Encapsulation housing for electronic circuit boards or the like and method of encapsulating

Abstract

A control device assembled on a circuit board is suitably encapsulated within a protective housing on a multiple unit basis especially suited for automation. A plurality of housings are arranged in an upright, side-by-side relation so that the associated circuit board may be inserted from a vertical direction and correctly positioned within the housing by a pair of guide rails and the action of gravity. The housings may then be suitably encapsulated utilizing a continuous and uninterrupted flow of encapsulating material.

The housing itself is fabricated of a non-metallic, thermosetting material unaffected during subsequent operation in elevated ambient temperatures. The housing further includes a laterally extending lip or ledge which overlies a top portion of the next adjacent housing during assembly and encapsulation. Mounting holes are provided of a configuration to permit a wide variety of mounting locations.

Description

BACKGROUND OF THE INVENTION

The present invention relates in general to housings for electrical or electronic components and more particularly to an improved method and apparatus for housing and encapsulating such components.

Without affecting any limitations as to other applications, the present invention is set forth and described in the environment of protective housings intended for control devices in vehicles such as, for example, electronic voltage regulators.

With the advent of semi-conductors and the development of companion technologies, such as the thick film art and the like, many new applications are being found for solid state control devices of one sort or another. This includes voltage regulators and other control circuitsa12i of the side wall 12i which extends to the top edge 12j of the ledge is a smooth extension of the channel 12e formed between the guide rails 18 and back wall 12b to assist in inserting the board 20 into the guide rails and starting to move it rearwardly toward the rear wall 12b of the housing.

The plurality of housings 12 are maintained in the afore-described side-by-side, vertically stacked, position by a pair of rod-like members or shafts 36, extending through apertures 14 and 16. In this referenced position, the circuit board assemblies 20 may be inserted into an associated housing 12 from essentially the vertical direction. As previously described, the action of gravity in conjunction with the referenced internal guide rails 18 at respective sides thereof is then effective to correctly position and maintain the circuit board assembly 20 within the housing 12.

With the completion of the insertion of circuit board assemblies 20, the interior of housings 12 may be suitably encapsulated. In the preferred form, the encapsulation will be accomplished by an automated process. However, even where a hand operation is utilized, the encapsulation itself may be effected on a multi-unit basis.

In operation, the encapsulating material may be dispensed into the vertically stacked housings from a stationary vessel (not shown) as the housings 12 themselves are transported or moved along a predetermined path as a group or assemblage. Troughs 12h are effective to maintain the liquid encapsulation material 30 within a prescribed area as defined by such troughs. The overlapping of the housings, i.e., ledge 12f positioned on top portion 12g of the next adjacent housing, serves to prevent the encapsulating material from spilling between housings. As a consequence, the pouring of the encapsulating material may be effected on a continuous basis, rather than a start and stop action for each individual housing. This is a particularly attractive feature, and especially with regard to adapting to a suitable automated process.

Alternatively, it may be preferred to first partially fill the interior of housing 12 with sand or like material, and then fill the remaining space with the usual encapsulation material. The latter permeates the sand or filled material before hardening to its final state. This procedure is attractive because the sand is far less in cost than any encapsulation material which can be used. Further, the sand enhances the heat dissipation capabilities of the assembly as a whole.

While certain specific embodiments have been disclosed and described herein, it is, of course, to be understood that other and further modifications and alternative constructions or procedures may be effected without departing from the true scope and spirit of the present invention. For example, it may be preferred to maintain the assemblage of housings 12 and as depicted in FIG. 5 in a stationary position while moving the vessel from which the encapsulation material is poured along a predetermined path. This, of course, would be the method employed when utilizing a hand operation. In any event, the appended claims are intended to cover all such modifications and alternative constructions that may fall within the true scope and spirit of the present invention.

Claims

1. An improved protective enclosure for encapsulating an electrical control circuit arranged on a circuit board, comprising:

a housing structure formed with a base, vertically upstanding side walls and front and back end walls, open at the top, with a pair of guide rails, each rail extending verticaly vertically on the interior of a respective one of said side walls, said guide rails defining a pair of congruent channels in said side walls extending contiguous to one of the end walls for guiding the control circuit board to a position flatly against the one end wall upon inserting the control circuit board into the housing;

said housing further including a ledge extending laterally and outwardly from the top of one end wall, said ledge having a bottom edge, said other end wall having a top edge, the height of the bottom edge of said ledge above said base in relation to the height of the top edge of the other end wall above said base being dimensioned such that said housing is adaptable for stacking in multiple units in a vertical, side-by-side relation whereby said laterally extending ledge of one housing overlies the top edge of the next adjacent housing.

2. An improved protective enclosure in accordance with claim 1 wherein the width of each of said channels measured in a plane parallel to the side walls progressively tapers from a point at the top of the side walls to a point toward the bottom of the side walls whereby the associated control circuit board may be inserted from a vertical direction and positioned as aforesaid within said housing by the action of gravity.

3. An improved protective enclosure in accordance with claim 2 wherein the width of each channel tapers progressively along the entire length of the channel.

4. An improved protective enclosure in accordance with claim 2 wherein the one end wall is the front end wall, the other end wall is the back end wall and the channels are contiguous the back end wall.

5. An improved protective enclosure in accordance with claim 4 wherein the ledge extends the full width of the front end wall, the ledge having a top edge surface, each side wall having a portion extending to the top edge surface of the ledge, the portion being formed as a smooth extension of the channel.

6. An improved protective enclosure in accordance with claim 1 wherein said housing is formed of a non-metallic, thermosetting but permanently stabilized material when set notwithstanding being subjected to elevated ambient operating temperatures, which said housing being compatible with encapsulating techniques.

7. An improved protective enclosure in accordance with claim 1 wherein said housing further includes a shallow trough positioned centrally of said laterally extending ledge for confining a stream of encapsulating material when poured into the interior of said housing to essentially the area of said trough.

8. An improved protective enclosure in accordance with claim 7 wherein said housing includes a pair of apertures extending through said front and back walls but sealed off from the interior of said housing, said apertures being of a size and configuration to permit mounting of said housing at a plurality of locations as well as being adaptable for providing a means of support for stacking of said housings together in multiple units during assembly and encapsulation of the associated control circuit board.

9. An improved protective enclosure in accordance with claim 1 wherein said edges lie in a plane substantially perpendicular to the vertical axis of the housing.

10. An improved method of encapsulating a plurality of circuit boards each having a control device assembled on a circuit board thereon comprising the steps of:

forming a plurality of housings, each housing being open at its top, with guide rails extending vertically downwardly in the interior thereof and a lip extending laterally and outwardly from a top portion;

vertically stacking a plurality of said housings in a side-by-side relation whereby said lip of one housing overlaps a top portion of the next adjacent housing;

inserting an associated circuit board in each of said housings,

positioning each circuit board within its respective housing by guiding the same on said guide rails; and

continuously pouring encapsulating material into each housing consecutively in an amount sufficient to cover the circuit board in each housing.

11. An improved method of encapsulating a control device in accordance with claim 10 wherein the positioning step includes guiding the each circuit board on said guide rails under the force of gravity to a position flatly against one of the end housing walls.

12. An improved method of encapsulating a control device in accordance with claim 10 wherein the forming step includes providing each said lip with a shallow trough in a substantially central location thereof, and further comprising the step of constraining the encapsulation material within essentially the area defined by said troughs during the pouring of the encapsulation material into said housings.

13. An improved method of encapsulating a control device in accordance with claim 10 wherein the forming step includes providing mounting holes in the bodies of said housings and the step of vertically stacking the plurality of housings in a side-by-side relation includes inserting rod-like members through said mounting holes to support said housings as a group.

14. An improved method of encapsulating a control device in accordance with claim 10 wherein the step of forming said plurality of housings includes the fabrication of the same by compression molding from a non-metallic, thermosetting, but permanently stabilized plastic material.

15. An improved method of encapsulating a control device in accordance with claim 10 wherein the pouring step includes first continuously pouring sand into said individual housings consecutively, said sand filling at least half of the internal volume of the respective housings, and then continuously pouring encapsulating material into each of said housings consecutively to fill the remaining volume thereof and further comprising curing the encapsulating material.

16. An improved method of encapsulating a heat sink circuit board having a control device assembled on a heat sink circuit board thereon comprising the steps of:

forming a housing having a base, upstanding front and rear end walls and side walls, open at its top, with a pair of guide rails each rail extending vertically downwardly on the interior of a respective one of the side walls;

inserting the circuit board into the housing;

positioning the circuit board within the housing flatly against one of the end walls by guiding the side edges of the circuit board on the guide rails; and

pouring encapsulating material into the housing in an amount sufficient to cover the control device assembled on the circuit board. 17. The method of encapsulating a control device assembled on a heat sink circuit board as claimed in claim 16 wherein

the forming step includes forming a plurality of the housings, each housing having a lip extending laterally and outwardly from a top portion of one of the end walls,

further comprising

vertically stacking a plurality of the housings in a side-by-side relation whereby the lip of one housing overlaps a top portion of the next ajdacent housing,

inserting and positioning a circuit board into each housing as aforesaid, and

continuously pouring encapsulating material into each housing consecutively in an amount sufficient to cover the circuit board in each housing. 18. The method of encapsulating a control device assembled on a heat sink circuit board as claimed in claim 17 wherein the lip extends from one end wall and the positioning step includes positioning the circuit board

against the other end wall. 19. An encapsulated electrical control circuit comprising

a housing structure formed by a base and vertically upstanding side walls and two end walls, open at the top, with a pair of congruent guide channels, each channel being in a respective one of the side walls and extending contiguous to one of the end walls, the housing defining an open cavity,

a circuit board having side edges and two major surfaces and being dimensioned for receipt within the housing structure

an electrical control circuit mounted on one of the major surface areas of the circuit board and dimensioned for encapsulation within the housing structure

at least one electrical lead connected to the control circuit,

the circuit board being received within the cavity of the housing and the side edges of the ccircuit circuit board being received within the guide channels, the circuit board being juxtaposed one end wall in flat touching relation therewith along substantially all of the one of its major surface areas which is away from the major surface area on which the electrical control circuit is mounted, the electrical lead extending externally of the housing, and

encapsulating material filling the remainder of the cavity of the housing located adjacent the major surface area of the circuit board on which the electrical control circuit is mounted in an amount sufficient to cover the

electrical control circuit. 20. An encapsulated electrical control circuit as claimed in claim 19 wherein the circuit board is a metallic heat sink and is also fully encapsulated by the encapsulating material, and further comprising a pair of apertures extending through the front and back end walls of the housing but sealed off from the interior of the housing, said apertures being of a size and dimensioned for mounting of said housing at a plurality of locations.

21. An improved protective enclosure for encapsulating an electrical control circuit and heat sink in a circuit board assembly, comprising a housing structure formed with a base, vertical sidewalls and front and back end walls, open at the top; positioning means to position the heat sink flatly against one end wall; said housing further including a ledge extending laterally and outwardly from the top of one end wall, said ledge having a bottom edge, said other end wall having a top edge, the height of the bottom edge of said ledge above said base in relation to the height of the top edge of the other end wall above said base being dimensioned such that said housing is adaptable for stacking in multiple units in a vertical, side by side relation whereby said laterally extending ledge of one housing overlies the top edge of the next adjacent housing.

22. An improved method of encapsulating a control device and heat sink in a circuit board assembly comprising the steps of:

forming a housing having a base, upstanding front and back end walls and side walls, open at its top, inserting the circuit board assembly into the housing, positioning the heat sink of the circuit board assembly within the housing flatly against one of the end walls and pouring encapsulating material into the housing in an amount sufficient to cover the control device assembled on the circuit board.

23. A method of encapsulating a plurality of heat sink circuit boards each having a control device assembled thereon comprising the steps of:

forming a plurality of housings, each housing having a base, upstanding front and rear end walls and sidewalls, open at its top, with a pair of guide rails each rail extending vertically downwardly on the interior of a respective one of a sidewall, each housing having a lip extending laterally and outwardly from a top portion of one of the end walls;

inserting a circuit board into each of the housings;

positioning the circuit boards within their respective housings flatly against one of the end walls by guiding the side edges of the circuit board on the guide rails;

vertically stacking a plurality of the housings in a side-by-side relation whereby the lip of one housing overlaps a top portion of a next adjacent housing; and

continuously pouring encapsulating material into each housing consecutively in an amount sufficient to cover the circuit board in each housing.

24. The method of encapsulating a plurality of circuit boards as claimed in claim 17 wherein the lip extends from one end wall and the positioning steps include positioning the circuit board against the other end wall.