Process for manufacturing electronic circuits

• US 20010039725A1
• Filed: 06/18/2001
• Published: 11/15/2001
• Est. Priority Date: 05/19/1995
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Fukuda, Hiroshi, Iwata, Yasuhiro, Ohta, Toshihiko, Tamura, Mitsunori, Kazui, Shinichi, Katayama, Kaoru, Shirai, Mitsugu
• Granted Patent: US 6,410,881 B2
• Time in Patent Office: Days
• US Class Current: 29/832
• CPC Class Codes: H01L 2224/1181 Cleaning, e.g. oxide removal step, desmearing
• CPC Class Codes: H01L 2224/13111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 2224/45014 Ribbon connectors, e.g. rectangular cross-section
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/75 Apparatus for connecting with bump connectors or layer connectors
• CPC Class Codes: H01L 2224/7501 Means for cleaning, e.g. brushes, for hydro blasting, for ultrasonic cleaning, for dry ice blasting, using gas-flow, by etching, by applying flux or plasma
• CPC Class Codes: H01L 2224/81014 Thermal cleaning, e.g. decomposition, sublimation
• CPC Class Codes: H01L 2224/81022 Cleaning the bonding area, e.g. oxide removal step, desmearing
• CPC Class Codes: H01L 2224/81801 Soldering or alloying
• CPC Class Codes: H01L 24/75 Apparatus for connecting with bump connectors or layer connectors
• CPC Class Codes: H01L 24/81 using a bump connector
• 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 2924/00014 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 2924/01004 Beryllium [Be]
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01019 Potassium [K]
• CPC Class Codes: H01L 2924/01024 Chromium [Cr]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/0105 : Tin [Sn]
• CPC Class Codes: H01L 2924/01075 : Rhenium [Re]
• 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 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/09701 : Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/12042 : LASER
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/15787 : Ceramics, e.g. crystalline carbides, nitrides or oxides
• CPC Class Codes: H01L 2924/16152 : Cap comprising a cavity for hosting the device, e.g. U-shaped cap
• CPC Class Codes: H01L 2924/166 : Material
• CPC Class Codes: H01L 2924/206 : Length ranges
• CPC Class Codes: H05K 3/3457 : Solder materials or compositions; Methods of application thereof
• CPC Class Codes: H05K 3/3489 : Composition of fluxes; Methods of application thereof; Other methods of activating the contact surfaces
• CPC Class Codes: Y10T 29/4913 : Assembling to base an electrical component, e.g., capacitor, etc.
• CPC Class Codes: Y10T 29/49144 : by metal fusion
• CPC Class Codes: Y10T 29/49155 : Manufacturing circuit on or in base
• CPC Class Codes: Y10T 29/49156 : with selective destruction of conductive paths
• CPC Class Codes: Y10T 29/49174 : Assembling terminal to elongated conductor

Abstract

This invention provides a process for manufacturing electronic circuits, according to which soldering can be carried out without using flux by applying a metal surface treatment procedure which allows oxide film, organic matters, carbon or the like on the surface of metal to be easily removed without using complex process nor unfavorably affecting electronic devices or circuit substrates.

A process of connecting an electronic device and a circuit substrate by means of solder comprises the steps of irradiating the solder with laser beam to clean the solder, aligning and mounting the electronic device on the circuit substrate, and hot-melting said solder in a low-oxygen content atmosphere to bond the electronic device and the circuit substrate.

Claims

1. A process for manufacturing an electronic circuit including disposing an electronic device on a circuit substrate, and hot-melting a solder on said electronic device or said circuit substrate to bond said electronic device and said circuit substrate, which comprises the steps of;

irradiating said solder with laser beam, aligning and mounting said electronic device at a desired position on said circuit substrate,

hot-melting said solder in a low-oxygen content atmosphere, and

bonding said electronic device and said circuit substrate.

2. A process according to

claim 1

, wherein said laser beam irradiation step further comprises the step of:

adjusting an energy density of said laser beam at a level lower than an energy density which allows said solder to melt.

3. A process according to

claim 2

, wherein said step of adjusting the energy density of said laser beam further comprises the step of:

adjusting the energy density of said laser beam at a value between 0.5 J/cm² and 4.0 J/cm².

4. A process according to

claim 3

, wherein said laser beam irradiation step further comprises the step of:

irradiating said solder with said laser beam at 6 to 10 cycles per part of said solder.

5. A process according to

claim 1

, wherein said step of mounting said electronic device on said circuit substrate further comprises the steps of:

feeding a liquid onto said circuit substrate, and

aligning and mounting said electronic device at the desired position on said circuit substrate having been fed with said liquid.

6. A process according to

claim 5

, wherein said liquid is a rosin-free alcoholic solution.

7. A process according to

claim 5

, wherein said step of hot-melting said solder in a treating vessel further comprises the step of:

regulating an evaporation rate of said liquid by controlling an inner pressure of said treating vessel.

8. A process according to

claim 1

, wherein said step of hot-melting said solder in a low-oxygen content atmosphere further comprises the steps of:

placing said circuit substrate in a treating vessel,

forming a low-oxygen content atmosphere with a predetermined oxygen content in said treating vessel, and

hot-melting said solder in said treating vessel.

9. A process according to

claim 8

, wherein said step of forming a low-oxygen content atmosphere with the predetermined oxygen content in said treating vessel further comprises the steps of:

evacuating said treating vessel, and

introducing a gas into said treating vessel.

10. A process according to

claim 9

, comprising the step of:

introducing a non-oxidizing or reducing gas as said gas.

11. A process according to

claim 1

, comprising the step of:

cooling said circuit substrate after said electronic device and said circuit substrate have been bonded.

12. A process for manufacturing electronic circuits including disposing an electronic component on a circuit substrate and hot-melting solder bumps or a solder layer on said electronic component or said circuit substrate to bond said electronic component and said circuit substrate, which comprises the steps of:

irradiating said solder bumps or solder layer with laser beam,

feeding a rosin-free alcoholic solution onto said circuit substrate,

aligning and mounting said component at a desired position on said circuit substrate fed with said solution,

placing said circuit substrate in a treating vessel,

forming a low-oxygen content atmosphere with a predetermined content in said treating vessel,

hot-melting said solder bumps or solder layer in said treating vessel, and

bonding said component and said circuit substrate.

13. A process according to

claim 12

, wherein said laser beam irradiation step further comprises the step of:

adjusting an energy density of said laser beam at a level lower than an energy density which allows said solder bumps or solder layer to melt.

14. A process according to

claim 13

, wherein said step of adjusting the energy density of said laser beam further comprises the step of:

adjusting the energy density of said laser beam at a value between 0.5 J/cm² and 4.0 J/cm².

15. A process according to

claim 12

, wherein said alcoholic solution is ethylene glycol or triethylene glycol.

16. A process according to

claim 12

, wherein said step of forming a low-oxygen content atmosphere with the predetermined oxygen content in said treating vessel further comprises the steps of:

evacuating said treating vessel, and

introducing a non-oxidizing or reducing gas into said treating vessel.

17. A process according to

claim 12

, wherein said step of hot-melting said solder bumps or solder layer in said treating vessel further comprises the step of:

regulating an evaporation rate of said liquid by controlling an inner pressure of said treating vessel.

18. A process according to

claim 12

, comprising the step of:

cooling said circuit substrate after said component and said circuit substrate have been bonded.

19. A process for manufacturing an electronic circuit including disposing an LSI provided with a plurality of solder bumps on its lower face on a circuit substrate and hot-melting said solder bumps on the lower face of said LSI in a treating vessel to bond said LSI and said circuit substrate, which comprises the steps of:

irradiating said solder bumps with laser beam adjusted at a level lower than an energy density which allows said solder bump to melt, so as to clean said solder bumps,

feeding a rosin-free alcoholic solution onto said circuit substrate,

aligning and mounting said LSI at a desired position on said circuit substrate fed with said alcoholic solution, to pre-set said LSI thereon,

placing said circuit substrate in a treating vessel,

forming a low-oxygen content atmosphere with a predetermined oxygen content within said treating vessel,

hot-melting said solder bumps in said treating vessel,

bonding said LSI and said circuit substrate, and

cooling said circuit substrate.

20. A process according to

claim 19

, wherein said step of hot-melting said solder bumps in said treating vessel further comprises the step of:

controlling an inner pressure of said treating vessel to regulate an evaporation rate so that said alcoholic solution may completely evaporate off when said solder bumps melt.