Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package
Reexamination Certificate
2001-11-20
2003-10-21
Loke, Steven (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
C257S693000, C257S694000, C257S695000, C257S696000, C257S697000
Reexamination Certificate
active
06635955
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a molded electronic component with numerous connection pins protruding on a single plane from a side surface area of an essentially cuboid housing, with top and bottom sides, and a circumferential ridge along the other side area surfaces on the level of the connection pins, the thickness of which ridge essentially corresponds to the thickness of the connection pins.
BACKGROUND OF THE INVENTION
Such a molded electronic component is known, for example, from the German patent publication DE 196 53 054 A1. In the case of such molded electronic components, semiconductor chips (optoelectronic transmitter and receiver, integrated circuit for signal processing) are first glued or soldered by machine onto a metal conductor strip and then contacted to one another and with the conductor strip by means of gold or aluminum wires. Then, using a mold process, semiconductor chips and conductor strips will in most cases be enveloped by means of a thermoplastic material such as a synthetic resin, thereby creating a housing for the protection of this assembly.
When the housing is manufactured, there remains an edge or protrusion of mold material in the separation plane of the mold form, between the top and bottom sections, which edge is also designated as a “ridge”. This is particularly disadvantageous if the ridge runs through a side surface of the housing which a suction needle from an automatic assembly machine will be docking onto at a later time, in order to take up the component and place the same onto a printed circuit board, for instance. Due to the ridge the suction needle does not connect tightly but draws in a great deal of external air, thus causing insufficient holding suction for any component to be taken up. In addition, when it is taken up the component will tilt over and assume a tilted and non-definable position on the suction needle. For this reason, an unacceptably large number of components are lost during transportation or are positioned imprecisely.
It is therefore attempted to keep the ridge as small as possible; however, this requires mold tools with very strict tolerances, very precise manufacturing, and additional controls. But these measures lead to significantly increased manufacturing costs without the problem having been really solved.
One possibility to avoid the ridge consists in not enveloping the electronic component with a synthetic resin by means of a mold process, but to produce a housing from a mold by encapsulation using a synthetic material suitable for casting.
However, compared to molding, the encapsulation method has many disadvantages; for example, that in comparison to molding great wall thicknesses are necessary and that these can be implemented only with relatively great tolerances and poor dimensional stability (major fluctuations) in the external dimensions. Therefore, a mold component can always be produced such that it is a more compact and space-saving product than an encapsulation component.
Furthermore, it is not possible to have a defined housing edge at the sprue side. Menisci are formed or the casting resin runs up along the connection pins of the electronic component, which will then prove to be very obstructive during the subsequent bending of the connection pins. Also, the awkward handling during the casting process is quite troublesome. Especially in the case of side view components (where the optical radiation direction is vertical to the direction of the still unbent pins), casting molds must be awkwardly and laboriously assembled for each casting process.
Another point regards cleanliness. Mixtures must be laboriously produced and the relevant level of cleanliness is difficult to maintain. In addition, defective resin mixtures are quite frequently prepared during such mixing processes. Casting molds are also quite expensive. High production costs arise additionally as cavity and, in part, sealing materials need to be used as consumables, and as a cavity change is necessary every 20 to 100 shots.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a molded electronic component of the above discussed general type, which can be taken up without difficulty by an automatic assembly machine and placed on a printed circuit board.
The above object has been achieved according to the invention in a molded electronic component comprising a substantially cuboid or rectangular block-shaped housing including a top surface, a bottom surface, opposite first and second side surfaces, opposite third and fourth side surfaces, and a plurality at electrical connection pins protruding along a single pin plane from the first side surface of the housing. A mold parting ridge or flash ridge of the molded housing material protrudes along the pin plane from the third and fourth side surfaces, and this ridge passes into a groove along the pin plane on at least a portion of the second side surface of the housing opposite from the electrical connection pins.
The molded electronic component in accordance with the invention features the advantage that it can be taken up without difficulty, held securely and placed exactly, by an automatic assembly machine without particularly strict tolerances having to be maintained during the production of the molded electronic component, without any special tools having to be used for its production, and without the problematic casting process having to be used.
The invention is particularly suitable for molded electronic components whose separation plane runs through that housing surface which serves as the docking surface for the suction needle of an assembly machine.
In the following, the invention will be explained in connection with an example embodiment with reference to the drawings.
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Fasse W. F.
Fasse W. G.
Loke Steven
Vishay Semiconductor GmbH
Vu Quang
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