WO2012051801A1

WO2012051801A1 - Test pin assembly with electrostatic discharge (esd) protection

Info

Publication number: WO2012051801A1
Application number: PCT/CN2011/001750
Authority: WO
Inventors: Kek Hing Kok
Original assignee: Esd Technology Consulting & Licensing Co., Ltd
Priority date: 2010-10-22
Filing date: 2011-10-21
Publication date: 2012-04-26
Also published as: CN103238076B; CN103238076A; MY154684A

Abstract

A test pin assembly with electrostatic discharge (ESD) protection comprising a tubular barrel which includes a crimp (14) separating said barrel into a first portion (11a) and a second portion (11b), a first resilient means (15) contained within said first portion (11a), a second resilient means (18) contained within said second portion (11b), a conductive plunger (13) inserted into said first portion (11a), a conductive insert (17) inserted into said second portion (11b), and a static dissipative receptacle (19) with a pointed tip (19a) facing outward and a cavity section (19b) facing inward, wherein said cavity section is filled with static dissipative material (19b) and attached to the tip end (17b) thereby forming a gap (20) between said receptacle (19) and plunger (13) to compel static charge flow through the static dissipative material (19b) first prior to closing of the gap (20) when said resilient means (15, 18) are unstressed for slowing down the transfer of static charge at the moment said receptacle (19) touches a test point of a device to be tested to minimize the creation of microspark.

Description

TEST PIN ASSEMBLY WITH ELECTROSTATIC

DISCHARGE (ESD) PROTECTION

FIELD OF THE INVENTION

The present invention relates to a test pin assembly, more particularly to a test pin assembly which is capable of eliminating or minimizing electrostatic discharge.

BACKGROUND OF THE INVENTION

The importance of electrostatic discharge (ESD) control in today's micro-electronics is already a well known fact and deserves the priority attention for all manufacturers of microchips. Much care is being taken in the manufacturing and handling of electrostatic discharge sensitive components with the objective to eliminate or minimize electrostatic discharge. People, equipments and materials have to be properly grounded to discharge harmful static charge that may reside on every people, equipments or materials.

In today's microchip test handler equipment, it is common to find more and more ionizers are being used in its design to counter the threat of ESD. At the microchip test point, ionizer or ionizers are often installed at strategic location(s) to neutralise any static charge that may be lurking around the pick-up and shuttle area and those reside on the body of a microchip prior to testing.

While it is common to use such ionisation technique in the prevention of ESD, there are several shortcomings encountered in a typical semiconductor manufacturing environment.

Firstly, in a large scale implementation, it involves high cost of investment. Not only high investment is needed in the purchase of high reliability ionizers, it also incur high maintenance cost in the regular checks, periodical calibrations, repair (especially after warranty period) and many other hidden cost like record keeping, human resources required and the provision of production space, etc.

Secondly, they are performance limitations in the use of the ionizer(s) installed around at the testing point of a test handler.

a) Neutralisation time is too slow in today's high speed and high output test handlers. Static decay time of an ionizer drop significantly over time of usage due to unavoidable accumulation of ammonium compound substance deposited at the needle tips of the ionizer in the presence of natural nitrogen (N₂) and moisture (H₂0) in the air. Effectiveness of an air ionizer will lost if the sharpness of the needle tip is lost. Therefore cleaning of the needle tips regularly inside the test handler in order to maintain the reliable performance of an ionizer is extremely difficult and cumbersome in today's highly compact test handler design.

b) Certain level of skill is required for the productive use of ionizer like good understanding of the air flow characteristic, positioning, re-positioning after servicing and the influence of conductive material along the flow path of the ionized air, etc. All these will directly affect the performance of an ionizer. In reality, investment must be put in to train technician or engineer with proper skill & practical knowledge in order to handle air ionizers productively.

PCT application No. PCT/MY2009/000072 disclosed new findings in microchip protection solution without the use of any ionizer.

However, such teachings possess the following weaknesses:-

- The wear and tear of the static dissipative material (non-metallic in nature) available in the market as highlighted is relatively weaker than metal. The static dissipative material may not able to withstand the massive repeated test cycles compared to the original metallic test pin head.

-There is also space limitation in the mechanical fabrication especially for small and compact test pins design. This will eventually become very critical as the trend is moving towards a smaller and more compact test system unit.

Therefore, there is a need for further research and development work to eliminate or overcome the above shortcomings of the prior art.

SUMMARY OF THE INVENTION

It is a known arts and practices in the electronics industry that metal to metal surface contact is to be avoided in the handling of a microchip to prevent the generation of microspark that can damage today's many highly sensitive microchips. The present invention goes against such practices and yet surprisingly able to achieve a relatively safe metal-to-metal contact in the microchips testing operations with reduction in both the magnitude and peak current thereby greatly reduce the threat of both the latent and catastrophic failure of the highly ESD-sensitive microchips.

The invention consists of a uniquely designed test pin that allows residue static charge that resides on a microchip be safely drained to ground. This is achieved by the great cut-down in the strength of the microsparking or the elimination of microsparking from electrostatic discharge (ESD).

The test pin is designed in such a way that the plunger tip is separated from the body of the test pin by a medium of static dissipative material to "slow down" the transfer of static electricity (static charge) to minimise the creation of microspark.

The plunger tip incorporates a "spring back" feature that allows usual high intensity testings without affecting its original durability and shelf-life of a test pin.

This microspark reduction technique is achieved without any modification to the original contact surface section of the plunger tip of a test pin. Retaining the original surface contact design structure of the plunger tip will ensure that the test pin is able to maintain the same composite material at the tip to achieve the same number of test cycles and durability of the shelf life of the original test pin. This unique feature and design of the invention not only helps to minimize the damaging impact of an ESD event but also effectively reduces the number of occurrence or the elimination of such electrostatic discharge events.

Another unique feature of the invention is that the modification of a test pin does not require the enlargement or the change of the size of the test pin to take advantage of the existing design space and minimize the modification cost.

The invention can be used as a grounding device in any production process, manufacturing & other microchip testing activities with the aim of draining away static charge safely with cut-down or elimination of microsparking from electrostatic discharge (ESD).

The invention achieves a microspark-safe microchip testing operations without the use of any air ionizer thus achieving a breakthrough in the traditional use of ionizer(s) for static charge reduction in the testing of microchips.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure la shows a cross-sectional view of a single sided test pin of the current invention;

Figure lb shows a cross-sectional view of a double-sided symmetrical test pins of the current invention;

Figure 2 shows a cross-sectional view of a modified plunger tip with external coiled spring surrounds the body of the plunger;

Figure 3 shows a cross-sectional view of a modified plunger tip with an internal coiled spring placed inside the body of the plunger;

Figure 4 shows a cross-sectional view of another design version of a plunger without a coiled spring;

Figure 5 shows a cross-sectional view of a test finger design without a coiled spring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known methods, procedures and/or components have not been described in detail so as not to obscure the invention. Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

Figure la shows a test pin assembly 10 with electrostatic discharge (ESD) protection in accordance to the preferred embodiment of the present invention. The test pin assembly 10 includes a tubular barrel 11 having a crimp 14 at substantially middle of the barrel 11 separating the barrel into two portions namely a first portion 11a and a second portion l ib wherein each end of the tubular barrel 11 has edge 12a, 12b of narrow diameter and a conductive plunger 13 has a tip end 13a and an enlarged base end 13b at the opposite end of the conductive plunger 13, which is biased against the inner edge 12a of the first portion 1 la of tubular barrel 11 by a first resilient means 15. The first resilient means 15 is contained in the first portion 11a with one end rest upon one surface of the crimp 14 and the other end on the enlarged base end 13b of the conductive plunger 13 when the first resilient means 15 is unstressed. The conductive plunger 13 includes a through channel 16 along its entire length.

A conductive insert 17 has an elongate body 17a with a tip end 17b and an enlarged base end 17c at the opposite end of the conductive insert 17 is inserted from the second portion l ib with its enlarged base end 17c biased against the surface of the other side of the crimp 14 by a second resilient means 18. The second resilient means 18 is contained in the second portion l ib with one end rest upon the inner edge 12b of the second portion l ib of tubular barrel 11 and the other end rest upon the enlarged base end 17c of the conductive insert 17 when the second resilient means 18 is unstressed. The elongate body 17a passed through the first resilient means 15 and the through channel 16 of the conductive plunger 13 with the tip end 17b of the conductive insert 17 slightly protruded at the tip end 13a of the conductive plunger 13.

The first resilient means 15 is preferably having stronger tension force than the second resilient means 18 and the resilient means are preferably micro springs.

A static dissipative receptacle 19 with a pointed tip 19a facing outward and a cavity section 19b facing inward, wherein the cavity section 19b is filled with static dissipative material is attached to the tip end 17b of the conductive plunger 13 as a medium to slow down the transfer of static electricity or static charge at the moment the receptacle 19 touches the often charge-laden test point of a device to be tested to minimize the creation of microspark.

During the test operations, when the pointed tip 19a of the static dissipative receptacle 19 of the test pin assembly 10 of the present invention touches the test point of a device to be tested, the conductive insert 17 together with this receptacle 19 will move inwards causing the enlarged base end 17c of the conductive insert 17 in the second portion l ib to push against and slightly displace the second resilient means 18 inwards due to a light compression force. This inward movement will automatically close the gap 20 between the static dissipative receptacle 19 and the tip end 13a of the conductive plunger 13. Such closure of the gap 20 will render the test pin assembly 10 to act and function like the original unmodified test pin assembly. The usual mechanical movement of a test pin assembly is then followed. A symmetrical double plungers design with same working principle is shown in Figure lb. An additional crimp 14' is provided at the tubular barrel 11 separating the barrel 11 into three portions with an additional third portion 11c.

In another embodiment of the present invention, a detachable plunger tip head 30 is affixed at a tip end of the tubular barrel 11. The plunger tip head 30 is electrically connected via a static dissipative element 31 in series to a resilient means 32 and form an one-piece attachment part 30. The attachment part 30 is then mounted onto the body of the conductive plunger 13. The open end of the resilient means 32 of the attachment part 30 is attached onto the barrel 11 by inserting its wire through a hole 33 provided at one location of the rim at the end of the barrel's 11 opening as shown in Figure 2.

When the plunger tip head 30 touches the test point of a device to be tested, the plunger tip head 30 will move to close the gap 35 between the plunger tip head 30 and the plunger 13. Such closure of the gap will render the test pin assembly 10 to act and function like the original unmodified test pin assembly. The usual mechanical movement of a test pin assembly is then followed.

When the test pin assembly is disengaged away after testing the device, the plunger tip head 30 biased back to slightly protruded at the tip of the test pin assembly as shown in Figure 2. In that way, the partially modified test pin assembly practically occupies no extra space compared to the original test pin assembly even with the coiled resilient means 32 surround the conductive plunger 13 as the diameter of the cylindrical coiled resilient means 32 is equal or smaller than the diameter of the body of the tubular barrel 11 except the plunger 13 is now just a little longer due to the extra tiny small gap at the plunger tip.

In another embodiment, a plunger tip head 30' having a tip head 41 attached with static dissipative element 32 and in series connected to a resilient means 32, wherein the resilient means 32 is inserted into a hollow cylindrical plunger 42, is affixed at a tip end of the tubular barrel 11 of the test pin assembly 10 as shown in Figure 3. This design has the advantage of only minimum spacing needed on the plunger compared to Figure 2.

When the plunger touches the test point of a device to be tested, the plunger tip head 30' will move inwards to close the gap 45 between the plunger tip head 30' and the body of the plunger. Such closure of the gap will render the test pin assembly to act and function like the original unmodified test pin assembly. The usual mechanical movement of a test pin assembly is then followed. When the test pin assembly is disengaged away after testing the device, the plunger tip head 30' biased back to slightly protruded at the tip of the test pin assembly as shown in Figure 3. In that way, the partially modified test pin practically occupies no extra space compared to the original test pin assembly except the plunger is now just a little longer.

Yet another embodiment of the present invention is to provide a modified conductive plunger 13' as shown in Figure 4. It includes a non-coiled means 51 to create a gap 52 between the static dissipative receptacle 19 and the conductive plunger 13'. A hook-shape conductive insert 51 includes a body 51a inserted through the channel 16 of the plunger 13' and a bent part 51b passed through another channel 53 provided at the enlarged base end 13b. When the receptacle 19 touches the test point of a device to be tested, the receptacle 19 will move to close the gap 52 between the receptacle 19 and plunger 13. Such closure of the gap 52 will render the test pin assembly to act and function like the original unmodified test pin. When the test pin assembly 10 is disengaged away after testing of the device, the static dissipative receptacle 19 biased back to slightly protruded at the tip of the test pin assembly as shown in Figure 4. In that way, the partially modified test pin assembly practically occupies no extra space compared to the original test pin assembly except the plunger is now just a little longer.

For a test system utilizing a test finger type, the placement of the test finger tip 60 can be controlled by means of a resilient means wire 61 as shown in Figure 5. The bending of the resilient means wire 61 is designed in such a way that it always leaves a small gap between the test finger tip 60 and its test finger body 62. When the test finger tip 60 touches the test point of a device to be tested, the test finger tip 60 will move to close the small gap between test finger tip 60 and the body 62 of the test finger. Such closure of the gap will render the test finger to act and function likes the original unmodified test finger. When the test finger is disengaged away after testing of the device, the tip head springs back to slightly protruded at the tip of the test finger as shown in Figure 5. In that way, the partially modified test finger practically occupies no extra space compared to the original test finger except the finger tip is now extended just a little longer.

As will be readily apparent to those skilled in the art, the present invention may easily be produced in other specific forms without departing from its essential characteristics. The present embodiments is, therefore, to be considered as merely illustrative and not restrictive, the scope of the invention being indicated by the claims rather than the foregoing description, and all changes which come within therefore intended to be embraced therein.

Claims

1. A test pin assembly with electrostatic discharge (ESD) protection, characterized in that comprising:

a tubular barrel (11) with each end of said barrel (11) has an edge (12a, 12b) of narrow diameter, wherein said barrel (11) includes a crimp (14) at substantially middle of said barrel separating said barrel into a first portion (11a) and a second portion (l ib);

a first resilient means (15) contained within said first portion (11a);

a second resilient means (18) contained within said second portion (l ib);

a conductive plunger (13) has a tip end (13a) and an enlarged base end (13b), inserted into said first portion (1 la) of the barrel (11), said enlarged base end (13b) is biased against an inner edge (12a) of said first portion (11a) with said tip end (13a) protruded out from said barrel (11) by said first resilient means (15);

a conductive insert (17) has an elongate body (17a) with a tip end (17b) and an enlarged base end (17c), inserted into said second portion (l ib) of the barrel (11 ), said enlarged base end (17c) is biased against one surface of said crimp (14) with said elongate body (17a) passed through said first resilient means (15) and a through channel (16) provided along the entire length of said conductive plunger (13) and having said tip end (17b) slightly protruded from said plunger (13); and a static dissipative receptacle (19) with a pointed tip (19a) facing outward and a cavity section facing inward, wherein said cavity section is filled with static dissipative material (19b) and attached to the tip end (17b) of said insert (17) thereby forming a gap (20) between said receptacle (19) and plunger (13) to compel static charge flow through the static dissipative material (19b) first prior to closing of the gap (20) when said resilient means (15, 18) are unstressed for slowing down the transfer of static charge at the moment said receptacle (19) touches a test point of a device to be tested to minimize the creation of microspark.

2. The test pin assembly as claimed in claim 1 , wherein said first resilient means (15) is having stronger tension force than the second resilient means (18).

3. The test pin assembly as claimed in claim 2, wherein said both resilient means (15, 18) are micro springs.

4. The test pin assembly as claimed in claim 3, wherein said first resilient means (15) is placed in said first portion (11a) of the barrel (11) with one end rest upon a surface of said crimp (14) and the other end on said enlarged base end (13b) of said conductive plunger (13).

5. The test pin assembly as claimed in claim 3, wherein said second resilient means (18) is placed in said second portion (l ib) of the barrel (11) with one end rest upon an inner edge (12b) of said second portion (l ib) and the other end upon said enlarged base end (17c).

6. The test pin assembly as claimed in claim 1 , wherein said tubular barrel (11) further comprising an additional crimp (14') which separates said barrel (11) with an additional third portion (11c) for accommodating a similar set of resilient means (15, 18), plunger (13), insert (17) and receptacle (19) for forming a symmetrical double plunger.

7. The test pin assembly as claimed in claim 1 , wherein said receptacle (19) can be attached to a non-coiled means (51) which includes a body (51a) inserted through said channel (16) of the plunger (13) and a bent part (51b) passed through another channel (53) provided at said enlarged base end (13b) thereby leaving a gap between said receptacle (19) and plunger (13).

8. A test pin assembly with electrostatic discharge (ESD) protection, characterized in that comprising:

a tubular barrel (11) with each end of said barrel (11) has an edge (12a, 12b) of narrow diameter;

a conductive plunger (13) slidably mounted within said tubular barrel (11); a plunger tip head (30) affixed with static dissipative element (31) and connected to a resilient means (32) at one end of said resilient means (32) collectively forming an one-piece attachment, wherein said attachment is attached to said conductive plunger (13) by inserting the other free end of said resilient means (32) through a hole (33) provided at said edge of said barrel (11) and thereby said resilient means (32) surrounding said plunger (13) leaving a gap between said tip head and plunger (13) to compel static charge flow through the static dissipative element (31) first prior to closing of the gap for slowing down the transfer of static charge at the moment said tip head (30) touches a test point of a device to be tested to minimize the creation of microspark.

9. The test pin assembly as claimed in claim 8, wherein said free end of said resilient means of the plunger tip head (30) can be inserted into a hollow cylindrical plunger (42).

10. A test finger with electrostatic discharge (ESD) protection, characterized in that comprising:

a finger body (62); and

a finger tip (60) which includes a cavity section filled with static dissipative material, wherein said finger tip (60) is attached to said finger body (62) via a resilient means wire (61) bent in such a way that it leaves a gap between said finger tip (60) and finger body (62) to compel static charge flow through the static dissipative material first prior to closing of the gap for slowing down the transfer of static charge at the moment said finger tip (60) touches a test point of a device to be tested to minimize the creation of microspark.