Metallic solderability preservation coating on metal part of semiconductor package to prevent oxide
Embodiments of the present invention are directed to metallic solderability preservation coating on connectors of semiconductor package to prevent oxide. Singulated semiconductor packages can have contaminants, such as oxides, on exposed metal areas of the connectors. Oxidation typically occurs on the exposed metal areas when the semiconductor packages are not stored in appropriate environments. Copper oxides prevent the connectors from soldering well. An anti-tarnish solution of the present invention is used to coat the connectors during sawing, after sawing, or both of a semiconductor array to preserve metallic solderability. The anti-tarnish solution is a metallic solution, which advantageously allows the semiconductor packages to not need be assembled immediately after fabrication.
1. A method of preventing contaminants from forming on metal surfaces of semiconductor package connectors, the method comprising:
a. performing a first cleaning of a semiconductor package using a cleaner agent, thereby reducing surface tension of unexpected material;
b. performing a first DI water rinsing of the semiconductor package, thereby removing the unexpected material and the cleaner agent;
c. performing a second cleaning of the semiconductor package;
d. performing a second DI water rinsing of the semiconductor package, thereby ensuring exposed surfaces of metal connectors are clean and ready for treatment;
e. predipping the semiconductor package, thereby activating the surfaces;
f. treating the semiconductor package with an anti-tarnish solution during a singulation process;
g. performing a third DI water rinsing of the semiconductor package, thereby cleaning excess chemical and ionic contaminants;
h. postdipping the semiconductor package, thereby protecting a metallic coating;
i. performing a fourth DI water rinsing of the semiconductor package; and
j. drying the semiconductor package.
2. The method of claim 1 , wherein the performing the first cleaning comprises immersing the semiconductor package in the cleaner agent.
3. The method of claim 2 , wherein the semiconductor package is immersed in the cleaner agent for five minutes at 50° C.
4. The method of claim 1 , wherein the cleaner agent is acid.
5. The method of claim 1 , wherein the second cleaning is micro-etching, wherein the micro-etching creates a uniform topography on the surfaces of the metal connectors.
6. The method of claim 1 , wherein the second cleaning comprises immersing the semiconductor package in a chemical bath.
7. The method of claim 6 , wherein the chemical bath is one of hydrogen peroxide, sulphuric acid and sodium persulfate.
8. The method of claim 6 , wherein the semiconductor package is immersed in the chemical bath for about 60 seconds at 40° C.
9. The method of claim 1 , wherein the predipping comprises removing oxides and wetting the clean surfaces for 30 seconds at 30° C. in a predip solution, wherein the wet surfaces promotes a homogeneous metallic surface finishing.
10. The method of claim 9 , wherein the predip solution is an organic aqueous dispersion that has an efficient anti-tarnishing effect.
11. The method of claim 1 , wherein the treating includes spraying the semiconductor package with the anti-tarnish solution.
12. The method of claim 1 , wherein the treating includes dipping the semiconductor package with the anti-tarnish solution.
13. The method of claim 1 , wherein the anti-tarnish solution is a metallic solution.
14. The method of claim 1 , wherein the anti-tarnish solution is applied to the semiconductor package at 45-52° C. or at 63-68° C.
15. The method of claim 1 , wherein the anti-tarnish solution is applied to the semiconductor package for four to twelve minutes.
16. The method of claim 1 , wherein a postdip solution is one of acid or alkaline base.
17. The method of claim 1 , wherein the metallic coating prevents oxidation.
18. A metallic solderability preservation method comprising:
a. loading a semiconductor array in a singulation machine, wherein the semiconductor array includes a plurality of semiconductor packages each package having a semiconductor device electrically coupled to package connectors;
b. singulating the semiconductor packages to expose cut portions of the package connectors;
c. removing contaminants from a semiconductor package; and treating the semiconductor package with an anti-tarnish solution after singulation, thereby protecting all exposed surfaces of semiconductor package connectors.
19. The metallic solderability preservation method of claim 18 , wherein the loading includes mixing the anti-tarnish solution with a cutting fluid.
20. The metallic solderability preservation method of claim 18 , wherein the treating includes dipping the semiconductor package with the anti-tarnish solution.
21. The metallic solderability preservation method of claim 18 , wherein the anti-tarnish solution is a metallic solution.
22. The metallic solderability preservation method of claim 21 , wherein the metallic solution is one of tin, silver, gold, and nickel-gold.
23. The metallic solderability preservation method of claim 18 , wherein the anti-metallic solution is applied at 45-52° C. or at 63-68° C.
24. The metallic solderability preservation method of claim 18 , wherein the anti-metallic solution is applied for four to twelve minutes.
25. A method of preventing contaminants from forming on metal surfaces of semiconductor package connectors, the method comprising:
a. performing a first cleaning of a semiconductor package using a cleaner agent, thereby reducing surface tension of unexpected material;
b. performing a first DI water rinsing of the semiconductor package, thereby removing the unexpected material and the cleaner agent;
c. performing a second cleaning of the semiconductor package;
d. performing a second DI water rinsing of the semiconductor package, thereby ensuring exposed surfaces of metal connectors are clean and ready for treatment;
e. predipping the semiconductor package, thereby activating the surfaces;
f. treating the semiconductor package with an anti-tarnish solution;
g. performing a third DI water rinsing of the semiconductor package, thereby cleaning excess chemical and ionic contaminants;
h. postdipping the semiconductor package, thereby protecting a metallic coating;
i. performing a fourth DI water rinsing of the semiconductor package; and
j. drying the semiconductor package.