Abstract
An electro-optical structure including at least one optical component and a plurality of electric components arranged on a common printed circuit board is disclosed herein. The printed circuit board includes a plate-shaped base body made of molybdenum or an Invar material. An optical bench including a printed circuit board with a plate-shaped base body of molybdenum or an Invar material is also disclosed herein.
Claims
1. An electro-optical structure, comprising: at least one optical component, and a plurality of electric components, wherein the at least one optical component and the plurality of electric components are arranged on a common printed circuit board.
2. The electro-optical structure according to claim 1, wherein the plurality of electric components are connected with each other via conductor traces, and wherein the conductor traces are integrated in the printed circuit board.
3. The electro-optical structure according to claim 1, wherein the printed circuit board has a thermal expansion coefficient smaller than 9 m/K.
4. The electro-optical structure according to claim 1, wherein the printed circuit board comprises a plate-shaped base body, and wherein the base body comprises molybdenum or an Invar material.
5. The electro-optical structure according to claim 4, wherein the Invar material is at least one of the following alloys: FeNi, FePt, FePd, FeMn, CoMn, FeNiPt, FeNiMn, FeNiCo, CoMnFe, CrFe, CrMn, CoCr, FeB, or FeP.
6. The electro-optical structure according to claim 4, wherein the Invar material is a FeNi alloy comprising 30 to 40 mass percent of Ni.
7. The electro-optical structure according to claim 4, wherein the base body comprises a copper coating on a first and a second side.
8. The electro-optical structure according to claim 1, wherein the printed circuit board comprises a symmetrical layer structure as seen in the cross section.
9. The electro-optical structure according to claim 1, wherein the electro-optical structure is an optical freespace communication system.
10. An optical bench comprising a printed circuit board.
11. The optical bench according to claim 10, wherein the printed circuit board comprises a plate-shaped base body, and wherein said base body comprises molybdenum or an Invar material.
12. The electro-optical structure according to claim 4, wherein the Invar material is an FeNiCo alloy comprising 25 to 35 mass percent of Ni and less than or equal to 20 mass percent of Co.
Description
[0026] Hereunder the invention is explained in detail with reference to the accompanying drawing in which:
[0027] FIG. 1 shows a cross-sectional view of a first layer structure of a printed circuit board for an electro-optical structure according to the invention,
[0028] FIG. 2 shows a cross-sectional view of a second layer structure of a printed circuit board for an electro-optical structure according to the invention,
[0029] FIG. 3 shows an electro-optical structure according to the invention,
[0030] FIG. 4 shows thermally insulated holes according to the invention, and
[0031] FIG. 5 shows thermally connected holes according to the invention.
[0032] In a first configuration of a printed circuit board 10, shown in FIG. 1, for an electro-optical structure according to the invention said printed circuit board comprises a plate-shaped base body 12. The plate-shaped configuration of the base body 12 and of the printed circuit board 10 in general is illustrated in FIG. 1 by the ellipses 14. The printed circuit board 10 merely has a thickness of a few millimeters, in particular 1.5 mm-10 mm. In contrast, the printed circuit board has a length and a width of several centimeters and is large enough for accommodating all electronic and optical components. The plate-shaped base body 12 of the printed circuit board is made from an Invar material, for example Fe65Ni35. The base body is coated or plated with a copper layer 16 on both sides. In addition, the printed circuit board 10 comprises an outer copper layer 18 both on the lower side 20 and on the upper side 22. Thus the structure of the printed circuit board 10 is symmetrical around the base body 12 made from the Invar material. In the outermost copper coating 18 on the upper side 22 conductor traces may be integrated which electrically connect the electric components, which can be arranged on the printed circuit board, according to a circuit diagram. Between the outermost copper layer 18 and the copper layer 16 directly connected with the base body 12 a respective filler layer 24 is arranged which electrically insulates the outer copper layer 18 from the inner copper layer 16. The filler layer 24 is made up of cured preimpregnated fibers, so-called Prepreg.
[0033] According to a second embodiment, shown in FIG. 2, the printed circuit board 26 comprised a first plate-shaped base body 28 made from an Invar material as well as a second plate-shaped base body 30 also made from an Invar material. Both the first base body 28 and the second base body 30 are directly coated with a copper layer 32 on both sides. The copper-plated first base body 28 is connected with the copper-plated second base body 30 via a filler layer 34. Both on the upper side 36 and on the lower side 38 an outer copper layer 40 is arranged which is respectively connected with the base bodies via a filler layer 42. In this exemplary embodiment, too, the structure of the printed circuit board 26 is symmetrical for minimizing thermal stresses caused by heat introduced by the electronic components arranged on the surface 36.
[0034] FIG. 3 schematically shows an electro-optical structure. Electric components, such as a laser diode 44, an amplifier 46, a controller 48 and a power supply unit 50, are arranged on a common printed circuit board 52. The common printed circuit board 52 again comprises an Invar base body copper-plated on both sided, for example, or, alternatively, a copper-plated molybdenum body. In addition, on the common printed circuit board 52 optical components, such as a mirror 54 or a lens 56, are arranged for guiding and modifying the laser light of the laser diode 44. Due to the structure of the common printed circuit board 52 the latter has a thermal expansion coefficient of smaller than 9 m/K such that the relative position of the optical components with respect to each other is changed only to a small extent by the local heat input generated by the electric components 44, 46, 48 and 50. Thereby, it is possible to arrange electric components 44, 46, 48 and 50 together with optical components 54, 56 on a common printed circuit board 52. Thus a separate optical bench is not required. Thereby, the structure of the electro-optical system is strongly simplified.
[0035] Another control of the heat balance of the printed circuit board is performed via the insulated fastening holes, in particular for optical components, as shown in FIG. 4. The printed circuit board 58 comprises two Invar base bodies 60 each of which is copper-plated. A bore 62 is copper-plated 64 from inside. The copper coating has no metallic connection to the two Invar base bodies 60. In particular, the gap 66 ensures that the heat transfer from the Invar base bodies 60 to the fastening sites or the optical components fastened to the fastening sites is small.
[0036] Alternatively, in particular electric components can be fastened in thermally connected holes, as shown in FIG. 5. The latter comprise a bore 68 whose inner surface is coated with copper 70. The inner coating 70 is directly connected with the two existing Invar base bodies 74 via webs 72 such that heat generated by the electric components fastened in the bore 68 can be effectively dissipated via a large surface formed by the copper-plated Invar cores. Thereby, generated heat is quickly distributed such that a reduction of the local excess temperature leads to a reduced thermal stress.
