Abstract:
A molded electronic component has numerous connection pins protruding on a single plane from a side surface area of an essentially cuboid housing, and a circumferential ridge of molded housing material protrudes from the other side area surfaces on the plane of the connection pins. The thickness of this ridge essentially corresponds to the thickness of the connection pins. On the side surface area located opposite the side surface area from which the connection pins protrude, in the plane of the connection pins, the ridge passes or transitions into a groove such that there is no ridge protruding outwardly beyond the side surface in this area. Thus, the component can be better placed by a tool such as a suction needle onto a printed circuit board without interference from such a ridge. The invention is particularly suitable for the production of molded electronic components whose separation plane runs through that housing surface which serves as a docking surface for a suction needle.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is related to U.S. application Ser. No. 09/991,348, filed Nov. 20, 2001. 
    
    
     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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG.  1 : a top view of an assembly consisting of a conductor strip already populated with contacted semiconductor components, 
     FIG. 2 a : a top view of an electronic component which comprises the assembly according to FIG.  1  and is additionally provided with a molded housing, 
     FIG. 2 b : a side view onto the molded electronic component according to FIG. 2 a,    
     FIG.  3 : a side view (sectional representation) onto the molded electronic component according to FIGS. 2 a  and  2   b  during a subsequent production step, 
     FIGS. 4 a-d : the completed molded electronic component in four different views and 
     FIG.  5 : a molded electronic component according to the state of the art. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a conductor strip  1  which, for example, consists of a copper alloy and is punched or etched out in a known fashion from thin sheet metal. Also by punching or etching, a large number of connection pins  2  with bond surfaces  3  and assembly surfaces  4   a ,  4   b , and  4   c  for electronic or optoelectronic semiconductor components  5   a ,  5   b , and  5   c  are formed. The semiconductor components  5   a ,  5   b , and  5   c —by means of an adhesion material such as for example a solder or a conducting adhesive—are attached material-positively to the assembly surfaces  4   a ,  4   b , and  4   c  of the conductor strip  1 . 
     The semiconductor component  5   a , for example, is an optoelectronic transmitter, semiconductor component  5   b , for example, is an optoelectronic receiver, and the semiconductor component  5   c , for example, is an integrated circuit for processing the electric signals output by the optoelectronic receiver  5   b . The semiconductor components  5   a ,  5   b , and  5   c  are connected to one another, or with the bond surfaces  3  of the connection pins  2 , by means of thin bond wires  6  made up of an aluminum or gold alloy. 
     Furthermore, the conductor strip  1  features a frame  8  with an inner boundary  8 ′ and frame sections  8 . 1  and  8 . 2 . The frame section  8 . 2  is provided with a positioning and transport aperture  7  in the form of a round hole, and frame section  8 . 1  is provided with apertures  9  in the form of longitudinal holes, with lands  21  being located between the apertures  9 . In addition, frame section  8 . 1  features a widening  10 . The meaning and purpose of the apertures  9 , lands  21 , and widening  10  are described below. 
     During the mold process, frame  8  is located between the top and bottom sections of the mold form. Its inner boundary  8 ′ here runs around the mold form proper, as it has a slightly larger diameter than the later housing  12  (FIGS. 2 a, b ) produced by the mold form. 
     The FIGS. 2 a  and  2   b  show an as yet uncompleted electronic component  11  consisting of the assembly shown in FIG. 1 for the directed bi-directional optical data transmission at a later stage of production. Such a component  11  is also designated as a transceiver (from Transmitter and Receiver). In order to produce a protective essentially cuboid housing  12 , the semiconductor components  5   a-c  (FIG. 1) and the bond wires  6  (FIG. 1) were enveloped with a thermoplastic synthetic material such as a synthetic resin (transparent for a specific wavelength range) by means of a mold process. 
     Here the housing  12  consists of two sections: a first housing section  12   a  with a recess  13  (into which the connection pins  2  will later protrude, FIG. 4 c ) and a second housing section  12   b . From a plane  26  between the two housing sections  12   a  and  12   b , in which the connection pins  2  are located, there protrude the parts of conductor strip  1  that have not yet been removed. The first housing section  12   a  contains the underside  27  (assembly side) of component  11  facing a printed circuit board; the second housing section  12   b  contains the topside  28  and two bulges  14   a  or  14   b , which are arranged as lenses before transmitter  5   a  (FIG. 1) or receiver  5   b  (FIG.  1 ). 
     The connection pins  2  protrude from the side surface area  22  of housing  12 ; side surface  24  is located opposite. From the drawing plane, the further visible side surface area  25  protrudes; side surface area  23  (which cannot be seen in this view) is located opposite. 
     FIG. 3 shows a side view (sectional representation) of the electronic component  11  according to FIGS. 2 a  and  2   b  during a subsequent production step. Parts of conductor strip  1  that are no longer required are removed by punching or cutting, and thus, for example, the connection pins  2  are shortened to their final length. 
     In the case of components according to the state of the art, the frame  8  of conductor strip  1  features a distance to housing  12 , which is why it is that during molding a mold material ridge  19  (FIG. 5) (synthetic resin) forms on all four side surface areas  22 ,  23 ,  24 , and  25 , which later can only be somewhat reduced at great effort and cost but not completely removed, thus causing major difficulties during take-up by an assembly machine. 
     The invention, however, provides for the frame  8 —with its inner boundary  8 ′—to be directly adjacent to the area of the later housing  12 , even protruding somewhat into the area of the later housing  12 , so that, on the side surface area  24  opposite the connection pins  2 , the ridge  19  will pass into a groove  17  within a connected part of side surface area  24  (as also clearly described in FIGS. 4 a-d  and the relevant explanations). The widening  10  of frame section  8 . 1  serves to prevent the formation of the ridge  19  on the side surface area  24 . 
     In order to be able to take out component  11  from the parts of conductor strip  1  that have not yet been removed, for example by pressing out with a small lever press, without this being prevented by the widening  10  of conductor strip  1  possibly protruding into housing  12  or housing  12  being damaged thereby, the conductor strip  1  is held by means of a holding device  15  in the area of frame section  8 . 1 , and frame section  8 . 1  is then re-shaped mechanically, for example by embossing, such that a deformation  16 , such as shown here for example in the form of a V-shaped bead, is produced. 
     It is advantageous if frame section  8 . 1  is provided with apertures  9 , for example in the form of longitudinal holes. These longitudinal holes  9  weaken the material of frame section  8 . 1 , such that the deformation  16  can be produced at reduced force and exactly along the lands  21  between these longitudinal holes  9 . 
     By producing the deformation  16  the frame section  8 . 1  is pulled away from the housing  12  (in an ideal case) or, in a case which is not ideal, drawn out from housing  12 , thus creating at that point a narrow and flat groove  17 . The expert with relevant training will know that, instead of the V-shaped bead shown here it is possible to produce for example a U-shaped bead or any other mechanical deformation  16  in any given fashion such that frame section  8 . 1  will be deformed, thus creating an intermediate space between frame section  8 . 1  and housing  12 . 
     The ideal case occurs if the widening  10  of frame section  8 . 1  and housing  12  are still just about in contact. If, in a non-ideal case, the widening of frame section  8 . 1  is somewhat wider or if the housing  12  is somewhat offset during molding or produced to a somewhat larger size, then frame section  8 . 1  will in some small measure protrude with the widening  10  into the housing  12 . When producing the deformation  16 , the above-mentioned groove  17  is created in housing  12  by drawing out frame section  8 . 1  from the housing  12 . 
     However, such a groove  17  only represents a minor “appearance defect” and does not have any further negative effects, as even in spite of a groove  17  a suction needle  18  will connect flush to the housing  12 , and as the groove  17 , which has the effect of a thin, flat channel running across the relevant surface area of housing  12 , will only cause a very low volume of external air to be drawn in. This only leads to an almost unnoticeable force reduction by means of which such a component  11  is taken up by the suction needle  18 . However, there will not be any tilting of component  11 . 
     FIGS. 4 a-d  show the completed molded electronic component  11  in four different views. The connection pins  2  protruding from the side surface area  22  are angled twice and protrude into the recess  13 . The remaining parts of conductor strip  1  arranged outside the housing  12 , in particular frame  8 , have been removed. 
     The double angling of the connection pins  2  provides two options for mounting component  11  on a printed circuit board. The first option is to mount the component  11  in side view position such that the component  11  is mounted with the side surface area  22 , from which the connection pins  2  protrude, on a printed circuit board as shown here. The second option is to mount the component  11  in top view position such that the component  11  is mounted with the underside  27  on a printed circuit board. 
     In the plane  26 , in which the connection pins  2  are also located, the ridge  19  runs around the side surface areas  22 ,  23 , and  25 . The thickness of the ridge  19  here corresponds essentially to the thickness of the connection pins  2 . The ridge  19  forms because the inner boundary  8 ′ of the frame  8  is located a distance away from the area of the later housing  12  (FIG. 2 a ). In contrast to the above, the widening  10  of frame section  8 . 1  now reaches close to the later housing  12  or even protrudes somewhat into the later housing  12 . This measure causes ridge  19  to pass via a connected part of side surface area  24  into groove  17 . 
     The suction needle  18  of an automatic assembly machine (not shown here) can now take up by suction component  11  on the side surface area  24  of housing  12  without any difficulty, securely hold and exactly place the same onto a printed circuit board, for example, without groove  17  having any negative effect. 
     Finally, FIG. 5 shows a molded electronic component  20  according to the state of the art. A ridge  19  on the side surface area  24  opposite to the connection pins  2 , which is formed during molding in the separation surface area of the mold tool between the housing sections  12   a  and  12   b  in plane  26  of the connection pins  2 , causes a distance to appear between the suction needle  18  and the housing  12 , such that the component  20  is not held at all or with reduced force and in tilted fashion only. In an unacceptably large number of cases, this has the consequence that the component  20  assumes a tilted position on suction needle  18 , for example one of the mis-positions  30  or  31  shown here, and is thus imprecisely positioned on the printed circuit board, necessitating manual and thus costly reworking. Furthermore, another consequence frequently is that the component  20  is not taken up or is lost during transportation. 
     The molded electronic component according to the invention can be taken up without difficulty by a tool (suction needle) and, for example, placed correctly onto a printed circuit board—without the component being taken up in a tilted fashion and thus incorrectly positioned on the printed circuit board or lost during transportation.