Realization of Ultra-Wideband, High-Resolution TDR for Chip-Carrier Packages

Abstract

In this paper, a state of the art TDR with a rise time of 9ps was employed in the characterization of multi-layer ball-grid array (BGA) or land-grid array (LGA) packages. The hardware used for 9ps rising time was the Picosecond Pulse Lab’s 4022 Source Enhancement Module that reduces a standard TDR rise time of 35–40ps to 9ps. The high-resolution TDR can clearly indicates a root cause of a multi-layer package signal integrity problem (impedance mismatching) in vertical transitions consisting of vias and planes which cannot be observed with a conventional TDR. In addition, due to its high-resolution, it was observed that the size of characteristic impedance testing transmission lines can be significantly scaled down. For example, a minimum length of 15–20 mm long transmission lines with a standard TDR can be reduced down to 3–4mm long for 9ps TDR. Using the TDR waveforms, reflection loss S11 (dB) was computed using direct convolution method and short-open-load (SOL) calibration method. The resulting (TDR generated) S11 agrees excellently with direct vector network analyzer (VNA) measurements up to 50 GHz which is the highest frequency available with Agilent 8364A.

Space Domain Reflectometry for opens detection location in microbumps

“…TDR uses a pulse generator and a high-speed oscilloscope to record in real time the reflection of a microwave signal by the open barrier [3,4]. TDR can at best provide resolution of about 1 mm making it most suitable for the high-pincount packages, such as quad flat package and ball grid array, but less convenient for smaller packages (less than 1 cm 2 ) [5], and more or less impossible to use on the latest development for connecting dies in wafer leveling packaging using microbumps.…”

Modular and deformable touch-sensitive surfaces based on time domain reflectometry

“…Such changes in characteristic impedance are caused by changes in the resistance, the inductance, or the capacitance of the wire pair. While initially developed to test cables, this has allowed TDR to also be used to measure soil humidity and detect soil movement [19], to locate microscopic defects in integrated circuits [11], and to recognize strains and fractures in buildings and bridges [31]. Engineers distinguish three termination types of TDR [33].…”