Alignment Apparatus for Electronic Device Package

This invention relates generally to alignment apparatus for use in mounting electronic device packages on printed circuit boards. More particularly, but not by way of limitation, this invention relates to alignment apparatus useful in mounting heat sinks and electronic device packages and the like on printed circuit boards.

In the assembly of electronic apparatus it is necessary to position electronic device packages which have multiple pin connectors and the like on multiple preformed locations on a printed circuit board. The multiple preformed locations for receiving the pin connectors on a printed circuit board may constitute holes in the printed circuit board or areas on the surface of the printed circuit board to which the pin connectors may be soldered such as shown in U.S. Pat. No. 4,625,260 entitled Fasteners for Surface Mounting of Printed Circuit Board Components. Frequently, it is also necessary to locate a heat sink on the electronic device package so that intimate thermal contact is maintained therebetween.

It is also sometimes necessary to attach the heat sink on the printed circuit board and this is commonly accomplished by structures projecting from the heat sink and mounted on preformed locations on the printed circuit board so that the heat sink can be securely attached to the printed circuit board such as by soldering. More often than not, these structures are separate components from the heat sink and include some releasable arrangement so that the heat sink can be removed from the printed circuit board if desired. Thus, in order to mount an electronic device package and a heat sink, it is necessary that a multiplicity of pin connectors and structures be simultaneously aligned with the preformed locations on the printed circuit board. In the past sub-assemblies of parts, such as heat sinks and transistors were manually assembled and then manually placed with the pin connectors and structures on the appropriate locations in the printed circuit board. Manifestly, such manual assembly techniques are slow, labor intensive and thus expensive.

Many electronic circuits are currently being assembled by robots or the like and, after the electronic device packages are placed on the printed circuit board, mass soldering techniques are utilized so that all the electronic components, including the electronic device packages and the heat sinks, are soldered to the printed circuit board simultaneously and virtually instantaneously. Up to now it has remained necessary, because of the alignment problems, to manually assemble the electronic device packages to their heat sinks and then manually assemble the sub-assembled parts on the printed circuit boards.

This invention provides alignment apparatus which permits electronic device packages and heat sink assemblies to be mounted on a printed circuit board with all the pin connectors of the electronic device package aligned for engagement with preformed printed circuit board locations so that the assembly can be made by the use of robotic techniques. It thus provides alignment apparatus for use in conjunction with printed circuit boards, heat sinks and electronic device packages having pin connectors and the like. The alignment apparatus includes an electrically insulating body having a plurality of holes extending through the body for receiving, aligning and retaining the pin connectors in a precise predetermined relationship. Means are provided to attach the heat sink to the body of the alignment apparatus with the electronic device package detachably secured in intimate thermal contact with the heat sink and to mount the alignment apparatus, electronic device package and heat sink, on the printed circuit board with the pin connectors of the electronic device package soldered to preformed locations on the printed circuit board.

So that the manner in which the above recited features and advantages of the invention, as well as others which will become apparent to those skilled in the art, are obtained and can be understood in detail, a more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof which are illustrated in the accompanying drawings, which drawings form a part of the specification and in which like numerals depict like parts in the several views. It is noted, however, that the appended drawings illustrate only a preferred embodiment of the invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIG. 1 is a front elevational view of a heat sink, electronic device package and alignment apparatus constructed in accordance with the invention and located on a printed circuit board.

FIG. 2A is a partial side view of the alignment apparatus, heat sink and electronic device package of FIG. 1 in a first position prior to mounting on the printed circuit board.

FIG. 2B is a partial side view of the alignment apparatus, heat sink and electronic device package of FIG. 2A in a second position and mounted on a printed circuit board.

FIG. 3 is a top view of the heat sink, electronic device package and alignment apparatus of FIG. 1.

FIG. 4 is a front elevational view of the body of the alignment apparatus of FIG. 1.

FIG. 5 is a top view of the body of the alignment apparatus of FIG. 4.

FIG. 6 is a side view of the body of the alignment apparatus of FIG. 4.

FIG. 7 is a longitudinal cross-sectional view of a first hole for receiving a pin connector taken along plane 7--7 of FIG. 5.

FIG. 8 is a transverse cross-sectional view of the first hole for receiving a pin connector taken along plane 8--8 of FIG. 5.

FIG. 9 is a longitudinal cross-sectional view of a second hole for receiving a pin connector taken along plane 9--9 of FIG. 5.

FIG. 10 is a transverse cross-sectional view of the second hole for receiving a pin connector taken along plane 10--10 of FIG. 5.

FIG. 11 is a front elevational view of the door of the alignment apparatus of FIG. 1.

FIG. 12 is a side view of the door of FIG. 11.

FIG. 13 is a top view of the door of FIG. 11.

Referring to the drawings and FIGS. 1-3 in particular, shown therein and generally designated by the reference numeral 10 is a sub-assembly consisting of a heat sink 12, an electronic device package 14, an alignment apparatus 16 and a printed circuit board 18 or the like. Heat sink 12 is generally constructed from material of high thermal conductivity such as aluminum or alloys thereof. The heat sink is usually anodized and thus is virtually impossible to solder directly to the printed circuit board. The electronic device package includes housing 20 mounted on flange 22 and one or more downwardly depending pin connectors 24. In the illustrated embodiment the electronic device package takes the form of a TO-220 type electronic device package and, more specifically, a Multi-Watt "R" type component manufactured by the SGS Semiconductor Corporation having two parallel rows of pin connectors extending from one longitudinal side edge of the housing (i.e. one row with seven pin connectors and a second adjacent row with eight pin connectors).

Alignment apparatus 16 includes a body 30 (shown in greater detail in FIGS. 4-6) defining top surface 32 and bottom surface 34. The body is preferably a monolithic molded piece formed from electrically insulating material such as nylon. Connection means are formed on the body to attach the heat sink to the body and includes three upwardly projecting spaced tabs 36, 38 and 40, respectively. The tabs are located in an alternating arrangement to receive the heat sink between the tabs 36 and 38 on one side and tab 40 on the other side. On the top surface of the alignment device are formed one or more spacing elements 42 (shown in FIGS. 4-6) for contacting the lower edge of the heat sink when inserted into the tab and to accurately position the heat sink with respect to the top surface of the alignment device body. The tabs 36 and 38 each include a tooth 44. Each tooth 44, is aligned with and engages a hole 46 formed in the heat sink when the heat sink is attached to the alignment apparatus body. The heat sink is detachable from the body 30 by manually deflecting the tabs 36 and 38 outwardly to release the teeth 44 from their respective holes 46 in the heat sink. On the bottom surface, the alignment device is provided with one or more protuberances 48 to maintain body 30 a predetermined distance above the surface of the printed circuit board. The protuberances provide access to the underside of the body of the alignment device, such as after flow soldering procedures, for cleaning purposes.

The body also includes a suitable number of pin connector holes extending from the top surface to the bottom surface. The shape, arrangement and size of the pin connector holes is determined by the electronic device package with which the alignment device is to be used and, in the illustrated embodiment, are formed in two parallel rows having seven (50a) and eight (50b) holes, respectively, in each row. The holes are formed with inwardly and downwardly tapering upper ends 52 and 54, respectively, as shown in FIGS. 7-10 for guiding the various pin connectors 24 into the holes as the electronic device package is positioned in the alignment apparatus body. The preformed holes in the printed circuit board are formed in the board with great accuracy so that the electronic device package will be properly located to form the desired circuits when mounted on the printed circuit board. To assure that the pin connectors are positioned to match the preformed locations in the printed circuit board, the alignment device is preferably die cast and the necessary holes located therein so that the relationship of all the holes will be within .+-.0.0003 inch.

For purposes of this invention, the term "hole" as applied to the holes 50a and 50b in the body also includes one or more similarly sized and shaped slots or grooves extending from the top to the bottom surface of the body along any of the edges of the body. The slots or grooves would function identically as herein described with respect to holes 50a and 50b.

Means are provided to secure the electronic device package in intimate thermal contact to the heat sink. The securing means includes attachment door 56 shown in greater detail in FIGS. 11-13. The attachment door preferably includes a unitary body formed from resilient metallic material. The door is pivotally attached to the body 30 by laterally projecting pegs 58 formed on the body engaging holes 60 in the door so that the door is shiftable between a first position shown in FIG. 2A for loading and unloading an electronic device package from the alignment apparatus and a second position shown in FIG. 2B for securing the electronic device package to the heat sink and for mounting the sub-assembly on a printed circuit board.

The attachment door also includes upwardly extending clip 64. The clip 64 is positioned on the attachment door for contact with the electronic device package intermediate the tabs 36 and 38 when the door is in its second position. The door acts to resiliently urge the electronic device package into good thermal contact with the heat sink and to secure the electronic device package in the desired position when mounted on the printed circuit board. Preferably, the clip 64 is positioned so as to apply force to the midpoint of the electronic device package.

Means are provided to latch the door in engagement with the body 30 of the alignment apparatus and secure the clip 64 in contact with the electronic device package. The latching means includes a pair of laterally spaced arms 66, each defining inwardly extending tangs 68. A pair of opposing shoulders 70 extends from the body of the alignment apparatus. As the door is shifted from its first position to its second position, the arms 66 encounter flanges 70 and are deflected outwardly until the tangs 68 pass the shoulders. At that point the tabs 66 spring inwardly and secure the door in its second position through contact between the tangs 68 and the shoulders 70.

Means are provided to attach the sub-assembly including the alignment apparatus, electronic device package and heat sink to a printed circuit board. A pair of integral mounting tabs 74 extend laterally from either side of the door. The lower ends of the mounting tabs are adapted for mounting on the printed circuit board by a solderable connection to preformed locations on the printed circuit board. Preferably, the mounting tabs are at least partially coated with a solder-promoting coating. Each of the mounting tabs includes two outwardly biased fingers 76 which frictionally engage the walls of aligned holes 78 in the printed circuit board. The fingers secure the sub-assembly to the printed circuit board with the pin connectors 24 likewise inserted into a plurality of aligned preformed holes 80 in the printed circuit board until the mounting tabs and the pin connectors are permanently soldered in place. Alternatively, the mounting tabs and the pin connectors could be adapted for attachment to the surface of the printed circuit board by soldering. In this alternate embodiment the mounting tabs and pin connectors include a surface disposed parallel with the surface of the printed circuit board and adapted for soldering to preformed mounting pads on the printed circuit board.

Thus, the alignment apparatus of this invention combines the functions of mounting the heat sink and electronic device package on the printed circuit board with all the pin connectors of the electronic device package aligned and located on preformed locations of the printed circuit board and of securing the electronic device package in intimate thermal contact with the heat sink. This enables the assembled heat sink and electronic device package to be automatically mounted on the printed circuit board with the attendant advantages discussed above.

Although the invention has been described above with regard to particular and preferred embodiments, these are advanced for illustrative purposes only and are not intended to limit the scope of this invention. For instance, the attachment door may be formed with a single mounting tab. It is frequently advantageous to connect two or more electronic device packages to the same heat sink to conserve surface on the printed circuit board and to reduce material and manufacturing costs. This may be accomplished by extending the body 30 on the other side of the heat sink and providing a second set of aligned holes (50a, 50b) for receipt of the pin connectors of a second electronic device package. A second pivotally connected door could also be provided to secure the second electronic device package in intimate thermal contact to the heat sink. The tab 40 could be eliminated and replaced by additional tabs opposing and substantially identical to tabs 36 and 38 for engaging holes 46 in the heat sink. It is also within the spirit and scope of this invention to provide alignment apparatus for mounting an electronic device package having pin connectors on a printed circuit board while omitting a heat sink. In such an embodiment the alignment apparatus would omit the connection means but include structure for contacting the electronic device package opposite the clip of the attachment door when latched in its second position. For instance, tab 40 could be constructed and positioned on the body 30 for such purposes.

Finally, it is within the spirit and scope of this invention to provide an attachment door 56 having a heat sink (not shown) projecting therefrom so that latching the attachment door 56 in its second position enables heat generated by the electronic device package to be conveyed through the clip 64 to the heat sink for rapid dissipation of the heat into the environment. In such an embodiment the heat sink 12 would be eliminated and the tab 40 adapted for contact with the electronic device package opposite clip 64. Preferably, the heat sink of the attachment door is integrally formed with the clip and mounting tabs. These variations remain within the scope of the invention as defined by the appended claims.