PCB droplet actuator fabrication

• US 8,268,246 B2
• Filed: 08/11/2008
• Issued: 09/18/2012
• Est. Priority Date: 08/09/2007
• Status: Active Grant

• Current Assignee: Advanced Liquid Logic, Inc. (Illumina Incorporated)
• Original Assignee: Advanced Liquid Logic, Inc. (Illumina Incorporated)
• Inventors: Srinivasan, Vijay, Pamula, Vamsee K., Pollack, Michael G.
• Primary Examiner(s): Ball, J. Christopher
• Application Number:
  US12/531,794
• Publication Number:
  US 20100126860A1
• Time in Patent Office: 1,499 Days
• Field of Search: 204/643, 422/81, 422/189, 422/82.05, 436/53, 436/180
• US Class Current: 422/81
• CPC Class Codes: B01L 2300/089 Virtual walls for guiding liquids
• CPC Class Codes: B01L 2300/12 Specific details about materials
• CPC Class Codes: B01L 2400/0427 Electrowetting
• CPC Class Codes: B01L 3/502707 characterised by the manufacture of the container or its components by shaping or joining plastic parts B29C59/00, B29C65/00; by laminating B32B37/00; manufacture of microstructural devices in general B81C
• CPC Class Codes: B01L 3/502784 specially adapted for droplet or plug flow, e.g. digital microfluidics automatic analysis using a stream of discrete samples in a tube system G01N35/08
• CPC Class Codes: B01L 3/502792 for moving individual droplets on a plate, e.g. by locally altering surface tension
• CPC Class Codes: H05K 1/113 Via provided in pad; Pad over filled via
• CPC Class Codes: H05K 2201/09527 Inverse blind vias, i.e. bottoms outwards in multilayer PCB; Blind vias in centre of PCB having opposed bottoms
• CPC Class Codes: H05K 3/0058 Laminating printed circuit boards onto other substrates, e.g. metallic substrates H05K1/0281 takes precedence
• CPC Class Codes: H05K 3/0067 onto an inorganic, non-metallic substrate
• CPC Class Codes: H05K 3/28 Applying non-metallic protective coatings H05K3/0091 takes precedence; methods for intermediate insulating layers for build-up multilayer circuits H05K3/4673
• CPC Class Codes: H05K 3/4038 Through-connections; Vertical interconnect access [VIA] connections H05K3/403, H05K3/42 take precedence
• CPC Class Codes: H05K 3/421 Blind plated via connections H05K3/422, H05K3/423 and H05K3/425 take precedence
• CPC Class Codes: H05K 3/427 initial plating of through-holes in metal-clad substrates
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor
• CPC Class Codes: Y10T 29/49124 On flat or curved insulated base, e.g., printed circuit, etc.
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base

Abstract

Alternative approaches to fabricating printed circuit boards for use in droplet actuator operations are provided. In one embodiment, a method of manufacturing a droplet actuator for conducting droplet operations includes positioning a dielectric material between a first metal layer configured to include an electrode and a second metal layer configured to include an interconnect pad. The method additionally includes forming a connection between the first and second metal layers. Droplet actuators and methods of fabricating and supporting printed circuit boards of droplet actuators are also provided.

Claims

1. A method of manufacturing a droplet actuator for conducting droplet operations, the method comprising:

(a) positioning a dielectric material between a first metal layer configured to include an electrode and a second metal layer configured to include an interconnect pad;

(b) forming a connection between the first and second metal layers;

(c) attaching a rigid support structure onto the second metal layer, wherein the rigid structure is selected to reduce warping caused by the dielectric material; and

(d) positioning a first plate proximate a second plate comprising the first and second metal layers, the dielectric material and the connection to form a gap between the two plates that provides a fluid flow path for droplet operations, wherein the gap has a gap tolerance of less than 10% of the expected droplet height.

2. The method of claim 1 further comprising applying a photoresist layer onto the first metal layer.

3. The method of claim 1 further comprising stripping a photoresist layer from the first metal layer.

4. The method of claim 1, wherein forming the connection further comprises forming a via connection between the first and second metal layers.

5. The method of claim 1, wherein forming the connection further comprises forming an opening through both the dielectric material and the second metal layer through to the first metal layer.

6. The method of claim 5 further comprising applying a photoresist layer onto the second metal layer in such a manner as to leave the opening exposed.

7. The method of claim 6 further comprising applying a metal plating into the opening to form the connection.

8. The method of claim 7 further comprising stripping the photoresist layer from the second metal layer.

9. The method of claim 1 further comprising forming the electrode from the first metal layer.

10. The method of claim 1 further comprising forming the interconnect pad from the second metal layer.

11. The method of claim 1 wherein the attaching comprises laminating a rigid structure onto the second metal layer using a bonding layer.

12. The method of claim 1, wherein the rigid structure comprises glass structure.

13. The method of claim 1 further comprising applying an electrowetting layer onto the first metal layer.

14. The method of claim 13, wherein applying the electrowetting layer to the first metal layer further comprises applying a dielectric substance onto the first metal layer.

15. The method of claim 13, wherein applying the electrowetting layer onto the first metal layer further comprises applying at least one of a liquid photoimageable soldermask and a non-florescent material onto the first metal layer.

16. The method of claim 1 further comprising applying a photoresist layer onto the second metal layer.

17. The method of claim 1 further comprising stripping a photoresist layer from the second metal layer.

18. The method of claim 1 further comprising forming the dielectric material from non-florescent material.

19. The method of claim 1 further comprising forming the first plate.

20. The method of claim 1, wherein the gap tolerance is from about 1 to about 5%.

21. A droplet actuator for conducting droplet operations, comprising:

(a) a first plate that includes;

(i) a first metal layer comprising an electrode;

(ii) a second metal layer comprising an interconnect pad;

(iii) a dielectric material positioned between the first and second metal layers; and

(iv) a via connecting the electrode to the interconnect; and

(b) a rigid support structure attached to the first plate and selected to reduce warping of the first plate;

(c) a second plate proximate the first plate and forming a gap therebetween that provides a fluid flow path for the droplet operations, wherein the gap has a gap tolerance of less than 10% of the expected droplet height.

22. The droplet actuator of claim 21 further comprising an electrowetting layer positioned on at least one of the first and second metal layers proximate the gap.

23. The droplet actuator of claim 21, wherein the via comprises metal applied in a hole formed through the second metal layer and the dielectric material.

24. The droplet actuator of claim 23, further comprising a photoresist layer protecting the second metal layer from the applied metal.

25. A method of fabricating and supporting a printed circuit board of a droplet actuator for conducting droplet operations, the method comprising:

(a) providing a core printed circuit board by positioning a dielectric material between a first metal layer configured to include an electrode and a second metal layer configured to include an interconnect pad;

(b) applying a photoresist layer onto the first metal layer and forming one or more openings in the dielectric material and the second metal layer;

(c) applying a photoresist layer onto the second metal layer and plating the one or more openings to form one or more blind vias, thereby forming a connection between the first and second metal layers;

(d) stripping the photoresist layer from both the first metal layer and the second metal layer;

(e) patterning the features on both the first metal layer and the second metal layer;

(f) applying an electrowetting dielectric layer to the first metal layer; and

(g) bonding a rigid support structure to the second metal layer wherein the rigid support structure ais selected to reduce warping of the printed circuit board, wherein the gap has a gap tolerance of less than 10% of the expected droplet height.

26. The method of claim 25, wherein the gap tolerance is from about 1 to about 5%.

27. A method of manufacturing a droplet actuator for conducting droplet operations, the method comprising:

(a) providing a printed circuit board (PCB) comprising electrodes arranged for conducting droplet operations;

(b) attaching a rigid structure to the PCB, wherein the rigid structure reduces warping of the PCB; and

(c) positioning a plate proximate the PCB to form a gap that provides a fluid flow path for conducting droplet operations;

wherein the gap has a gap tolerance of less than 10% of the expected droplet height.

28. The method of claim 27, wherein the gap tolerance is from about 1 to about 5%.