Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2003-02-21
2004-10-19
Tang, Minh N. (Department: 2829)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S761010, C324S762010, C219S121660, C072S342100
Reexamination Certificate
active
06806723
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to contactors for testing electronic devices and, more particularly, to a contactor having contact electrodes which make a contact with terminals of an electronic device such as a semiconductor substrate (wafer) or a wiring board so as to perform an electrical test on the electronic device.
2. Description of the Related Art
In recent years, miniaturization of wiring and densification of circuits have been progressed in semiconductor devices such as, for example, a large-scaled integrated circuit chip (hereinafter referred to as LSI) so as to satisfy the demand for downsizing or upgrading of a product to which the LSI is incorporated. With such progression, miniaturization of LSI terminals and increase in the number of terminals are progressing rapidly.
For example, development is progressing so that the terminals of an LSI chip used by SIP (System In Package) may attain a pitch of about 20 &mgr;m. Moreover, for the SIP application, the thickness of LSI chips has been rapidly reduced from, for example, 500 &mgr;m to 100 &mgr;m, 50 &mgr;m or even 25 &mgr;m. Accordingly, the following subjects are imposed also to contactors (probes) used for testing such an LSI chip.
1) It is necessary to develop immediately a contactor (probe) which can provide a good position accuracy (±5 micrometers or less) in association with the miniaturization and increase in the number of LSI terminals.
2) Since LSIs become thinner, there is a possibility of breakage when an excessive contact force is applied thereto. For this reason, it is indispensable to control variation in a spring force of a probe to be as small as possible.
3) The area array type LSI has been increasing as arrangement of LSI terminals (terminals are arranged like a lattice over the whole area of LSI chip), and the contactor must correspond to the area array type LSI. That is, not only the conventional peripheral type LSI (terminals are arranged in the periphery of an LSI chip) but also the area array type LSI (terminals are arranged like a lattice over the whole area of an LSI chip) has been increasing, and a contact probe used for such an area array type LSI must have a higher density of electrodes than a probe for the peripheral type LSI. Thus, generally it is difficult to arrange and form the needles of the contactor.
4) In the case of a CSP (chip-size package) which has small pitch terminals or area array terminals, even for a packaged LSI, it has become difficult to maintain a previous cost of a contactor (socket) manufactured by a conventional technique.
There are two kinds of probe card systems.
A: Cantilever System (for peripheral type)
The cantilever system is a mainstream system in wafer probe cards. With respect to the structure of a probe of the cantilever system, ends (unbent side) of rod-like conductive members (needles) having bent ends are joined to terminals of a wiring board so that the bent ends of the rod-like members are pressed manually using an elongated tool so as to locate the bent ends within a desired range of position accuracy. The pitch of the ends on the wiring board side tends to be larger than that of the chip contact (needle tip)
B: Vertical Probe System (for area array type)
Since it is necessary to arrange pins in the shape of a lattice, a plurality of pins are arranged on a board fundamentally in a state where the pins are stood vertically to the board. However, if the pins are simply arranged vertically, the pins may contact with each other since a direction of bending of each pin, when it is pressed while being contacted with an LSI, cannot be the same. Thus, in a mainstream structure, the pins are previously bent in a predetermined direction. In order to make the pins stood together in large number, it is difficult to maintain a position of each pin while bending. Thus, the cost of the vertical probe system is more than twice the cantilever system.
A) Problems in the Cantilever System
I) There is a limitation in reducing the pitch.
A pitch of about 45 &mgr;m is a limit since it is difficult to attain a positional accuracy of the needle tips (XY accuracy: less than ±5 &mgr;m). As mentioned above, the final adjustment of the position of the needle tips is carried out by a small displacement by mechanical contact pressurization. There is an actual example in which the needle tip accuracy (±10 &mgr;m) is attained for the level of pitch of about 45 &mgr;m. However, it is difficult to deal with a smaller pitch for the following reason.
(1) The distance between the needles is so small that a tool for position adjustment cannot be inserted.
(2) Even if the tool is inserted forcibly, it is difficult to maintain a movable area in which the needle tip can be displaced. Considering the spring back of the needle, it is impossible to maintain the movable area for obtaining a required displacement due to a relationship with adjacent needles.
II) It is difficult to obtain a uniform force with a narrow pitch.
Similar to the A) cantilever system, it is difficult to perform a work to adjust the height of the needle tips. If the needles are mechanically pressurized so as to adjust the height, a pressing tool tends to interfere with adjacent pins, which deteriorates easiness of work.
III) Basically, It cannot be applied to an area array type. It is considered that a two-row arrangement is a limit.
B) Problems in the Vertical Probe System
I) there is a processing limit in a narrow pitch.
Although a pitch of more than 150 &mgr;m is mainly in use now, there is the same problem as A) cantilever system. That is, since there are adjacent pins on the right and left sides and front and back sides, which pins are obstructive, it is very much difficult to carry out a position correction with a high accuracy after the pins are formed on a board.
II) It is difficult to obtain a uniform force for a narrow pitch. Similar to A) cantilever system, it is difficult to adjust the pins in the same height.
III) Cost is high.
Since the adjacent pins becomes more obstructive as the pitch becomes smaller, it becomes difficult to perform a bending process (formation of bent portion), thereby inevitably increasing a manufacturing cost. Although there is a means to mount needles, which are previously bent, it is difficult to position the needles with the same direction of bending, thereby an increase in the manufacturing cost cannot be avoided.
C) Socket for CSP (Area Array of the Vertical Probe System)
Basically, there are problems similar to the problems of the above-mentioned B) vertical probe system. Additionally, it is necessary to plant small pins in a main part of a mold with higher accuracy as the pitch is decreased. The guide for pins, which accurately aligns the needle tips with the package terminals, requires a higher accuracy than a processing accuracy required for a conventional socket. In the case of CSP which uses solder balls as terminals, deformation of the solder balls become remarkable even when a contact pressure is slightly increased. Since the diameter and volume of each ball is decreased as the pitch becomes smaller, the degree of influence due to reduced pitch becomes remarkable, which causes a serious problem.
Thus, similar to the position accuracy of the pins, it is a subject to achieve a uniform contact force and reduce an increase in the cost. In order to solve the problems in the manufacturing methods of the conventional contactors as mentioned above, the applicants considered manufacturing a contactor suitable for a purpose of a prove by deforming needles or pins of the contactor using a laser bending technique.
As a conventional laser processing technology, the autumn convention academic lecture collection paper of the Japanese Society of Precision Engineering discloses on page 166 a laser processing technology which is considered to be applicable to a laser bending technique under the title “micro-forming of thin film metal glass by laser local heating”. Conventionally, laser processing has not
Fukuda Keisuke
Imakado Masayuki
Kumatabara Takumi
Maruyama Shigeyuki
Matsushita Naohisa
Tang Minh N.
Westerman Hattori Daniels & Adrian LLP
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