GB2419469A

GB2419469A - Cooling of electronic or optical devices

Info

Publication number: GB2419469A
Application number: GB0423341A
Authority: GB
Inventors: Declan Reilly; David John Kenneth Meadowcroft
Original assignee: Agilent Technologies Inc
Current assignee: Agilent Technologies Inc
Priority date: 2004-10-21
Filing date: 2004-10-21
Publication date: 2006-04-26
Also published as: GB0423341D0

Abstract

A rack for optical transceiver devices 4 has a cooling unit, which fits over multiple juxtaposed devices. The cooling unit has a fan and a series of heat exchangers 52, one per device. Each heat exchanger may be biased by a pair of springs downwardly through an opening in a housing to press against a device or its EMI shield. The cooling unit allows excellent control over the environment for the devices.

Description

"Cooling of electronic or optical devices"

Introduction

The invention relates to temperature control of devices such as transceivers (transponders), which generate heat in use.

At present, it is known to provide a rack of such devices, temperature control being achieved by a fan blowing or sucking air over the devices. The fan is typically mounted on the rack or on a cabinet at a position chosen to have best effect on all heat-generating devices. However, it is often not possible to achieve a uniform airflow at all devices and so particular devices may operate at a temperature higher than specified. This, in turn, leads to faults.

The increasing power consumption density in racks of such devices has compounded this problem. For example, optical transceivers for high-speed communication have both electronic circuits and lasers or diodes, which consume in the range of l to 5W each. If there are in the region of hundreds of such components in a rack considerable heat is generated in a small space. Also, the temperature distribution across a rack of devices is often very uneven.

Thus, while there has been increased miniaturization in the electronic circuits and in the optical components of such devices, the heat generated by the devices has been a barrier to achieving greater densities.

The invention addresses these problems.

Statements of Invention

According to the invention, there is provided a cooling unit for a plurality of optical transceiver devices, the cooling unit comprising a housing containing a heat sink, a fan, - 2 and a cooling channel for flow of air across the heat sink, and means for mounting on the devices.

In one embodiment, the housing is of elongate configuration, for mounting over a plurality of juxtaposed devices.

In another embodiment, the cooling unit fits over a row of devices, allowing devices to be removed at the front.

In a further embodiment, the cooling unit comprises a heat sink associated with each device.

In one embodiment, the unit comprises a biasing means for pressing the heat sink against the device.

In another embodiment, there are at least two springs for pressing each heat sink against a device.

In a further embodiment, each heat sink is pressed through an aperture in the cooling unit housing.

In one embodiment, each heat sink extends through the housing sufficiently to also extend through an EMI shield of the associated device.

A cooling unit as claimed in any preceding claim, wherein the heat sink extends across the top of the heat sinks.

In another aspect, the invention provides an optical transceiver rack comprising a plurality of device sockets juxtaposed on a substrate; a front panel having openings to receive devices being inserted into the sockets, and a cooling unit mounted on top of the sockets.

In one embodiment, the cooling unit housing fits behind the front panel.

Detailed Description of the Invention

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which: Fig. l is a perspective view of a device rack of the invention; Fig. 2 is a similar view, in this case with a top wal] partly cut away to illustrate heat sinks; Fig. 3 is a cross-sectional view of the rack; Fig. 4 is an underneath perspective view of part of a cooling unit of the rock, with one heat sink removed so that biasing springs are visible; Fig. 5 is a perspective view showing a cooling unit of the rack being placed in position on heat-generating devices; 2 5 Fig. 6 is a set of plots illustrating heat distribution performance of the rack; and Fig. 7 is a partly cut-away top perspective view showing an alternative heat sink arrangement.

Referring to Figs. l to 3 a transceiver device rack l has a front panel 2 having cut-outs 3 through which heat-generating optical transceiver devices 4 protrude. The devices 4 are connected to an electrical power and signal board S. - 4 For cooling the devices 4, there is a cooling unit 10 placed on top of the devices 4 for efficient and uniform heat removal from al] of the devices 4. The cooling unit lo comprises a fan 11 for drawing cooling air through and around heat sinks 15 after passing through an inlet 12. The heat sinks 15 are pressed down against the device EMI shields 13 by coil springs 18. The shields 13 have heat convection apertures 16. Fig. 3 particularly shows a cooling channel 20 extending across and over the heat sinks 15 for uniform air flow over the devices 4 and out through the fan 11.

Fig. 4 shows particularly how the heat sinks 15 are pressed down against the device shields 13 by the springs 18. There is an individual cut-out 25 in a cooling unit housing 26 for each device 4. The heat exchangers 1 S extend through the cut-outs 25 so that they directly contact the EMI shields 13.

Fig. 5 shows that the cooling unit 10 is removable from the rack 1 for easy repair or replacement in a modular manner. It is connected to the remainder of the rack by nut and bolt fasteners, although other suitable fasteners may be used.

The springs 18 are chosen to minimise the contact resistance between the device 4 and the heat sink 1 S. The heat sinks I 5 can be used to mate directly with either the EMI shields of the devices 4 as illustrated' or they can mate directly with the device if a cut-out is provided in the EMI-shield.

The drawings show a single fan, but any suitable number of fans could be positioned along the length of the rack. The fans could be arranged to blow or suck air across the devices, or a combination of both.

Referring to Fig. 6, in prior art arrangements, the optical device nearest the fan (or air source) tends to be the coolest in operation, with each adjacent device operating at a slightly higher temperature to its predecessor. This typically results in a somewhat - 5 "linear" temperature increase of each adjacent device. This is undesirable as the devices furthest away can regularly over-heat.

If a common heat sink is placed over all of the devices, a slight improvement is achieved, as shown by the second plot. However, with use of the cooling unit of the invention a lower temperature is achieved, and this is much more uniform across the devices.

The heat sinks may be of any suitable configuration. For example, referring to Fig. 7 a rack 50 comprises a cooling unit 51 having plate finned heat exchangers 52.

It will be appreciated that the invention provides for heat transfer from optical devices, whereby the heat transfer mechanism is not dependent on the surroundings. The manufacturer has full control over the device's environment. The heat transfer from the device can be accurately predicted, by computer simulation, as there is no need to know or model the end user's environment. There is particularly effective heat transfer from the optical device, by minimizing the contact resistance between device and heat sink, by using a pre-loaded heat sink. The invention allows all devices to operate at an equivalent temperature, and there is good thermal heat sinking whilst maintaining pluggability of the individual devices. There is also ducting of airflow direct form the air source to the optical devices with minimum pressure drop.

The invention is not limited to the embodiments described but may be varied in construction and detail.

Claims

I - 6 Claims 1. A cooling unit for a plurality of optical transceiver

devices, the coohug unit comprising a housing containing a heat sink, a fan, and a cooling channel for flow of air across the heat sink, and means for mounting on the devices.
2. A cooling unit as claimed in claim l, wherein the housing is of elongate configuration, for mounting over a plurality of juxtaposed devices.
3. A cooling unit as claimed in claim 2, wherein the cooling unit fits over a row of devices, allowing devices to be removed at the front.
4. A cooling unit as claimed in claims 2 or 3, wherein the cooling unit comprises a heat sink associated with each device.
S. A cooling unit as claimed in claim 4, comprising a biasing means for pressing the heat sink against the device.
6. A cooling unit as claimed in claim 5, wherein there are at least two springs for pressing each heat sink against a device.
7. A cooling unit as claimed in claims
S or 6, wherein each heat sink is pressed through an aperture in the cooling unit housing.

2 5 8. A cooling unit as claimed in claim 7, wherein each heat sink extends through the housing sufficiently to also extend through an EMI shield of the associated device.
9. A cooling unit as claimed in any preceding claim, wherein the heat sink extends across the top of the heat sinks. t

i - 7
10. An optical transceiver rack comprising a plurality of device sockets juxtaposed on a substrate; a front panel having openings to receive devices being inserted into the sockets, and a cooling unit mounted on top of the sockets.
11. An optical transceiver rack as claimed in claim 10, wherein the cooling unit housing fits behind the front panel.