Circuit module

1. A circuit module comprising:

a substrate;

a plurality of photonic conversion units placed on the substrate; and

a retention assembly, comprising:

a heat sink situated in thermal contact with the plurality of photonic conversion units; and

a fastener mechanically coupled to both the substrate and the heat sink, and configured to press the heat sink against the plurality of photonic conversion units,

wherein the plurality of photonic conversion units are removably secured to the substrate by the retention assembly without the use of a bonding material.

2. The circuit module of claim 1 , further comprising an ASIC soldered to the substrate and in electrical connection with at least one of the photonic conversion units.

3. The circuit module of claim 2 , wherein the ASIC is soldered to the substrate with lead-free solder.

4. The circuit module of claim 1 , further comprising a thermally conductive compound situated between the heat sink and at least one photonic conversion unit.

5. The circuit module of claim 1 , wherein the fastener is releasably coupled to the substrate.

6. The circuit module of claim 1 , wherein the fastener is releasably coupled to the heat sink.

7. The circuit module of claim 1 , wherein the fastener includes one of a spring clip and a screw.

8. The circuit module of claim 1 , wherein the photonic conversion units are oriented on the substrate by a pin-and-guide hole mechanism.

9. The circuit module of claim 1 , wherein the photonic conversion units are oriented on the substrate by an interposer socket.

10. The circuit module of claim 1 , wherein the photonic conversion units include a fiber pigtail.

11. The circuit module of claim 1 , wherein the photonic conversion units include a VCSEL.

12. A method of co-packaging electronic and photonic function in a circuit module, comprising:

soldering an ASIC to a substrate;

placing a plurality of photonic conversion units directly on the substrate without use of a bonding material;

placing a heat sink against the plurality of photonic conversion units to provide thermal contact between the heat sink and at least one of the photonic conversion units;

coupling a fastener to the substrate and to the heat sink so that the fastener presses the heat sink against the plurality of photonic conversion units, thereby removably securing the plurality of photonic conversion units to the substrate.

13. The method of claim 12 , further including soldering the substrate to a printed circuit board.

14. The method of claim 12 , wherein thermal contact is further provided by including a layer of a thermally conductive compound between the heat sink and at least one photonic conversion unit.

15. The method of claim 12 , wherein the fastener includes one of a spring clip and a screw.