Microcircuit testing device

Details Microcircuit testing device Microcircuit testing device

1998-11-30

2001-03-06

Metjahic, Safet (Department: 2858)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

C324S761010, C324S765010

Reexamination Certificate

active

06198297

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a microcircuit testing device.
More particularly, the device relates to a device for testing integrated circuits, or microcircuits, and particularly to methods for manufacturing devices whereby said integrated circuits, before splitting a silicon wafer, are placed in electrical contact with the testing device.
It is known that the devices commonly used to test a silicon wafer by connecting simultaneously all the pads of the microcircuit to the device, commonly known as probe cards, are constituted by a printed circuit board having variable shapes and complexities, which is provided with a hole also having various shapes and into which elastic metallic needles, known as probes, protrude, the tip of said needles making contact with a pad of the microcircuit.
Automatic alignment and movement systems ensure that each microcircuit that is present on the silicon wafer is sequentially arranged so as to face the hole of the probe card and is moved towards it, so that each probe tip makes contact with the respective pad.
Among the various probe assembly systems of the prior art, the one most widely used for applications with a high density of probes per microcircuit is disclosed by U.S. Pat. Nos. 3,835,381 and 3,905,098 in the name of Garretson et al and is duplicated with minor variations in other documents.
This system provides for probes made of tungsten or copper-beryllium or other conducting materials, arranged so as to form a radiating array along the generatrices of a frustum-shaped ring whose apex angle is almost flat; the tips of said needles are directed towards the center of the ring and bent downward. The probe supporting ring is usually made of materials which are as temperature-stable as possible, in order to allow maximum positioning constancy for the probe tips.
The probes are locked in position by pouring a resin which also has the best possible characteristics in terms of thermal stability and electrical insulation.
Conventional microcircuit testing devices, however, are affected by some drawbacks which are described hereinafter.
Use of a printed circuit board as a support for the probe supporting ring entails problems in terms of limited mechanical rigidity which are inherent in the material, which is usually epoxy resin embedding a mat of glass fiber.
Moreover, the conventional almost-horizontal arrangement of the needles, i.e., approximately parallel to the probe card, has some shortcomings if simultaneous probing of a plurality of microcircuits is required.
This is particularly necessary for example in the testing of memory microcircuits, in which case it is necessary to probe two, four or more columns, each bearing four, eight or more microcircuits arranged side by side, as shown schematically in
FIG. 1
, which illustrates by way of example the simultaneous probing of four columns, each composed of two microcircuits.
In
FIG. 1
, the reference numeral
50
designates a silicon wafer and the reference numerals
51
/
52
,
53
/
54
,
55
/
56
and
57
/
58
designate respectively the pairs of microcircuits arranged side by side which must be tested by the testing device.
Also in the most favorable case, in which each microcircuit has contact pads arranged along a single median row, as shown in
FIG. 2
, which is an enlarged-scale detail view of the four pairs of microcircuits shown in
FIG. 1
, with the probes designated by the reference numeral
60
, which make contact with respective pads, designated by the reference numeral
61
, of the microcircuits arranged side by side, the probe system with horizontal needles (probes
60
) limits to two the number of columns that can be contacted. If one wishes to access more than one row of pads
61
from either side of the ring, the difference in length of the probes between one row and the next would have to be approximately equal to the pitch between the columns, producing needles
60
having considerably uneven lengths, with a great difference in the elastic contact forces, making it therefore impossible to obtain uniform contact resistances among the probes
60
.
SUMMARY OF THE INVENTION
The aim of the present invention is therefore to provide a microcircuit testing device which allows access to a plurality of parallel columns by means of suitably supported probes.
Within the scope of this aim, an object of the present invention is to provide a microcircuit testing device in which the needles of the probes are shaped so as to simultaneously make contact with any number of microcircuits.
Another object of the present invention is to provide a microcircuit testing device in which the length differences of the elastic part among the probes become negligible, allowing substantially equal pressures.
Another object of the present invention is to provide a microcircuit testing device in which the electric circuit is standardized, so as to make it independent of the shape of the support.
Another object of the present invention is to provide a microcircuit testing device which is highly reliable, relatively easy to manufacture and at competitive costs.
This aim, these objects and others which will become apparent hereinafter are achieved by a microcircuit testing device, characterized in that it comprises an element for supporting a plurality of probes which are meant to make contact with pads of microcircuits to be tested which are formed on a wafer, said probes being directed substantially vertically to said supporting element, and connection means suitable to connect ends of said probes, which are arranged opposite to ends for contact with said pads, to an element for providing an electrical interface between said connection means and electric connector means.


REFERENCES:
patent: 3611128 (1971-10-01), Nagata
patent: 4599559 (1986-07-01), Evans
patent: 5317255 (1994-05-01), Suyama et al.
patent: 5550480 (1996-08-01), Nelson et al.
patent: 5635846 (1997-06-01), Beaman et al.
patent: 87 01 195 (1987-05-01), None
patent: 87 13 754 (1988-02-01), None
patent: 0 708 338 (1996-04-01), None

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