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US-12624418-B2 - Solder material for semiconductor device

US12624418B2US 12624418 B2US12624418 B2US 12624418B2US-12624418-B2

Abstract

A lead-free solder has a heat resistance temperature which is high and a thermal conductive property which is not changed in a high temperature range. A semiconductor device includes a solder material containing more than 5.0% by mass and 10.0% by mass or less of Sb and 2.0 to 4.0% by mass of Ag, an element selected from the group consisting of: more than 0 and 1.0% by mass or less of Si, more than 0 and 0.1% by mass or less of V, 0.001 to 0.1% by mass of Ge, 0.001 to 0.1% by mass of P, and more than 0 and 1.2% by mass or less of Cu, and the remainder consisting of Sn and inevitable impurities. A bonding layer including the solder material, is formed between a semiconductor element and a substrate electrode or a lead frame.

Inventors

  • Hirohiko Watanabe
  • Shunsuke Saito
  • Yoshitaka Nishimura
  • Fumihiko Momose

Assignees

  • FUJI ELECTRIC CO., LTD.

Dates

Publication Date
20260512
Application Date
20210914
Priority Date
20150917

Claims (19)

  1. 1 . A solder material comprising: more than 5.0% by mass and 10.0% by mass or less of Sb; 2.0 to 4.0% by mass of Ag; an element selected from a group consisting of: more than 0 and 1.0% by mass or less of Si, more than 0 and 0.1% by mass or less of V, 0.001 to 0.1% by mass of Ge, and 0.001 to 0.1% by mass of P; and a remainder consisting of Sn and inevitable impurities, wherein a thermal conductivity rate of the solder material at a temperature from 100° C. to 200° C. is greater than or equal to a thermal conductivity rate of the solder material at a temperature of 25° C., and Ni is present only as one of the inevitable impurities.
  2. 2 . The solder material according to claim 1 , comprising 0.1 to 0.4% by mass of Si.
  3. 3 . The solder material according to claim 1 , comprising 0.01 to 0.08% by mass of V.
  4. 4 . The solder material according to claim 1 , wherein the element is 0.001 to 0.1% by mass of Ge.
  5. 5 . The solder material according to claim 1 , wherein the element is 0.001 to 0.1% by mass of P.
  6. 6 . The solder material according to claim 1 , comprising 0.1 to 0.9% by mass of Cu.
  7. 7 . The solder material according to claim 1 , wherein the element is 0.1 to 0.4% by mass of Si and 0.001 to 0.1% by mass of P.
  8. 8 . The solder material according to claim 1 , wherein the element is 0.01 to 0.08% by mass of V and 0.001 to 0.1% by mass of P.
  9. 9 . The solder material according to claim 1 , wherein the element is 0.001 to 0.1% by mass of Ge and 0.001 to 0.1% by mass of P.
  10. 10 . The solder material according to claim 2 , wherein the element is 0.001 to 0.1% by mass of Ge.
  11. 11 . The solder material according to claim 3 , wherein the element is 0.001 to 0.1% by mass of Ge.
  12. 12 . The solder material according to claim 6 , wherein the element is 0.001 to 0.1% by mass of Ge.
  13. 13 . The solder material according to claim 2 , wherein the element includes 0.001 to 0.1% by mass of P, and 0.001 to 0.1% by mass of Ge.
  14. 14 . The solder material according to claim 3 , wherein the element includes 0.001 to 0.1% by mass of P, and 0.001 to 0.1% by mass of Ge.
  15. 15 . The solder material according to claim 6 , wherein the element includes 0.001 to 0.1% by mass of P, and 0.001 to 0.1% by mass of Ge.
  16. 16 . The solder material according to claim 1 , wherein a thermal conductivity rate at 100° C. to 200° C. is not lower than a thermal conductivity rate at 25° C.
  17. 17 . A semiconductor device comprising a bonding layer in which the solder material according to claim 1 is between a semiconductor element and a substrate electrode or a lead frame.
  18. 18 . The semiconductor device according to claim 17 , wherein the semiconductor element is a Si or SiC semiconductor element.
  19. 19 . The solder material according to claim 1 , wherein the solder material does not include Cu, other than an inevitable impurity.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a divisional application of U.S. application Ser. No. 16/893,707 filed on Jun. 5, 2020 which is a divisional application of U.S. application Ser. No. 15/688,404 filed on Aug. 28, 2017 which is a Continuation of PCT Application No. PCT/JP2016/073406 filed on Aug. 9, 2016, and claims benefit of foreign priority to Japanese Patent Application No. 2015-184264, filed on Sep. 17, 2015 and Japanese Patent Application No. 2016-007022, filed on Jan. 18, 2016, the entire contents of which are incorporated by reference herein. BACKGROUND OF THE INVENTION Technical Field The present invention relates to a solder material, and more particularly, relates to a highly reliable solder material used for bonding of a semiconductor device. Background Art In recent years, Pb-free solders containing no lead components have replaced Sn—Pb-based solders from an environmental viewpoint. Among available lead-free solders of different compositions which are usable as a solder material applied to an IGBT module (power module) or other such semiconductor devices, a Sn—Ag-based Pb-free solder is often adopted because of relatively well-balanced properties particularly in terms of bondability (solder wettability), mechanical characteristics, thermal resistance, etc. as well as due to the fact that it has been actually applied to products. It is known that in a semiconductor device having a layered bonding structure containing a radiator plate, an insulating substrate placed on the sink, and a semiconductor element attached thereonto by solder bonding, a solder bonding structure is used, in which a Sn—Sb-based solder as a high-temperature lead-free solder is applied to a lower bonding portion, and a lead-free solder is applied to an upper bonding portion, the lead-free solder having such a composition that an element such as Cu is added to a Sn—Ag-based solder having a lower melting point than the Sn—Sb-based solder (see, for example, Patent Literature 1). Also, the following structure is known as well: a lead frame, also serving as a heat spreader, is bonded as a wire member onto an upper electrode of a semiconductor element (IGBT) mounted by soldering onto an insulating substrate, and heat generated in a semiconductor element is let to dissipate to the lead frame so as to prevent the generated heat from accumulating in a certain portion (see, for example, Patent Literature 2). A Sn—Sb—Ag-based tape- or wire-like solder material, having high rolling property at 170° C. and high cold forming property, has been also known as a solder material effective to avoid cracking at high temperature resulting from heat generation of the semiconductor element (see, for example, Patent Literature 3). LIST OF PRIOR ART REFERENCES Patent Literature Patent Literature 1: JP 2001-35978 APatent Literature 2: JP 2005-116702 APatent Literature 3: JP H7-284983 A SUMMARY OF INVENTION Technical Problem MOS or IGBT elements called a power semiconductor generate heat by themselves during operations, and reach high temperatures. Through repetitive heat generation and cooling, the solder-bonded element repeatedly suffers from distortion at a soldered portion and consequently deteriorates. It is preferable to use a solder alloy excellent in heat radiation for bonding a semiconductor element that operates at high temperatures. A SnAg-based solder material as a typical Pb-free solder increases heat resistance and lowers heat radiation characteristics as the temperature rises. In case of using a SnAg-based solder material that decreases thermal conductivity rate at high temperature at a bonding portion of a power semiconductor subject to heat cycles for a long time, if a larger amount of power is applied, the semiconductor may generate more heat. In recent years, demand for power semiconductors with high current specifications has increased and accordingly, elements tend to generate a large amount of heat. Also, there is increasing demand for in-vehicle power semiconductors or other such devices capable of operating at an environmental temperature of over 175° C. In such circumstances, low thermal conductivity rate of a solder could be a bottleneck to power supply relative to an applicable output of the element. In case the thermal conductivity rate of a solder lowers when the element temperature rises from the room temperature to high temperature due to self-heating or environmental temperature, a chip cannot easily release the heat. Consequently, the chip temperature further increases. Currently, it is earnestly desired to ensure that the maximum of power applied to an element is used so that the element can be used even if generating heat with the temperature closer to a melting point of a solder. In order to meet such a demand, a solder material that is less likely to lower its thermal conductivity rate at high temperature is required. Solution to Problem The inventors of the present invention have made ext