US20060243361A1

US20060243361A1 - Ageing process for sealed product

Info

Publication number: US20060243361A1
Application number: US11/242,392
Authority: US
Inventors: Cheng-Hui Lin; Fei Han; Zheng Li
Original assignee: Foxconn Technology Co Ltd
Current assignee: Foxconn Technology Co Ltd
Priority date: 2005-04-29
Filing date: 2005-10-03
Publication date: 2006-11-02
Also published as: CN1858571A; CN100453993C

Abstract

Disclosed is an ageing process (100) for a group of sealed products to cause defective products among the group of sealed products, if any, to appear in advance so that the defective products can be subsequently detected easily and further removed from the group of sealed products. The ageing process includes the following steps: placing the sealed products into an ageing oven (10); releasing the gas originally existing in the ageing oven, and filling nitrogen gas and hydrogen gas into the ageing oven until the gas pressure inside the ageing oven reaches a first value; heating the sealed products until the temperature inside the ageing oven reaches a second value; conducting ageing on the sealed products under a specified time period and taking the sealed products out of the ageing oven after the time period is over.

Description

TECHNICAL FIELD

The present invention relates generally to an auxiliary method for evaluating the product yield rate of a group of sealed products, and more particularly to an ageing process conducted on the group of sealed products to cause defective products among the group of sealed products, if any, to appear in advance so that the defective products can be subsequently detected easily and further removed from the group of sealed products.

BACKGROUND

A variety of sealed products, such as heat pipes, vapor chamber-based heat spreaders, are extensively used for removing heat from heat-generating components. For example, in electronic field, heat pipes and vapor chamber-based heat spreaders are widely used for removing heat from integrated circuit chips such as central processing units (CPUs). A heat pipe or a vapor chamber-based heat spreader is usually a vacuum vessel which defines therein a chamber for containing a working fluid such as water. Preferably, a wick structure, such as mesh or sintered powder, is provided in the chamber, lining the inside walls of the vessel. As an integrated circuit chip is maintained in thermal contact with the heat pipe or the heat spreader, the working fluid contained in the chamber at the contacting hot location evaporates into vapor. The vapor spreads quickly from the hot location to be full of the chamber, and wherever the vapor comes into contact with a cooler wall of the vessel, it condenses and releases its latent heat for evaporation. The latent heat is dissipated to atmosphere environment by, for example, fins thermally engaging with the wall of the vessel and a forced airflow through the fins. The condensed liquid then returns back to the hot location via capillary action developed by the wick structure to begin a next cycle of evaporation and condensation. Thus, the heat generated by the chip is continuously removed and the temperature of the chip is accordingly lowered down.
The heat pipe and the vapor chamber-based heat spreader are made of thermally conductive material such as copper and generally involves, among others, the following two steps. One step is to make the chamber of the vessel a vacuum space by drawing the air originally existing in the chamber out of the vessel. The other step is to seal the vacuum vessel via soldering, welding or any other methods that can hermetically seal the vacuum vessel. However, due to some manufacturing factors, the foregoing first step cannot ensure that the original air in the chamber is totally removed from every product. Some products may still remain in the chamber thereof a relatively large amount of air. The excessive remaining air and the working fluid contained in the chamber will gradually experience complicated chemical reactions with the inside walls of the vessel and the wick structure in the chamber. The reactions will generate a large amount of non-condensable gas to be full of the chamber, thereby influencing the heat transfer capability of the involved product. With respect to the above-mentioned second step, if the product is not hermetically sealed due to some manufacturing factors, it will result in a micro-leakage phenomena and ambient air will gradually penetrate into the chamber via the sealing junction portion until the chamber loses its vacuum condition. Hereinafter, the products that have excessive remaining air in the chambers thereof and the products that have micro-leakage problem are totally referred to as “defective products”.
Concerning the above facts, it is necessary that the manufactured products should be tested or evaluated before sent for applications in order to remove the defective products therefrom and ensure that every product sent for applications is qualified in quality and reliability. An auxiliary method currently available for evaluating a group of sealed products is to conduct an ageing process on the group of sealed products. The ageing process accelerates the aging of the potentially defective products and to cause the defective products to appear in advance. Then, the defective products can be detected easily and further removed from the group of sealed products. According to conventional art, one ageing process currently available is to heat the group of sealed products in order to accelerate the chemical reactions occurred inside the potentially defective products. However, this heating process causes serious oxidization problem to outer surfaces of the vessels of the group of products, making the products having an unattractive appearance. Another ageing process currently obtainable is to fill helium gas (He), a small-sized single molecular inert gas, into a pressurized container in which the group of sealed products are contained, to cause the molecules of the helium gas to penetrate into the chamber of a defective product that has micro-leakage problem until the chamber thereof loses vacuum condition. However, the helium gas is expensive and difficult to obtain.
In view of the above-mentioned disadvantages of the conventional ageing processes, there is a need for an ageing process which can prevent the sealed products being evaluated from being oxidized. What is also needed is a cost-effective ageing process.

SUMMARY

The present invention relates to an ageing process for a group of sealed products. A preferred ageing process in accordance with the present invention includes the following steps: placing the sealed products into an ageing oven; releasing the gas originally existing in the ageing oven, and filling a mixture of nitrogen gas and hydrogen gas into the ageing oven until the gas pressure inside the ageing oven reaches a first value; heating the sealed products until the temperature inside the ageing oven reaches a second value; conducting ageing on the sealed products under a specified time period and taking the sealed products out of the ageing oven after the specified time period is over.
Compared with the conventional art, the ageing process can avoid oxidization problem because before heating, the air originally existing in the ageing oven has been removed. Also, the ageing process is cost-effective because the filled nitrogen gas and hydrogen gas can be easily and economically obtained.
Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart showing the main steps of a preferred ageing process of the present invention;
FIG. 2 is an isometric view of an ageing oven for conducting the ageing process of FIG. 1; and
FIG. 3 is a cross-sectional view of a defective sealed product, illustrating the micro-leakage phenomena that the product experiences when conducted by the ageing process of FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 is a flow chart showing the main steps 101, 102, 103, 104 of a preferred ageing process 100 of the present invention. The ageing process 100 is an auxiliary method for evaluating the product yield rate of a group of sealed products such as heat pipes or vapor chamber-based heat spreaders. The ageing process 100 is conducted on the group of sealed products in order to accelerate ageing of defective products among the group of sealed products, if any, and to cause the defective products to appear in an earlier time. Thus, after the ageing process 100, the defective products can be subsequently detected easily and further removed from the group of sealed products, ensuring that every product remained is qualified in quality and reliability.
FIG. 2 schematically illustrates an ageing oven 10 used for conducting the ageing process 100. The ageing oven 10 is in cylindrical form and is supported on a base 20. The ageing oven 10 defines therein a chamber 11, and includes a door 12 and a nozzle 13 at opposite ends thereof. The first step 101 of the ageing process 100 includes placing the group of sealed products into the ageing oven 10. That is, the group of sealed products that need evaluation are placed into the chamber 11 of ageing oven 10, and then, the door 12 of the ageing oven 10 is closed.
The second step 102 includes exhausting the original air in the ageing oven 10, filling nitrogen gas and hydrogen gas into the ageing oven 10 and heating the sealed products. In particular, the air that originally exists in the chamber 11 is exhausted from the ageing oven 10 and the gases are filled into the chamber 11 via the nozzle 13. The original air in the chamber 11 can be evacuated before the nitrogen gas and hydrogen gas are filled into the ageing oven 10 or be expelled out of the chamber 11 when the nitrogen gas and hydrogen gas are filled into the ageing oven 10. The nitrogen gas and hydrogen gas are preferably filled into the chamber 11 in a mixed form, with a ratio in volume of about 97:3. The sealed products are heated by an electric heater (not shown) which is provided in the chamber 11 of the ageing oven 10. The heating to the sealed products is preferably conducted after the gases are filled into the ageing oven 10 since, at that time, the original air in the chamber 11 has been removed from the ageing oven 10. Preferably, the gases are filled into the chamber 11 until the gas pressure inside the chamber 11 reaches to a predetermined value that is higher than atmospheric pressure. For example, the gas pressure may be 2˜5 times higher than atmospheric pressure. The sealed products are preferably heated until the temperature inside the chamber 11 reaches to a predetermined value that is higher than 100 degrees centigrade. For example, the predetermined value of temperature may be about 125 degrees centigrade. Both the predetermined temperature and the predetermined gas pressure in the chamber 11 of the ageing oven 10 are preferably kept constant during the ageing process 100. In this embodiment, the nitrogen gas is typically applied to pressurize the chamber 11 of the ageing oven 10 and to expel the original air out of the chamber 11.
The step 103 includes conducting ageing on the sealed products in the ageing oven 10 under a specified time period. The time period can be adjusted according to the selected temperature and gas pressure. The general rule is that higher you select the temperature and gas pressure in the chamber 11 of the ageing oven 10, the less time you will require to finish this step. For example, if the selected temperature is above 100 degrees centigrade and the selected gas pressure is above atmospheric pressure, a time period of 24 hours will generally be sufficient. Thus, the ageing process 100 is carried out under a high temperature and pressurized environment over the given time period. By this step, the products that have excessive remaining air in their chambers will generate a large amount of non-condensable gas in the chambers because the chemical reactions occurred in the chambers are accelerated due to high temperature, while the products that have micro-leakage problem will gradually lose vacuum condition in their chambers because the small-sized hydrogen molecules in the ageing oven 10 can gradually penetrate into the chambers of the products through their sealing junction portions. FIG. 3 shows a defective product 30 having micro-leakage problem and the hydrogen molecules (H₂) are passing through a sealing junction portion 32 of the product 30 into a chamber 34 thereof.
The step 104 includes removing the sealed products out of the ageing oven 10. That is, after the specified time period is over and the temperature of the ageing oven 10 is lowered down and the gas pressure in the chamber 11 of the ageing oven 10 is released, the sealed products are taken out of the ageing oven 10. The ageing process 100 is thus finished. After the ageing process 100, the sealed products can then be tested through conventional testing instruments or methods, for example, by testing every product the extent of vacuum condition in its chamber, or by testing every product its thermal resistance, to thereby decide whether the product tested is qualified or unqualified.
According to the present invention, the ageing process 100 can avoid oxidization problem because before heating, the air originally existing in the chamber 11 of the ageing oven 10 has been removed. Also, the ageing process 100 is cost-effective because the filled nitrogen gas and hydrogen gas can be easily and economically obtained.
It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. An ageing process for a group of sealed products comprising the following steps:

placing the sealed products into an ageing oven;

exhausting the gas originally existing in the ageing oven, and filling nitrogen gas and hydrogen gas into the ageing oven until the gas pressure inside the ageing oven reaches a first value;

heating the sealed products until the temperature inside the ageing oven reaches a second value;

conducting ageing on the sealed products under a specified time period; and

taking the sealed products out of the ageing oven after the specified time period is over.

2. The ageing process of claim 1, wherein the sealed products are heat pipes.

3. The ageing process of claim 1, wherein the sealed products are vapor chamber-based heat spreaders.

4. The ageing process of claim 1, wherein the nitrogen gas and hydrogen gas are filled into the ageing oven in a mixed form.

5. The ageing process of claim 4, wherein a ratio of the nitrogen gas and the hydrogen gas in volume is about 97:3.

6. The ageing process of claim 1, wherein the first value is above atmospheric pressure.

7. The ageing process of claim 1, wherein the second value is above 100 degrees centigrade.

8. The ageing process of claim 1, wherein the first value and the second value are kept constant during the specified time period.

9. An ageing process for a sealed product comprising the following steps:

providing an ageing oven, the ageing oven defining therein a chamber;

placing the sealed product into the chamber of the ageing oven;

filling two kinds of gases with different molecule sizes into the ageing oven; and

taking the sealed product out of the ageing oven after a specified time period.

10. The ageing process of claim 9, further comprising steps of exhausting the oxygen that originally exists in the chamber before the gases are filled into the ageing oven and heating the sealed product.

11. The ageing process of claim 9, further comprising steps of exhausting the oxygen that originally exists in the chamber when the gases are filled into the ageing oven and heating the sealed product.

12. The ageing process of claim 9, wherein the two kinds of gases are nitrogen gas and hydrogen gas, respectively.

13. The ageing process of claim 9, wherein the sealed product is one of a heat pipe and a vapor chamber-based heat spreader.

14. An ageing method comprising following steps:

putting a sealed hollow product in an oven, wherein the sealed hollow product is vacuumed and has liquid and a wick structure therein;

heating the sealed hollow product under a temperature while injecting a mixture of nitrogen gas and hydrogen gas into the oven under a pressure;

maintaining the temperature and pressure for a period of time; and

removing the sealed hollow product from the oven.

15. The ageing method in accordance with claim 14, wherein the mixture of nitrogen gas and hydrogen gas has a ratio in volume of about 97:3.

16. The ageing method in accordance with claim 14, wherein the temperature is higher than 100 degrees centigrade.

17. The ageing method in accordance with claim 16, wherein the temperature is about 125 degrees centigrade.

18. The ageing method in accordance with claim 16, wherein the period of time is about 24 hours.

19. The ageing method in accordance with claim 14, wherein the pressure is about 2-3 times of atmosphere pressure.

20. The ageing method in accordance with claim 19, wherein the period of time is about 24 hours.