The Determination of the Technological Maturity of Ultrasonic Welding

Nathan Gibson
TE 589A
North Carolina State University
April 29, 1999

Under the direction of:

Dr. Michael Slocum
Adjunct Assistant Professor
North Carolina State University

Dr. Tim Clapp
North Carolina State University


The maturity of a technological system tends to evolve in a way analogous to that of any biological system. Technological systems go through stages comparable to pregnancy, birth, childhood, adolescence, maturity, and decline.  This evolution is related as a function of time to four primary S-curve descriptors: the number of inventions in the field, the level of those inventions, the performance of the technology, and the profitability of the technology.  Data pertaining to these descriptors can indicate the position of the technology on the main biological S-curve.  From there, it is possible to predict how the technology will continue to evolve.  This can be a valuable tool for those who make important decisions concerning the approach that should be used in the future such as whether to invest further in the technology or to focus on its successor.

Such an analysis of technological maturity will be performed on the field of ultrasonic welding.  The methods for obtaining the data as well as the results (S-curves) and analysis will be presented.  There will also be an examination of the possible future state of the technology and an assessment of likely technological management strategies as a result of the predicted technological evolution.

Ultrasonic Welding Overview

Ultrasonic welding is used for joining materials (thermoplastics or metals) together in a manner that is much quicker and safer than most traditional bonding methods.  High-frequency electrical energy is converted to high-frequency mechanical energy and directed to the materials to be joined, which are secured under pressure.  The mechanical energy, which is a vertical motion exceeding 15,000 cycles per second, is transferred through a horn to the materials under pressure. This generates frictional heat at the interface of the two materials, thus melting the materials together in the desired region, where they solidify to a weld when pressure and vibration cease.  Many factors contribute to a successful weld, but it is imperative to have a correct balance between amplitude of the vibration, time, and pressure.  This technology is widely used in many industries with many different metallic and thermoplastic materials.

Mapping Technological Evolution

The position of a technological system on the biological S-curve can be gauged by determining the position of the current technology on the four descriptor S-curves; the number of inventions, level of inventiveness, profitability, and performance (Fig.1). 

Fig.1.  S-curve descriptors

Data were collected in order to create the three of the four descriptor curves in Fig. 1 for the technology of ultrasonic welding.  

Number of Inventions

Fig. 2  Number of Ultrasonic Welding Inventions From 1976 to 1998.

A patent search was performed to find inventions that pertain to ultrasonic welding (or ultrasonic seaming, bonding, joining, etc.) and the development of the technology both for it and its peripherals.  The data for the number of patents was plotted and a second-order polynomial fit was inserted (Fig.2).  The graph shows a gradual downward trend in the number of inventions over time, with an increasing trend beginning in the early 1990ís.

Level of inventiveness 

The level of inventiveness is determined by analyzing the patents found for their respective inventive level, which ranges from 1 (lowest) to 5 (highest).  The grading criteria are located in the Appendix.  The field of ultrasonic welding began very high in level of inventiveness, because it was a new concept in the field of materials joining.  From there, it had other notable inventions, but over time, the overall level of inventiveness decreased slowly.  Recently, inventions have hovered in the 1 and 2 level range, with most being simple additions to the technology or adaptations that were made to accommodate use in different areas.  The inventive level data were determined by analysis of the above patents, and their plot is shown in Fig. 3 with a second-order polynomial fit.

Fig.3  Inventive Level of Ultrasonic Welding Patents, 1950-1998


To determine the profitability of ultrasonic welding over time, given a lack of adequate financial data, an assumption was used: the number of inventions that used ultrasonic welding (not the same ones used in the Number of Patents curve, which improved ultrasonic welding technology) is proportional to the profitability of the technology.  These data are shown in Fig.4 with a second order polynomial fit insertion.  The profitability increased significantly in the early 1990ís to present.

Fig.4.  Profitability (# of Patents Using) of Ultrasonic Welding Technology, 1976-1998.

Data Analysis

The next step in determining the position of ultrasonic welding on the biological S-curve is comparing the experimental descriptor plots to the predicted descriptor plots.

Number of Inventions

There are two places on the predicted plot that could correspond to the experimental data.  Further analysis by correlation will show that the first is the correct region. 

Level of Inventiveness

There are two places on the predicted plot that could correspond to the experimental data.  However, it is likely that the second region corresponds because the first region begins to slope back up at a level that the experimental data is already below.


In this comparison, there is a clear correlation between the highlighted regions on the experimental curve and the predicted curve.

From the analysis of the three experimental descriptor curves, it can be seen that there is a clear trend revealing the similar locations of ultrasonic welding technology on three of the four descriptor curves, and the fourth can be extrapolated.

These data correspond to the following position on the biological S-curve:

This curve along with the descriptor curves show that ultrasonic welding is about to enter or is in the beginning of the maturity stage.

Future State of Ultrasonic Welding

This field can look forward to a strong maturity stage.  Recently, much demand has arisen for this technology and it is very likely that this trend will continue.  Ultrasonic welding is a versatile field with numerous possible applications.  Businesses would be wise to direct resources toward this field to propel it into maturity and reap the benefits.  Eventually, like all technological systems, ultrasonic welding will experience a decline as it exits the maturity stage.  At that point, another breakthrough is likely to occur in the field of materials joining and a new biological S-curve will begin.  From this analysis, however, donít expect this to occur too soon.