# US 12,113,032 B2 · Substrate having undercut portion for stress mitigation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,113,032 B2 - Document ID: US12113032B2 - Status: Granted - Kind: B2 - Application number: 17/667,645 - Filed: 2022-02-09 - Published: 2022-05-26 - Granted: 2024-10-08 - Earliest claimed: 2019-10-31 - Assignees: Avago Technologies International Sales Pte. Limited - Applicants: Avago Technologies International Sales Pte. Limited - Inventors: YongIk Choi; Chris Chung; Michael Leary; Domingo Figueredo; Chang Kyu Choi; Sarah Haney; Li Sun - Web page: https://patentgrep.com/patent/US12113032B2 ## CPC - H10W 42/121: {protecting against mechanical damage (H10W76/00, H10W74/00 take precedence)} - H05K 3/3452: Solder masks - H10W 42/267: {Patterned shielding planes} - H10W 42/273: {the arrangements being between laterally adjacent chips, e.g. walls between chips} - H10W 70/05: of insulating or insulated package substrates, or of interposers, or of redistribution layers (manufacture or treatment of leadframes H10W70/04) - H10W 70/65: Shapes or dispositions of interconnections - H10W 70/68: Shapes or dispositions thereof - H10W 70/685: comprising multiple insulating layers - H10W 70/687: {characterized by the outer layers being for protection, e.g. solder masks, or for protection against chemical or mechanical damage} - H10W 72/30: Die-attach connectors - H10W 90/701: {characterised by the relative positions of pads or connectors relative to package parts} - H05K 3/3465: Application of solder - H05K 2201/099: Coating over pads, e.g. solder resist partly over pads - H05K 2203/041: Solder preforms in the shape of solder balls - H10W 42/20: protecting against electromagnetic or particle radiation, e.g. light, X-rays, gamma-rays or electrons - H10W 70/69: Insulating materials thereof - H10W 74/00: Encapsulations, e.g. protective coatings - H10W 74/15: on active surfaces of flip-chip devices, e.g. underfills - H10W 90/00: Package configurations - H10W 90/724: {between a chip and a stacked insulating package substrate, interposer or RDL} - H10W 90/734: {between a chip and a stacked insulating package substrate, interposer or RDL} - H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10 - H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS ## Abstract A device and substrate are disclosed. An illustrative device includes a substrate having a first surface and an opposing second surface, a solder material receiving curved surface exposed at the second surface of the substrate, a solder resist material that at least partially covers the solder material receiving curved surface such that a middle portion of the solder receiving curved surface is exposed and such that an edge portion of the solder material receiving curved surface is covered by the solder resist material and forms an undercut, and a solder material disposed within the solder material receiving curved surface and within the undercut. ## Claims ### Claim 1 A substrate, comprising: a first surface; a second surface that opposes the first surface; and a metal layer that is exposed at the first surface, wherein the metal layer comprises: a curved surface configured to receive solder material, the curved surface having an edge portion that is partially covered by a solder resist material such that an undercut is formed between the solder resist material and the edge portion so as to trap a portion of the solder material within the undercut and on the edge portion of the curved surface at a location past an edge of the solder resist material. ### Claim 2 (depends on 1) The substrate of claim 1, wherein the curved surface further comprises a middle portion that is substantially planar. ### Claim 3 (depends on 2) The substrate of claim 2, wherein a dimension of the undercut is no larger than one tenth a width of the middle portion. ### Claim 4 (depends on 2) The substrate of claim 2, wherein the edge portion extends 2 um to 4 um from an outer perimeter of the middle portion. ### Claim 5 (depends on 1) The substrate of claim 1, further comprising: a vertical stack of metal interconnect structures, wherein a penultimate metal layer in the vertical stack of metal interconnect structures comprises the metal layer. ### Claim 6 (depends on 1) The substrate of claim 1, wherein the undercut comprises a width of at least 2 um and a height of at least 2 um. ### Claim 7 (depends on 1) The substrate of claim 1, wherein the undercut comprises a width in between 2 um and 6 um and a height between 2 um and 4 um. ### Claim 8 (depends on 1) The substrate of claim 1, wherein the undercut comprises a first width, the edge portion comprises a second width, and the first width is equal to the second width. ### Claim 9 (depends on 1) The substrate of claim 1, wherein the metal layer comprises a metal trace that extends across at least a portion of the first surface. ### Claim 10 A device, comprising: a substrate comprising a first surface and an opposing second surface; a curved surface configured to receive solder material, the curved surface exposed at the first surface of the substrate; a solder resist material that at least partially covers the curved surface such that a middle portion of the solder receiving curved surface is exposed and such that an edge portion of the curved surface is covered by the solder resist material and forms an undercut; and wherein the solder material is disposed within the curved surface and within the undercut. ### Claim 11 (depends on 10) The device of claim 10, wherein the solder material is formed into a solder ball, the device further comprising: an air gap provided between the solder ball and an adjacent circuit component that is electrically connected to the substrate. ### Claim 12 (depends on 11) The device of claim 11, wherein the solder ball comprises a diameter at least about ten times larger than a dimension of the undercut. ### Claim 13 (depends on 11) The device of claim 11, wherein the adjacent circuit component comprises at least one of a passive circuit component and an Integrated Circuit (IC) chip, wherein the curved surface comprises a metal trace, and wherein the middle portion is substantially planar. ### Claim 14 (depends on 10) The device of claim 10, wherein a portion of the solder material that is disposed within the undercut forms a mushroom-shaped interlocking structure. ### Claim 15 An electronic device, comprising: a cavity disposed in a substrate such that the substrate has a first top surface positioned above the cavity and a second top surface positioned within the cavity; an inner substrate wall surrounding the second top surface so as to define the cavity; and a substantially looped conductive trace disposed in the substrate such that an inner substantially looped portion of the substantially looped conductive trace is disposed on the second top surface and an outer substantially looped portion of the substantially looped conductive trace is enclosed within the substrate under the inner substrate wall. ### Claim 16 (depends on 15) The electronic device of claim 15, further comprising a curved surface configured to receive solder material, the curved surface having an edge portion that is partially covered by a solder resist material such that an undercut is formed between the solder resist material and the edge portion. ### Claim 17 (depends on 16) The electronic device of claim 16, wherein a portion of the solder material is disposed within the undercut to define a mushroom-shaped interlocking structure. ### Claim 18 (depends on 16) The electronic device of claim 16, wherein a width of the solder material is at least ten times larger than a dimension of the undercut. ### Claim 19 (depends on 16) The electronic device of claim 16, wherein the undercut comprises a first width, the edge portion comprises a second width, and the first width is equal to the second width. ### Claim 20 (depends on 16) The electronic device of claim 16, wherein the undercut comprises a width of at least 2 um and a height of at least 2 um.