Method for assembling components implementing a pre-treatment of the solder bumps allowing an assembly by fluxless and residue-free soldering

Patent metadata

Field	Value
Publication number	US-11855038-B2
Application number	US-202017432354-A
Country	US
Kind code	B2
Filing date	Feb 20, 2020
Priority date	Feb 20, 2019
Publication date	Dec 26, 2023
Grant date	Dec 26, 2023

Abstract

A method for assembling components includes assembling a first component including solder bumps with a second component including connectors. The assembly of the components is preceded by pre-treating the first and second components wherein the solder bumps are contacted with a pre-treatment liquid configured to at least partially remove an oxide layer initially present on the solder. The pre-treatment liquid is an aqueous solution containing carboxylic acids or polycarboxylic acids. The assembly of the components is carried out after the pre-treatment in the absence of liquid or gas flux.

First claim

The invention claimed is:

1. A solder bump assembly method, comprising:
assembling a first component including solder bumps with a second component including connectors,
the assembly of the first and second components being preceded by pre-treating the first and second components wherein the solder bumps are contacted with a pre-treatment liquid configured to at least partially remove an oxide layer initially present on the solder, and
carrying out the assembly of the components after the pre-treatment in the absence of liquid or gas flux,
wherein the pre-treatment liquid is an aqueous solution containing carboxylic acids or polycarboxylic acids.

2. The method according to claim 1 , wherein the contacting with the pre-treatment liquid is configured to leave a thin film on a surface of the first and second components, with a thickness less than 100 nm, the thin film having a property of promoting effective soldering without leaving residues after assembly, the method comprising prolonging action of the pre-treatment so that soldering can be done more than one hour after the pre-treatment without reducing the assembly efficiency.

3. The method according to claim 1 , the aqueous solution containing amines or polyamines.

4. The method according to claim 1 , the aqueous solution containing amino acids or poly amino acids.

5. The method according to claim 1 , wherein the pre-treatment liquid is an aqueous solution containing glutamic acid hydrochloride, in a concentration comprised between 10 and 20% by mass.

6. The method according to claim 1 , wherein the pre-treatment liquid contains a strong acid in an amount sufficient for the pre-treatment liquid to reach a pH of less than 2.

7. The method according to claim 1 , wherein the pre-treatment liquid contains an acid detergent.

8. The method according to claim 1 , further comprising rinsing the first and second components immediately after contact with the pre-treatment liquid with a solvent allowing the solubilisation of the solutes present in the pre-treatment liquid at an amount of at least 10%, so that only an adsorbed molecular film remains on the solder.

9. The method according to claim 1 , further comprising rinsing the first and second components immediately after contact with the pre-treatment liquid with a solvent allowing dissolution of not more than 0.1% of the solutes present in the pre-treatment liquid, so that a thin film of nanometric thickness comprised between 1 and 100 nm remains on the treated components.

10. The method according to claim 1 , further comprising drying the first and second components immediately after contact with the pre-treatment liquid, then washing with a poor solvent from the solutes present in the pre-treatment liquid.

11. The method according to claim 1 , wherein the contact with the pre-treatment liquid is made by immersion, and a contact time with the pre-treatment liquid is between 1 and 5 minutes, the assembly by soldering then being carried out less than four hours after the pre-treatment, in a presence of air or under neutral gas.

12. The method according to claim 3 , wherein the pre-treatment liquid is a solution containing a basic detergent, the pH of said solution being between 11 and 13.

13. The method according to claim 1 , wherein the pre-treatment liquid is a solution containing an acid detergent, the pH of said solution being between 1 and 3.

14. The method according to claim 12 wherein the detergent is non-foaming, the contact with the pre-treatment liquid can be made by immersion, the contact time with the pre-treatment liquid is between 1 and 5 minutes, and the contact with the pre-treatment liquid is followed by rinsing, then by drying, the assembly by soldering then being carried out less one hour after the pre-treatment.

15. The method according to claim 14 , wherein
the rinsing is carried out with one of water and isopropanol, and
the drying is carried out under a neutral gas atmosphere.

16. The method according to claim 6 , wherein the strong acid is hydrochloric acid, with a concentration comprised between 0.1% and 1% by mass.

17. The method according to claim 8 , wherein the solvent is water.

18. The method according to claim 9 , wherein the solvent is isopropanol.

19. The method according to claim 10 , wherein the solvent is isopropanol.

20. The method according to claim 11 , wherein the immersion comprises immersing in an ultrasonic bath.

Assignees

• Commissariat Energie Atomique

Inventors

• Castany Olivier
• Caicedo Panqueva Nohora-Lizeth
• Miloud-Ali Nadia
• Zonou Yezouma-Dieudonne

Classifications

• H10W90/722

  between stacked chips · CPC title

• H10W72/07236

  Soldering or alloying · CPC title

• H10W72/07211

  Treating the bond pad before connecting, e.g. by applying flux or cleaning · CPC title

• H10W72/01271

  Cleaning, e.g. oxide removal or de-smearing · CPC title

• H10W72/255

  of outermost layers of multilayered bumps, e.g. material of a coating · CPC title