Decapsulation of Electronic Devices

Abstract

The invention is directed to a method for treating an electronic device that is encapsulated in a plastic package, said method comprising the steps of providing a gas stream comprising a hydrogen source; inducing a hydrogen-containing plasma stream from said gas; and directing the hydrogen-containing plasma stream to the plastic package to etch the plastic package.

Claims

1. A method for treating an electronic device that is at least partially encapsulated in a plastic package, said method comprising decapsulating and the steps of a) providing a gas stream comprising a hydrogen source; b) inducing a hydrogen-containing plasma stream from said gas; c) directing the hydrogen-containing plasma stream to the plastic package to etch the plastic package; wherein treating the electronic device does not comprise cleaning and/or deflashing.

2. The method according to claim 1, wherein the electronic device is at least one of an encapsulated semiconductor device and a printed circuit board.

3. The method according to claim 1, wherein the electronic device comprises copper, silver, gold, palladium, platinum, rhodium, ruthenium, nickel, iridium, aluminum, tin or alloys thereof.

4. The method according to claim 1, wherein the gas stream comprises 0.01 to 100 vol % of the hydrogen source.

5. The method according to claim 1, wherein the hydrogen source is hydrogen and/or hydrocarbon.

6. The method according to claim 1, wherein the gas stream further comprises one or more carrier gasses.

7. The method according to claim 1, wherein the gas stream essentially consists of hydrogen gas and/or hydrocarbon and optionally one or more carrier gasses.

8. The method according to claim 1, wherein the gas stream comprises less than 5 vol % oxygen gas and/or less than 5 vol % of a fluorine source.

9. The method according to claim 1, wherein the plastic package comprises a molding compound comprising 10-30 wt % organic material, or 70-90 wt % inorganic material.

10. The method according to claim 1, wherein step c) is followed by step d) comprising subjecting the electronic device to ultrasonic cleaning in a liquid.

11. The method according to claim 10, comprising 5 to 20 cycles of steps a-d.

12. The method according to claim 1, wherein steps b and c are carried out at 0.05 to 1 bar.

13.-14. (canceled)

15. The method according to claim 1, wherein the electronic device comprises silver or an alloy thereof.

16. The method according to claim 1, wherein the gas stream comprises 0.1 to 50 vol % of the hydrogen source.

17. The method according to claim 1, wherein the gas stream comprises 0.3 to 20 vol % of the hydrogen source.

18. The method according to claim 1, wherein the gas stream comprises 0.5 to 5 vol % of the hydrogen source.

19. The method according to claim 6, wherein the one or more carrier gases comprise one or more noble gasses and/or nitrogen.

20. The method according to claim 8, wherein the fluorine source is tetrafluoromethane.

21. The method according to claim 1, wherein the gas stream comprises less than 1 vol % oxygen gas and/or less than 1 vol % of a fluorine source.

22. The method according to claim 21, wherein the fluorine source is tetrafluoromethane.

23. The method according to claim 9, wherein the organic material comprises epoxy.

24. The method according to claim 9, wherein the inorganic material comprises one or more silica fillers, and/or organic polymer die attachment materials, film over wire materials, die coating materials, silicone materials, or redistribution layer materials.

25. The method according to claim 10, wherein the liquid comprises deionized water, an organic solvent or a combination thereof.

26. The method according to claim 1, wherein steps b and c are carried out at atmospheric pressure.

Description

[0037] A further aspect of the present invention is a treated electronic device, preferably a decapsulated semiconductor device, comprising one or more components that comprise silver, e.g. silver bond wire, silver plated leadframe and/or silver surface on which the die is placed, that is obtainable by the method for decapsulation according to the invention as described herein above. Said one or more components of the treated electronic device comprise a surface that remains essentially undamaged when the method for decapsulation in accordance with the present invention is carried out. The decapsulated device comprising silver according to the present invention thus comprises a surface that is smoother and less damaged than decapsulated devices comprising silver, for instance showing essentially no or less cracks, pitting or the presence of silver oxide, that are not obtained by the present method but by for instance MIP etching with an oxygen-containing gas stream or conventional acid decapsulation methods.

[0038] FIG. 1 illustrate a decapsulated semiconductor device comprises silver bond wires in accordance with the present invention.

[0039] FIG. 2 illustrate comparative decapsulated semiconductor device comprises silver bond wires that are not in accordance with the present invention.

[0040] Another aspect of the present invention is a plasma etching apparatus comprising a plasma discharge tube that comprises an oxygen-free material like aluminum nitride (AlN) or boron nitride (BN) as material suitable for containing the hydrogen-containing plasma. It was found that AlN and BN materials have a particularly high melting point, a good heat conductivity, and are electronic insulator. In addition, their oxygen-free characteristics reduces the undesired effects of oxygen as described herein-above.

[0041] The apparatus according to the present invention is preferably a modified version of the MIP etching apparatus as described in WO 2013/184000, which is incorporated in its entirety. Preferably, the apparatus according to the present invention comprises a Beenakker cavity as a plasma source that is connected to the plasma discharge tube with the materials as described above.

[0042] Typically, the apparatus according to the present invention comprises a plasma source (e.g. a Beenakker cavity) allows sustained generation of the plasma from the gas stream under atmospheric conditions, obviating the need for vacuum creation components. The plasma source is provided with a plasma discharge tube for discharging the plasma in the form of a plasma jet. The plasma jet is directed toward the electronic device's package surface along a predetermined flow trajectory by means of the discharge tube. The gas supply conduit and plasma discharge tube are connected and the discharge tube extends through the center of the plasma source. This discharge tube comprises the oxygen-free material like aluminum nitride (AlN) or boron nitride (BN), and may have an outer tube diameter of between 2 to 10 mm (e.g. about 6 mm), and inner tube diameter of about 0.5 to 3 mm (e.g. about 1.2 mm). The discharge tube length may be 30 to 150 mm (e.g. about 10 cm). The discharge tube effectively isolates the gas flowing inside the discharge tube which is inside the plasma source from the remaining void enclosed by the hollow structure forming the cavity's resonance chamber.

[0043] The present apparatus further typically comprises a sample holder positioned at a substantially perpendicular distance from the plasma discharge tube. The sample holder provides a surface for holding the sample.

[0044] For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.

[0045] The present invention can be illustrated by the following examples.

EXAMPLE 1

[0046] In a MIP etching apparatus commercially available by Jiaco Instruments B.V. (Delft, the Netherlands) and described in WO 2013/184000, a plasma was induced from gas stream consisting of argon and hydrogen gas (95:5) with a flow rate of 400 sccm using an argon flow of 1400 sccm as the carrier gas. This plasma in combination with ultrasonic cleaning was used to decapsulate a semiconductor device comprising silver bond wires and a plastic package of 10% epoxy and 90% silica fillers. A decapsulated semiconductor device showing a clean wire surface upon visual inspection was obtained (FIG. 1).

EXAMPLE 2

[0047] The experiment described in Example 1 was repeated with a gas stream consisting of argon gas, nitrogen gas and hydrogen gas (viz. a mixture of a first stream of argon (100 vol %) at 1400 sccm and a second stream of nitrogen and hydrogen (95 and 5 vol % respectively) at 25 sccm. A decapsulated semiconductor device showing an acceptably clean and slightly damaged silver wire surface upon visual inspection was obtained.

COMPARATIVE EXAMPLES

[0048] The experiment described in Example 1 was repeated with a gas stream consisting of Ar/N.sub.2, Ar/O.sub.2 (FIG. 2), O.sub.2/CF.sub.4 (no ultrasonic cleaning) or decapsulation was achieved using a conventional acid decapsulation method. The results are summarized in table 1.

TABLE-US-00001 TABLE 1 Comparative examples Etching method Observations MIP with Ar/N.sub.2 No decapsulation observed. MIP with Ar/O.sub.2 Decapsulation observed, but a severely damaged silver wire with a rough surface was obtained. (FIG. 2) Conventional vacuum Decapsulation observed, but severely damaged plasmas with O.sub.2/CF.sub.4 silver wire with a rough surface was obtained. Acid with HNO.sub.3/ Decapsulation observed, but severely damaged H.sub.2SO.sub.4 silver wire with a rough surface was obtained.