De-bonding of Silicon Wafers Adhered with Adhesives to Glass using Detergents

I. Purpose

The purpose of this test was to evaluate the efficiency of the de-bonding of silicon wafers adhered to glass with VALTRON^® epoxies.

II. Parameters of the Experiment

1. Conditioning of the Substrates:
   Sliced silicon wafers were submitted by the customer to evaluate de-bonding.  Glass beams cut to 6.5 inches x 2 inches were evenly sanded for improved adhesion. Fifteen (15) silicon wafers evenly spaced were adhered to each glass beam with one of the epoxy systems listed in the table below:

VALTRON Epoxy	Ratio (Part A: Part B)
AD1339-A/AD3905-B	1:1
AD1339-A/AD3939-B	1:1



2. Preparation of De-bonding Solutions:
   40% Acetic Acid
   12% & 57% VALTRON^® DP164 Epoxy Remover/Detergent
   15% VALTRON^® SP2560 High Alkaline Detergent
   50% Citric Acid Solution with Low Foaming Nonionic Surfactant
   16% Lactic Acid, Polyethylene Glycol, & Surfactant Solution
   Deionized Water
   
   

   500mL each, of the above solutions were poured into separate 1000mL stainless steel trays. The solutions were heated to, and maintained at temperatures of 131°F/55°C to 194°F/90°C.

III. The Experiment

1. The VALTRON^® epoxy system was prepared by mixing 1 part by weight of the AD1339-A resin with 1 part by weight of the AD3905-B hardener in a mixing cup.
2. A set of 15 wafers, evenly spaced, were adhered with the epoxy to a glass beam.
3. The epoxy was allowed to cure for 24 hours at room temperature.
4. Next, the substrate was given a 15 second spray rinse of low-pressured deionized water at room temperature.
5. The prepared substrate was placed in the solution and soaked until the wafer de-bonded from the glass beam.  The de-bonding time was recorded.
6. The experiment was repeated as follows:
   1. Steps 1-5 were repeated using the AD1339-A/AD3905-B epoxy system with 12% VALTRON^® DP164 at 131°F/55°C, 12% VALTRON^® DP164 at 158°F/70°C, 57% VALTRON^® DP164 at 131°F/55°C, 15% VALTRON^® SP2560 at 185°F/85°C, 50% Citric acid solution at 131°F/55°C, and 16% Lactic acid solution at 131°F/55°C.
   2. Steps 1-5 were repeated using the AD1339-A/AD3939-B epoxy system with 40% Acetic acid at 158°F/70°C, 12% VALTRON^® DP164 at 158°F/70°C, and 15% VALTRON^® SP2560 at 185°F/85°C.
   3. Steps 1-5 were repeated using the AD1339-A/AD3905-B epoxy system with deionized water at 194°F/90°C.
7. The de-bonding times are listed in the table below.

IV. Results

De-bonding of Silicon Wafers from Glass Beams

V. Conclusion

In this experiment, five solutions as well as plain deionized water were evaluated in the de-bonding of silicon wafers from glass beams adhered with VALTRON^® epoxies. 40% Acetic acid was capable of de-bonding the wafers in 3-4 minutes. 12% & 57% VALTRON^® DP164 de-bonded the wafers in 11 to 12 minutes. A 15% solution of VALTRON^® SP2560 de-bonded the wafers in 20 to 30 minutes, and the use of deionized water at 90°C required a de-bonding time of 38 minutes. A 50% Citric acid solution did not de-bond the wafers after 45 minutes of soaking and therefore is not an effective method of de-bonding. A 16% Lactic acid solution fortified with Polyethylene Glycol 300 (PEG 300) resulted in a de-bonding time of 15 minutes. Achieving a de-bonding time below 15 minutes can only be accomplished by soaking the substrates in a 12% solution of VALTRON^® DP164 epoxy remover/detergent at a temperature of 131°F/55°C to 158°F/70°C.

While the use of 40% Acetic acid solution for de-bonding the silicon wafers from glass beams required the least amount of time as compared to either 12% VALTRON^® DP164 or 15% VALTRON^® SP2560, it requires special handling and protective equipment such as the use of a respirator and operation under a fume hood in order to minimize worker exposure to the extremely irritating fumes that it generates at elevated temperatures. The VALTRON^® DP164 and SP2560, on the other hand, can safely be used under general mechanical ventilation.

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