Tin Plating

ACTIVATION CHEMICAL ETCHING RATE VS WEIGHT LOSS STUDY Joshua B. Dacles Plating Process End of Line Engineering Department OJT Trainee [email protected] ABSTRACT

that is constantly maintained to provide optimum results.

The current activation process is needed for the oxide removal in the lead frame surface. This paper shows the different weight loss vs different concentration and time. Results show that the data is normally distributed and the concentration and processing time is directly proportional to the etching strength.

Slotetch 21 is a weak acidic, fluoride-free activator for copper alloys which contains small quantities of silicon and nickel. In conventional, fluoride-free copper activations, these copper alloys form a black film. Activation Slotetch 21 has a low stripping rate. Copper oxide layer are removed without attacking the base material. Hydrogen peroxide is present in the solution because of its cleaning properties. Hydrogen peroxide increases the stripping rate of the activation solution. This is needed as the process is in automated equipment with processing time completed in seconds only.

1.0 INTRODUCTION In these modern times, technology is fast progressing. Developing new alternatives, processes, machines, electronics, that could make man’s job and life easier and more comfortable. Among the industry that is rapidly growing nowadays is the semiconductor industry. They have been the center of development of new and more efficient quality products of integrated chips and transistors that is essential in the production of electronic machines. On Semiconductor is one of the major and renowned manufacturing companies in the field of semiconductor.

1.1Objective The objective of this report is to determine the etching rate of the activation solution with different concentrations and processing time basing from the weight loss obtained from the experiment. 1.2 Scope

In order to come up with the final product in a semiconductor facility, it will foremost undergo a lot of processing in order for it to prepare and be set in order. One of these processes is the plating process wherein the leadframe of the different type of packages are being plated with a metal to enhance its solderability properties, to prevent oxidation, and for aesthetic purposes as well.

This evaluation is limited to all copper leadframe packages only. 2.0 EXPERIMENTAL SECTION The technical data sheet (TDS) and material safety data sheet (MSDS) of the different chemistries being qualified were carefully reviewed. Based on these TDS, the Design of Experiment (DOE) leg per chemistry was devised in determining the best parameter which will be used in the evaluation of the good units.

In the On Semiconductor Philippines Inc. Cebu, they are using tin as the plating material for their products. The usual lead frame that they are using is copper-based. The package will be exposed to many chemical solutions in the plating process and the activation solution is one of them.

This study explores the effect of the Slotetch21 solution and Hydrogen Peroxide on the following input parameter and output response: 1) concentration

Activation process is essential because during the process, the metal oxides present in the packages are removed by the solution. The activation solution is composed of Slotetch 21, Hydrogen peroxide and water. In the plating area, they have a specific concentration

2) processing time 3) weight loss

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2.1 Materials 1. PQFN dummy panel, used for the evaluation. 2. Slotetch 21 and H2O2. 3. Petri dishes, graduated cylinders, beakers, and Erlenmeyer flasks. Table 1. Parameters

DOE Leg 1 2 3 4 5 6 7 8 9 10 11 12

Input Parameter Conc S21 Conc H2O2 (ml/L) (ml/L) 100 50 300 5 200 27.5 100 50 300 50 300 5 300 5 100 5 100 5 300 50 100 50 100 5

The panels were weighed prior to the immersion in the solution. The panels were then immersed on the solution in a Petri dish by using the proposed processing time. After immersion, the panels were then washed with DI water to remove the Time (sec) chemicals. Then, they were dried in the oven at 5 approximately 60ºC for 2-3 minutes.

20 12.5 20 20 5 5 5 20 5 5 20

The panels were then weighed again in the analytical balance to obtain its final weight. 3.0 RESULTS AND DISCUSSION Table 3.1 Weights of Panels in their DOE LEG DOE LEG 1 2

This table shows the different concentrations of Slotetch 21 and H2O2 with corresponding processing time. These data was provided by the SAS JMP software. For Slotetch 21, 100-300 ml/L; for H2O2, 50-100 ml/L; the time, 5-20 seconds.

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2.2 Procedure 5

The PQFN 8x8 panel types were prepared by cutting the strips into its four panels. There were a total of 40 panels prepared for the experiment, but only 24 panels is needed, the remaining panels are only for reservation in case the first trials fails. The panels were then numbered from 1 to 40 using a scriber.

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After the calculation of the volumes required for the different concentrations of solution, the chemicals’ volume were then measured using 100, 25 and 10 ml graduated cylinders. The Slotetch 21 was first added to the water in the beaker. The solution is continuously mixed using the hotplate with magnetic stirrer. After the solution has been completely mixed, H2O2 was then added to complete the activation solution Figure 1.1 Figure 1.1 shows the actual PQFN dummy panel-type frame used in the experiment.

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weight 1 (g) 9.57 10.1497 9.8324 9.6099 10.174 10.1791 10.2311 10.1872 9.6991 9.7354 9.8275 9.7684 9.5191 9.5315 9.4778 9.5193 9.5937 9.586 9.5686 9.7732 10.1435 9.5606 10.2127

weight 2 (g) 9.5668 10.146 9.8306 9.608 10.1718 10.174 10.2277 10.1846 9.6948 9.7294 9.8252 9.7652 9.5171 9.5304 9.4769 9.5176 9.5914 9.5838 9.5655 9.7708 10.1399 9.5576 10.2107

and 50ml/L H2O2 with a processing time of 20 seconds. The lowest value came from DOE LEG 8 that has a average weight loss of 0.0013g.

10.1979 10.1949 This table shows the obtained weights of the panels before and after the immersion in the solution. Analytical balance was used to measure the weights.

Table 3.2 Weight loss and Average Weight loss DOE LEG 1

Weight Loss Average (g) Weight Loss 0.0032 0.00345 0.0037 2 0.0018 0.00185 0.0019 3 0.0022 0.00365 0.0051 4 0.0034 0.003 0.0026 5 0.0043 0.00515 0.006 6 0.0023 0.00275 0.0032 7 0.002 0.00155 0.0011 8 0.0009 0.0013 0.0017 9 0.0023 0.00225 0.0022 10 0.0031 0.00275 0.0024 11 0.0036 0.0033 0.003 12 0.002 0.0025 0.003 This table shows the weight loss of each panel by subtracting the new weight from its original weight and then getting the mean of the two weights to obtain the average weight loss.

Figure 3.1 Variability Chart

3.1 Variation in Average Weight Loss The variability chart shown in fig. 3.1 shows the variance between each DOE-LEG. There is a big gap between the two data that has the same/equal parameters. LEG 6 and 7 has the same concentration of S21 (300ml/L) and H2O2 (5ml/L) with equal processing time of 5 seconds. The desired results must have an almost equal average weight loss for the same concentration and time. Instead the data results from the experiment have a difference of 0.0012. This large variation signifies that there is some assignable in the evaluation.

From the data shown in table 3.2, the highest average weight loss was obtained in the DOE LEG 5 of 0.00515g, which has a concentration of 300ml/L of S21 3

This error is caused by immersing two panels at a time in the solution. The ideal procedure is to use only one panel at a time in order for the panel to be fully expose to the solution, because if there are two panels, most likely, there will be some parts of the panel that is not exposed to the solution. Figure 3.2 Normal Distribution

The data obtained from the experiment was found out as normal as shown in figure 3.1. Despite of the error that was found on the variability chart, the data was still within the normal range or anticipated results. This means that the solutions were prepared correctly and the concentrations are followed as expected.

To check if the data is normal, the value for Prob<W must be greater than 0.05. The obtained value was 0.6253 which is above the limit value for Prob>W. Figure 3.4 Prediction Profiler

Figure 3.3

Since the data is normal, it was able to have its prediction profiler. It will show the overall weight loss of the panels you have used in the experiment. In this section you can also verify if the concentration data and processing time is directly proportional to the weight loss. In the profiler, you can change the values of the parameters and it will give you different overall weight loss. 4.0 CONCLUSION In conclusion, based on the results of the experiment, the etching rate of the activation solution is faster when the concentration is higher for both constituents (Slotetch 21 and H2O2).

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5.0 RECOMMENDATIONS It is recommended to use the optimum parameter which will give the higher weight loss but less processing time. 6.0 ACKNOWLEDGEMENT The author would like to express his utmost gratitude to his manager and mentor: Engr. Graciela Delos Santos. She is an effective mentor and teaches her trainee all the necessary information to be a good professional in the near future. The author would also like to thank the people in the plating area: Ate Liza, Kuya Bryan, Ate Dindin, Ate Gloria, Ate Elena, Kuya Ronnie, and Ate Precy for being so kind and helpful to the author on the course of his on-the-job training. 7.0 REFERENCES 1.

Technical Data Sheets of SLOTETCH 20 by Schloettter Galvanotechnik.

8.0 ABOUT THE AUTHOR

9.2 Panels before immersion

Joshua B. Dacles is an OJT trainee in the Plating Department. He is currently a 4th year student taking up Bachelor of Science in Chemical Engineering at Central Philippine University-Iloilo City.

9.0 Appendices 9.1 Constituents of the Activation Solution

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9.3 Panels after immersion in the Activation Solution

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