Dynamic magnetic information storage or retrieval – Fluid bearing head support – Disk record
Reexamination Certificate
1998-12-18
2001-07-31
Cao, Allen T. (Department: 2754)
Dynamic magnetic information storage or retrieval
Fluid bearing head support
Disk record
Reexamination Certificate
active
06268980
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a magnetic head apparatus which includes a slider with at least one thin-film magnetic head element, a resilient suspension for supporting the slider and a head IC chip.
DESCRIPTION OF THE RELATED ART
In such magnetic head apparatus, the thin-film magnetic head element for writing magnetic information into and/or reading magnetic information from a magnetic recording medium such as a magnetic disk is in general formed on the slider flying in operation above the magnetic recording medium. The slider is supported by the suspension made of a resilient thin metal plate extended from one end of a movable arm of a magnetic disk drive unit.
The head IC chip is used for amplifying writing current to the magnetic head element, for amplifying reading current from the head element and for controlling the writing and reading operations of the head element. The head IC chip had been mounted on the movable arm located in a rearward position of the suspension or on a flexible printed cable (FPC) at a rearward position of the suspension. However, if the IC chip is mounted on the movable arm or on the FPC, lead lines for electrically connecting the magnetic head element with the IC chip become long causing noises to be easily generated. Also, the long lead lines provide some delay in rising and falling times of pulse signals due to parasitic capacitance and inductance of these lead lines causing the high rate transfer of data to make difficult.
In order to suppress the generation of noises from the lead lines, Japanese patent unexamined publications nos. 53(1978)-69623, 55(1980)-150130 and 3(1991)-108120 propose a magnetic head apparatus wherein the length of the lead lines is shortened by mounting the head IC chip on the slider or on the suspension.
However, if the IC chip is mounted on the slider or on the suspension, the IC chip itself is heated to a high temperature due to the writing current flowing through the IC chip during recording operation. This causes reliability of the head IC chip to lower. Therefore, how dissipate the generated heat from the head IC chip becomes very important.
The head IC chip is in general connected to pads formed on the suspension by flip chip bonding and C.T.E. (Coefficient of Thermal Expansion) of the IC chip and of the suspension differ with each other. Thus, if the IC chip is heated to the high temperature, the stress that is generated due to C.T.E. difference will not be sufficiently absorbed at the soldered bonding portion causing the remaining stress to directly apply to the head IC chip.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a magnetic head apparatus, whereby stress generated due to increase in temperature of a head IC chip can be prevented from being applied to the head IC chip itself.
According to the present invention, a magnetic head apparatus includes a slider with at least one magnetic head element, a suspension having one end portion, one surface and connection pads formed on the one surface, for supporting the slider at the one end portion, a head IC chip flip chip bonded on the connection pads, and an overcoat layer formed on the one surface of the suspension to cover at least a part of each of the connection pads, the overcoat layer with anti-running structures for controlling flow of solder while the IC chip is flip chip bonded.
Since the overcoat layer with anti-running structures such as openings is formed on the suspension to cover a part of each of the connection pads, flow of the solder during flip chip bonding is controlled by the openings so as to prevent the solder from spreading out. Thus, the height and the shape of soldered bonding portions can be correctly controlled. In addition, since the overcoat layer with the openings is formed on the suspension to cover a part of each of the connection pads, the head IC chip disposed on the openings on the connection pads during the flip chip bonding is self-aligned due to the surface tension of the solder in liquid state. Namely, when the head IC chip is bonding, the surface tension of the solder in liquid state moves the head IC chip to the correct position so as to align the pads formed on the bottom of the head IC chip with the openings on the connection pads. Also, since the overcoat layer is formed on the suspension to cover a part of each of the connection pads, no shunt or no short-circuit problem of the connection pads on the suspension due to incorrect positioning of the pads of the head IC chip will occur.
As the height and the shape of soldered bonding portions are correctly controlled, the stress which is generated under high or low temperature due to C.T.E. difference between the head IC chip and the suspension can be sufficiently absorbed at the soldered bonding portions so as to prevent the stress to directly apply to the head IC chip. Also, since the height of the soldered bonding portions is correctly controlled, problems that the IC chip is mounted on the suspension at an angle and that the edge of the inclined head IC chip accidentally contacts with the conductors on the suspension can be prevented from occurring. Thus, correct and stable mounting of the head IC chip can be expected, and furthermore reliability for bonding by the soldered bonding portions extremely increases.
In addition, since outflow of solder from the bonding portions during the flip chip bonding is suppressed to ensure a sufficient height of the soldered bonding portions, a space is provided between the suspension and the head IC chip. Therefore, underfill with good heat conductivity (filler material with good heat conductivity) can be easily injected into the space so that heat generated from the IC chip can be easily dissipated through the underfill into the suspension to extremely improve heat radiation characteristics.
It is preferred that each of the anti-running structures of the overcoat layer is an opening formed at each of the connection pads. In this case, preferably, shape of the connection pad is a circle, and shape of the opening of the overcoat layer is a circle.
It is also preferred that the head IC chip has solder bumps, and that a diameter of the opening of the overcoat layer is larger than a diameter of each of the solder bumps. More preferably, the diameter of the opening of the overcoat layer is 120-150% of the diameter of each of the solder bumps.
It is preferred that the overcoat layer has a thickness of 5 &mgr;m or less. Thus, adequate flexibility for the suspension can be ensured. Also, the overcoat layer is preferably made of polyimide resin or high temperature endurance coating or film material.
It is also preferred that the apparatus further includes a resin layer with high heat conductivity filled between the suspension and the head IC chip.
By thus filling the high heat conductivity resin, heat generated from the IC chip can be easily dissipated through the resin layer into the suspension to extremely improve heat radiation characteristics. In addition, the filled resin layer improves not only mechanical strength of this portion but also reliability of the IC chip because the resin layer covers the bottom surface of the IC chip.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.
REFERENCES:
patent: 5901017 (1999-05-01), Sano et al.
patent: 53-69623 (1978-06-01), None
patent: 55-150130 (1980-11-01), None
patent: 3-108120 (1991-05-01), None
Morita Haruyuki
Sakai Masanori
Shiraishi Masashi
Takano Ken-ichi
Umehara Tsuyoshi
Arent Fox Kintner & Plotkin & Kahn, PLLC
Cao Allen T.
TDK Corporation
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