advanced decapsulation technique_cm belotendos et al

23rd ASEMEP National Technical Symposium

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ADVANCED DECAPSULATION TECHNIQUE ON REMOVAL OF GLOB TOP ON IC PACKAGE USING BOILING CONCENTRATED SULFURIC ACID

Cherry Mae M. Belotendos

Lylanie B. Delos Santos Nina Corazon T. Oruga

Failure Analysis Group – Quality and Reliability Department

STMicroelectronics Calamba, 9 Mt. Drive LISP II, Brgy. La Mesa, Calamba City 4027 [email protected]; [email protected]; [email protected]

ABSTRACT

In failure analysis, removal of glob top material on the integrated circuit (IC) package is necessary to inspect the internal silicon die and bond wires. However, glob top has an excellent resistance to acid [3] making it difficult to remove during decapsulation. Current decapsulation technique using Fuming Nitric Acid (HNO3) cannot easily remove the glob top. Fuming Nitric Acid can damage the substrate before the encapsulation material is completely removed. These damages include over-etched heat sink, loosened copper trace and disturbed wire and ball bond placement. To address the problem, a new technique of decapsulating the glob top from the package must be established. In this paper, the results of decapsulation experiments using concentrated Sulfuric Acid (H2SO4) were described. Several experiments using dummy units were conducted. Several factors were considered such as the mixture of acid, their properties and behavior, their temperature, the samples and hot plate, and the chemical reaction of the solvents used in rinsing. The properties of glob top material and its reaction to different acids and solvents were also carefully observed. The advanced decapsulation technique using boiling concentrated Sulfuric Acid was recommended. Bond wires and silicon die were successfully exposed without inducing damage on the IC package.

1. 0 INTRODUCTION

In conventional Chip-on Board packaging, unpackaged ICs are bonded directly to an interconnecting substrate and are protected with a glob top encapsulant. This requires a protective coating for the chips to prevent corrosion or mechanical damage. The chip on substrate approach offers advantages in both cost and performance since it eliminates several components and assembly steps as well as the

thermal and electrical impedance of additional packaging interfaces. However, it requires high confidence in functional die before assembly, and sophisticated testing methods are needed for the assembled board [2]. 1.1 Problem Statement Prolonged etching time is needed to remove the Glob top compound from the package using Fuming Nitric acid (100%). It may result to over-etched substrate, misplaced Silicon die, unclean die surface, loosened copper trace and disturbed wires. Handling of the sample due to substrate over etching is also a problem. Figure 1 illustrates these common problems.

Figure 1. Induced damage on IC package during glob top removal using Fuming Nitric Acid 100%

silicon die

loosened copper trace

disturbed wires

Over-etched heat sink

Over-etched substrate

Misplaced silicon die


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With these challenges against the need to provide an accurate and on-time failure analysis of the decapsulated unit, it is evident that an improved and innovative process of removing the glob top material from the package must be explored. It is with this objective that this study has been pursued. 1.2 Scope of the Study The experiment is mainly focused on the decapsulation process of IC (Integrated Circuit) with glob top compound. It considers the specified properties of the current glob top material being used, with the intent of performing the decapsulation process without inducing damage to the sample. Analysis covers contributing factors such as properties of the glob top, chemical solution, temperature and timing.

2. 0 REVIEW OF RELATED LITERATURE 2.1 The Glob Top Material Glob top compounds are ideal for the encapsulation of semiconductor chips and wire bonds mostly in Chip-on-Board (COB) applications. These formulations offer protection against moisture, chemicals and contaminants. Additionally, they minimize the thermal mismatch between chips and substrates. They also provide mechanical support and electrically insulative properties [3]. Figure 2 shows the illustration of the package structure with the glob top.

Figure 2. Typical Chip-On-board (COB) construction. Glob top is a type of Epoxy Anhydride. Anhydride epoxy compounds are primarily employed for encapsulation and potting purposes, especially for applications which have high temperature demands or large volume usage. Properties of glob top include characteristics such as physical and mechanical strength, chemical resistance, operating temperature range and thermal cycling, dimensional stability and resistance to shock and vibration. The typical glob top curing time is 2 to 4 hours by convection oven to establish

full properties [3]. Glob-top resins are providing a low cost packaging solution for chip on board technology [4]. 2.2 Decapsulation Decapsulation is a failure analysis step performed to open a plastic package to facilitate the inspection of the internal silicon die, bond wires and other internal features of the package. It is the process of removing the coating or encapsulant by means of chemical, mechanical and automated etching. In chemical etching, the coating is slowly attacked by certain chemicals such as strong acids and bases to expose the internal silicon die and bond wires [4]. Manual chemical etching consists of manually dispensing some acid on the surface of a package to remove the plastic material covering of the die. Red fuming Nitric acid (HNO3) or Sulfuric acid (H2SO4) is often used for this purpose [5]. Plastic (mold compound) type, size of the part, and type of substrate help determine the best parameters for decapsulation. Ceramic substrate devices are easier to decap than organic substrate devices, because acids can destroy organic substrate before the encapsulation material is completely removed. Care must be taken to inspect these devices frequently during chemical decapsulation to avoid damaging the organic substrate to the point where the entire device becomes useless to inspect [6]. 2.3 Nitric Acid Nitric acid (HNO3), also known as aqua fortis and spirit of niter, is a highly corrosive strong mineral acid. Red fuming nitric acid, or RFNA, contains substantial quantities of dissolved nitrogen dioxide (NO2) leaving the solution with a reddish-brown color. One formulation of RFNA specifies a minimum of 17% NO2, another specifies 13% NO2. Because of the dissolved nitrogen dioxide, the density of red fuming nitric acid is lower at 1.490 g/mL [6]. Nitric acid is normally considered to be a strong acid at ambient temperatures. [5] Nitric acid reacts with most metals but the details depend on the concentration of the acid and the nature of the metal. Dilute nitric acid behaves as a typical acid in its reaction with most metals. Magnesium, manganese and zinc liberate H2. Others give the nitrogen oxides. Nitric acid is a strong acid and a powerful oxidizing agent, it reacts violently with many non-metallic compounds and has been widely used in various decapsulation techniques [6]. 2.4 Mixture of Fuming Nitric Acid and Sulfuric Acid Typical nitration syntheses apply so-called "mixed acid", a mixture of concentrated nitric acid and sulfuric acids [7]. This mixture produces the nitronium ion (NO2+), which is


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the active species in aromatic nitration. This active ingredient, which can be isolated in the case of nitronium tetrafluoroborate [8] also effects nitration without the need for the mixed acid. In mixed-acid syntheses, sulfuric acid is not consumed and hence acts as a catalyst as well as an absorbent for water. In the case of nitration of benzene, the reaction is conducted at 50 °C. Alternative mechanisms have also been proposed, including one involving single electron transfer (SET)[9][10]. 2.5 Sulfuric Acid Sulfuric acid (alternative spelling sulphuric acid) is a highly corrosive strong mineral acid with the molecular formula H2SO4. It is a colorless to slightly yellow viscous liquid which is soluble in water at all concentrations [11]. The historical name of this acid is oil of vitriol [12]. At temperatures above 150°C when oleum vapor is present, plastic encapsulant is rapidly removed, with minimal metal etching. At lower temperatures however, with less oleum vapor present, longer etch times are needed, leading to the possibility of excessive metal loss [11]. Sulfuric acid is a diprotic acid and shows different properties depending upon its concentration. Its corrosiveness on other materials, like metals, living tissues (e.g. skin and flesh) or even stones, can be mainly ascribed to its strong acidic nature and, if concentrated, strong dehydrating and oxidizing property. Moreover, it is hygroscopic, readily absorbing water vapour from the air [11] 2.6 Concentrated Sulfuric Acid Although nearly 99% sulfuric acid can be made, the subsequent loss of SO3 at the boiling point brings the concentration to 98.3% acid. The 98% grade is more stable in storage, and is the usual form of what is described as "concentrated sulfuric acid." Other concentrations are used for different purposes. The boiling point of Sulfuric is at 290 °C. When the boiling point is reached, Sulfuric Trioxide gas (SO3) and Water (H2O) were released. Safety is of paramount importance when concentrating Sulfuric Acid [15]. 2.6.1 Pre-Boiling Pre-boiling process involves pouring the dilute acid to be concentrated into an appropriate boiling container (Pyrex® labware or equivalent), then heating the liquid by gradually increasing the temperature setting from 100 to 300 °C on the hot plate [15].

2.6.2 Boiling When the acid begins to boil, water (steam) will be the most predominant vapor evolved from the solution. As the water leaves, the Sulfuric Acid is left behind in a smaller and more concentrated solution. As the acid becomes more concentrated, its boiling point will rise. [15]. 2.6.3 Fuming After a substantial portion of the water has boiled away, thick, white fumes of SO3 gasses will begin to evolve from the boiling acid. [15]. The fumes containing the SOx gasses will grow thicker as the concentration of the acid increases allowing one to use them as a crude method gauging the concentration of the acid. 2.7 Isopropyl alcohol (IPA) Isopropyl alcohol is miscible in water, alcohol, ether and chloroform. It will dissolve ethyl cellulose, polyvinyl butyral, many oils, alkaloids, gums and natural resins [16]. It is insoluble in salt solutions. Unlike ethanol or methanol, isopropyl alcohol can be separated from aqueous solutions by adding a salt such as sodium chloride, sodium sulfate, or any of several other inorganic salts, since the alcohol is much less soluble in saline solutions than in salt-free water. The process is colloquially called salting out, and causes concentrated isopropyl alcohol to separate into a distinct layer [17]. Like most alcohols, isopropyl alcohol reacts with active metals such as potassium to form alkoxides which can be called isopropoxides. Isopropyl alcohol may be converted to 2-bromopropane using phosphorus tribromide, or dehydrated to propene by heating with sulfuric acid. Like most alcohols, isopropyl alcohol reacts with active metals such as potassium to form alkoxides which can be called isopropoxides. The reaction with aluminium (initiated by a trace of mercury) is used to prepare the catalyst aluminium isopropoxide [18].

3.0 EXPERIMENTAL SECTION The study was performed using the following set of materials, chemicals, equipment and methodology. 3.1 Materials

- Beakers & Petri dish - Dropper (small nozzle) - Tweezers (particularly fine point) - Paper Towels - Dispenser Spray for Acetone


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3.2 Chemicals

-Fuming Nitric Acid 100% (HNO3) -Sulfuric Acid 95-97% (H2SO4) -Acetone -Isopropyl Alcohol (IPA)

3.3 Equipment

-Hotplate with Temperature Control Setting -Fumehood

3.4 Personal Protective Equipment (PPE)

-Anti-Acid Apron and Arm guard -Disposable Anti-acid gloves -Gas Mask

3.5 Procedure The experiment was performed following the trial runs indicated in Table 1. The factors considered are the chemical etchant, solvent used in rinsing, hot plate temperature, and the etching duration. A total of sixteen runs were considered in the experiment. 3.5.1 Sample Preparation In all runs of the experiment, IC package samples with glob top were prepared. The glob top of the samples was parallel grinded using 400 microns Silicon carbide to flatten the top surface, as shown in Figure 3. This will prevent acid overflow when dispensed on the glob top.

Figure 3. Flattened surface on glob top after parallel grinding

3.5.2 RUNS 1-4 For Runs 1 – 4, Nitric acid and Sulfuric acid were mixed using two different ratios (1:1 and 1:2) and three hot plate temperatures (200 °C, 250 °C and 300 °C). The IC package was placed on the hot plate, then the mixture was dropped on the center of the glob top and was left to drench for 10 seconds. Acetone was used to rinse the samples. The procedure was repeated until the bond wires and silicon die were exposed. Etching time was 10-15 minutes.

3.5.3 RUNS 5-8 For these runs, Sulfuric acid (95-97%) was used together with a 250 °C and 300 °C hot plate, at varying etching duration. The mixture was dropped on the center of the glob top and was left to drench for 10 seconds. Acetone was used to rinse the samples. The procedure was repeated until the bond wires and silicon die were exposed. Etching time was varied as follows; 60-70 seconds, 40-50 seconds and 30-40 seconds respectively.

3.5.4 RUNS 9-12 Concentrated Sulfuric acid (95-97%) was boiled at 300 °C, with varying hot plate temperatures of 300 °C, 250 °C and 200 °C respectively. The mixture was dropped on the center of the glob top and was left to drench for 10 seconds. Acetone was used to rinse the samples. The procedure was repeated until the bond wires and silicon die were exposed. Etching time was varied accordingly as 30-40 seconds and 40-50 seconds.

3.5.5 RUNS 13-15 For these runs, concentrated Sulfuric acid (95-97%) was boiled at 300 °C for several minutes. The time of boiling is set at 10, 15 and 20 minutes respectively. Two hot plates were used. One hot plate was set to 300 °C and was used to boil 10 ml of Sulfuric acid to produce concentrated Sulfuric acid. The concentrated acid was not removed from the hot plate for the duration of decapsulation. Another hot plate was set at 200 °C and was used for the initial first 2 drops of concentrated Sulfuric acid on the glob top (sample placed on a petri dish). Initially, the sample was heated at 200 °C for 30 seconds, then the concentrated Sulfuric acid was dropped on the center of the glob top for 3 seconds and was washed with acetone immediately. At this time, loop wire was already exposed, as shown in Figure 4. Once the die surface was already partially exposed, the acid was again dropped onto the die area and immediately rinsed with acetone afterwards.

Figure 4. Exposed wire loop on initial decapsulation.

Flattened surface


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Table 1. Summary of Experimental Combinations

Run Chemical Etchant

Rinsing Solvent

Hot Plate Temp

Etching Time

1 1:1 ratio of Fuming Nitric Acid (100%) and Sulfuric

Acid (95-97%)

Acetone 200 °C 10-15 minutes


Acid (95-97%)



Acid (95-97%)



Acid (95-97%)


5 Sulfuric Acid 95-97%

Acetone 250 °C 60-70 seconds







9 Concentrated Sulfuric Acid

(boiled 300°C)



(boiled 300°C)



(boiled 300°C)



(boiled 300°C)



(boiled 300°C for 10 minutes)

Acetone 200 °C initial decap

40-60 seconds

Room temp (after loop wires were exposed)




40-60 seconds





40-60 seconds




IPA 200 °C initial decap

40-60 seconds


Afterwards, the IC package was heated on a 200 °C hotplate for 3 seconds and was directly placed on a petri dish at room temperature. Then it was instantly subjected to continuous three (3) drops of concentrated Sulfuric acid for 3 seconds. The IC package was immediately washed with acetone. This step was repeated two (2) times until the whole bond wires and silicon die were exposed. The same procedure was performed in boiling the concentrated Sulfuric acid (95-97%) at 300 °C for 15 minutes and 20 minutes respectively. Acetone was used in rinsing. Etching time of glob top was within 40-60 seconds. 3.5.6 RUNS 16 For this run, the concentrated Sulfuric acid (95-97%) was boiled at 200 °C for 30 minutes. Similar procedure done in runs 13-15 was performed except that this time, IPA instead of acetone was used for rinsing. The idea forwarded here was that heating the IC package at 200 °C would enable the glob top compound to absorb the heat. When the glob top compound was heated, the acid dropped on its center would not overflow thus etching most of the gob top compound and not the substrate. The sample was subjected to the acid for 3 seconds only to avoid over-etching.

4.0 RESULTS AND DISCUSSION The summary of the results is shown in Table 2. The Glob top on IC package was successfully removed without causing damage on the sample. This was realized using concentrated Sulfuric acid. One factor that affected the etching of glob top was the excellent acid-resistant property of the compound. In the first four runs of the experiment, Nitric acid and Sulfuric acid were mixed using 1:1 ratio at 200 and 250 °C hot plate followed by 1:2 ratio at 250 and 300 °C hotplate. Time of etching was 10-15 minutes. Post decapsulation results for these runs were not successful, as can be seen in Figure 5. Glob top was difficult to remove using Nitric and Sulfuric mixture because the glob top annealed when exposed to Nitric acid.

Figure 5. Damage on IC package after glob top removal

dirty die surface

loosened copper trace

disturbed wires

over-etched substrate


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Table 2. Summary of Experimental Results Run Chemical

Etchant Rinsing Solvent

Hot Plate Temp

Etching Time

RESULTS

1 1:1 ratio Mixture

Acetone 200 °C 10-15 minutes Fail

2 1:1 ratio Mixture


3 1:2 ratio Mixture


4 1:2 ratio Mixture


5 Sulfuric Acid

Acetone 250 °C 60-70 seconds Fail

6 Sulfuric Acid


7 Sulfuric Acid


8 Sulfuric Acid


9 Boiled Conc

Sulfuric Acid


10 Boiled Conc

Sulfuric Acid


11 Boiled Conc

Sulfuric Acid


12 Boiled Conc

Sulfuric Acid


13 Conc Sulfuric

Acid (boiled

10 minutes)

Acetone 200 °C initial, Room temp (after

exposing wires)

40-60 seconds

Fail

14 Conc Sulfuric

Acid (boiled

15 minutes)


exposing wires)

40-60 seconds

Fail

15 Conc Sulfuric

Acid (boiled

20 minutes)


exposing wires)

40-60 seconds

Fail

16 Conc Sulfuric

Acid (boiled

30 minutes)

IPA 200 °C initial, Room temp (after

exposing wires)

40-60 seconds

Pass

On runs 5-8, Sulfuric acid was able to remove the glob top successfully without damaging the sample as shown in Figure 6. However, Sulfuric in its “normal state” was highly

corrosive, and was also attacking the Aluminum on bond pad, hence the over-etched Aluminum bond pad. To confirm this observation noted on the discolored area of the bond pad, an EDX analysis of the bond pad is conducted. The analysis on Figure 7 showed presence of Silicon and Oxygen, confirming that Sulfuric acid has penetrated the underlying metal.

Figure 6. Decapsulation result with Glob top removed, without damage on wires and substrate.

Figure 7. EDX analysis of the bond pad. On runs 9-12, concentrated Sulfuric acid (95-97%) boiled for 10, 15, and 20 minutes respectively at 300 °C was able to remove the glob top (see Figure 8) without any damage to the wires and substrate. However, Aluminum on bond pad was still slightly over etched by the acid as shown in Figure 9. The acetone used in rinsing made the corrosion on aluminum faster.

Figure 8. Result for Runs 9 -12 showing no damage to wires

and substrate.

Exposed underlying metal on bond pad (Aluminum was over etched)

Bond pad

Bond pad

Si


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Figure 9. Over-etching of Aluminum on bond pad.

On run 16, concentrated Sulfuric acid (95-97%) was boiled for 30 minutes at 300 °C. The glob top was totally removed. There was no damage noted on the sample. There were no traces of over etching observed on Aluminum bond pad layer, as confirmed on Figures 10 and 11. IPA seemingly prevented the fast corrosion of Aluminum on Sulfuric acid.

Figure 10. Result of successful decapsulation - exposing the wires and silicon die. No misplaced wires, no over etching on substrate, no loose copper trace and no disturbed wires.

Figure 11. EDX Analysis of the bond pad showing intact Aluminum layer.

The last run showed that after 30 minutes of boiling 10 ml of Sulfuric acid at 300 °C, the capability of the acid to etch the glob top without attacking the Aluminum of bond pad was most efficient. Moreover, the solution should be used within 20 minutes after boiling. Sulfuric acid boils off with

the water due to too much boiling, making it less efficient in etching the glob top. The glob top must be parallel grinded to expose its top surface to enable the acid to etch most of the center of the glob top. Heating the IC package at 200 °C enabled the glob top compound to absorb the heat. When the glob top compound was heated, the acid dropped on its center did not overflow thus etching most of the gob top compound and not the substrate. The sample was subjected to the acid for 3 seconds only to avoid over-etching. The complete details of the results of the experiment are shown in Appendix 1.

5.0 CONCLUSION The most effective and efficient way of removing glob top from the studied IC package without inducing any damage to the internal structure is through the use of boiled (300 °C for 30 mnutes) concentrated Sulfuric acid, using IPA as rinsing solvent, hot plate temperature of 200 °C, and etching duration of around 40 – 60 seconds. These conditions preserve the placement of wire looping and do not result to the excessive etching of the substrate and Aluminum bond pad, which are critical information when conducting Failure Analysis.

6.0 RECOMMENDATIONS The author recommends further studies on the use of IPA for lower etching duration (40 – 50 seconds), which can be a good opportunity to further improve the cycle time for Failure Analysis of glob-topped packages. The concentration of IPA to be used can also be explored further.

7.0 ACKNOWLEDGMENT We recognize the significant contributions of STMicroelectronics Calamba Failure Analysis group, Priscila Abarquez and George Sia, who gave us the motivation and unequivocal support for the realization of this project. We also thank Dr. Terence Lacuesta, Violy Andal and Liza Beronio for their valuable inputs; and special thanks to Dr. Bernie Redoña and Trixie Chiu.

Exposed underlying metal on bond pad (Aluminum was over etched)

Preserved aluminum on bond pad

Al


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8.0 REFERENCES

[1] Advanced Packaging - Aug-Sep 2007 Vol. 16, No. 6; page 27; ISSN 1065-0555; Published by PennWell books.google.com.ph [2] Multichip Module Technologies and Alternatives: The Basics by Daryl Ann Doane, Paul D. Franzon Springer, 1993 - Computers – page 302 [3] Integrated Circuit Packaging, Assembly and Interconnections by William J. Greig Springer, Jan 1, 2007–Technology & Engineering, page 97 [4] Electronic Materials Handbook: Packaging Merrill L. Minges; ASM International, 1989 - Technology & Engineering – page 243 [5] IUPAC SC-Database A comprehensive database of published data on equilibrium constants of metal complexes and ligands [6] Catherine E. Housecroft; Alan G. Sharpe (2008). "Chapter 15: The group 15 elements". Inorganic Chemistry, 3rd Edition. Pearson. ISBN 978-0-13-175553-6. [7] John McMurry Organic Chemistry 2nd Ed. [8] George A. Olah and Stephen J. Kuhn, "Benzonitrile, 2-methyl-3,5-dinitro-", Org. Synth., Vol. 5: 480 [9] Esteves, P. M.; Carneiro, J. W. M.; Cardoso, S. P.; Barbosa, A. G. H.; Laali, K. K.; Rasul, G.; Prakash, G. K. S.; e Olah, G. A. (2003). "Unified Mechanism Concept of Electrophilic Aromatic Nitration Revisited: Convergence of Computational Results and Experimental Data". J. Am. Chem. Soc. 125 (16): 4836. doi:10.1021/ja021307w. PMID 12696903. [10] Queiroz, J. F.; Carneiro, J. W. M.; Sabino A. A.; Sparapan, R.; Eberlin, M. N.; Esteves, P. M. (2006). "Electrophilic Aromatic Nitration: Understanding Its Mechanism and Substituent Effects". J. Org. Chem. 71 (16): 6192. doi:10.1021/jo0609475. PMID 16872205. [11] "Sulfuric acid safety data sheet". http://www.arkema-inc.com/msds/01641.pdf. "Clear to turbid oily odorless liquid, colorless to slightly yellow." [12] Sulfuric acid. Chicago: Encyclopædia Britannica. 2010. [13] "The Columbia Encyclopedia". 2008. http://www.encyclopedia.com/topic/sulfuric_acid.aspx. Retrieved 2010-03-16. [14] "Sulphuric acid". Encyclopædia Britannica. 26 (11th ed.). 1910–1911. pp. 65–69

[15] 2005 - 2013 Amazing Rust .com InternationalChemical Supply;http://www.amazingrust.com/Experiments/how_to/Concentrating_H2SO4.html [16] Yaws, C.L. (1999). Chemical Properties Handbook. McGraw-Hill. ISBN 0-07-073401-1. [17] Doolittle, Arthur K. (1954). The Technology of Solvents and Plasticizers. New York: John Wiley & Sons, Inc.. p. 628. [18] Young, W.; Hartung, W.; Crossley, F. (1936). "Reduction of Aldehydes with Aluminum Isopropoxide". J. Am. Chem. Soc. 58: 100–2. doi:10.1021/ja01292a033.

9.0 ABOUT THE AUTHORS Cherry Mae Belotendos is a graduate of Electrical Engineering Technology from Technological University of the Philippines in Negros Occidental. She has thirteen (13) years of experience in the field of Reliability Engineering and Failure Analysis. She has done various notable and extensive analyses on subjects of STODxx Electrical Overstress phenomenon, Package solderability, and Package reliability qualifications of copper wire. She is a 3-Year Zero Defect Idol for 2011 and has been awarded as the Plantwide 2012 Best Technician. She is currently working as a Junior Failure Analysis Technician of STMicroelectronics Calamba. Lylanie Delos Santos is a graduate of technical course major in Electronics from Camarines Sur Polytechnic Colleges, Camarines Sur. She has nine (9) years of experience in the semiconductor industry - engaged in Reliability and Failure Analysis section. She is a Junior Failure Analysis Technician. She has established and implemented various effective and efficient de-encapsulation techniques applicable to the different packages manufactured by the company. She is one of the 5-Year Zero Defect Idol of ST Microelectronics Calamba for the year 2012. Niña Corazon Oruga is currently working as a Senior Failure Analysis (FA) Engineer. She is a graduate of Bachelor of Science in Chemical Engineering from Far Eastern University in Morayta, Manila. She has 19 years of experience in the semiconductor industry. Her main task is to perform FA on top key priorities that include External Customer Complaints, Production Line Failures and other urgent qualification and evaluation activities / projects. She has established “Fault Isolation” procedure on package / substrate related issues with the aid of a UPD, employing planar lapping technique. She’s also established a local procedure as an alternative Polyimide Quartz removal on specific devices. She was awarded as the Best Engineer of ST Microelectronics Calamba for the year 2011.


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APPENDIX 1 – Summary of Results of Experiment

Run Chemical Etchant Rinsing Solvent

Hot Plate Temp

Etching Time

RESULTS

Remarks Glob Top Removed

Substrate Not Over Etched

Wires Not Misplaced

Clean Die Surface

Unetched Al Bond

Pad 1 1:1 ratio of

Fuming Nitric Acid (100%) and Sulfuric Acid (95-97%)

Acetone 200 °C 10-15 minutes √ X X X X Fail

2 1:1 ratio of Fuming Nitric Acid (100%) and Sulfuric Acid (95-97%)






5 Sulfuric Acid 95-97% Acetone 250 °C 60-70 seconds √ √ √ √ X Fail

6 Sulfuric Acid 95-97% Acetone 250 °C 40-50 seconds X √ √ √ X Fail

7 Sulfuric Acid 95-97% Acetone 300 °C 40-50 seconds √ √ √ √ X Fail

8 Sulfuric Acid 95-97% Acetone 300 °C 30-40 seconds X √ √ √ X Fail

9 Concentrated Sulfuric Acid (boiled 300°C)

Acetone 300 °C 30-40 seconds √ √ √ √ X Fail






Acetone 200 °C 30-40 seconds X √ √ √ X Fail

13 Concentrated Sulfuric Acid (boiled 300°C for 10

minutes)

Acetone 200 °C initial decap,

Room temp (after

exposing wires)

40-60 seconds

√ √ √ √ X Fail


minutes)


Room temp (after

exposing wires)

40-60 seconds

√ √ √ √ X Fail


minutes)


Room temp (after

exposing wires)

40-60 seconds

√ √ √ √ X Fail


minutes)

IPA 200 °C initial decap,

Room temp (after

exposing wires)

40-60 seconds

√ √ √ √ √ PASS

advanced decapsulation technique_cm belotendos et al

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