International Business Machines Corporation

Michael Juergen Kessler

Manfred Schmidt

Joerg Georg Appinger

William F Beausoleil

Chon Cheong Lei

Tak-kwong Ng

Lawrence A Thomas

N James Tomassetti

Jac Anders Burke

Axel W Deegen

A method and system for efficiently coding test pattern for ICs in scan design and build-in linear feedback shift register (LFSR) for pseudo-random pattern generation. In an initialization procedure, a novel LFSR logic model is generated and integrated into the system for test data generation and test vector compression. In a test data generation procedure, test vectors are specified and compressed using the LFSR logic model. Every single one of the test vectors is compressed independently from the others. The result, however, may be presented all at once and subsequently provided to the user or another system for further processing or implementing in an integrated circuit to be tested. According to the present invention a test vector containing 0/1-values for, e.g., up to 500.000 shift registers and having, e.g., about 50 so called care-bits can be compressed to a compact pattern code of the number of care-bits, i.e., 50 bits for the example of 50 care-bits.

Method and system for coding test pattern for scan design

A plurality of pseudo random bit-pattern generators (PRPGs), advantageously linear feedback shift registers (LFSRs), having predetermined lengths and individual different tap locations for providing a respective sequence of pseudorandom bit-patterns. An output from a predetermined respective tap location at each LFSR is fed to a common OR-gate, a selected subset of the LFSRs are initialized with all bit storing locations to '0' in order to generate a respective permanent '0'-bit sequence, and the output of the OR-gate is used for reading the weighted or flat random bit output-pattern thereof. By controlling the number of zero-set LFSRs&#x2014;a subset of the LFSRs&#x2014;the weight of the generated output-pattern can be controlled.

Random pattern weight control by pseudo random bit pattern generator initialization

Chips requiring high temperature reflow for attachment to a module substrate are attached first and then a eutectic water soluble solder paste and/or water soluble flux is dispensed on both the TSOP and the PBGA chip pads instead of using the paste screening techniques. The dispensing is done by injecting solder on the solder sites individually. Characteristics of the solder paste used is that it must be fluid enough to be injected onto the individual sites yet have enough body that it remains in place and does not run from site to site once dispensed. A paste capable of providing such characteristics is one having: a ) a very fine particle size in the range of 400 to 500 mesh and preferably between 400 and 450 mesh; b) a low viscosity (below 500 k centerpoise and preferably between 425 to 375 cps); and c) a solid content of 86% or lower and preferably between 84 and 80%. The chips to be joined to the module using low temperature module joining are then placed on the module substrate surface and then put in an oven for reflow to attach these chips to the surface. After the joining process, the modules are cleaned by spraying deionized water on them to remove any flux or solder residues and the modules are electrically tested to determine if the joining process has resulted in connection with the proper mechanical and electrical characteristics.

Assembly of multi-chip modules using eutectic solders

An arrangement for testing electric samples, such as, circuit components, circuit assemblies, and circuit cards having a plurality of probe contact points. An electromagnetic holding plate is provided on which several testing heads of the same and/or different probe contact point configuration are releasably mounted. The individual testing heads are arranged on the holding plate in accordance with the respective configuration of the sample. Each of the testing heads contains a number of testing tips which are adapted to the configuration of the probe contact points of their associated parts of the sample. The testing heads are connected to a suitable control unit which provides supply voltage and test pulses.

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Herrenberg, Germany

Michael Juergen Kessler