Abstract

This article discusses a patented 1-Wire^® Contact Package solution for electromechanical contact applications. It discusses traditional packaging solutions and demonstrates the superiority of the 1-Wire Contact Package solution. The article recommends ways to attach the solution to an accessory or consumable. Mechanical specification and reliability analysis are provided.

Introduction

Adding electronic functionality to traditionally nonelectronic peripherals and consumables is becoming a common system requirement. Typical system-driven requirements include storage of calibration data or manufacturing information, or OEM authentication of the peripheral, accessory, or consumable. Besides selecting the proper memory and security functionality for these electronic requirements, one must add an electrical connection between the host system and peripheral.

The patented 1-Wire Contact Package (formerly known as the SFN package) is specially designed for electromechanical contact environments. Typical applications of this package include object identification/authentication and automatic calibration using data stored in the memory chip. Authentication ensures reliability and quality, which otherwise could be undermined by low quality cloned products. The package is ideally suited for applications such as printer consumables, medical sensors, and reagent bottles.

The 1-Wire Contact Package is designed for contact applications only and cannot be soldered.

The 1-Wire Contact Package

The 1-Wire Contact Package is a superior solution to the problem of incorporating electromechanical contacts into an application. The integration of the IC and contact pads into a single package reduces the footprint and increases mechanical reliability. Figure 1 demonstrates the basic design of the 1-Wire Contact Package.

Package Characteristics

The 1-Wire Contact Package is available in three sizes (Table 1). Figure 2 shows the relative dimensions of the three packages.

The lead frame is made of CDA194 copper alloy. The pads are plated with 1.02 µm nickel, 0.02 µm palladium, and a 0.005 µm gold finish. The mold compound is Sumitomo^® G600 or G770 or a similar product. For additional mechanical data, refer to the package outline drawing listed in Table 1.

Attachment Methods

The preferred method of attachment is a mechanical clip. Because every application is unique, end customers must design mechanical clips compatible with their end product. Figure 3 shows the theoretical design of one custom retaining clip. Figure 4 shows a commercial application of a mechanical clip integrated into an object to be authenticated. The package can also be injection-molded into a plastic object as described in “Injection Molding an IC Into a Connector or Consumable Item.”

Feasible alternatives to clips are double-coated foam tapes and double-coated tapes. The 3M^® Company manufactures pressure-sensitive adhesives designed to operate in a wide variety of environments.

Choosing a Connector

The 1-Wire Contact Package was purposefully designed to be compatible with low cost, industry-standard connectors. Two commercial connectors are shown here, as well as the approximate dimensions for a custom connector.

Example 1: Bourns 70AB/Male—Modular Contact

Figure 5 shows the approximate points of contact for this 1.27 mm pitch connector. This contact is suitable for the 6.5 mm × 3.5 mm and 6.0 mm × 6.0 mm packages and performs a wiping of the contact as it is inserted.

Example 2: Mill-Max Series 811/813 Spring-Loaded Contact

Figure 6 shows the approximate points of contact for this 2.54 mm pitch piston connector. The contact points of this connector make it suitable for all three packages.

Example 3: Guidance for Custom Contact Design

Figure 8 provides guidance for the construction of a through-mounted, custom spring contact. This design has the advantage of the package sliding against the spring and wiping as it is inserted.

Reliability Testing

Qualification tests are performed on the packages to ensure the package meets the same reliability requirements as conventional IC packages for the industrial temperature range from -40°C to +85°C.

A qualification test report for the 1-Wire Contact Package is available on our website.

Conclusion

The 1-Wire Contact Package is a cost-effective alternative to mounting a PCB module with a chip onto the peripheral object to be identified. Attachment options include clip-style retainers integrated into the nonelectric object and double-sided adhesive tape. Inexpensive connectors like those for mobile battery applications can provide the electrical connection. The package’s reliability matches that of conventional IC packages.

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