugged into holes of the printed circuit board, as in plug-in mounting, but are put in place on terminal pads on the printed circuit board and soldered thereto. Components for surface mounting can be smaller than for plug-in mounting since hole and solder lug diameters of the printed circuit board no longer determine the grid dimension of the terminals. The holes needed only for equipping are also eliminated from the printed circuit board, whereby the holes now required only for through-contacting can be implemented as small as technologically possible. Since a double-sided equipping of the printed circuit board is also additionally possible, a considerable space-saving and substantial cost reduction can be achieved by the surface mounting. An especially slight structural height of the semiconductor component thereby derives whe
Beer Gottfried
Winterer Jurgen
Easthom Karl D.
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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