FABRICATING AN INTEGRATED LOUDSPEAKER PISTON AND SUSPENSION

• US 20170078800A1
• Filed: 07/28/2016
• Published: 03/16/2017
• Est. Priority Date: 09/10/2015
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Guthy, Csaba, Nielsen, Ole Mattis, Hayner, Mark A.
• Granted Patent: US 10,609,489 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04R 2201/003 Mems transducers or their use of the electrostatic type H04R19/005
• CPC Class Codes: H04R 2231/003 Manufacturing aspects of the outer suspension of loudspeaker or microphone diaphragms or of their connecting aspects to said diaphragms
• CPC Class Codes: H04R 2307/025 Diaphragms comprising polymeric materials
• CPC Class Codes: H04R 2307/204 Material aspects of the outer suspension of loudspeaker diaphragms
• CPC Class Codes: H04R 31/00 Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor manufacture of microstructural arrangements of deformable or non-deformable structures in general B81C1/00182
• CPC Class Codes: H04R 31/003 for diaphragms or their outer suspension
• CPC Class Codes: H04R 31/006 Interconnection of transducer parts of diaphragm and outer suspension by moulding H04R31/003
• CPC Class Codes: H04R 7/04 Plane diaphragms
• CPC Class Codes: H04R 7/20 Securing diaphragm or cone resiliently to support by flexible material, springs, cords, or strands
• CPC Class Codes: H04R 9/04 Construction, mounting, or centering of coil
• CPC Class Codes: H04R 9/06 Loudspeakers

Abstract

A diaphragm and suspension for an electroacoustic transducer are formed by depositing a layer of compliant material on a first surface of a solid substrate and removing material from a second surface of the solid substrate. The removal leaves a block of substrate material suspended within an inner perimeter of an outer support ring of the substrate material by the compliant material, the block providing the diaphragm.

Claims

1. A method of forming an electroacoustic transducer having a diaphragm and suspension, the method comprising:

depositing a layer of compliant material on a first surface of a solid substrate; and

removing material from a second surface of the solid substrate, the removal leaving a block of substrate material suspended within an inner perimeter of an outer support ring of the substrate material by the compliant material, the block providing the diaphragm.

2. The method of claim 1, wherein the compliant material has an elastic strain limit of at least 50 percent.

3. The method of claim 1, wherein the compliant material has an elastic strain limit of at least 150 percent.

4. The method of claim 1, further comprising curing the compliant material.

5. The method of claim 1, wherein the compliant material comprises liquid silicone rubber (LSR).

6. The method of claim 1, wherein the step of removing material from the substrate comprises removing material from a portion of the substrate in some areas to form the block, and removing all material of the substrate in other areas to form a gap between the inner perimeter of the outer support ring and the suspended block.

7. The method of claim 6, wherein the step of removing material from the substrate comprises deep reactive ion etching (DRIE), material being removed from a portion of the substrate by a single DRIE etch, and material being removed from the entire substrate by multiple DRIE etches.

8. The method of claim 6, wherein the substrate comprises a silicon-on-insulator (SOI) wafer, and the step of depositing the layer of compliant material is performed after the step of removing material from a portion of the substrate to form the block, but before the step of removing all material from other areas to form the gap.

9. The method of claim 8, wherein the step of removing material from the substrate comprises deep reactive ion etching (DRIE), material being removed from a portion of the substrate by a single DRIE etch, and material being removed from the entire substrate by multiple DRIE etches through the main Si wafer, an etch of the insulator layer, and an etch of the top Si layer.

10. The method of claim 6, wherein the substrate comprises a silicon wafer, and the step of depositing the layer of compliant material is performed before the steps of removing material from the substrate.

11. The method of claim 1, wherein removing material from the substrate leaves the block having a side wall retaining most of the thickness of the substrate around an outer perimeter of the block facing the inner perimeter of the outer support ring, and a thinner portion of the substrate remaining bounded by the side wall leaving a void in the interior of the block.

12. The method of claim 11, further comprising attaching a bobbin to the block, the bobbin located adjacent to an inter perimeter of the side wall.

13. The method of claim 12, wherein the bobbin is attached to the block by adhesive, the adhesive being contained by the side wall such that it does not contact the suspension.

14. The method of claim 13, wherein the side wall of the block acts as an alignment guide for the attachment of the bobbin.

15. The method of claim 1, wherein removing material from the substrate leaves the outer support ring having a wall retaining most of the thickness of the substrate and forming the inner perimeter of the outer support ring, and a thinner portion of the substrate at the top of the wall forming a lip around an outer perimeter of the outer support ring.

16. The method of claim 15, further comprising attaching a ferromagnetic housing to the outer support ring, the housing located adjacent to an outer perimeter of the outer support ring wall and the lip.

17. The method of claim 16, wherein the housing is attached to the outer support ring by adhesive, the adhesive being prevented by the side wall from contacting the suspension between the block and the outer support ring.

18. The method of claim 16, wherein the outer support ring acts as an alignment guide for the attachment of the housing.

19. The method of claim 16, further comprising cutting through the compliant material at the location of the outer perimeter of the outer support ring, separating the block, the outer support ring, and the compliant layer suspending the block within the outer support ring from the substrate.

20. The method of claim 19, wherein an inner perimeter of the silicon substrate surrounding the outer support ring aligns a cutting tool for cutting through the compliant material.

21. The method of claim 19, wherein the step of cutting is performed after the step of attaching the ferromagnetic housing to the outer support ring.

22. The method of claim 21, wherein the ferromagnetic housing aligns a cutting tool for cutting through the compliant material.

23. The method of claim 1, wherein the step of removing material forms a plurality of diaphragms and corresponding outer support rings over the area of the substrate.

24. The method of claim 23, further comprising attaching a plurality of bobbins to the diaphragms and a plurality of housings to the outer support rings, simultaneously, while the diaphragms and outer support rings remain attached to the substrate and each other by the layer of compliant material.

25. The method of claim 24, further comprising cutting through the compliant material at the locations of the plurality of outer support rings, the plurality of housings serving as alignment guides for a cutting tool.

26. A diaphragm and suspension assembly for an electroacoustic transducer, the assembly comprising:

a piston comprising a disk of silicon having a flat surface and serving as the diaphragm;

a support ring of silicon surrounding the piston and separated from the piston by a gap;

a layer of compliant material adhered to a top surface of the support ring and to the flat surface of the piston, suspending the piston in the gap.

27. The piston and suspension assembly of claim 26, wherein the piston further comprises a void within the disk of silicon, bounded by a perimeter wall of the disk and the top surface of the disk.

28. The piston and suspension assembly of claim 26, wherein the support ring comprises an inner perimeter wall of silicon facing the gap, and an outer lip having less height than the inner perimeter wall.

29. The piston and suspension assembly of claim 26, wherein the compliant material has an elastic strain limit of at least 50 percent.

30. The piston and suspension assembly of claim 26, wherein the compliant material has an elastic strain limit of at least 150 percent.

31. The piston and suspension assembly of claim 26, wherein the compliant material has a Young'"'"'s modulus and a thickness that together result in the compliant material surrounding the piston in the gap having a mechanical stiffness in the range of 5-100 N/m.

32. The piston and suspension assembly of claim 26, wherein the compliant material comprises liquid silicone rubber (LSR).

33. The piston and suspension assembly of claim 26, wherein the support ring has an outer diameter of around 4 mm.

34. The piston and suspension assembly of claim 26, wherein the piston has a thickness of between 10 and 100 μ

m.

35. The piston and suspension assembly of claim 34, wherein the piston has a thickness of about 50 pm.

36. The piston and suspension assembly of claim 26, wherein the layer of compliant material is between 10 and 500 μ

m thick.

37. The piston and suspension assembly of claim 26, wherein the layer of compliant material is around 50 μ

m thick.

38. An electro-acoustic transducer comprising:

a piston comprising a disk of silicon having a flat surface and serving as a diaphragm of the transducer;

a support ring of silicon surrounding the piston and separated from the piston by a gap;

a layer of compliant material adhered to a top surface of the support ring and to the flat surface of the piston, suspending the piston in the gap;

a bobbin coupled to the piston;

a ferromagnetic housing coupled to the support ring; and

a magnet/voice-coil system coupled to the housing and bobbin for converting electrical current to motion of the piston.

39. The transducer of claim 38, wherein:

the piston further comprises perimeter wall of the disk and the top surface of the disk, the perimeter wall and top surface bounding a void within the disk of silicon; and

the bobbin is adjacent to an inner perimeter of the perimeter wall of the disk.

40. The transducer of claim 38, wherein:

the support ring comprises an inner perimeter wall of silicon facing the gap, and an outer lip having less height than the inner perimeter wall; and

the ferromagnetic housing is adjacent to an outer perimeter surface of the inner perimeter wall and a bottom surface of the outer lip.

41. A method of forming a diaphragm and suspension for an electroacoustic transducer from a silicon-on-insulator (SOI) wafer having a top layer of Si, an intermediate layer of SiO₂, an inner layer of Si, and a bottom layer of SiO₂, the method comprising:

coating the bottom layer of SiO₂ with first photoresist;

masking the bottom of the wafer and exposing the wafer to a light source corresponding to the first photoresist;

developing the photoresist;

etching the bottom SiO₂ layer, the etching masked by the photoresist;

stripping the first photoresist and coating the bottom of the wafer with a second coat of photoresist;

masking the bottom of the wafer and exposing the wafer to a light source corresponding to the second photoresist;

developing the second photoresist;

deep reactive ion etching (DRIE) through a first thickness of Si on the bottom of the wafer, less than the full thickness of the inner layer of Si, the etching masked by the second photoresist;

stripping the second photoresist;

DRIE etching from the bottom of the wafer through the complete thickness of the inner Si layer at the locations where the first DRIE etch was performed, the etching masked by the SiO₂ left after the first etching of the SiO₂,

wherein portions of the inner Si layer having the first thickness remain in the area masked by the photoresist during the first DRIE etch, forming the plate of the diaphragm and the top surface of a support ring, and

the areas masked by the SiO₂ form walls of the diaphragm and support ring;

etching the remaining portions of the bottom SiO₂ layer and portions of the top SiO₂ layer now exposed by the areas etched completely through the inner Si layer;

applying a layer of liquid silicone rubber (LSR) on the top of the wafer; and

etching through portions of the top Si layer exposed by the areas etched completely through the inner Si layer and upper SiO₂ layer, leaving the diaphragm suspended from the support ring by the LSR where both layers of Si were removed.

42. A method of forming a piston and suspension for an electroacoustic transducer, the method comprising:

growing first and second layers of SiO₂ on top and bottom surfaces of a Si wafer;

depositing a layer of Cr on the first layer of SiO₂;

coating a layer of liquid silicone rubber (LSR) on the Cr layer;

coating the top and bottom of the wafer with photoresist;

masking the bottom of the wafer and exposing the wafer to a light source corresponding to the photoresist;

developing the photoresist;

reactive ion etching (RIE) or HF etching the bottom SiO₂ layer;

stripping the exposed photoresist and coating the wafer with a new coat of photoresist;

again masking the bottom of the wafer and exposing the wafer to a light source corresponding to the photoresist;

again developing the photoresist;

deep reactive ion etching (DRIE) through a first thickness of Si on the bottom of the wafer;

stripping the bottom layer of photoresist;

DRIE etching from the bottom of the wafer through the complete thickness of Si at the locations where the first DRIE etch was performed, the etching masked by the SiO₂,

wherein portions of the Si having the first thickness remain in the area masked by the photoresist during the first DRIE etch, forming the plate of the diaphragm and the top surface of a support ring,

the areas masked by the SiO₂ form rings of the diaphragm and support ring, and

the diaphragm is suspended from the support ring by the LSR where the Si was completely removed; and

removing the remaining exposed SiO₂ and photoresist.