Cooling subrack for logic cards

A subrack has a plurality of logic cards disposed in a planar arrangement. The logic cards are surrounded by a plug connector which has a cooling plate. In order to produce a good and uniform thermal contact to a further cooling plate, which is assigned in common to all logic cards, the logic cards are positioned in chambers of a grid frame to which the common cooling member is connected. Each cooling plate is individually pressed against the common cooling plate by way of a releasable connection, such as a screw.

CROSS REFERENCE TO RELATED APPLICATIONS 
This application is related to an application Ser. No. 526,371 filed Aug. 
24, 1983 and to an application Ser. No. 526,375 filed Aug. 24, 1983, now 
abandoned. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a subrack comprising a motherboard, a 
plurality of logic cards in a planar disposition, first cooling members 
assigned to each of the logic cards, and second cooling members to which 
all first cooling members are releasably attached in common. 
2. Description of the Prior Art 
Increasing miniaturization of integrated modules and a high packing density 
have resulted in a great heat emission from the modules which can easily 
lead to transgression of the permissible module temperatures. For purposes 
of cooling by convection to the surrounding air, it is known from the 
German published application 23 47 751 to respectively provide logic 
cards, planarly plugged onto a motherboard, with a large-surface metal 
plate which is in thermal contact with the modules. With its one side 
directed towards the outside, it is embedded -in a plug connector 
encompassing the logic card. 
Known, further, from U.S. Pat. No. 3,993,123 is a cooling device for one or 
more heat-emitting electronic modules which are contacted to one side of a 
flat carrier. The modules are disposed with thermal contact below a 
thermally-conductive cap to which a cooling member traversed by a coolant 
and terminating nearly flush with the carrier is flanged. When, however, a 
larger plurality of such devices is disposed on a printed circuitboard, 
then an at least correspondingly large plurality of line sections must be 
provided in order to guarantee the supply of all coolant circulations. 
This, however, can require a considerable expense for assembly and 
maintenance. 
Further known from the German published application 29 26 076 is an 
arrangement for cooling electronic modules wherein the stray heat is 
diverted over thermally-conductive paths of a carrier card onto a plug-in 
frame which accepts a plurality of cards in a parallel disposition and is 
dissipated from the plug-in frame onto a housing wall which serves as a 
cooling member. For supporting and covering, the plug-in ring surrounds a 
structure which is put in place on the housing wall and inside of which 
springs are supported against the plug-in frame such that the frame is 
pressed against the housing wall. As a result thereof, however, long heat 
transfer paths and a plurality of heat transfers arise, so that the 
cooling effect is relatively low. Moreover, the danger also exists that 
the thermal contact between the frame and the housing wall will be 
interrupted given mechanical shocks since it only depends on the spring 
forces which, however, cannot be arbitrarily high in consideration of the 
mechanical stability of the structure. 
SUMMARY OF THE INVENTION 
It is therefore the primary object of the invention to provide a subrack of 
the aforementioned type which is characterized by a simple structure and 
which guarantees a good and uniform thermal contact between first cooling 
members carried by the logic cards and second cooling members carried by 
the subrack. 
The above object is achieved, according to the invention, in that a grid 
frame for receiving the logic cards is secured to a motherboard; in that a 
second cooling member is releasably connected to the grid frame at that 
side lying opposite the motherboard; and in that the first cooling members 
are respectively connected to the second cooling member by a releasable 
clamp connection element. The present invention has the advantage that the 
subrack can be simply assembled and that the individual logic cards can be 
easily replaced. 
When the spacing between the motherboard and the second cooling member is 
greater than the thickness of the logic cards including the first cooling 
members, then a contact pressure of equal strength for all logic cards is 
produced by drawing the first cooling members against the second cooling 
member. This is particularly achieved when the clamp connecticn elements 
are respectively centrally disposed with respect to the first cooling 
members. The clamp connecting elements thereby advantageously comprise 
screws. 
A planar alignment of the first cooling members relative to the second 
cooling member is achieved in that the second cooling member is screwed to 
the points of intersection of the grid frame. The mutually corresponding 
portions of the clamp connecting elements are aligned relative to one 
another before connection by at least one centering or guide pin on the 
frame and a corresponding recess in the second cooling member for 
accepting the pin so that assembly is thereby facilitated. Particularly 
when a releasable slinging device between the grid frame and the second 
cooling member is provided, comprising a clevis-type connector and a 
slinging pin, rapid application of the clamp connection is guaranteed. 
An advantageous further feature of the invention is characterized by a 
stationary connection of the second cooling member to a housing frame.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As the two figures illustrate, the subrack comprises a motherboard 19, a 
grid frame 6, a plurality of logic cards 1 which are respectively provided 
with a first cooling member 7, and a second cooling member 12 which is 
assigned, in common, to all of the first cooling members. 
The external shape of the logic cards 1 is determined by a plug connector 
which encompasses the four narrow edges of the logic card 1 and on whose 
one flat side is provided with a plurality of contacts 2' which are 
located in recesses distributed in a grid pattern or matrix. A first 
cooling member 7 (FIG. 2) is embedded in the plug connector on a second 
flat side, whereby a narrow collar terminating flush with the first 
cooling member 7 arises. Integrated electronic modules (not shown) with 
direct thermal contact to the first cooling member 7 are within the logic 
cards 1. 
The contacts 2' comprise pins or contact springs whose cooperating contacts 
2 are secured on the motherboard 19 within the grid chambers. For purposes 
of illustration, one of the logic cards 1 has been swung upwardly in the 
direction of an arrow out of the appertaining grid chamber and thus 
provides a clear view of the contact elements 2' and their cooperating 
contacts 2. The remaining logic cards 1 are respectively plugged into the 
grid chambers in a planar disposition such that the first cooling members 
7 face the second cooling member 12 with their external surfaces facing 
away from the printed motherboard 19. 
The second cooling member 12 comprises a stable, metallic hollow body which 
exhibits superplanarity on its side facing the components. It is 
stationarily connected to a recooling system and to a housing frame 
(neither illustrated). Driven by the recooling system, a liquid or gas 
coolant circulates within the cooling member 12. The housing frame can 
also receive further such subracks. The connection to the frame and the 
circulating coolant have been schematically illustrated in FIG. 2. 
As can be seen from the exploded view of FIG. 1 and FIG. 2, the second 
cooling member 12 comprises approximately the same side lengths of the 
grid frame 6 and therefore covers all of the first cooling members 7. 
Clevis-type connectors 5 are secured to the four corners of the second 
cooling member 12, the function unit comprising the printed motherboard 
19, the grid frame and the logic parts being suspended in the clevis-type 
connector 5 by way of pins 8 which laterally project from the grid frame 
6. A second cooling member 12 is also screwed to the grid frame 6 by 
screws 14 which are turned into threaded bores 16 at the points of 
intersection of the grid frame 6. Each individual first cooling member is 
pressed against the second cooling member 12 by way of a respective clamp 
connecting element 13, as specifically shown in the lower portion of FIG. 
2, the clamp connecting element 13 comprising a screw which is inserted 
through the second cooling member 12 and which engages in a threaded bore 
15 centrally located in the first cooling member 7. A pre-centering of the 
screw connections occurs by way of pins 9 projecting perpendicularly from 
the grid frame 6, the pins being accepted by corresponding recesses 20 in 
the second cooling member 12. Plug-in sockets 3 at the edge of the 
motherboard 19 serve for the connection of signal lines. 
The upper half of FIG. 2 shows a clamp connection between a first cooling 
member 7 and the second cooling member 12 which is still open, whereas the 
clamp connection has been tightened in the lower half of the figure and 
produces a tight, planar, thermal contact between the two cooling members. 
The assembly of the subrack is described below with reference to the 
drawings. After the insertion of all logic cards 1 in the chambers of the 
grid frame 6, the same is suspended in the clevis-type connectors 5 at the 
second cooling member 12, whereby a pre-centering by the pins 9 occurs. 
Since the spacing between the printed motherboard 19 and the second 
cooling member 12, determined by the thickness of the grid frame 6, is 
greater than the thickness of the logic cards 1, a small, defined 
clearance 4 remains between the logic cards 1 and the second cooling 
member 12, the relative size of the clearance 4 having been shown in an 
exaggerated fashion in FIG. 2. After screwing the second cooling member 12 
to the grid frame 6, each individual logic card is pulled away from the 
printed circuit motherboard 19 by the path length corresponding to the 
clearance 4 due to tightening of the clamp connections, whereby all of the 
first cooling members 7 are pressed against the second cooling member 12. 
Since the clearance 4 between the logic cards 1 and the printed 
circuitboard 19 has now been displaced, a sufficient galvanic connection 
must be guaranteed by an appropriate dimensioning of the contacts 2' and 
their cooperating contacts 2. The cooling of the modules occurs by heat 
emission to the first cooling members 7 and over forced conduction to the 
coolant in the second cooling member 12. The thermal resistance is thereby 
reduced by applying a thermally-conductive grease (not shown) to the 
contacting surfaces. 
Although I have described my invention by reference to particular 
illustrative embodiments thereof, many changes and modifications of the 
invention may become apparent to those skilled in the art without 
departing from the spirit and scope of the invention. I therefore intend 
to include within the patent warranted hereon all such changes and 
modifications as may reasonably and properly be included within the scope 
of my contribution to the art.