Semiconductor module with serial bus connection to multiple dies

Abstract

A semiconductor module is provided which includes a beat heat spreader, at least two semiconductors thermally coupled to the heat spreader, and a plurality of electrically conductive leads electrically connected to the semiconductors. At least one of the electrically conductive leads is common to both of the semiconductors. The semiconductor module also includes a termination resistor electrically coupled to at least one of the semiconductors. A method of making a semiconductor module is also taught, whereby a plurality of electrically conductive leads are provided. At least two semiconductors are electrically coupled to the plurality of electrically conductive leads, where at least one of the electrically conductive leads is common to both of the semiconductors. The semiconductors are then thermally coupled to a heat spreader. Subsequently, a termination resistor is electrically coupled to at least one of the semiconductors.

Description

1115 (FIG. 10) to protect the semiconductor from electromagnetic forces. In addition, adhesive may be placed between the tape and the base of the heat spreader to cushion the contact points and ensure contact between the contact points and the PCB.

The semiconductor module of the invention eliminates the need for a separate heat spreader. The invention reduces overall cost and weight through shared common contact points or nodes. The common contact points also allow for a constant footprint to be maintained independent of the size or number of semiconductors used. Furthermore, the module is reliable as the semiconductors are not exposed to as high thermal stresses. The module also substantially improves heat dissipation by exposing greater surface areas to the surrounding air.

Multi-Chip Modules

As explained above in the background section of this specification, many existing semiconductor modules position their embedded semiconductors relatively far from the circuit board to which they are attached. Each semiconductor in such semiconductor modules connects to a transmission channel via its own electrical lead. A signal passing along the transmission channel from lead to lead is degraded by a load placed on the signal by each successive lead. The longer the stub, the more the signal is degraded. Each successive lead further degrades the signal, until such time as the signal has been degraded so as to be useless. Most semiconductor modules also include a termination resistor at the end of each transmission channel on the printed circuit board. The present invention addresses the problem associated with signal degradation in semiconductor modules having relatively long electrical leads.

Impedance matching of an electrical load to the impedance of a signal source and the characteristic impedance of a transmission channel is often necessary to reduce reflections by the load, back into the transmission channel. As the length of a non-terminated transmission line increases, reflections become more problematic. When high frequency signals are transmitted or passed through even very short transmission lines, such as printed circuit board (PCB) traces, a termination resistor may be inserted at the load to avoid reflections and degradations in performance.

In the multi-chip modules of the present invention, termination resistors are preferably internal to the MCM's. The use of external termination resistors presents a number of drawbacks. The placement of a termination resistor outside an MCM results in an additional stub or short transmission line between the termination resistor and the integrated circuit device. External termination resistors also require significant circuit board space, and increase circuit board layout complexity and cost.

FIG. 12 shows a side view of a semiconductor module 1200 according to yet another embodiment of the invention. A number of semiconductors 1204 are electrically coupled to a plurality of traces or electrically conductive leads 1202 (only one is shown) by any conventional method such as wire bonding or thermocompression bonding. The electrically conductive leads 1202 are preferably incorporated into a flexible circuit or tape 1210, which preferably consists of copper traces within a thin dielectric substrate (such as polyimide, epoxy, etc.).

The semiconductors 1204 on the flexible circuit 1210, are preferably bonded directly to a heat spreader 1218. Alternatively, as shown and described in relation to FIG. 2, the flexible circuit 1210 may be bonded directly to the heat spreader 1218. The bond may be made by any means but is preferably made by gluing the semiconductors 1204 or flexible circuit 1210, with an epoxy or the like, to the side of the heat spreader 1218. The glue is chosen to closely match the thermal expansion properties of the semiconductor 1204, heat spreader 1218, and flexible circuit 1210. The glue should also have good thermal conduction properties. This embodiment, where the semiconductors 1204 are bonded directly to the heat spreader 1218 is favored due to the direct conduction of heat from the semiconductors 1204 to the heat spreader.

The heat spreader 1218 is preferably made from a material with good heat dissipation properties, such as a metal. In a preferred embodiment, the semiconductors 1204 are positioned on opposing sides of the heat spreader 1218. The electrical leads 1202 connect the semiconductors 1204 to electrical contact points 1216 at the base of the semiconductor module 1200. In use, electrical contact points 1216 may for example comprise solder balls or bond pads. The electrical contact points 1216 electrically couple the electrical leads 1202 to a transmission channel 1214 on a printed circuit board 1212. Electrical signals are transmitted along the transmission channel 1214 to electrical contact points 1216. The electrical signals are then passed from the electrical contact points 1216 through the electrical leads 1202 to each of the semiconductors 1204.

In this embodiment, the semiconductors 1204, on opposing sides of the heat spreader 1218, are connected to one another in series by the electrical lead 1202. It should be noted that multiple (i.e., more than two) semiconductors 1204 may be connected together in series. The final semiconductor in the series, remote from the transmission channel, electrically couples to a termination resistor 1208. The termination resistor 1208 is preferably thermally coupled to the heat spreader 1218 so that any heat built up in termination resistor 1208 can dissipate through the heat spreader.

The termination resistor 1208 connected in series to the semiconductors 1204 substantially reduces any degradation of the signal caused by a load placed on the signal from the electrical leads 1210, as the signal is not being split as is the case with stubs in existing semiconductor modules. A signal is transmitted from a signal source along the transmission channel 1214, along an electrical lead 1202, to each semiconductor 1204 connected in series, and is terminated at the termination resistor 1208. Furthermore, by incorporating the termination resistor 1208 into the semiconductor module 1200, the need for a termination resistor on the printed circuit board 1214 is eliminated.

This embodiment of the invention is particularly useful now that the memory capacity of individual semiconductors has increased to a point where only a few semiconductors are needed for many applications.

FIG. 13 is a front view of the semiconductor module 1300 according to a further embodiment of the invention. This semiconductor module 1300 is identical to the semiconductor module 100 shown in FIG. 1, except for a termination resistor 1302 disposed on the heat spreader. FIG. 14 is a side view of the same semiconductor module 1300 shown in FIG. 13. In this embodiment, the semiconductors 1304 are not connected in series, but rather each semiconductor connects to its own transmission channel. Likewise, each termination resistor 1302 connects to a single semiconductor. In use, a signal is transmitted along each transmission channel, to its respective semiconductor, after which it is terminated at a termination resistor 1402 to eliminate reflections.

The resistance value of the termination resistor 1208 (FIG. 2) or 1302 (FIGS. 13 and 14) is selected such that its impedance substantially matches the impedance of the transmission channel and signal source to which it is connected. Furthermore, any form of termination may be used, such as parallel termination, Thevenin termination, series termination, AC termination, Schotty-diode Schottky-diode termination or the like.

FIG. 15 is a flow chart of a method 1500 of making a semiconductor module according to another embodiment of the invention. According to the method 1500 a plurality of electrically conductive leads are provided (step 1502). At least two semiconductors are electrically coupled (step 1504) to the plurality of electrically conductive leads, where at least one of the electrically conductive leads is common to both of the semiconductors. The semiconductors are then thermally coupled (step 1506) to a heat spreader. Subsequently, a termination resistor is electrically coupled (step 1508) to at least one of the semiconductors.

The semiconductors may be electrically coupled in series, where the semiconductors are capable of being electrically coupled to a transmission channel. Moreover, an additional termination resistor may be electrically coupled to the semiconductor not already connected to the termination resistor, where each of the semiconductors is capable of being electrically coupled to a separate transmission channel.

While the foregoing description and drawings represent the preferred embodiments of the present invention, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope of the present invention as defined in the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other specific forms, structures, arrangements, proportions, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and not limited to the foregoing description.

Claims

1. A semiconductor module, comprising:

a heat spreader comprising a solid block of heat spreading material having a substantially planar first side, a substantially planar opposing second side and a respective edge between the first side and the second side;

a flexible circuit including a first portion bonded to at least part of the first side of the heat spreader, a second portion wrapped around the respective edge of the heat spreader, and a third portion bonded to at least part of the second side of the heat spreader;

at least two semiconductors coupled to the flexible circuit and thermally coupled to said the heat spreader, wherein one of the semiconductors is disposed at the first side of the heat spreader and another one of the semiconductors is disposed at the second side of the heat spreader; and,

a plurality of electrically conductive leads electrically connected to said semiconductors, where at least one of said electrically conductive leads is common to both of said semiconductors; and

a termination resistor electrically coupled to at least one of said semiconductors.

a plurality of electrical contacts disposed on the flexible circuit proximate to the second portion of the flexible circuit, where each of the plurality of electrical contacts is electrically coupled to at least one of the semiconductors via the flexible circuit, wherein the plurality of electrical contacts are configured to removeably couple the semiconductor module to corresponding electrical contacts formed in a slot on a circuit board when a portion of the semiconductor module, including the respective edge of the heat spreader, the second portion of the flexible circuit wrapped around the respective edge of the heat spreader, and the plurality of electrical contacts, is inserted into the slot.

2. A semiconductor module according to claim 1, wherein said at least some of the semiconductors are electrically coupled to one another in series, and where said the semiconductors are capable of being electrically coupled to a transmission channel.

3. A semiconductor module according to claim 2, further comprising a termination circuit electrically coupled to at least one of the semiconductors, wherein a final semiconductor in said series, remote from said the transmission channel, is electrically coupled to said the termination resistor circuit.

4. A semiconductor module according to claim 1, wherein one each semiconductor of the at least two semiconductors is not connected to said termination resistor, and an additional termination resistor is electrically coupled to the one semiconductor not connected to said termination resistor. a separate transmission channel, where each transmission channel is separately terminated.

5. A semiconductor module according to claim 1, further comprising a termination resistor electrically coupled to at least one of the semiconductors, wherein a resistance value of the termination resistor is selected such that an impedance of said the termination resistor substantially matches an impedance of a transmission channel and a signal source to which said the termination resistor is connected.

6. A semiconductor module according to claim 1, further comprising a termination circuit electrically coupled to at least one of the semiconductors, wherein said the termination resistor's form of termination is selected from a group consisting of: parallel termination, Thevenin termination, series termination, AC termination, and Schotty-diode Schottky-diode termination.

7. A semiconductor module according to claim 1, further comprising a termination circuit electrically coupled to at least one of the semiconductors, wherein said the termination resistor circuit is thermally coupled to said the heat spreader.

8. A semiconductor module according to claim 1, further comprising a termination circuit electrically coupled to at least one of the semiconductors, wherein said the termination resistor is bonded directly to a side wall of said the heat spreader.

9. A semiconductor module according to claim 1, wherein said the two semiconductors are mounted on opposing side walls of said the heat spreader.

10. A semiconductor module according to claim 2, wherein each of said semiconductors are bonded directly to said side wall of said heat spreader.

11. A semiconductor module according to claim 1, wherein said leads form part of a the flexible circuit at least partially attached to said heat spreader includes a plurality of electrically conductive leads electrically connected to the semiconductors, where at least one of the electrically conductive leads is common to both of the semiconductors.

12. A semiconductor module according to claim 11, wherein said the flexible circuit is a flexible dielectric tape.

13. A semiconductor module according to claim 12, wherein said the flexible circuit is bonded directly to said the side wall of said the heat spreader.

14. A semiconductor module according to claim 11, wherein said the common electrically conductive lead is selected from a group consisting of a voltage supply node, a reference voltage node, and an electrical ground node.

15. A semiconductor module according to claim 1, wherein said heat spreader is a solid block of heat dissipating material.

16. A semiconductor module according to claim 1, wherein said heat spreader is “u” shaped.

17. A method of making a semiconductor module, comprising:

providing a heat spreader comprising a solid block of heat spreading material having a substantially planar first side, a substantially planar opposing second side and a respective edge between the first side and the second side;

attaching a flexible circuit to the heat spreader including bonding a first portion to at least part of the first side of the heat spreader, wrapping a second portion around the respective edge of the heat spreader, and bonding a third portion to at least part of the second side of the heat spreader;

providing a plurality of electrically conductive leads;

electrically coupling at least two semiconductors to said plurality of electrically conductive leads, where at least one of said electrically conductive leads is common to both of said semiconductors; the flexible circuit;

thermally coupling said the at least two semiconductors to a the heat spreader, wherein one of the semiconductors is disposed at the first side of the heat spreader and another one of the semiconductors is disposed at the second side of the heat spreader; and

electrically coupling a termination resistor to at least one of said semiconductors.

providing a plurality of electrical contacts disposed on the flexible circuit proximate to the second portion of the flexible circuit such that each of a plurality of electrical contacts is electrically coupled to at least one of the semiconductors via the flexible circuit, wherein the plurality of electrical contacts are configured to removeably couple the semiconductor module to corresponding electrical contacts formed in a slot on a circuit board when a portion of the semiconductor module, including the respective edge of the heat spreader, the second portion of the flexible circuit wrapped around the respective edge of the heat spreader, and the plurality of electrical contacts, is inserted into the slot.

18. A method according to claim 17, initially comprising electrically coupling said at least some of the semiconductors in series, where said the semiconductors are capable of being electrically coupled to a transmission channel.

19. A method according to claim 17, further comprising wherein electrically coupling at least two semiconductors to the flexible circuit includes electrically coupling an additional termination resistor to the semiconductor not already connected to said termination resistor, where each of said semiconductors is capable of being electrically coupled each semiconductor to a separate transmission channel, where each transmission channel is separately terminated.

20. A method according to claim 17, including electrically coupling a termination circuit to at least one of the semiconductors; and bonding said the termination resistor directly to a side wall of said the heat spreader.

21. A method according to claim 17, including mounting said the two semiconductors on opposing side walls of said the heat spreader.

22. A method according to claim 17, including bonding each of said semiconductors directly to a side wall of said heat spreader.

23. A method according to claim 17, wherein said leads form part of a the flexible circuit at least partially attached to said heat spreader, said method including bonding said flexible circuit directly to a side wall of said heat spreader includes a plurality of electrically conductive leads electrically connected to the semiconductors, where at least one of the electrically conductive leads is common to both of the semiconductors.

24. A semiconductor module according to claim 1, further comprising a fastening mechanism for anchoring the semiconductor module to a circuit board.

25. A semiconductor module according to claim 24, wherein clamps anchor the semiconductor module to the circuit board.

26. A semiconductor module according to claim 1, wherein the plurality of electrical contacts disposed on the flexible circuit are a linear array of electrical contact pads coupled to the heat spreader.

27. A semiconductor module according to claim 26, wherein the plurality of electrical contact pads are an array of bond pads.

28. A semiconductor module according to claim 26, wherein the plurality of electrical contact pads are an array of metal points.

29. A semiconductor module according to claim 1, wherein the flexible circuit is at least partially bonded to the heat spreader using a bonding adhesive with thermal expansion properties similar to those of the flexible circuit and the heat spreader.

30. A semiconductor module according to claim 1, wherein the plurality of electrical contacts are disposed at on a section the flexible circuit that is bonded to the heat spreader, and the section the flexible circuit having the plurality of electrical contacts disposed thereon is bonded to the heat spreader proximate to the respective edge of the heat spreader.

31. A semiconductor module according to claim 1, wherein the plurality of electrical contacts disposed on the flexible circuit are electrically and mechanically coupled to a section of the flexible circuit that is bonded to the heat spreader near an apex of the heat spreader.

32. A semiconductor module according to claim 1, wherein the first side of the heat spreader and the second side of the heat spreader are substantially perpendicular to the circuit board when the semiconductor module is coupled to the electrical contacts formed in the slot.

33. A method according to claim 17, wherein the first side of the heat spreader and the second side of the heat spreader are substantially perpendicular to the circuit board when the semiconductor module is coupled to the electrical contacts formed in the slot.

34. A method according to claim 18, further comprising electrically coupling a termination circuit to at least one of the semiconductors, wherein a final semiconductor in the series, remote from the transmission channel, is electrically coupled to the termination circuit.

35. A method according to claim 17, further comprising electrically coupling a termination resistor to at least one of the semiconductors, wherein a resistance value of the termination resistor is selected such that an impedance of the termination resistor substantially matches an impedance of a transmission channel and a signal source to which the termination resistor is connected.

36. A method according to claim 17, further comprising electrically coupling a termination circuit to at least one of the semiconductors, wherein the termination circuit's form of termination is selected from a group consisting of: parallel termination, Thevenin termination, series termination, AC termination, and Schottky-diode termination.

37. A method according to claim 17, further comprising electrically coupling a termination circuit to at least one of the semiconductors, wherein the termination circuit is thermally coupled to the heat spreader.

38. A method according to claim 23, wherein the flexible circuit is a flexible dielectric tape.

39. A method according to claim 17, wherein the flexible circuit includes a plurality of electrically conductive leads electrically connected to the semiconductors, where at least one of the electrically conductive leads is common to both of the semiconductors.

40. A method according to claim 39, wherein the common electrically conductive lead is selected from a group consisting of a voltage supply node, a reference voltage node, and an electrical ground node.

41. A method according to claim 17, further comprising mechanically coupling the semiconductor module to a fastening mechanism for anchoring the semiconductor module to a circuit board.

42. A method according to claim 30, wherein the fastening mechanism for anchoring the semiconductor module includes a clamp.

43. A method according to claim 17, wherein the plurality of electrical contacts disposed on the flexible circuit are a linear array of electrical contact pads coupled to the heat spreader.

44. A method according to claim 43, wherein the plurality of electrical contact pads are an array of bond pads.

45. A method according to claim 43, wherein the plurality of electrical contact pads are an array of metal points.

46. A method according to claim 17, wherein the flexible circuit is at least partially bonded to the heat spreader using a bonding adhesive with thermal expansion properties similar to those of the flexible circuit and the heat spreader.

47. A method according to claim 17, wherein the plurality of electrical contacts are disposed at on a section the flexible circuit that is bonded to the heat spreader, and the section the flexible circuit having the plurality of electrical contacts disposed thereon is bonded to the heat spreader proximate to the respective edge of the heat spreader.

48. A method according to claim 17, wherein the plurality of electrical contacts disposed on the flexible circuit are electrically and mechanically coupled to a section of the flexible circuit that is bonded to the heat spreader near an apex of the heat spreader.

49. A semiconductor module, comprising:

a heat spreader comprising a solid block of heat spreading material having a substantially planar first side, a substantially planar opposing second side and a respective edge between the first side and the second side;

at least two semiconductors each comprising circuitry, where the semiconductors are thermally coupled to the heat spreader, and one of the semiconductors is disposed at the first side of the heat spreader and another one of the semiconductors is disposed at the second side of the heat spreader;

a flexible circuit including a first portion bonded to at least part of the first side of the heat spreader, a second portion wrapped around the respective edge of the heat spreader, and a third portion bonded to at least part of the second side of the heat spreader, wherein the flexible circuit comprises a plurality of electrically conductive leads that are electrically connected to the semiconductors, where at least one of the electrically conductive leads is common to both of the semiconductors;

a termination resistor electrically coupled to the circuitry of at least one of the semiconductors; and

a plurality of electrical contacts disposed on the flexible circuit proximate to the second portion of the flexible circuit, where each of the plurality of electrical contacts is electrically coupled to at least one of the semiconductors via the flexible circuit, wherein the plurality of electrical contacts are configured to removeably couple the semiconductor module to corresponding electrical contacts formed in a slot on a circuit board when a portion of the semiconductor module, including the respective edge of the heat spreader, the second portion of the flexible circuit wrapped around the respective edge of the heat spreader, and the plurality of electrical contacts, is inserted into the slot.