This invention relates to an electronic component for surface mount technology (SMT), having a component body comprised of an electrically insulating material, and at least one conductor element mounted on said body, which conductor element is comprised of electrically conducting material and has a contact region which is exposed to the exterior of the component body, which contact region serves to connect the component to a printed circuit board (PCB) or the like.
Customarily, an electronic component is connected to a PCB by inserting the conductor elements of said component into bores provided in the PCB, and then soldering the conductor elements in said bores.
To simplify the automated mounting of electronic components onto PCBS, in recent years a soldering technology has been developed which is known as SMT (surface mount technology), as a replacement for the traditional bore soldering technology. With SMT, the contact regions of the conductor elements are placed against a surface region of the PCB which region is typically coated with a soldering paste comprising materials which can be caused to produce a soldered joint. The soldering paste is then heated by IR radiation, to produce a connection between the electronic component and the PCB. This technique is known as the "reflow method". Alternatively, a vapor phase soldering process may be used, wherein the entire electronic component is enclosed in a space filled with a solvent and steam; the heat of condensation of the steam on the cold electronic component brings about the solder joint. However, this technique is objectionable because it poses environmental problems. The reflow method will now be described, with reference to FIGS. 3a and 3b of the accompanying drawings.
The fixing of an electronic component in the form of a plug connector, to a PCB (230, in FIG. 3a) will be described, with reference to FIG. 3a of the drawings: The plug connector is comprised of a body 210 of insulating material having a plate-shaped bottom member 212 and a wall 214 extending perpendicular thereto. Two conductor elements 220 pass through the bottom member 212. Outside of the body 210 the conductor elements have exposed contact regions 222, and inside of body 210 the conductor elements have plug-like regions 224 which can be inserted in a contact socket.
To fix the plug connector to the PCB according to the known "reflow method", the contact regions 222 are applied to a region of the PCB bearing a soldering paste, and then said paste is melted by means of infrared (IR) radiation applied to the contact region in the directions indicated by arrows 226, and the melted solder is allowed to solidify. The result is a strong and durable connection between the PCB and the plug connector.
To avoid shadow formation, caused by neighboring components, and which interferes with the action of the IR irradiation on the contact region, it has been proposed to chamfer the body 210 at the transition between the plate-shaped bottom member 212 and the wall 214 extending perpendicularly thereto (see inclined surfaces 218 FIG. 3b). This state of the art is disclosed, for example, in German OS 42 03 605 A1. If the other geometric parameters are left unchanged, the introduction of the chamfer increases the maximum angle of incidence, .alpha., with respect to the PCB (230), of the IR radiation incident on the contact region 222 without shadow formation. The chamfer feature enables a higher density of electronic components to be mounted on the area of the PCB using the surface soldering technique, due to the fact that the maximum angle of incidence of irradiation is increased by the chamfers 218, which in turn reduces the minimum separation between components which is required to avoid formation of shadows by neighboring components.
Although the mounting density of components on a PCB can be greatly increased by the feature, the maximum achievable angle of incidence .alpha. is still limited, and thus the maximum achievable mounting density is limited, e.g. by the constraints imposed generally by the geometry of the component, namely the extent of the wall 214. Further, a problem is presented with the customary arrangement of electronic components fixed to a PCB by means of surface soldering techniques, namely that the range of angles at which the IR radiation may be supplied to the contact region is small, and the greater the mounting density the smaller becomes said range of angles. For a given IR source, this reduces the IR power available for melting, and thereby increases the time required to achieve melting.