Electrical connector comprising multilayer base board assembly

A PGA connector for a microprocessor has a multilayer base board assembly with alternating conductive and dielectric layers of preselected thicknesses through which signal pins, current source pins and a grounding pin extend. The signal pins are insulated from the conductive layers and the current and grounding pin are connected to preselected conductive layers. A series of connecting apertures formed by holes with respective conductive linings extend through the layers at selected locations between pins to interconnect selected conductive layers. The connecting apertures interconnect all conductive layers of the base board or, in another example, alternately positioned connecting apertures interconnect only respective different sets of alternately positioned conductive layers of the base board enabling improved shielding and impedance regulation and matching.

FIELD OF THE INVENTION 
The invention relates to an electrical connector comprising a multilayer 
base board assembly having alternating conductive and dielectric 
(insulating) layers in which connecting pins are anchored for effecting 
connection, for example, between contacts of an integrated circuit 
component, such as a pin grid array of a microprocessor, and a printed 
circuit board. 
BACKGROUND OF THE INVENTION 
The increasing integration and complexity of electronic components such as 
integrated circuits has resulted in the requirement to transfer large 
quantities of data with a correspondingly marked increase in the number of 
leads required for electronic components. At the same time, the inexorable 
demand for miniaturization requires reduction of the lead pitch to a 
minimum which increases the incidence of cross-talk between signal pins 
connected to the leads. The problem of cross-talk, is also exacerbated by 
the progressive increase in data processing rates, for example, in clock 
frequencies of central processing units (CPUs), increasing current surges 
arising from semiconductor switching in the high frequency range, while 
variations of current source voltages in current supply circuits can 
readily occur, resulting in an increased risk of operational errors in the 
circuitry. Furthermore, with increasing signal speeds, the regulation of 
impedances between pins tends to decrease increasing the risk of 
mismatching impedances with other, connecting circuits. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide an electrical connector structure 
for connecting, for example, an integrated circuit, such as a 
microprocessor, to a printed circuit board, while alleviating cross talk 
between signal pins, reducing the impedances of current source and 
grounding lines and affording impedance matching of signal lines. 
The invention provides an electrical connector for connecting an integrated 
circuit such as a microprocessor to a circuit board comprising: a 
multilayer base board assembly having opposite faces and comprising a 
series of conductive and dielectric layers of preselected thicknesses 
arranged alternately; a plurality of connecting pins including signal pins 
and at least one of current source pins and a grounding pin, the 
connecting pins having connecting portions and board anchoring portions 
and the said at least one of current source pins and a grounding pin 
having, respectively, conductive layer contacting portions, the connecting 
pins being inserted in and anchored by their board anchoring portions in 
the board assembly with the connecting portions exposed to opposite faces 
and with the conductive layer contacting portions electrically connected 
to selected conductive layers and with the signal pins insulated from the 
conductive layers; and, a series of connecting apertures formed by holes 
with respective conductive linings and formed through layers at selected 
locations between connecting pins so that the connecting apertures are 
electrically connected to selected conductive layers thereby electrically 
interconnecting those selected conductive layers. 
In one embodiment, the conductive layers are located at both opposite faces 
of the base board and a conductive layer on one face is connected to 
current source pins by their conductive layer contacting portions. 
The connecting pins and connecting apertures may be arranged as respective 
matrices so that individual connecting apertures are located medially 
between respective groups of four adjacent connecting pins. 
In one arrangement, the connecting apertures interconnect all conductive 
layers of the base board. 
In an alternative arrangement, alternately positioned connecting apertures 
interconnect only respective different sets of alternately positioned 
conductive layers of the base board and there are four conductive layers 
and a first and a fourth of the conductive layers are located at 
respective opposite faces of the base board assembly, the ground and 
signal connecting pins being connected by their respective conductive 
layer contacting portions to the fourth and first conductive layers, 
respectively, thereby providing ground shield and power layers alternating 
throughout the board assembly and at respective opposite faces thereof. 
At least some of the pins may include socket forming portions opening to 
one face for mating connection with respective leads of a microprocessor. 
As the dielectrics forming the laminated base plate perform a shielding 
function, signal cross-talk between the signal pins is reduced. 
Furthermore, as the connecting apertures which extend through the base 
board or base plate between the connecting pins have respective conductive 
linings or layers which are electrically connected to the conductive 
layers, the conductive layers and apertures provide shields between 
adjacent signal pins, further reducing cross-talk between the signal pins. 
In addition, the connection of the conductive layers with the current 
source or grounding pins results in a large reduction of the impedances of 
the current source and grounding lines connected thereto. Furthermore, the 
thicknesses of the portions of dielectric which extend both between the 
conductive layers and which surround the signal pins can be adjusted to 
regulate the impedances of the signal pins enabling impedance matching 
with other circuits connected through the signal pins.

DESCRIPTION OF TICULAR EMBODIMENTS 
As shown in FIGS. 1(a)-3, the first embodiment of electrical connector is a 
pin grid array (PGA) integrated circuit (IC) socket connector comprising a 
laminated base board or plate 1, having series of signal pins 2 and 
current source pins 3 installed thereon. 
As shown in FIGS. 2 and 3, the base board 1 is formed by laminating first 
to fourth conductive layers 11a-11d, respectively, alternately with first 
to third dielectric layers (insulating layers) 15a-15c, respectively so 
that the first and fourth conductive layers 11a and 11d are exposed at 
front, component connecting and rear, printed circuit board connecting 
faces, respectively and the dielectric layers 15a-15c are sandwiched 
between the conductive layers 11a-11d. 
A series of pin receiving through-holes 1a extend perpendicularly through 
the base board 1 in a matrix formation so as to be surrounded by tubular 
dielectric portions 16 and either a signal pin 2 or a current source pin 3 
is force-fitted in each through-hole. 
The signal and current source pins are of similar construction to those 
described in my application 08/248067, the disclosure of which is 
incorporate herein by reference. 
Each signal pin 2 comprises a one-piece outer body 20, which has a main 
tubular sleeve-forming anchoring portion 21 with a radially outward 
extending flange 22 and a depending lead portion 23 on upper and lower 
ends thereof, respectively. An upward opening inner sleeve 25 is force 
fitted into an aperture 24 formed in the outer sleeve 20. The flanges 22 
provide insertion stops engaging the front face of the board when the 
signal pins are forcibly inserted in the respective through-holes 1a. 
The outer diameter of each flange portion 22 is smaller than the outer 
diameter of the tubular dielectric portion 16 so that the flange 22 
contacts the upper surface of the tubular dielectric layer 16, suitably 
insulated from the conductive layers. 
Each current source pin 3 comprises a one-piece outer body 30, which has a 
main tubular sleeve-forming anchoring portion 31 with a radially outward 
extending flange 32 and a depending lead portion 33 on upper and lower 
ends thereof. An upward opening inner sleeve 35 is force-fitted into an 
aperture 34 formed in the outer sleeve 30. 
The flange portions 32 provide conductive layer contacting portions as 
their outer diameters are larger than the outer diameter of the tubular 
dielectric portion 16 so that the flange portions 32 are forced into 
engagement with the conductive layer on the front surface of the base 
board during installation. Reliability of connection is assured by the 
provision of depending annular teeth 32a on the outer peripheral edges of 
the flange portions which teeth bite into the first conductive layer 11a. 
A second series of through-holes 1b are formed in the base board 1 between 
the holes 1a, also in a matrix formation, as shown in FIG. 1. As shown in 
FIG. 2, the through-holes 1b, are formed through the conductive layers 
11a-11d and the dielectric layers 15a-15c, and a fifth conductive layer or 
lining 12 is formed on their inner surfaces providing a connecting 
aperture which interconnects all of the first to fourth conductive layers 
11a-11d. 
The first to fourth conductive layers 11a-11d, formed as laminated layers, 
and the fifth conductive layers 12 lining the through-holes 1b are 
positioned between the main through-holes 1a so that they act as shield 
layers, so that the signal cross-talk between the signal pins 2 in the 
main through-holes 1a is greatly reduced. 
FIG. 4 shows the empirical data for cross-talk between adjacent signal pins 
in the socket connector of the invention described above and for a 
conventional socket connector) which utilizes a base plate consisting 
essentially only of a dielectric, without any of the first to fifth 
conductive layers). 
As shown, if the socket connector of this invention is used, the cross-talk 
property can be reduced by approximately 20 dB, compared to the 
conventional socket connector. 
In general, the capacitance C between 2 conductors facing each other is 
given by: 
EQU C=.SIGMA..multidot.A/d, 
where A is the surface area of portions of two conductors facing each 
other, d is the distance between the conductors, and .SIGMA. is the 
permittivity of the dielectrics, etc., embedded between the conductors. 
The impedance is given by: 
EQU Z=1/(2.pi.fC), 
where f is the frequency. 
Thus, by selecting suitable thicknesses of dielectrics 15a-15c and of the 
tubular dielectric portions 16 enclosing the signal pins 2, one can 
(within limits) produce any desired impedance of the signal pins 2 
permitting the impedances to easily be matched with other circuits 
connected to the signal pins 2. 
The second embodiment of the invention shown in FIG. 5, is generally 
similar to the first embodiment shown in FIG. 1-3, with identical parts 
having been given references to those of the first embodiment. 
The connector is formed by force fitting signal pins 2, current source pins 
3, and a grounding pin 4 into through-holes holes 1a of a first series, 
formed in a base board 1. The grounding pin 4 has a flange 42 on the lower 
end of a main body 41, and is forced into a main penetrating hole 1a from 
the lower face of the base board 1 until the flange 42 engages the lower 
face of the base board 1. The outer diameter of flange 42 is larger than 
the outer diameter of tubular dielectric portion 16 so that the flange 42 
establishes electrical connection with the fourth conductive layer 11. 
A second series of through-holes 1b are formed in the base board 1 and a 
fifth conductive layer or lining 12 or 12' is formed on their inner 
surfaces. Alternating fifth conductive layers 12 and 12', respectively, 
connect with the first and third conductive layers 11a and 11c and the 
second and fourth conductive layers 11b and 11d, respectively, so that 
first and third conductive layers 11a and 11c are electrically connected 
through the fifth conductive layers 12, and are also connected with the 
current source pin 3 through the first conductive layer 11. Additionally, 
the second and fourth conductive layers 11b and 11d are electrically 
connected through the fifth conductive layers 12', and are also connected 
electrically with the grounding pin 4 through the fourth conductive layer 
11d. 
In the second embodiment also, signal cross-talk between adjacent signal 
pins 2 can be greatly reduced, and impedances matched with other circuits 
connected through the signal pins 2. Additionally, the impedances of the 
current source lines connected to the current source pins 3 and the 
grounding line connected to the grounding pin 4 can also be greatly 
decreased. 
In general, when the connector is required to reduce cross-talk between 
signal pins, grounding pins are used in the base board assembly and when 
the connector is required to reduce the the current source impedance, the 
current source pins are used.