Probe card assembly and kit, and methods of using same

• US 6,246,247 B1
• Filed: 09/18/1998
• Issued: 06/12/2001
• Est. Priority Date: 11/15/1994
• Status: Expired due to Term

• Current Assignee: FormFactor Incorporated
• Original Assignee: FormFactor Incorporated
• Inventors: Mathieu, Gaetan L., Eldridge, Benjamin N., Grube, Gary W., Khandros, Igor Y.
• Primary Examiner(s): BROWN, GLENN WARNER
• Application Number:
  US09/156,957
• Time in Patent Office: 998 Days
• Field of Search: 324/754, 324/757, 324/760, 324/761, 324/762
• US Class Current: 324/762.01
• CPC Class Codes: B23K 20/004 Wire welding
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: C23C 18/31 Coating with metals
• CPC Class Codes: C23C 18/32 Coating with nickel, cobalt or mixtures thereof with phosphorus or boron C23C18/50 takes precedence
• CPC Class Codes: C25D 21/02 Heating or cooling
• CPC Class Codes: C25D 5/12 at least one layer being of nickel or chromium
• CPC Class Codes: C25D 5/605 Surface topography of the layers, e.g. rough, dendritic or nodular layers
• CPC Class Codes: C25D 7/0607 Wires
• CPC Class Codes: G01R 1/06711 Probe needles; Cantilever beams; "Bump" contacts; Replaceable probe pins
• CPC Class Codes: G01R 1/0675 Needle-like
• CPC Class Codes: G01R 1/06761 related to layers
• CPC Class Codes: G01R 1/07342 the body of the probe being at an angle other than perpendicular to test object, e.g. probe card
• CPC Class Codes: G01R 1/07378 using an intermediate adapter, e.g. space transformers G01R1/07371 takes precedence
• CPC Class Codes: G01R 31/2889 Interfaces, e.g. between probe and tester G01R31/31905 and G01R1/07364 take precedence
• CPC Class Codes: H01L 21/4853 Connection or disconnection of other leads to or from a metallisation, e.g. pins, wires, bumps
• CPC Class Codes: H01L 21/4889 Connection or disconnection of other leads to or from wire-like parts, e.g. wires
• CPC Class Codes: H01L 21/563 Encapsulation of active face of flip-chip device, e.g. underfilling or underencapsulation of flip-chip, encapsulation preform on chip or mounting substrate
• CPC Class Codes: H01L 21/76897 Formation of self-aligned vias or contact plugs, i.e. involving a lithographically uncritical step self-aligned silicidation on field effect transistors H01L29/665
• CPC Class Codes: H01L 22/20 Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
• CPC Class Codes: H01L 2224/05001 Internal layers
• CPC Class Codes: H01L 2224/05023 : the whole internal layer protruding from the surface
• CPC Class Codes: H01L 2224/05085 : with additional elements, e.g. vias arrays, interposed between the stacked layers
• CPC Class Codes: H01L 2224/05556 : in side view
• CPC Class Codes: H01L 2224/05568 : the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05599 : Material
• CPC Class Codes: H01L 2224/1134 : Stud bumping, i.e. using a wire-bonding apparatus
• CPC Class Codes: H01L 2224/13099 : Material
• CPC Class Codes: H01L 2224/16145 : the bodies being stacked
• CPC Class Codes: H01L 2224/45015 : being circular
• CPC Class Codes: H01L 2224/45144 : Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48 : of an individual wire connector
• CPC Class Codes: H01L 2224/49109 : outside the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/73203 : Bump and layer connectors
• CPC Class Codes: H01L 2224/81801 : Soldering or alloying
• CPC Class Codes: H01L 2224/85201 : Compression bonding
• CPC Class Codes: H01L 2225/0651 : Wire or wire-like electrical connections from device to substrate
• CPC Class Codes: H01L 2225/06527 : Special adaptation of electrical connections, e.g. rewiring, engineering changes, pressure contacts, layout
• CPC Class Codes: H01L 2225/06555 : Geometry of the stack, e.g. form of the devices, geometry to facilitate stacking
• CPC Class Codes: H01L 2225/06572 : Auxiliary carrier between devices, the carrier having an electrical connection structure
• CPC Class Codes: H01L 23/49811 : Additional leads joined to the metallisation on the insulating substrate, e.g. pins, bumps, wires, flat leads H01L23/49827 takes precedence
• CPC Class Codes: H01L 24/11 : Manufacturing methods for bumps on insulating substrates H01L21/4853
• CPC Class Codes: H01L 24/12 : Structure, shape, material or disposition of the bump connectors prior to the connecting process
• CPC Class Codes: H01L 24/13 : of an individual bump connector
• CPC Class Codes: H01L 24/16 : of an individual bump connector
• CPC Class Codes: H01L 24/45 : of an individual wire connector
• CPC Class Codes: H01L 24/49 : of a plurality of wire connectors
• CPC Class Codes: H01L 24/72 : Detachable connecting means consisting of mechanical auxiliary parts connecting the device, e.g. pressure contacts using springs or clips
• CPC Class Codes: H01L 24/81 : using a bump connector
• CPC Class Codes: H01L 25/0652 : the devices being arranged next and on each other, i.e. mixed assemblies
• CPC Class Codes: H01L 25/16 : the devices being of types provided for in two or more different main groups of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. forming hybrid circuits
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00013 : Fully indexed content
• CPC Class Codes: H01L 2924/00014 : the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01005 : Boron [B]
• CPC Class Codes: H01L 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01012 : Magnesium [Mg]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01015 : Phosphorus [P]
• CPC Class Codes: H01L 2924/01019 : Potassium [K]
• CPC Class Codes: H01L 2924/01022 : Titanium [Ti]
• CPC Class Codes: H01L 2924/01027 : Cobalt [Co]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01042 : Molybdenum [Mo]
• CPC Class Codes: H01L 2924/01045 : Rhodium [Rh]
• CPC Class Codes: H01L 2924/01046 : Palladium [Pd]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/0105 : Tin [Sn]
• CPC Class Codes: H01L 2924/01051 : Antimony [Sb]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/01322 : Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/10253 : Silicon [Si]
• CPC Class Codes: H01L 2924/10329 : Gallium arsenide [GaAs]
• CPC Class Codes: H01L 2924/12042 : LASER
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/1532 : the connection portion being formed on the die mounting surface of the substrate
• CPC Class Codes: H01L 2924/15787 : Ceramics, e.g. crystalline carbides, nitrides or oxides
• CPC Class Codes: H01L 2924/19041 : being a capacitor
• CPC Class Codes: H01L 2924/20752 : larger or equal to 20 microns less than 30 microns
• CPC Class Codes: H01L 2924/20753 : larger or equal to 30 microns less than 40 microns
• CPC Class Codes: H01L 2924/20757 : larger or equal to 70 microns less than 80 microns
• CPC Class Codes: H01L 2924/30107 : Inductance
• CPC Class Codes: H01L 2924/3011 : Impedance
• CPC Class Codes: H01L 2924/3025 : Electromagnetic shielding
• CPC Class Codes: H01R 12/52 : connecting to other rigid printed circuits or like structures
• CPC Class Codes: H05K 1/141 : One or more single auxiliary printed circuits mounted on a main printed circuit, e.g. modules, adapters H05K1/142 and H05K1/147 take precedence
• CPC Class Codes: H05K 2201/0397 : Tab forming integral conductive tabs H05K3/4092
• CPC Class Codes: H05K 2201/068 : wherein the coefficient of thermal expansion is important
• CPC Class Codes: H05K 2201/1031 : Surface mounted metallic connector elements
• CPC Class Codes: H05K 2201/10318 : Surface mounted metallic pins
• CPC Class Codes: H05K 2201/10378 : Interposers
• CPC Class Codes: H05K 2201/10719 : Land grid array [LGA]
• CPC Class Codes: H05K 2201/10734 : Ball grid array [BGA]; Bump grid array
• CPC Class Codes: H05K 2201/10757 : Bent leads
• CPC Class Codes: H05K 2201/10878 : Means for retention of a lead in a hole
• CPC Class Codes: H05K 2201/10909 : Materials of terminal, e.g. of leads or electrodes of components
• CPC Class Codes: H05K 2201/10946 : Leads attached onto leadless component after manufacturing the component
• CPC Class Codes: H05K 3/20 : by affixing prefabricated conductor pattern H05K1/187, H05K3/046, H05K3/4658, H05K3/4682 takes precedence
• CPC Class Codes: H05K 3/308 : Adaptations of leads connectors to printed circuits H01R12/00
• CPC Class Codes: H05K 3/326 : the printed circuit having integral resilient or deformable parts, e.g. tabs or parts of flexible circuits H05K3/365 takes precedence
• CPC Class Codes: H05K 3/3421 : Leaded components
• CPC Class Codes: H05K 3/3426 : characterised by the leads
• CPC Class Codes: H05K 3/368 : parallel to each other H05K3/361 takes precedence
• CPC Class Codes: H05K 3/4015 : using auxiliary conductive elements, e.g. pieces of metal foil, metallic spheres
• CPC Class Codes: H05K 3/4092 : Integral conductive tabs, i.e. conductive parts partly detached from the substrate
• CPC Class Codes: H05K 7/1069 : with spring contact pieces
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 29/49004 : including measuring or testing of device or component part
• CPC Class Codes: Y10T 29/4913 : Assembling to base an electrical component, e.g., capacitor, etc.
• CPC Class Codes: Y10T 29/49147 : Assembling terminal to base
• CPC Class Codes: Y10T 29/49149 : by metal fusion bonding
• CPC Class Codes: Y10T 29/49204 : Contact or terminal manufacturing
• CPC Class Codes: Y10T 29/49208 : by assembling plural parts
• CPC Class Codes: Y10T 29/4921 : with bonding
• CPC Class Codes: Y10T 29/49211 : of fused material
• CPC Class Codes: Y10T 29/49213 : Metal
• CPC Class Codes: Y10T 29/49222 : forming array of contacts or terminals

Abstract

A probe card assembly includes a probe card, a space transformer having resilient contact structures (probe elements) mounted directly thereto (i.e., without the need for additional connecting wires or the like) and extending from terminals on a surface thereof, and an interposer disposed between the space transformer and the probe card. The space transformer and interposer are “stacked up” so that the orientation of the space transformer, hence the orientation of the tips of the probe elements, can be adjusted without changing the orientation of the probe card. Suitable mechanisms for adjusting the orientation of the space transformer, and for determining what adjustments to make, are disclosed. The interposer has resilient contact structures extending from both the top and bottom surfaces thereof, and ensures that electrical connections are maintained between the space transformer and the probe card throughout the space transformer'"'"'s range of adjustment, by virtue of the interposer'"'"'s inherent compliance. Multiple die sites on a semiconductor wafer are readily probed using the disclosed techniques, and the probe elements can be arranged to optimize probing of an entire wafer. Composite interconnection elements having a relatively soft core overcoated by a relatively hard shell, as the resilient contact structures are described.

Claims

1. An interposer comprising:

a substrate having first and second opposed sides with a first set of terminals on the first side and a second set of terminals on the second side;

a first set of resilient contact structures, each having a portion connected to a respective one of the terminals of the first set of terminals, a contact region distant from the substrate, and an elongate section extending from the portion to the contact region, the elongate section resiliently bending upon depression of the contact region towards the substrate, wherein the contact regions of two adjacent resilient contact structures are spaced differently than the terminals of the adjacent resilient contact structures and wherein respective ones of the second set of terminals are coupled to corresponding ones of the first set of terminals; and

a second set of resilient contact structures, each having a portion attached to a respective one of the terminals of the second set of terminals, a contact region distant from the substrate, and an elongate section extending from the portion to the contact region, the elongate section resiliently bending upon depression of the contact region towards the substrate.

2. Interposer, according to claim 1, further comprising:

tip structures mounted to ends of the first plurality of resilient contact structures.

3. Interposer, according to claim 1, wherein:

the first plurality of resilient contact structures are composite interconnection elements.

4. Interposer, according to claim 1, wherein:

the first plurality of resilient contact structures are fabricated on a sacrificial substrate prior to mounting the first plurality of resilient contact structures directly to the first plurality of terminals.

5. Interposer, according to claim 1, further comprising:

a subset of the second set of resilient contact structures mounted directly to the second set of terminals.

6. Interposer, according to claim 5, wherein:

the second plurality of resilient contact structures are composite interconnection elements.

7. Interposer, according to claim 5, wherein:

the second plurality of resilient contact structures are fabricated on a sacrificial substrate prior to mounting the second plurality of resilient contact structures directly to the second plurality of terminals.

8. Probe Card Assembly, comprising:

a probe card having a first surface, a second surface and a plurality of contact terminals on the first surface thereof;

an interposer having a first surface, a second surface, a second plurality of elongate resilient contact structures extending from the second surface thereof and a first plurality of elongate resilient contact structures extending from the first surface thereof; and

a space transformer having a first surface, a second surface, a plurality of contact pads disposed on the second surface thereof, and a third plurality of elongate resilient contact structures extending from the first surface thereof;

wherein;

the second plurality of elongate resilient contact structures effect a pressure connection with the contact terminals of the probe card; and

the first plurality of elongate resilient contact structures effect a pressure connection with the contact pads of the space transformer.

9. Probe Card Assembly, according to claim 8, wherein:

the third plurality of elongate resilient contact structures are mounted directly to terminals on the first surface of the space transformer.

10. Probe Card Assembly, according to claim 8, wherein:

the first plurality of elongate resilient contact structures are composite interconnection elements.

11. Probe Card Assembly, according to claim 8, wherein:

the second plurality of elongate resilient contact structures are composite interconnection elements.

12. Probe Card Assembly, according to claim 8, wherein:

the third plurality of elongate resilient contact structures are composite interconnection elements.

13. Probe Card Assembly, according to claim 8, wherein:

one or more of the first plurality of elongate resilient contact structures are a composite structure, wherein the composite structure includes a resilient material of sufficient dimension to act resiliently, the resilient material connected to a precursor material, the precursor material having a springable shape but not having material properties and dimensions to act resiliently in the absence of the connected resilient material.

14. Probe Card Assembly, according to claim 8, wherein:

one or more of the second plurality of elongate resilient contact structures are a composite structure, wherein the composite structure includes a resilient material of sufficient dimension to act resiliently, the resilient material connected to a precursor material, the precursor material having a springable shape but not having material properties and dimensions to act resiliently in the absence of the connected resilient material.

15. Probe Card Assembly, according to claim 8, further comprising:

a front mounting plate made of a rigid material, having a first surface and a second surface, and disposed with its second surface against the first surface of the probe card;

means for affixing the front mounting plate to the first surface of the probe card; and

means for urging the space transformer towards the first surface of the probe card.

16. Probe Card Assembly, according to claim 15, wherein:

the front mounting plate is made of stainless steel.

17. Probe Card Assembly, according to claim 15, wherein the means for urging the space transformer comprises:

a mounting ring; and

a plurality of screws holding the mounting ring to the front mounting plate with the space transformer captured therebetween.

18. Probe Card Assembly, according to claim 17, wherein:

the mounting ring is made of a springy material.

19. Probe Card Assembly, according to claim 17, further comprising:

a spacer ring disposed between the mounting ring and the top surface of the space transformer.

20. Probe Card Assembly, according to claim 15, wherein the means for affixing the front mounting plate comprises:

a rear mounting plate made of a rigid material, having a first surface and a second surface, and disposed with its first surface against the second surface of the probe card; and

a plurality of screws extending between the front mounting plate and the rear mounting plate, through the probe card.

21. Probe Card Assembly, according to claim 20, wherein:

the rear mounting plate is made of stainless steel.

22. Probe Card Assembly, according to 8, further comprising:

means for adjusting the orientation of the space transformer relative to the probe card without changing the orientation of the probe card.

23. Probe Card Assembly, according to claim 22, wherein the means for adjusting the orientation of the space transformer comprises:

a plurality of differential screws, each including an outer differential screw element and an inner differential screw element, acting upon the second surface of the space transformer.

24. Probe Card Assembly, according to claim 23, further comprising:

a pivot sphere disposed on an end of one of the inner differential screw elements.

25. Probe Card Assembly, according to claim 23, further comprising:

an actuator mounting plate disposed beneath the probe card;

wherein;

the differential screws are threaded into the actuator mounting plate.

26. Probe Card Assembly, according to claim 22, wherein the means for adjusting the orientation of the space transformer comprises:

an actuator, responsive to a computer, acting upon the space transformer.

27. Probe Card Assembly, according to claim 8, wherein:

the contact pads are disposed at a first pitch on the second surface of the space transformer;

third plurality of elongate resilient contact structures are disposed at a second pitch on the first surface of the space transformer; and

the first pitch is greater than the second pitch.

28. Probe Card Assembly, according to claim 8, wherein:

the first plurality of elongate resilient contact structures are disposed at a first pitch on the first surface of the interposer;

the second plurality of elongate resilient contact structures are disposed at a second pitch on the second surface of the interposer; and

the first pitch is substantially the same as the second pitch.

29. Probe Card Assembly, according to claim 8, wherein:

the contact pads are disposed at a first pitch on the second surface of the space transformer;

the third plurality of elongate resilient contact structures are disposed at a second pitch on the first surface of the space transformer;

the first plurality of elongate resilient contact structures are disposed at the first pitch on the first surface of the interposer;

the second plurality of elongate resilient contact structures are disposed at the first pitch on the second surface of the interposer; and

the first pitch is greater than the second pitch.

30. Probe Card Assembly, according to claim 8, wherein at least some of the elongate resilient contact structures comprise:

a composite interconnection element having an end; and

a pre-fabricated tip structure joined to the end of the composite interconnection element.

31. Probe Card Assembly, according to claim 8, wherein:

the third plurality of elongate resilient contact structures are connected to terminals on the first surface of the space transformer.

32. Probe Card kit, comprising:

a space transformer having a first surface, a second surface, a plurality of contact pads disposed on the second surface thereof, and a plurality of elongate contact structures connected to the first surface thereof, said space transformer adapted in use such that contact regions of the plurality of elongate contact structures pressure contacts with a corresponding plurality of contact areas on a semiconductor wafer; and

an interposer having a first surface, a second surface, a first plurality of elongate resilient contact structures extending from the first surface thereof, said interposer adapted in use such that contact regions of the first plurality of elongate resilient contact structures make pressure connections with the plurality of contact pads on the second surface of the space transformer, the interposer having a second plurality of elongate resilient contact structures extending from the second surface thereof, said interposer adapted in use for contact regions of the second plurality of elongate resilient contact structures making pressure connections with a plurality of terminals on a probe card.

33. Probe Card Kit, according to claim 32, wherein:

the contact pads are disposed at a first pitch on the second surface of the space transformer;

the plurality of elongate contact structures are disposed at a second pitch on the first surface of the space transformer; and

the first pitch is greater than the second pitch.

34. Probe Card Kit, according to claim 32, wherein:

the second plurality of elongate resilient contact structures are disposed at a first pitch on the second surface of the interposer;

the first plurality of elongate resilient contact structures are disposed at a second pitch on the first surface of the interposer; and

the first pitch is substantially the same as the second pitch.

35. Probe Card Assembly, according to claim 32, wherein:

the contact pads are disposed at a first pitch on the second surface of the space transformer;

the plurality of elongate contact structures are disposed at a second pitch on the first surface of the space transformer;

the second plurality of elongate resilient contact structures are disposed at the first pitch on the second surface of the interposer;

the first plurality of elongate resilient contact structures are disposed at the first pitch on the first surface of the interposer; and

the first pitch is greater than the second pitch.

36. Probe Card Assembly, comprising:

a probe card having a first surface, a second surface and a plurality of contact terminals on the first surface thereof;

a space transformer having a first surface, a second surface, a plurality of contact pads disposed on the second surface thereof, and a first plurality of elongate resilient contact structures mounted adjacent to and extending from the first surface thereof;

wherein the plurality of contact pads are connected to the plurality of contact terminals of the probe card.

37. Probe Card Assembly, according to claim 36, wherein:

the first plurality of elongate resilient contact structures are mounted directly to terminals on the first surface of the space transformer.

38. Probe Card Assembly, according to claim 36, wherein:

the first plurality of elongate resilient contact structures are connected to terminals on the first surface of the space transformer.

39. Probe Card Assembly, according to claim 36, wherein:

the first plurality of elongate resilient contact structures are composite interconnection elements.

40. Probe Card Assembly, according to 36, further comprising:

means for adjusting the orientation of the space transformer relative to the probe card without changing the orientation of the probe card.

41. Probe Card Assembly, according to claim 40, wherein the means for adjusting the orientation of the space transformer comprises:

a plurality of differential screws, each including an outer differential screw element and an inner differential screw element, acting upon the second surface of the space transformer.

42. Probe Card Assembly, according to claim 41, wherein the means for adjusting the orientation of the space transformer comprises:

an actuator, responsive to a computer, acting upon the space transformer.

43. Probe Card Assembly, according to claim 36, wherein:

the contact pads are disposed at a first pitch on the second surface of the space transformer;

the first plurality of elongate resilient contact structures each having a contact region, the contact regions disposed at a second pitch; and

the first pitch is greater than the second pitch wherein the first pitch is a shortest distance between any two adjacent contact pads and the second pitch is a shortest distance between any two adjacent elongate contact structures.

44. Probe Card Assembly, comprising:

a probe card having a first surface, a second surface and a plurality of contact terminals on the first surface thereof;

a space transformer having a first surface, a second surface, a plurality of contact pads disposed on the second surface thereof, and a first plurality of elongate contact structures mounted adjacent to and extending from the first surface thereof;

wherein the plurality of contact pads are connected to the plurality of contact terminals of the probe card.

45. Probe Card Assembly, according to claim 44, wherein:

the first plurality of elongate contact structures are mounted directly to terminals on the first surface of the space transformer.

46. Probe Card Assembly, according to claim 44, wherein:

the first plurality of elongate contact structures are connected to terminals on the first surface of the space transformer.

47. Probe Card Assembly, according to claim 44, wherein:

the first plurality of elongate contact structures are composite interconnection elements.

48. Probe Card Assembly, according to 44, further comprising:

means for adjusting the orientation of the space transformer relative to the probe card without changing the orientation of the probe card.

49. Probe Card Assembly, according to claim 48, wherein the means for adjusting the orientation of the space transformer comprises:

a plurality of differential screws, each including an outer differential screw element and an inner differential screw element, acting upon the second surface of the space transformer.

50. Probe Card Assembly, according to claim 49, wherein the means for adjusting the orientation of the space transformer comprises:

an actuator, responsive to a computer, acting upon the space transformer.

51. Probe Card Assembly, according to claim 44, wherein:

the contact pads are disposed at a first pitch on the second surface of the space transformer;

the first plurality of elongate contact structures each having a contact region, the contact regions disposed at a second pitch; and

the first pitch is greater than the second pitch wherein the first pitch is a shortest distance between any two adjacent contact pads and the second pitch is a shortest distance between any two adjacent elongate contact structures.