Patents by Inventor Yoshihiro Maesaki

Yoshihiro Maesaki has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20090287362
    Abstract: A monitored burn-in test method includes: subjecting an element set, including elements, to a writing process for writing data into each of the elements, the elements requiring a refresh process; subjecting the element set to the refresh process after the writing process; and interrupting the refresh process for a selected one or ones of the elements, when instructions for readout of data are supplied to the selected one or ones during the refresh process, and subjecting the selected one or ones to a readout process in accordance with the instructions.
    Type: Application
    Filed: July 31, 2009
    Publication date: November 19, 2009
    Applicant: FUJITSU LIMITED
    Inventors: Yoshihiro MAESAKI, Hiroshi TESHIGAWARA, Yukihiko KODAIRA, Naoe SEKIGUCHI
  • Patent number: 7023229
    Abstract: An infrared sensor is provided in a burn-in chamber. The surface temperatures of two or more semiconductor devices are measured by the sensor. A control unit calculates the internal temperatures of the semiconductor devices based on the thermal resistance values of the semiconductor device packages and controls the temperature inside the burn-in chamber so that the average of the internal temperatures is brought to a desired temperature by using a temperature controller. Further, an acceleration coefficient is obtained based on the internal temperatures, a burn-in time is determined based on the acceleration coefficient and a preliminarily given accelerated period, and a burn-in acceleration test is conducted. Moreover, when a defective semiconductor is found, the defective portion of the defective semiconductor device is specified based on the surface temperature distribution of the semiconductor device measured by the infrared sensor.
    Type: Grant
    Filed: June 18, 2004
    Date of Patent: April 4, 2006
    Assignee: Fujitsu Limited
    Inventors: Yoshihiro Maesaki, Hiroshi Teshigawara
  • Patent number: 7023228
    Abstract: In a dynamic burn-in apparatus wherein a signal output from a signal generator is input to a semiconductor device to be tested in the burn-in tank, a converter is arranged at the output of the signal generator. The converter increases, by N times, the frequency of the signal output from a signal generator. The signal having the increased frequency and output from the converter, is input to the semiconductor device to be tested in the burn-in tank when the burn-in is operated at high-speed. The frequency of the signal is converted to the higher frequency, and the signal having the higher frequency is provided to the semiconductor device. As the result, the burn-in can be done in a shorter time for a high-speed sophisticated semiconductor device.
    Type: Grant
    Filed: March 10, 2004
    Date of Patent: April 4, 2006
    Assignee: Fujitsu Limited
    Inventors: Yoshihiro Maesaki, Hiroshi Teshigawara
  • Patent number: 6967495
    Abstract: In an adapter card, is a clock signal converting circuit converts a clock signal, output from a signal generator of a burn-in apparatus, from a lower—to a higher-frequency clock signal. Plural delay circuits synchronize each burn-in signal output from the signal generator with the clock signal. A connector of an adapter is connected between a burn-in card and a connector mounted in a burn-in chamber, to burn in a semiconductor device mounted on the burn-in card. The output of the signal generator is fed into the adapter card via its connector, and the output of the adapter card is supplied to the semiconductor device mounted on the burn-in card to burn in the semiconductor device.
    Type: Grant
    Filed: September 21, 2004
    Date of Patent: November 22, 2005
    Assignee: Fujitsu Limited
    Inventors: Yoshihiro Maesaki, Hiroshi Teshigawara, Sadao Ishihara, Yukio Tabuchi
  • Publication number: 20050099197
    Abstract: An adapter card is provided which comprises: a clock signal converting circuit (1) which converts a clock signal, output from a signal generator contained in a burn-in apparatus, into a higher-frequency clock signal; and a plurality of delay circuits (2) for causing each burn-in signal output from the signal generator to synchronize with the clock signal, wherein a connector (4) of the adapter (10) is connected between a burn-in card and a connector mounted in a burn-in chamber, to burn in a semiconductor device mounted on the burn-in card. Alternatively, the input connector (4) of the adapter card (10) is connected to a connector mounted, for example, on the rear side of a back board of the burn-in apparatus; then, the output of the signal generator is fed into the adapter card via its connector (4), and the output of the adapter card (10) is supplied to the semiconductor device mounted on the burn-in card to burn in the semiconductor device.
    Type: Application
    Filed: September 21, 2004
    Publication date: May 12, 2005
    Inventors: Yoshihiro Maesaki, Hiroshi Teshigawara, Sadao Ishihara, Yukio Tabuchi
  • Publication number: 20040232933
    Abstract: An infrared sensor (1b) is provided in a burn-in chamber (1). The surface temperatures of two or more semiconductor devices are measured by the sensor (1b). A control unit (12) calculates the internal temperatures of the semiconductor devices based on the thermal resistance values of the semiconductor device packages and controls the temperature inside the burn-in chamber (1) so that the average of the internal temperatures is brought to a desired temperature by using a temperature controller (10). Further, an acceleration coefficient is obtained based on the internal temperatures, a burn-in time is determined based on the acceleration coefficient and a preliminarily given accelerated period, and a burn-in acceleration test is conducted. Moreover, when a defective semiconductor is found, the defective portion of the defective semiconductor device is specified based on the surface temperature distribution of the semiconductor device measured by the infrared sensor (1b).
    Type: Application
    Filed: June 18, 2004
    Publication date: November 25, 2004
    Applicant: FUJITSU LIMITED
    Inventors: Yoshihiro Maesaki, Hiroshi Teshigawara
  • Publication number: 20040169524
    Abstract: In a dynamic burn-in apparatus wherein a signal output from a signal generator is input to a semiconductor device to be tested in the burn-in tank, a converter is arranged at the output of the signal generator. The converter increases, by N times, the frequency of the signal output from a signal generator. The signal having the increased frequency and output from the converter, is input to the semiconductor device to be tested in the burn-in tank when the burn-in is operated at high-speed. The frequency of the signal is converted to the higher frequency, and the signal having the higher frequency is provided to the semiconductor device. As the result, the burn-in can be done in a shorter time for a high-speed sophisticated semiconductor device.
    Type: Application
    Filed: March 10, 2004
    Publication date: September 2, 2004
    Applicant: FUJITSU LIMITED
    Inventors: Yoshihiro Maesaki, Hiroshi Teshigawara
  • Patent number: 6161117
    Abstract: A waveform pattern file storage section is used for specifying a waveform pattern of a control signal, and storing waveform pattern bit strings formed from bits each of which specifies 1 logical state (an NRZ waveform). A waveform input section reads out the waveform pattern bit string. A waveform recognition section recognizes 1 cycle waveform pattern consisting of 3 consecutive bits in the waveform pattern bit string that has been read out. As a result, if an RZ waveform pattern has been recognized, an RZ waveform is generated with respect to the RZ waveform section; if an NRZ waveform pattern is recognized, an NRZ waveform is generated with respect to the NRZ waveform section.
    Type: Grant
    Filed: July 9, 1998
    Date of Patent: December 12, 2000
    Assignee: Fujitsu Limited
    Inventors: Yoshihiro Maesaki, Hiroshi Teshigawara