CA1289678C

CA1289678C - Apparatus for electrically testing printed circuit boards having contact pads in an extremely fine grip

Info

Publication number: CA1289678C
Application number: CA000546343A
Authority: CA
Inventors: Hubert Driller; Paul Mang
Original assignee: Mania Elektronik Automatisation Entwicklung und Geraetebau GmbH
Current assignee: MANIA TECHNOLOGIE AG
Priority date: 1986-09-08
Filing date: 1987-09-08
Publication date: 1991-09-24
Anticipated expiration: 2008-09-24
Also published as: US4851765A; ES2021640B3; US4952872A; ES2121743T3; EP0406919A3; DE3752227D1; EP0406919B1; ATE172306T1; EP0263244A1; JPS6370174A; DE3630548A1; EP0406919A2; EP0263244B1; ATE63169T1; DE3769741D1

Abstract

ABSTRACT OF THE DISCLOSURE
A circuit board testing apparatus includes a plurality of contact elements located in a contact array plane. The contact elements are connected to an electronic control and test structure and during testing are connected through longitudinally rigid test pins to contact portions of a connection carrier or circuit board to be tested. The contact elements are mounted to yield resiliently and are supported against the contact pressure applied during testing. The contact elements are in the form of electrically conductive compression springs located and guided directly in bores in a spring contact array body formed of an electrically insulating material. The rigid test pins seat directly on the compression springs.

Description

RAC~CGROUND OF THE INVEN~It)N
The present in~ention relates to apparatus for electronically testinq pri.nted circllit boards and of thc type including a plurality of contact elements located in a contact array plane, the contact elements bcing cohnected to an electronic control and test means and adapted to be connected through longitudinally rigid test pins ta contact positions of a connection carrier or circuit board to be kested, and the contact elements being mountbd to yield ~esiliently and being supported against a contacting pressure applied during a test.
Because of increasing commercial pressure for miniaturization and also because of the concomita~t redttctions in manttfacturing expenses, producers all over the lS world have begun providing electronic modules o~ the basis o~ circuit boards having connection sites or contact pads in an extremely fine grid (1/20 to 11100 inch grid) and .. utilizi~g SMD technology, with component leads that are not lnserted through bores tpossibly through-contactedJ in multi-layer circuit boards but that are connected to oontact pads on the component placement side of each board.
Also, manufacturers have realized that bare boards .
sbould be tested ~or unotionality prior to component placement to ensure that there are not more or not less, but precisely the number o~ conne.ctions requirea. As a resttl~, . the manufacturers of circuit board testin~ apparatus must of necess~ty offer equipment now which enables al~ost any size . ' ' ~

. .

:: . ' . .: .
: . . .:. ' .:

~:~E39~

l and configuration of printed circuit boards having contact pads on an extremely find grid tl/20 to 1/100 inch grid) to be tested without difficulties.
German Patent 33 40 180, corresponding to U.S.
Patent No. 4,674,006, discloses a contact array assembly ~or computer-controlled circuit board testing apparatus using the 1/10 inch grid in which the contact array is subdivided to define contact array sections each removably supported by elongated supporting struts on a base plate. Tlle space 50 created i5 used for accommodating the electronic components associated with each conta~t array section. These;
components are connected through a plug-type connection with a two-dimensionai control circuit provided OD a base plat~.
These sections ~referred to as "eontaet array modules") are identically constructed and exchangea~le f~r each other at any pOsition of the base plate~ This design concept results in circuit board testing apparatus comprising a falrly larye basic contact array (having e.g. 2S6 contacts in each of the -X and Y directions), yet operabie with a very small number o~ electronic modules, the number of which may he lnereased as needed ~ithout problems.
The desire underlying the present invention is to realize that same basic concept for apparatus operating with an extremely ~ine grid ~l/2~ to l/lOD inch gr~d). In the ;
past, ~o-ealled "reduetion adaptars" as described in German Patent 33 40 179, oorrespond~ns to ~.S. Pa~ent No.
4,614,386, were used to reduce the up to 64,000 eont~et positions o~ the initial 1/10 inch grid in the X and Y
directions o the aontaet array to a 1/20 inch g~id.

.

~ -2-~ ' ' ' . :

.
.

: : , ...... .~ .. .... . . .

9~i78 1 However, to obtain such red~lction, the maximum pcrmissible circu-t board dimensions had to be reduccd by 50 perccnt in either direction. As a result, realiz~tion on the 1/20 inch grid of the circuit board testing apparatus of German Patent 33 40 180 appears to be constrained by the limits iDherent in miniaturization itself, as wil] be explained in detail hereina~ter. It should be noted that the same limits apply regarding expcnditures. In circuit board testing apparatus having a contact array assembly as proposed in German Patent 33 40 180, contact between the connection points or pads on the circuit board under test and the contact elements of the contact array assembly is made by means of test needles each ha~-ing a tip telescoping resiliently in the longitudinal ; airection thereo~. In the case of the conventional 1/10 inch grid, these ontact needles are relatively simple and inexpensive to fabricate. Problems arise, however, if the contact spacing is reduced to 1/20 inch or less,~since in .

suc~h case the te~t needles cannot have a diameter greater thi~n 0.8 mm. Test pins so thin will buckle and be damaged beyond repair under even tbe slightest o~ transverse forces.
Be!:ides, resiliently telescoping test pins of this kind are-of necessity very complex ~echanically so that their manufacturing costs may cause problems, given the large ~ ;
: number of suc~ test pins required. Where the previous l/1D

inch gr~d c~mprised a maximum o~ 64,000 contact positions and requlred ~ cor~esponding number af test pin9, the 1~20 lnch grid results in up to 256,000 aont~at posi~ion~ within thE sflme external dimensions of the contact array. Quite obvlously, as very large numbers of ~est pins may be .

, ~ ~3~
``'~ ' ' ~:

: . ~ : . . .
- ~
',~ :
: ~' ~, ' 1~396~78 necessary, the cost therefor may be considerable and decide the potential user against purchasing the equipment. Thus, for using the principle proposed in German Patent 33 40 180 where applied to an extremely fine contact grid of 1/20 inch or less, it would be necessary to provide means and structure as simple in con.struction and as inexpensive in fabrication as possible.
Canadian Patent 1,224,557, which issued November 8, 1988, proposes the use of uncontoured test pins whi.ch are longitudinally rigid and do not have resiliently telescoping contact tips, particularly in case localized connection site densities on the circuit boards are higher than the average c~nnection site density on the 1/10 :~
inch fundamental grid of the contact array of the circuit board test equipment. Since rigid uncountoured contact pins readily can be made to have a rather small diameter, allowing their use at connection site densities higher (at least locally) than the fundamental grid of the circuit board testing equipment without creating a serious risk of the indivldual test pins shorting against each other, and since uncontoured rigid test pins of this nature are rather inexpensive to fabricate, the use of rigid test pins i~ the testing of circuit boards laid out on a 1/20 inch grid appear,s to be obvious initially. It should be kept in mind, however, that the "Flexadapter" approach proposed in Canadian Patent 1,224,557 uses a so~called "active fundamental contact array" which provides for length compensation of all of the rigid test pins used ~Z8~678 and thus for reliable contact between each one of the test pins and the object under test, such as a printed circuit board, a ceramic connector support or a flexible circuit carrier. such length compensation is necessary to compensate for possible bending of the rigid test pins and for variable thicknesses of the printed circuit boards, and in order to ensure sufficient contact pressure. An active contact array of this nature is formed by the resilient portions of the contact pins being transferred to the fundamental contact array of the circuit board testing board testing equipment utilized through the use of short contact pins in the form of sleeve-shaped members having an end in the shape of a contact tip and another end internally tapered, each pin being supported by a spring inside the sleeve and provided to receive one end of the rigid test piD. As a result, the active contact array assembly comprises a plurality of short internally tapered test pins corresponding in number to the connection sites to be accommodated and housed in suitable structure above the contact array proper of the circuit board testing apparatus.
As a conseguence, these internally tapered test pins, being expensive to make, do not relieve the problem of elevated manufacturing expenses. Also, it is most difficult, if not impossible, to reduce sleeve-like test pins having a compression spring therein to a diameter on the order of 0.8 mn, as long as springs so thin and weak are supposed to create sufficient contaot pressure, and material strength considerations prohibit a reduction of sleeve wall thickness ' .

.
.

i7~3 ; .

1 to less than 0.2 mm. As a rcsult, the problems created by an active contact array of this nature o,n a 1/20 inch grid ultimately would be prohibitive.

SVMMARY OF T~E INVENTIOM
For the above reasons, it is the fundamental objc~t of the present invention to improve on the manner cantacting a circuit hoard to be tested s~ that the use o~
- an extremely fine grid tl/20 to 1/100 inch gria) will not create strength or cost problems of the nature discussed.
The above and other objects of the present inventlon are a~hieved by the provision that the aontact e3.ements comprise electrically conductive compression , springs locatea and guided directly in bores in a spring '~ aontact array bady formed of an electrically insulating material. The rigid test pins are seated directly on the, " ' c~mpression springs. By providing compression springs which themselves receive the rigid test pins and are structured ~ccordingly, an operable contaat array assembly may be reali~ed at reasonable costs despite the reguired -~0 ~in~aturizat~on ~1/20 inch grld or ~ess). Making the body of the spring contact array of ceramlc or plastic materia?
i~s particularly advantageous i~ that manu~acturing techniques may be u~ed which ,ensure very ti~ht tol~rances.
Also, these material3 facllitate the manuacture ~$ the contact array body ln that it may be combined from small units to be assembled to form the contact array body.
'~ .

.: , ~ ' :

`: ', ' ' . `

.
:

~289~ii7~

l In ordcr to enable the available portion of each compression spring for the total ~ontacting pressure to be used effectively for reliable conta~ting, it may be of particular advantage to coil one or both ends of each compression spring into a pin-shape or a cone-shape. Also, it may be of advantage to coil one or both ends of ea~h compression spring to form an internal taper for directly reeiving a testing or contacting pin. As a result, the pln wi:Ll be retained safely by the compression spring itself.
In order to obtain excellent compression ~pring guidance inside the associated bores, the ends o~ the springs can be contiguous maximum diameter turns. For fucther improvement of the mechanical prope~ties of the ~ompression springs, the contiguous tu~ns thereof may be interconnected mechanically such as by a coating o~ metal deDosited galvanically on the compression springs~ which will be made of sprinq stee~ in most instances. As a result, the contiguous turns o~ the compression spring will be joined together. A coating of a special coDtact material, provided galvaniaaily if desired, on the end ."
portions of the compression springs may considerably reduce contact resistances.
In case the spring contact array body having therein bores receiving the compression springs is combined ~Iom smalle~ se~ments adapted to be assembled in array ~orm, it has turned out to be o~ particular advantage to mount the same on a plug-in supporting member in the eOrm of a so-ca]led "bed of nails", i.e. which has extending therefrom contact pins to extend into respective bores in the ,. .

:'' ' ~ -7-.~; . , .
.
:. ~
: :

'' ', ' ' ~, , . ':

~L2B9~78 1 contact array body ta electrically contact respoctive compre,ssion sp~ings therein. Such supporting member also transmits applied pressures and to this end is s~itably supported in the circuit board testing apparatus. In case this plug-in supporting me~ber is relatively l~rge.in comparison with body segments from which the spring contact array is asse~bled, it will contribute to holding the individual se~nents together in the assembly.
.
-,.

BRIEF DESCRIPTION OF THE DRAWING5 ?

; 10 An embodiment of the pr,esent invention will not be described with reference to the accompanying drawings, wherein:
' Flg. 1 is a schematic perspective view sho~ing the principles of a circuit board testing apparatus, only a :, 15 por.tion of which i5 shown, constructed in accordance with ; the present invention~
; Figs. 2a and 2b respectively are end and side elevation views of a so-called driver card having at a top end thereof a connector and supporting member and supported ~, ~0 'on bar elements: ' '' Fig. 3 ls a perspective sectional view of the contacting assembly of the invention, disposed between the driver card containing test eIe~tronics, and rlgid test , pins; and 25, Figs. 4a-4c are sectional views showing various alternative compression spring designs in a sprlng contact array Lo~y.

.
, " , .
.

- ~ .

' ~

6~

DETAILED DESCRIP~ION OF THE INVI~NTION
Fig. 1 schematLcally shows an arrangement of and the manner of supporting individual components which make up a contaet array 2 having, for example, up to about 256,000 contact positions 4 to be connected through test pins 6 to a connector carrier or to a printed circuit board 8 under test. Contacts 4 are arranged in sets of 4 x 32 or 4 x 64, each to be associated with a contact array plug 10 of the so-called "bed-of-nails" type which is provided at the top end of a so-called driver card 12 supporting electronic components contributing to the electronic testing of the lZ8 (i.e. 4 x 32) contacts 4 to be contacted by each contact array plug 10. At the bottom end of dr~ver cards 12 there are provided eontaet plugs (not shown ) to individually connect driver cards 12 ~contact array modules~, which may be up to a`oout 2,000 in nu~ber, with electronic control and test means (not shown) located in the bottom portion of the test apparatus. Such control and test means need not kR
discussed herein;
As shown in Figs. 1 and 2, eaeh of the contact array plugs 10 engages or rests on, by opposite narrow edge end portions thereof, supporting members 14 formed by vertical plate elements to transmit contaet pressures, whieh may have eonsiderable magnitude, to frame 16 of the circuit board testing apparatus. A circuit board 8 to be tested requires eontaet pressures of abaut 1-2 Uewton per eontaet q to make reliable contaet, ~iven the a~or~said maximum of 256,00~ contaets, supportlng members 14 together must ~ transmit a total contaet pressure of about 32 tons, ':
. ~ .
_9_ . .
,!`.
,~
.~ , ' " ' ,', ' ~ . , ' " ` ' ~ ~
' ': ~ ' ' '' . ' ' ' ' ` ` .

Contact array plug 10 consists of an electrically non-conductive plastic or ceramic material and has on its top end surface, for example, a total of 4 x 32 = 128 or 4 x 64 = 256 upright contact pins 18 each having a diameter on the order of 0.8 mm and a height of 2.5 mm. Pins 18 of plug 10 are extended therein by way of co~ductors 20 each connected to a contact site 22 on printed circuit driver card 12 to establish electrical connections to electronic components 24 ~only one shown in Figs. 2a-2b) on driver card 12 which are part of the test circuitry in the circuit board testing apparatus.
Each one of contact pins 18 extends into a respective bore 25 in a spring contact array body 26 containing and substantially filled by a respective contact 4 in the form of a compression spring 28 made of an electrically conductive material. In the preferred ~` embodiment shown in Fig. 3, spring contaet array body 26 is in the form of a plurality of strips or segments each having ~; a series of bores therethrough lin accordance with the contact pin arrangement). It is evident, however, that this element does not have to be a strip-shaped element eontaining only one row of bores 25. It is within the purview of the present invention to have any number of rows of bores in a correspondingly sized spring contact array body 26, as the size of such bodies depends ultimately on the ease of fabricatlng them. At present, it is preferred to use bodies in strip shape haviny therein a single row of four bores as ~t is easier to fabricate them to close toleranees. Such bodies may be arranged on contact arr~y plug 10 as is shown . .
.` ~

.
: ' -' ' ' ,' : ' ' ' '' ' " ' ' ' ' ., ' , ' .

., . :

~2~96~

l in Fig. 3. It is also possible to arrange them transversely thereto (not shown) so that they extend over the width of each contact array plug 1~. Each hody is about 50 mm in helght and about 1.27 r~m in width, with the bores therein having a diameter of about 0.8 r~m and being spaced 1.27 ~m in a~cordance with the ~onnection site grid.
Spring contact array bodies 26 are plugged on tap of the contaat plugs lO. Each bore 25, which i5 closed a~
the bottom end by a respectlve contact pin 18, receives a pressure spring 28 of a special design which f ill5 that bore completely, i.e. the coils in the resilient portion of the pressure spring engage the inner walls of the bores so that maximum dia~eter springs may be ~sed despite the restricted s~ace condition~.
Ends 30, 31 of springs 28 (shown schematically orly in Fig. 3) are formed in a particular manner for directly contacting contact pins 18 of plug 10 or rig~d test pins 6. As shown in Fig. 4a, spring 28 is coiled at its two ends (outwardly of its resilient portion 82 having spaced turns) to have longitudinally contiguous turns the diameters oi which decrease and then increase in the coilin~ direction to form an internally tapered portion. Thère thus is defined at either end of the spring a tapered recess 34 for receiving the tip of a contact pin 18 or a test pin 6, respectively. Preferably, springs 28 rnay be wound of spring steel and may be plated with ~ s~itablc contact material to ~oin the con~iguous turns at the ends of the sprln~.
Fig. 4b shows an alterriative form of a contacting arrangernent. The sprinq is configured in its top portion as ' .

' , ' ' ` .

~2~
.

I described above for engagement of test pin 6, i.e. it has an internally tapered portion 34 coiled as described above, whereas its opposite end is coiled to form a pin-shaped extension 36 the individual turns 33 of which are contiguous. The aforesaid pin-like extension extends into a conical xecess in a pin in contact array plug 10 which may be tapered or cup-shaped. This recess is to be considered - an alternative to the previously described contact pin 18.
Fig, 4c shows another alternative form of the I~ compression spring. The end of spring 28 facing the contac~
array plug 10 or the driver card 1~, respectively, is provided with a contact tongue portion 42 extending longitudinally of the spring to the associated connection s1te or contact pad on the surface of driver card 12. As a re:;ult, the contact array plug 10 has to be provided with properly positio~ed small-diameter bores 44 through which onLy the tongues 42 are passed during a~sembly o~ the contact array. In this case, too, the end of spring 28 fa~-ing test pin 6 i5 coiled to form an internal taper 34 of 2~ lo~gltudinally contiguous spring turns.
It is evl~ent that the particular manner of contacting longitudinally rigid test pins 6 as provided for by the inventio~, i.e. through (helical) compression springs~
forming contact elements, can be used advantageously ln ..
2~ circuit board testing apparatus hard-wlred ~or a ~rid of contacts or connection sites and no~t lncluding a plurality of identlcal contact array modules for use at any positlon of the baslc array plate. ~'he present invention is of partlcular advantage for such latter deslgn concept as it .' ' , '~' ' , . ' .
:
.~ . .
. . - , - .

~ : '. ' - :
., '. ~ '' ' " ' .
,, ' . " ~ ' .' . ' ' .

~2~391~7~

: l 5eeks, as does the present invention, to greatly reduce the costs incurred by the contacts required for testing a circuit board or connection carrier.
. Further, although the present invention has been described and illustrated with respect to a preferred embodiment, it will be apparent to those skilled in the art that various changes and modification~ may be made to the specifically described and illustrated features without dppartlng fro~ the scope pf the p-esent lnvention.

.

, : ` :
~`: . , , : : ' . ,.
.
: ~ .

~: :

,:
: .

.

,'' '

Claims

1. A contact element assembly for use in a printed circuit board testing apparatus to provide electric connection between electronic control and test means of the testing apparatus and, through longitudinal test pins, contact positions of a connection carrier or circuit board to be tested, said assembly comprising:
a spring contact array body formed of an electrically insulating material and having therethrough a plurality of bores;
a plurality of electrically conductive compression springs, each said spring being located in a respective said bore, each said spring having at a first end thereof means for achieving electrical contact with a longitudinal test pin of the testing apparatus and for centering and guiding the respective longitudinal test pin, at a second end thereof means for achieving electrical connection with the electronic control and test means of the testing apparatus, and between said first and second ends thereof a resiliently yieldable portion;
the relative dimensions of each said bore and the respective said spring being such that, upon application to said spring by the respective longitudinal test pin of a testing contact pressure, said resiliently yieldable portion of said spring engages the surface of said spring contact array body defining said bore; and a driver card supporting electronic control components, a contact array plug on one end of said driver card, said contact array plug including means for making direct electric contact with said means at said second ends of said compression springs and means for transmitting contact pressure to support elements of the circuit board testing apparatus, said electric contact means comprising contact pins extending from said contact array plug to be introduced into said bores in said spring contact array body.

2. An assembly as claimed in claim 1, wherein said spring contact array body is made of a ceramic or a plastic material.

3. An assembly as claimed in claim 1, wherein said spring contact array body is formed of a plurality of segments assembled in array form.

4. An assembly as claimed in claim 1, further comprising a plurality of longitudinally rigid test pins extending into respective said bores and electrically connected to first ends of respective said spring therein.

5. An assembly as claimed in claim 4, wherein said test pins are seated directly on said first ends of said respective springs.

6. An assembly as claimed in claim 1, wherein said means at at least one of said first and second ends of said compression spring is formed by contiguous turns of incrementally and/or gradually reduced coil diameter to form a pin-like shape.

7. An assembly as claimed in claim 1, wherein said means at at least one of said first and second ends of said compression spring is formed by contiguous turns of incrementally and/or gradually reduced coil diameter to form a tapered shape.

8. An assembly as claimed in claim 1, wherein said means at at least one of said first and second ends of said compression spring is formed by contiguous turns of first decreasing and then increasing diameter to define a portion internally tapered for directly receiving an end of a test or contact pin.

9. An assembly as claimed in claim 1, wherein each said compression spring has at least one end portion thereof formed by contiguous turns having maximum diameter for stable guidance inside the respective said bore in said spring contact array body.

10. An assembly as claimed in claim 1, wherein each said compression spring includes contiguous turns interconnected mechanically by means such as a coating of metal plated thereon.

11. An assembly as claimed in claim 1, wherein end portions of said compression springs are coated with a contact material for improved electrical contact.

12. An assembly as claimed In claim 1, wherein said means at said second end of each said compression spring includes a resilient contact tongue extending longitudinally from said compression spring for direct engagement with contact areas of said driver card supporting said electronic control components.

13. An assembly as claimed in claim 12, wherein said resilient contact tongues extend through respective bores in said contact array plug.

14. A contact assembly comprising:
a plurality of contact elements assemblies for use in a printed circuit board testing apparatus to provide electric connection between electronic control and test means of the testing apparatus and, through longitudinal test pins, contact positions of a connection carrier or circuit board to be tested, each said assembly comprising:
a spring contact array body formed of an electrically insulating material and having therethrough a plurality of bores;
a plurality of electrically conductive compression springs, each said spring being located in a respective said bore, each spring having at a first end thereof means for achieving electrical contact with a longitudinal test pin of the testing apparatus and for centering and guiding the respective longitudinal test pin at a second end thereof means for achieving electrical connection with the electronic control and test means of the testing apparatus, and between said first and second ends thereof a resiliently yieldable portion; and the relative dimensions of each said bore and the respective said spring being such that, upon application to said spring by the respective longitudinal test pin of a testing contact pressure, said resiliently yieldable portion of said spring engages the surface of said spring contact array body defining said bore;
said spring contact array bodies of said plurality of assemblies having different densities of said compression springs therein; and a plurality of respective electronic control components and driver cards supporting respective contact array plugs having means for making direct electric contact with said means at said second ends of said compression springs of said plurality of spring contact array bodies, said plurality of spring contact array bodies being exchangeably connectable to different of said plurality of contact array plugs.

15. An assembly as claimed in claim 14, wherein said spring contact array bodies are made of a ceramic or a plastic material.

16. An assembly as claimed in claim 14, wherein each said spring contact array body is formed of a plurality of segments assembled in array form.

17. An assembly as claimed in claim 14, further comprising a plurality of longitudinally rigid test pins extending into respective said bores and electrically connected to first ends of respective said springs therein.

18. An assembly as claimed in claim 17, wherein said test pins are seated directly on said first ends of said respective springs.

19. An assembly as claimed in claim 16, wherein said means at at least one of said first and second ends of said compression spring is formed by contiguous turns of incrementally and/or gradually reduced coil diameter to form a pin-like shape.

20. An assembly as claimed in claim 16, wherein said means at at least one of said first and second ends of said compression spring is formed by contiguous turns of incrementally and/or gradually reduced coil diameter to form a tapered shape.

21. An assembly as claimed in claim 14, wherein said means at at least one of said first and second ends of said compression spring is formed by contiguous turns of first decreasing and then increasing diameter to define a portion internally tapered for directly receiving an end of a test or contact pin.

22. An assembly as claimed in claim 14, wherein each said compression spring has at at least one end portion thereof formed by contiguous turns having maximum diameter for stable guidance inside the respective said bore in said spring contact array body.

23. An assembly as claimed in claim 14, wherein each said compression spring includes contiguous turns interconnected mechanically by means such as a coating of metal plated thereon.

24. An assembly as claimed in claim 14, wherein end portion of said compression springs are coated with a contact material for improved electrical contact.

25. An assembly as claimed in claim 14, wherein said electric contact means of each said contact array plug comprise contact pins extending from said contact array plug to be introduced into said bores in said spring contact array bodies.

26. An assembly as claimed in claim 14, wherein said means at said second end of each said compression spring includes a resilient contact tongue extending longitudinally from said compression spring for direct engagement with contact area of one of said driver cards supporting said electronic control components.

27. An assembly as claimed in claim 26, wherein said resilient contact tongues extend through respective bores in said contact array plugs.

28. A contact element assembly for use in a printed circuit board testing apparatus to provide electric connection between electronic control and test means of the testing apparatus and, through longitudinal test pins, contact positions of a connection carrier or circuit board to be tested, said assembly comprising:
a spring contact array body form substantially of an electrically insulating material and having therethrough a plurality of bores;
a plurality of electrically conductive compression springs, each said spring being located in a respective said bore, each said spring having at a first end thereof means for achieving electrical contact with a longitudinally test pin of the testing apparatus and for centering and guiding the respective longitudinal test pin, at a second end thereof means for achieving electrical connection with the electronic control and test means of the testing apparatus, and between said first and second ends thereof a resiliently yieldably portion;
a driver card supporting electronic control components and having contact areas; and said means at said second end of each said compression spring including a resilient contact tongue extending longitudinally from said compression spring and directly engaging with a said contact area of said driver card supporting said electronic control components.

29. An assembly as claimed in claim 28, wherein said spring contact array body is substantially made of a ceramic or a plastic material.

30. An assembly as claimed in claim 28, wherein said spring contact array body is formed of a plurality of segments assembled in array form.

31. An assembly as claimed in claim 28, further comprising a plurality of longitudinally rigid test pins extending into respective said bores and electrically connected to first ends of respective said springs therein.

32. An assembly as claimed in claim 31, wherein said test pins are seated directly on said first ends of said respective springs.

33. An assembly as claimed in claim 28, wherein said means at said first end of said compression spring is formed by contiguous turns of incrementally and/or gradually reduced coil diameter to form a pin-like shape.

34. An assembly as claimed in claim 28, wherein said means at said first end of said compression spring is formed by contiguous turns of incrementally and/or gradually reduced coil diameter to form a tapered shape.

35. An assembly as claimed in claim 28, wherein said means at said first end of said compression spring is formed by contiguous turns of first decreasing and then increasing diameter to define a portion internally tapered for directly receiving an end of a test pin.

36. An assembly as claimed in claim 28, wherein each said compression spring has at least one end portion thereof formed by contiguous turns having maximum diameter for stable guidance inside the respective said bore in said spring contact array body.

37. An assembly as claimed in claim 28, wherein each said compression spring includes contiguous turns interconnected mechanically by means such as a coating of metal plated thereon.

38. An assembly as claimed in claim 28, wherein end portions of said compression springs are coated with a contact material for improved electrical contact.

39. An assembly as claimed in claim 28, further comprising a contact array plug at one end of said driver card, and wherein said resilient contact tongues extend through respective bores in said contact array plug.

40. An assembly as claimed in claim 28, wherein the relative dimensions of each said bore and the respective said spring are such that, upon application to said spring by the respective longitudinal test pin of a testing contact pressure, said resiliently yieldable portion of said spring engages the surface of said spring contact array body defining said bore.

41. A contact array comprising:
a plurality of contact element assemblies for use in a printed circuit board testing apparatus to provide electric connection between electronic control and test means of the testing apparatus and, through longitudinal test pins, contact positions of a connection carrier or circuit board to be tested, each said assembly comprising:
a spring contact array body formed substantially of an electrically insulating material and having therethrough a plurality of bores; and a plurality of electrically conductive compression springs, each said spring being located in a respective said bore, each said spring having at a first end thereof means for achieving electrical contact with a longitudinal test pin of the testing apparatus and for centering and guiding the respective longitudinal test pin, at a second end thereof means for achieving electrical connection with the electronic control and test means of the testing apparatus, and between said first and second ends thereof a resiliently yieldable portion;
said spring contact array bodies of said plurality of assemblies having different contact densities.

42. A contact array as claimed in claim 41, comprising a plurality of respective electronic control components and driver card supporting respective contact array plugs having means for making direct electric contact with said means at said second ends of said compression springs of said plurality of spring contact array bodies.

43. A contact array as claimed in claim 41, wherein, for each said spring contact array body, the relative dimensions of each said bore and the respective said spring are such that, upon application to said spring by the respective longitudinal test pin of a testing contact pressure, said resiliently yieldable portion of said spring engages the surface of said spring contact array body defining said bore.

44. A contact array as claimed in claim 41, wherein said spring contact array bodies are substantially made of a ceramic or a plastic material.

45. A contact array as claimed in claim 41, wherein each said spring contact array body is formed of a plurality of segments assembled in array form.

46. A contact array as claimed in claim 41, further comprising, for each said assembly, a plurality of longitudinally rigid test pins extending into respective said bores and electrically connected to first ends of respective said springs therein.

47. A contact array as claimed in claim 46, wherein said test pins are seated directly on said first ends of said respective springs.

48. A contact array as claimed in claim 41, wherein said means at at least one of said first and second ends of said compression spring is formed by contiguous turns of incrementally and/or gradually reduced coil diameter to form a pin-like shape.

49. A contact array as claimed in claim 41, wherein said means at at least one of said first and second ends of said compression spring is formed by contiguous turns of incrementally and/or gradually reduced coil diameter to form a tapered shape.

50. A contact array as claimed in claim 41, wherein said means at at least one of said first and second ends of said compression spring is formed by contiguous turns of first decreasing and then increasing diameter to define a portion internally tapered for directly achieving an end of a test pin.

51. A contact array as claimed in claim 41, wherein each said compression spring has at least one end portion thereof formed by contiguous turns having maximum diameter for stable guidance inside the respective said bore in the respective said spring contact array body.

52. A contact array as claimed in claim 41, wherein each said compression spring includes contiguous turns interconnected mechanically by means such as a coating of metal plated thereon.

53. A contact array as claimed in claim 41, wherein end portions of said compression springs are coated with a contact material for improved electrical contact.