AIAA 99-2555, Proceedings of 35th Joint Propulsion Conference, Los Angeles, CA, June 1999.

A Low Cost, Reliable, Hermetically Sealed, Chip Slapper Detonator Suitable for Various Aerospace Applications

Barry T. Neyer, Senior Member AIAA
John T. Adams
James C. Edwards
Terry L. Stoutenborough
Robert J. Tomasoski
EG&G Optoelectronics
Miamisburg, OH 45342-0529
937 865-5586

Current Address
Barry T. Neyer
Excelitas Technologies
1100 Vanguard Blvd
Miamisburg, OH 45342
(937) 865-5586
(937) 865-5170 (Fax)
Barry.Neyer@Excelitas.com

Abstract

EG&G Optoelectronics has developed a low cost, reliable, hermetically sealed, chip slapper detonator for the US Armys anti-tank weapons platforms. This detonator is also qualified and under consideration for several US Navy and Air Force programs. This detonator would also be suitable for various aerospace applications.

The design goal for this detonator was to develop a detonator that was as cost efficient as possible and yet was extremely reliable. The detonator was also designed to survive the most severe environments. The detonator has been subjected to a wide variety of electrical, mechanical, and thermal conditioning and has performed successfully afterwards.

The detonators were designed to be a commercial off-the-shelf detonator that would be suitable for almost any application. It uses an insensitive explosive compound, HNS-IV, to eliminate the hazards inherent in the more common hot-wire detonators.

All of the detonator components, including the explosive, were manufactured from readily available starting materials. The HNS IV explosive meets EG&G specifications based on the military specifications. The detonator, packaged in a TO-5 can, comes in three configurations: a "plug in" detonator, a surface mount design, and a detonator that can be attached to a flexible cable. This paper will present the detonator design and test results. The full test report is contained in an EG&G Technical Report.

Technical Papers of Dr. Barry T. Neyer

Introduction

EG&G Optoelectronics has a long history of producing detonators for the Aerospace, DOD, and DOE community. In the past, each detonator was designed for a specific program, or possibly a family of similar programs. The main reason for the specific design was that each program had unique environmental requirements, size and weight constraints, and input and output requirements. It was necessary to produce many unique detonators because no one program would pay for the development and qualification testing of a universal detonator that would be suitable for many applications.

The general operating environment has now changed. Reduced government budgets have put pressure on all suppliers of ordnance to do more with less. The qualification of a single component for use on multiple programs would result in reduced long-term cost for each of the programs that use it. Industry has shown that there are tremendous cost advantages to using commercially available constituent components in a design to minimize production costs.

The motivation to produce this detonator was the award to EG&G Optoelectronics by Lockheed Martin of a contract to produce the Firing Module (FM) for the Common Electronic Safe, Arm, and Fire (C-ESAF). The C-ESAF was designed and qualified for use on the US Army family of anti-tank weapon systems, including the Hellfire, Javelin, and Longbow. The contract called for production on the order of one thousand FMs and detonators per month. One of the main features of the competition was cost. Cost of the system was the main driver.

EG&G had to produce a detonator that would be cost effective, while being able to meet the requirements for multiple programs. Furthermore, the detonator had to be developed using EG&G money.

Because it was internally funded, EG&G made the decision to try to develop a truly universal detonator, suitable not just for the US Army program, but rather a detonator that would be suitable for almost any program requirement.

The design requirements were to make a detonator that was low cost, safe from inadvertent functioning, environmentally robust, and hermetically sealed. To ensure that the detonator could be manufactured without modification for many years, it should use EG&G Optoelectronics manufacturing for all of the critical items, with the remaining components being commodity items available from a number of vendors. The detonator should require relatively low energy for functioning and should provide output sufficient to initiate almost any next stage device. EG&G believes that the Blue ChipTM Detonator fits the bill.

Component Description

The EG&G Optoelectronics Blue ChipTM Detonator is a "chip slapper" detonator packaged in a TO-5 transistor style assembly. A schematic diagram of the device in one configuration is shown in Figure 1. The device consists of an exploding foil "chip" slapper mounted to an industry standard TO-5 header. The figure shows a 2-pin header, but other configurations are also made for different applications.

Figure 1: Blue ChipTM Detonator
(4 X Actual Size,
2 pin through hole design)

The explosive used in the design is HNS-IV manufactured by EG&G Optoelectronics to an internal specification based on the outdated MIL-E-82903. This explosive is on the MIL-STD 1316D list of explosives approved for use in inline systems. The HNS-IV explosive was chosen for this design based on the long design history and its high temperature stability. The HNS-IV is pressed into a stainless steel sleeve to ensure uniform detonation propagation and consistent flying plate performance.

The chip slapper is manufactured by EG&G Optoelectronics. A schematic diagram is shown in Figure 2. Using conventional micro-electronic manufacturing techniques, metal is selectively etched away from a ceramic substrate. A layer of polyimide material is spun onto the surface of the wafer. The wafers are then cut and the individual chips mounted onto TO-5 headers.

Figure 2: Chip Slapper

The chip slapper is connected to the header pins via a barrel/connector. The barrel/connector provides a low resistance and inductance connection to the pins. At the same time, it also provides the required standoff between the chip slapper and the explosive subassembly.

The headers are TO-5 type transistor headers. The header is composed of the industry standard Kovar and sealing glass. The header is then plated with a nickel strike and a flash of gold. An industry standard 10 mil thick Nickel TO-5 can is laser welded onto the header subassembly to complete the detonator. Figure 3 shows several configurations of the detonator.

Figure 3: Various Configurations of Blue ChipTM Detonators

EG&G Optoelectronics has several patents pending on some of the unique design features of the Blue ChipTM Detonator.

Firing System Requirements

The Blue ChipTM Detonator is designed to be fired with a Capacitor Discharge Unit (CDU) fireset with a capacitor in the range of 0.05 to 0.3 F. The CDU supplies a rapidly rising current pulse on the order of several thousand amps to the detonator to cause it to function.

Because the detonator will not function without such a quickly rising high current pulse, it is not as susceptible to inadvertent firings as a hot wire detonator would be.

Qualification Tests

The qualification test plan for the Blue ChipTM Detonator was designed to ensure that the detonator would meet the requirements of most Aerospace, Commercial, DOD, and DOE systems. The qualification test matrix, shown in Table 1, was adapted from the MIL-STD-331 proposed test G1 specification. The only deviation from this standard was to add the requirement that the devices remain hermetic and have unchanged resistance after experiencing the various environments.

Table 1: Blue ChipTM Detonator Qualification Matrix

Requirement

A

B

C

D

E

F

G

H

I

J

K

L

M

Total

Number

30

30

30

20

20

50

50

50

40

40

40

20

20

440

Individual Unit Acceptance

X

X

X

X

X

X

X

X

X

X

X

X

X

440

Threshold Ambient

X

 

 

 

 

 

 

 

 

 

 

 

 

30

Threshold Hot, +107 C

 

X

 

 

 

 

 

 

 

 

 

 

 

30

Threshold Cold, -62 C

 

 

X

 

 

 

 

 

 

 

 

 

 

30

Max No Damage Current

 

 

 

X

 

 

 

 

 

 

 

 

 

20

No Damage Stimuli

 

 

 

 

X

 

 

 

 

 

 

 

 

20

Visual Inspection

 

 

 

 

X

 

 

 

 

 

 

 

 

20

Thermal Shock

 

 

 

 

 

X

X

X

 

 

 

 

 

150

2 meter drop

 

 

 

 

 

X

X

X

 

 

 

 

 

150

Electro Static Discharge

 

 

 

 

 

X

X

X

 

 

 

 

 

150

Vibration

 

 

 

 

 

X

X

X

 

 

 

 

 

150

Shock

 

 

 

 

 

X

X

X

 

 

 

 

 

150

Thermal Shock/Humidity

 

 

 

 

 

 

 

 

 

 

 

 

X

20

Leakage

 

 

 

 

 

X

X

X

 

 

 

 

 

150

Resistance

 

 

 

 

 

X

X

X

 

 

 

 

 

150

No Damage Stimuli Hot

 

 

 

 

 

 

X

 

 

 

 

 

 

50

High Temperature Aging

 

 

 

 

 

 

 

 

X

X

X

 

 

120

All Fire Ambient

 

 

 

 

 

X

 

 

X

 

 

 

 

90

All Fire Hot, +107 C

 

 

 

 

 

 

 

X

 

X

 

 

 

90

All Fire Cold, -62 C

 

 

 

 

 

 

X

 

 

 

X

 

X

110

High Voltage Fire

 

 

 

 

 

 

 

 

 

 

 

X

 

20

Individual Unit Acceptance Tests

Each detonator is screened as part of the normal manufacturing process to ensure that it meets several standards. The detonators are checked for leak rate, resistance, dielectric withstanding, and general workmanship. During the initial qualification production, a significant fraction of the detonators had an unacceptable leak rate. The cause was traced to a leaky header. The header used to qualify the design had thick pins, with a limited amount of glass around the pins. Approximately one third of these leaked. Due to time constraints, the leaky headers were used in the qualification test matrix. The other Blue ChipTM Detonator designs with different headers have not had any of these leakage problems.

Recent production of the various detonator designs has established an Individual Unit Acceptance Test pass rate of over 99%.

Threshold Tests

These tests were conducted to determine the amount of energy that was required to reliably initiate the detonator. The same test was also used to determine the no-fire level for the detonator. A Neyer D-Optimal threshold test was performed on three groups of detonators. One group was tested at normal laboratory conditions, a second at a temperature of at least 107 C, and a third at or below -62 C. The temperature conditioned detonators were held at the required temperatures for at least two hours before the start of testing. All detonators were tested within 5 minutes from the time they were removed from the thermal chamber. In a few instances, the detonator could not be fired within the 5-minute window. In such cases, it was returned to the chamber, where it remained for at least 4 times the duration that it was exposed outside the chamber before it was tested.

Table 2: Threshold Test Results

Temp

Mean

Std Dev

All Fire

No-Fire

Hot (+107 C)

1196

22

1380

993

Ambient

1226

11

1343

1094

Cold (-62 C)

1300

30

1602

969

All-Fire and No-Fire levels have 95% confidence

The results of the test are shown in Table 2. The results of the tests show that the detonators are extremely consistent. As expected, the threshold is slightly higher for colder temperatures than it is for hotter temperatures. The standard deviation is different for the various temperatures, but we believe that this variation is due to the limited sample size for the tests. Figure 4 shows the analysis of the results of another threshold test using a fireset with a larger capacitor. In this case the mean is 785 and the standard deviation is 14 volts.

Figure 4: Probability of Detonation

A good measure of the consistency of a detonator is the ratio of the standard deviation to the mean. The Blue ChipTM Detonator has a ratio of approximately 2% or less. This small ratio ensures that the Blue ChipTM Detonator will have consistent performance.

Maximum No Damage Current

The Maximum No Damage Current (MNDC) test established the amount of direct current that could be applied to the detonator without causing any damage to the device. Development testing established that the Blue ChipTM Detonator heats up before the bridge opens. Thus, this test also established the Maximum No Fire Current (MNFC). Detonators in this group were subjected to a three minute constant current, with the amplitude chosen by the Neyer D-Optimal sensitivity test procedure. After the current was applied, the resistance of the detonator was measured. If it showed any resistance, the detonator was then tested at the All-Fire level. The operator recorded a success if the detonator functioned, and a failure if the detonator failed or if the resistance measurement showed that the bridge was open. The sensitivity test program determined the next current level. Because increasing current levels will degrade the detonator, the program calculated the next level using an inverted response. The test was conducted using a logarithmic response assumption.

The data was analyzed according to the Likelihood Ratio Test method. Both a logarithmic and a linear response were used to analyze the data. Both produced similar results; it was not possible to determine the probability function from the limited sample size. The MNDC was determined using the inverse log response.

The MNDC level is defined as the computed 0.005 probability level at 95% confidence. The MNDC determined from the test is 4.3 amps. This large value for the MNDC indicates that the C-ESAF Detonator is insensitive to stray currents.

The detonators were also subjected to a constant current at 45% of the MNDC level established for the detonators (2 Amps) for three minutes. After being subjected to the constant current, the detonators also were subjected to a pulse from a 0.1 F capacitor charged to 75 volts. Five detonators were dissected and the explosive surface and slapper exposed.

Visual inspection of the header subassembly and explosive showed that there was no visibly observed change to either item. The constituent parts of the detonator looked the same as when they were first manufactured. These series of tests showed that not only is the detonator safe with stray currents, but that it will also remain undamaged.

Thermal, Electrical, and Mechanical Environments

These tests were conducted to ensure that the detonators would function properly after being subjected to various environments. No detonator functioned as a result of these tests, and no detonator was damaged, except for the dents produced by the 2-meter drop test. After experiencing the environments, the leak rate and resistance of the detonators were measured. These values were essentially the same as the values recorded upon initial production. Thus the series of environmental tests had essentially no effect on the detonator.

Thermal Shock

The specified detonators were subjected to thermal shock between temperatures of -46 C and +71 C. The detonators were subjected to a total of 35 cycles, beginning with the cold temperature. The detonators were moved between thermal chambers in less than 1 minute, and were subjected to a dwell time of at least 20 minutes at each temperature extreme.

Two meter drop

The detonators were dropped in a random orientation from a height of two meters onto a two-inch thick steel plate. Most of the detonators exhibited a dent in one location, presumably the location of impact. The orientation of these dents was randomly distributed over the surface of the detonator, indicating that the impact orientations were randomly distributed.

Electro Static Discharge

The tester supplied a pulse from a 500 pF 5% capacitor charged to 25KV 500 V to the detonator. One pulse was delivered between the pins-in-common and the case. A second pulse was delivered pin-to-pin through a 5 KW resistor.

Vibration Testing

The random vibration spectrum for this test was the envelope of the vibration spectrum for the BAT, Hellfire, Javelin, and Longbow programs. The vibration test was conducted at ambient temperature for Group F, -46 C for group G, and +71 C for Group H. The detonators were allowed to stabilize for a minimum of one hour at the required temperature before the vibration started. The vibration was applied for three hours to each axis of the components according to the random transportation vibration spectra shown in Figure 5. In addition, the vibration was applied for three and one half minutes to each axis of the components according to the random flight vibration spectra shown in Figure 5. (This later requirement is for the BAT program.)

Figure 5: C-ESAF Detonator Vibration Spectrum

Two Group G detonators of the original design failed subsequent functional testing. The cause of the failure was determined and an additional 50 detonators were subjected to the same test sequence, along with 40 additional detonators for other groups.

Shock Testing

The detonators were subjected to a half sine pulse, with amplitude of 2000 gs for 0.5 ms. The test took place on a drop test apparatus. The shock was applied at least three times in each direction along three perpendicular axes for a total of 18 shocks. All tests were conducted at ambient temperatures.

Thermal and Humidity Shock

The purpose of this test is to determine the ability of the detonator to function properly after being subjected to the thermal shock and humidity environment. The temperature-shock / humidity / altitude cycle consists of quick transitions between the temperatures of 65 F, ambient, and +161 F. The humidity is kept at 95% RH at the high temperature, and 50% at the middle temperature. The atmospheric pressure is 0.65 PSI at the cold temperatures.

No Damage Stimuli (Hot)

This test was conducted to ensure that the detonators would not be damaged by constant current applied to detonators that are hot. Constant current of 2 Amps (45% of the MNDC level established for the detonators) was applied to the detonators for three minutes. After being subjected to the constant current, the detonators also were subjected to a pulse from a 0.1 F capacitor charged to 75 volts. These detonators were subsequently test fired.

High Temperature Aging

This test was conducted to ensure that the detonators would function properly after being subjected to high temperature for an extended length of time. The high temperature was used to simulate aging of a much longer duration at lower temperatures. The detonators were subjected to 28 days at a temperature of at least +71 C.

Subsequent destructive testing showed that the high temperature aging did not damage the detonators.

All-Fire Tests

After experiencing the various environments, the detonators were tested with a firing system charged to 2400 volts. Seven groups of detonators were tested according to the matrix in Table 1. An additional group was tested at an over voltage of 3000 Volts. The temperature for hot firing was a few degrees above +107 C, while the cold temperature was a few degrees below -62 C.

 

Figure 6: Dent Depths as a function of Charge Voltage

All detonators produced dents in excess of the requirements. The minimum dent at ambient temperatures was 17.2 mils and the minimum at cold temperatures was 14.7. Figure 6 shows a chart of the dent depths of all the detonators in the qualification lot. (Some of the data points are shifted left or right to separate the figures on the chart. The variation in the measurements is due to operator variation and the inherent variation in dent block measurements.)

Summary

EG&G Optoelectronics has produced a general-purpose detonator. This detonator is safe to use, will function in a wide range of adverse environments, functions with a well-characterized electrical input pulse, and delivers a well-defined output detonation pulse. This detonator can be used for a wide variety of aerospace, commercial, and military systems. Because it is already in production in large quantities for military systems, the cost is much less than a traditional aerospace component, while the reliability remains high.

References

MIL-STD-331B, "Fuze and Fuze Components, Environmental and Performance Tests for."

Barry T. Neyer (1999c) "C-ESAF Detonator Qualification Test Report," Technical Report RP1013, EG&G Optoelectronics, Miamisburg, OH.

Barry T. Neyer (1994) "A D-Optimality-Based Sensitivity Test," Technometrics, 36, 61-70.

Barry T. Neyer (1992) "An Analysis of Sensitivity Tests," Technical Report MLM-3736, EG&G Mound Applied Technologies, Miamisburg, Ohio.