Pickering Interfaces LXI High-density Matrix Modules Selected for Opens and Shorts Testing of Semiconductor Packages
Amkor Technology is one of the world’s largest providers of contract semiconductor assembly and test services. Founded in 1968, Amkor pioneered the outsourcing of IC assembly and test and is now a strategic manufacturing partner for more than 300 of the worlds leading semiconductor companies and electronics OEMs.
Amkor’s Korean division was specifying a new test system — one section of the system was to be used for opens and shorts testing for semiconductor packages. A large matrix was defined for the task — a 3072x4 matrix switch configuration to perform 4-wire measurement, I/V characterization, as well as 2-wire measurement. As it is with many test applications, it needed to be acquired at the lowest price with the highest performance as possible.
After researching their options, Amkor decided to use three Pickering Interfaces LXI high-density matrix modules (model 60-553-008). These LXI matrix modules had the type of EMRs needed to provide the lowest price in the market as well as allow up to 1027 simultaneously closed crosspoints.
Additionally, from the viewpoint of Testmation, the selected test system integrator, this LXI matrix module includes Pickering’s BIRST (Built-In-Relay-Self-Test) function, which made it the preferred choice for easy and quick maintenance support.
Amkor’s New Test System - with up close view of LXI matrices inside tester
Background on Opens and Shorts Testing:
Below is some background on opens and shorts testing, also called structural test and why Pickering’s LXI Matrix Module was the best choice for Amkor’s application.
Opens and shorts testing is the most generally used way for evaluating and verifying a semiconductor package prior to functional test. In addition to the test, it can also be used in failure analysis of the package where I/V characterization tests are implemented.
- For a system configuration for this type of application, one or more SMUs (Source and Measure Units) and one or more
matrix switch modules are essential. The SMU can be either a benchtop or PXI modular depending on the test specification
and the number of test pins of the semiconductor package.
For matrix switch modules, the matrix is used in either a 2-wire (Nx2) or 4-wire measurement (Nx4), depending on the application. If only open and short test is needed, the Nx2 configuration can be used. However, if a low resistance measurement and high precision I/V characterizations are needed in order to eliminate switch and cable path resistances (also called 4-wire or Kelvin measurement) as in Amkor’s requirements, then Nx4 must be selected.
For the Nx4 configuration, one of the following three relay types used in matrix modules was considered—each has advantages and disadvantages.
- Reed Relays
- Fast operate times
- High reliability (hermetically sealed)
- Higher cost & lower power switching capacity
- Electro-Mechanical Relays (EMRs)
- Higher switching capacity & lowest cost
- Slower operate times, shorter life & minimum switching capacity issues
- Solid-State Relays (SSRs)
- Virtually unlimited life & very fast (with no switch bounce)
- Bandwidth, leakage, resistance & voltage limitations
- Custom design – One system’s integrator offered to build the switching matrix from scratch rather than going to a COTS provider. This offering had the advantage of being the lowest cost. However, the matrix required a 2-meter cabinet, making it extremely unwieldy and not a good fit.
- VXI has been recognized as a very reliable form factor especially for military, avionics and aerospace test application, but it is old technology and has lower density of channels. It is mainly implemented for very long-term support of existing applications. As this was a new application and the number of available switching module available in VXI was dwindling, this platform was dismissed as an option.
- PXI or PXI Express is a newer generation form factor and suitable for mixed instrumentation applications in a chassis. If low channel counts of matrix switches are needed with an SMU, it might be a proper solution. However, it is not a good solution if a system needs a large number of channel counts of matrix switches (as in the Amkor system). For instance, if 512-crosspoint of PXI/PXIe modules are selected for 1024x4 configuration, eight modules will be needed, making it a much more expensive solution than the chosen LXI 1024x4 High-density Matrix Switch Module. Additionally, PXI Backplane power supplies limit the maximum number of simultaneously closed crosspoints is 40 or 64 per module, depending on the relay type - that can make the test very difficult to implement.
- LXI is also a new generation form of modular instrumentation that is controlled via Ethernet LAN. An LXI chassis can include various types of instruments or switches depending on the manufacturer. The advantages include a high power backplane chassis that can simultaneously close more crosspoints and any size can be implemented unlike the PXI/PXIe form factor. It was also the smallest solution, allowing a 3072x4 matrix to be created using only three 1U high LXI modules.
Pickering Interfaces was selected as the vendor of choice for several reasons: size, flexibility and competitive pricing. Equally important was the fact that Pickering developed a new configuration of their LXI high-density matrix module for Amkor’s application.
Pickering’s engineers listened to Amkor’s requirements and created the right system for the application. This new configuration is now a standard item in Pickering’s catalog of LXI switching systems.