Electricity: conductors and insulators – Boxes and housings – Hermetic sealed envelope type
Reexamination Certificate
2001-09-13
2004-11-09
Ngo, Hung V. (Department: 2831)
Electricity: conductors and insulators
Boxes and housings
Hermetic sealed envelope type
C228S180210, C257S780000
Reexamination Certificate
active
06815613
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an electronic component with external connection elements and to a method of electrically connecting and/or fixing the electronic component and a printed-circuit board.
To make the most optimum possible use of the surface area of printed-circuit boards, they are provided with components on both sides. The fixing and electrical connecting of electronic components on both sides of the printed-circuit board surface, performed for example by soldering, in many cases requires additional adhesive fixing points between the component and the printed-circuit board, in particular for the components which are to be electrically bonded on the underside of the printed-circuit board, since otherwise there is the risk of these components falling off.
SUMMARY OF THE INVENTION
The object of the invention is to specify an electronic component with external connection elements with which additional fixing points on the components become superfluous and which ensures adhesive bonding of the component when it is being connected to a printed-circuit board, so that a printed-circuit board can be provided with components on both sides without the components on the underside of the printed-circuit board falling off during the connecting operation.
According to the invention, the electronic-component has external contact elements which are connected to contact connection areas of a leadframe or to contact connection areas of a chip. In this case, at least one external connection element is designed as a capillary element which protrudes out of the component and has at its protruding end a suction opening with capillary action. This solution has the advantage that, by means of the suction opening with capillary action of its capillary element, the electronic component significantly increases the adhesion in a liquid drop of solder which is adhering to the printed-circuit board, in comparison with external connection elements with no capillary action. The increased adhesion of the component in relation to a printed-circuit board brought about by means of capillary action has the effect that the component is secured against falling off the underside of a printed-circuit board provided with components on both sides. What is more, on account of the external connection elements according to the invention in the form of capillary elements, a solid extensive material bridge can develop between the component and the printed-circuit board in the form of a solder column, so that it is possible to dispense with additional fixing points, for example of epoxy adhesive.
The elements on the electronic component which bring about the capillary effect may be created already during component production. In addition, this electronic component has the advantage that, when it is being connected to the printed-circuit board, additional mechanical protection of the component contacts against damage due to compression or shearing is formed by the development of a solid-extensive material bridge such as a solder column. Finally, the use of only one material, that is for example a solder, for connecting and fixing the electronic component on a printed-circuit board, dispensing with adhesive fixing points, greatly simplifies the exchange of electronic components on printed-circuit boards, since no other additional fixing materials have to be removed and replaced for the exchange to be carried out.
Consequently, the external connection elements of the electronic component according to the invention allow the distance between the component and the printed-circuit board to be bridged by capillary action and allow extensive contacts which greatly increase the adhesion between the component and the printed-circuit board to develop. In addition, a possible way of mechanically stabilizing sensitive contacts is created, needing no additional materials or processes and consequently being entirely suitable for production. All that is required for this purpose is that the electronic component according to the invention has capillary elements as external connection elements.
In an embodiment of the invention, the suction opening with capillary action of the external connection elements is formed as a capillary slit. A capillary slit of this type can be made in any previously known external contact element without great effort, preferably by slitting the external connection element in its longitudinal direction. This provides the possibility of achieving additional adhesion by the capillary action of the longitudinal slit when the electronic component is being connected to the printed-circuit board.
In a further embodiment of the invention, the suction opening with capillary action may be formed as a ring. This variant is advantageous if the electronic component has pins as external connection elements, it being possible for these pins to be replaced by longitudinally slit hollow pins to form the annular suction opening with capillary action, thereby achieving an additional capillary action which can hold the component in position, even underneath a printed-circuit board, on account of the increased adhesion.
A further embodiment provides that the capillary element has a multiple arrangement of vertical contact elements which form a capillary gap. Vertical contact elements of this type may be produced, for example, by simple folding of conventional flat external connection elements. Such contact elements have an increased capillary action on account of the large-area capillary gap and are therefore suitable for large-volume electronic components.
A further embodiment of the invention provides that the capillary element has twin bumps, which are arranged at a distance from each other with capillary action. Twin bumps of this type may be arranged directly on the contact areas of a chip, so that this embodiment is particularly suitable for semiconductor chips which are to be arranged directly on a printed-circuit board.
A further embodiment of the invention provides a multi-layer printed-circuit board to be connected to the electrical component, with conductor tracks of a copper alloy. The surfaces of multi-layer printed-circuit boards of this type are provided with electronic components on both sides, use of the electronic component according to the invention preventing the components which are to be arranged on the underside from falling off.
With a further embodiment of the invention, the adhesion is increased by the capillary elements having a surface coating to enhance the wetting properties with respect to molten solder. A surface coating of this type has in one embodiment a nickel-gold alloy.
In one embodiment of the invention, the suction opening with capillary action has an opening width of between 50 &mgr;m and 500 &mgr;m. This opening width depends substantially on the wetting properties of the surface of the capillary element with respect to a liquid solder. The better the wetting properties, the larger the opening width may be, so that a larger material bridge develops between the printed-circuit board and the component.
In a further embodiment of the invention, a slit with capillary action is provided for a slit width of 50 &mgr;m to 500 &mgr;m. It must also be taken into account in respect of the slit width that, the better the wetting properties of the surface of the capillary element become, the larger the slit width can be.
In a further embodiment of the invention, it is provided that the vertical contact elements have in relation to the component surface an inclination at an angle &agr;. On account of this inclination, the flexibility of the contact elements with respect to a 90° arrangement is increased and the loading of the component according to the invention is reduced. What is more, the adhesive action at the same distance between the electronic component according to the invention and the printed-circuit board is increased on account of the inclination of the contact elements in relation to the component surface, since the wetting area
Gebauer Uta
Strutz Volker
Greenberg Laurence A.
Locher Ralph E.
Ngo Hung V.
Stemer Werner H.
Technologies AG
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