Low profile board-to-board electrical connector

A connector (10) for interconnecting a daughter card to a mother board using a flexible circuit element (64) joining the connector contacts (54) to the daughter card traces (76), while pin sections (56) of the contacts depend from the connector for insertion into mother board through-holes. A plate (82) of dielectric material is placed atop the terminations of the flexible circuit element to the contacts, with plate apertures (86) receiving the upper contact sections (66) and solder terminations thereinto, with potting compound (98) then placed in the apertures embedding and sealing the terminations, whereafter the plate provides enhanced strain relief.

FIELD OF THE INVENTION 
The present invention is related to electrical connectors and more 
particularly to connectors adapted to interconnect a daughter card to a 
mother board. 
BACKGROUND OF THE INVENTION 
Certain electrical connectors contain an array of electrical contacts 
having pin sections coextending from a mounting face of the connector to 
be received into respective through-holes of a circuit element such as a 
mother board to become electrically connected with circuits of the board. 
The dielectric housing of the connector includes passageways in which the 
contacts are respectively retained in selected spacings and positions so 
that the pin sections coextend in a selected pattern. Such connectors are 
adapted to be affixed to edges of daughter cards on an opposed or second 
face of the connector, with the contacts including other contact sections 
electrically connected to circuits on major surfaces of the daughter card 
proximate the edge thereof. Many such connectors are of the type including 
a card-receiving recess thereinto, with the other contact sections 
disposed along sides of the recess to enter biased engagement with the 
corresponding card traces, all permitting withdrawal of the card therefrom 
during unmating. For example, see U.S. Pat. No. 4,077,694. 
In U.S. Pat. Nos. 5,409,384 and 5,348,488, is disclosed a connector 
utilizing an element of flexible film circuitry for electrical 
interconnection of contacts of the daughter card to contacts of the 
connector. The dielectric housing has a thin substantially planar body 
section defining a board-proximate face and a board-remote face, an array 
of contact members including pin sections coextending from the 
board-proximate face of the body section to be received into corresponding 
through-holes of a mother board, and short second pin sections coextending 
from the board-remote face. The flexible circuit element includes defined 
thereon an array of circuits extending from termini located in a first 
interconnecting region associated with the second pin sections in a 
complementary pattern, along at least one side portion of the element 
formed upwardly from sides of the housing to contact sections exposed in 
at least one second interconnection region and associated with an array of 
circuits disposed on a surface of a daughter card to be interconnected 
therewith. 
The termini include pin-receiving apertures therethrough, so that when the 
flexible circuit element is properly oriented and its first 
interconnecting region pressed against the array of second pin sections of 
the connector contacts, the second pin sections enter through the 
pin-receiving apertures. With the traces and trace termini defined on the 
housing-remote surface of the flexible circuit element, the second pin 
sections protruding above the associated termini can easily be soldered 
thereto to establish the electrical connections. The side portion or 
portions of the flexible circuit element is or are then formed upwardly. 
Potting material is then deposited atop the first interconnecting region 
to a selected thickness, embedding and sealing and protecting the 
electrical connections, and also providing a mechanical retention of the 
flexible circuit element to the connector housing. 
In one embodiment of connector disclosed in U.S. Pat. No. 5,409,384, the 
flexible circuit element includes opposing side portions upwardly formed 
for second interconnecting regions on each to oppose each other and define 
a card-receiving region therebetween, into which an edge of a card is 
inserted for the traces on both surfaces to be soldered to exposed trace 
sections of the flexible circuit element. In another embodiment for a 
connector with fewer contacts, one such side portion and second 
interconnecting region extends upwardly to be secured to a corresponding 
surface of a daughter card and the exposed traces soldered to respective 
traces on that surface. The connectors provide a low profile 
board-to-board connector adapted for use in very confined spaces 
especially in a closely spaced array, wherein the electrical connections 
of the flexible film circuitry to contacts of the connector are sealed for 
long-term in-service life. 
SUMMARY OF THE INVENTION 
The present invention provides a low profile board-to-board connector that 
incorporates a flexible film circuit element for connecting traces of a 
daughter card to contacts of the connector which contacts include pin 
sections for interconnecting to circuits of a mother board at 
through-holes thereof. A premolded dielectric plate is provided above the 
array of solder joints of the flexible circuit element traces to the 
connector contacts. An array of holes corresponding to the sites of the 
soldered electrical connections permits potting compound to be disposed in 
the holes around the solder joints embedding and sealing the electrical 
connections. Control of the flow of potting compound results, with a 
defined boundary to the potted board-remote interface. The plate may be 
adhered to the surface of the flexible film circuit element prior to 
potting, if desired, and the plate thus adhered and potted provides strain 
relief benefits. 
An embodiment of the present invention will now be described by way of 
example with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates a connector of the prior art, such as that disclosed in 
U.S. Pat. Nos. 5,409,384 and 5,348,488. Connector assembly 10 includes a 
dielectric housing 12 with an array of contacts 14 affixed thereto in two 
rows, having pin sections 16 depending from a board mounting face 18 of 
housing 12 for eventual insertion into through-holes of a mother board 
(not shown). An organizer or alignment plate 20 is shown disposed below 
the housing and along free ends of the contact pins sections and the guide 
posts 22 at each end of the array, for maintaining the pin sections 
aligned to facilitate board mounting, with the organizer movable along the 
pin sections toward and to the housing during board mounting. Flexible 
film circuit element 24 includes circuits electrically connected to upper 
sections of contacts 14 at a first interconnection region 26, and the 
circuits extend to exposed portions 28 at a second interconnection region 
30 for eventual electrical connections to corresponding traces of a 
daughter card (not shown). Potting compound 32 is shown applied to the 
upper face of the connector to a selected depth embedding the electrical 
connections of the traces to the connector contacts and also upper ends of 
guide posts 22. Embossments 34 are disposed at each corner of the upper 
face of the connector housing, serving to provide housing surface to which 
the potting compound is adhered to enhance the bond. 
The present invention is illustrated in FIGS. 2 to 7 with an alternate 
embodiment shown in FIG. 8. Connector 50 is configured to be similar to 
connector 10 of FIG. 1 in most ways. A dielectric housing 52 includes an 
array of contacts 54 affixed thereto in two rows, having pin sections 56 
depending from a board mounting face 58 for eventual insertion into 
through-holes of a mother board (not shown). An alignment plate 60 of 
dielectric material is shown disposed below the housing and along free 
ends of the contact pins sections and the guide posts 62 at each end of 
the array, for maintaining the pin sections aligned to facilitate board 
mounting, with the plate movable along the pin sections toward and to the 
housing during board mounting. Flexible film circuit element 64 includes 
circuits electrically connected to upper sections 66 of contacts 54 by 
soldering at a first interconnection region 68 along upper or 
card-proximate face 70, and the circuits extend to exposed portions 72 at 
a second interconnection region 74 for eventual electrical connections to 
corresponding traces 76 of a daughter card 78. Embossments 80 are disposed 
at each corner of the upper face of the connector housing. 
In accordance with the present invention, a plate 82 of dielectric material 
is utilized to traverse the card-proximate face 70 of the connector atop 
the upper surface of first interconnection region 68 of flexible circuit 
element 64. End flanges 84 are disposed between each pair of embossments 
80 at each end of the connector. Holes 86 extend through plate 82 at each 
location of a solder connection between an upper contact section 66 and a 
circuit trace, and also at the upper end 88 of each guide post 62. Potting 
compound 98 is disposed in each hole 86 to embed and thus seal each 
electrical connection therein. 
The pattern of traces of an example flexible circuit element 64 is seen in 
FIG. 3, and at first interconnection region 68 each trace 90 includes an 
annular ring 92 surrounding a pin-receiving aperture 94 at each site of an 
upper contact section of the connector, for soldering thereto, and also an 
exposed portion 72 at second interconnection region 74 for eventual 
connection with a trace 76 of a daughter card 78 (FIG. 2). Upper or 
card-proximate connector face 70 of connector 50 is shown in FIG. 4 
showing upper contact sections 66 and upper ends of guide posts 62. 
FIGS. 5 to 7 depict the assembling of connector 50. In FIG. 5, the traces 
of flexible circuit element 64 have been soldered to respective upper pin 
sections 66 of the connector extending above card-proximate face 70 of 
housing 52. Preferably a thin layer of potting compound 96 such as epoxy 
resin (or another adhesive material) may be disposed over first 
interconnection region 68 prior to placement of plate 82 thereover, 
bonding it to the flexible film element and the housing. In FIG. 6, plate 
82 has been placed in position to housing 52 and flexible circuit element 
64, with upper pin sections 66 and the terminations to the traces disposed 
in respective apertures 86 of plate 82; the apertures should be large 
enough to contain the entire solder joint when plate 82 is disposed 
against the surface of the flexible film element. In FIG. 7, apertures 86 
have been filled with potting compound 98. 
An alternate embodiment of the present invention is illustrated in FIG. 8. 
Connector 100 includes four rows of contacts 102 retained within housing 
104, and flexible circuit element 106 includes traces extending from first 
interconnection region 108 and terminations to respective ones of the two 
rows of contacts thereat, to a pair of opposed second interconnection 
regions 110 disposed on end sections 112. End sections 112 will be 
disposed along opposed major surfaces of a two-sided daughter card for the 
exposed trace portions 114 to become terminated to the corresponding 
traces on the daughter card. Plate 116 includes four rows of apertures 118 
corresponding to the terminations of the flexible circuit traces to the 
associated connector contacts 102, and the apertures 118 are filled with 
potting compound 120 as in FIG. 7. 
The use of plates 82,116 provides enhanced strain relief protecting the 
terminations of the traces of the flexible circuit element to the 
connector contacts if stress is applied to the flexible circuit element 
relative to the connector. The plates also provide control over the flow 
of potting compound used in the prior art. Such potting compound may be 
for example, an epoxy resin. The housing, the organizer and the plate may 
all be molded for example of a thermoplastic resin such as VECTRA 
glass-filled LCP polyester sold by Hoechst-Celanese Corp. of Chatham, N.J. 
The film layers of the flexible circuit element may be adhesive-backed 
KAPTON polyimide film sold by E. I. DuPont de Nemours & Co. of Wilmington, 
Del. 
Variations and modifications may occur to the specific embodiments of the 
invention disclosed herein, that are within the spirit of the invention 
and the scope of the claims.