JP3493874B2 - Helium leak test equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a helium leak test apparatus useful for inspecting a sealed container for leaks, IC cracks, and the like. . A helium leak test apparatus is one of the most effective means for performing a sealing test or a sealing test. FIG. 3 shows the basic structure of the mass spectrometer (ANAL) 1 for detecting only helium, a chamber 2 for accommodating a workpiece W to be measured, the mass spectrometer 1 and the chamber 2.
Oil rotary vacuum pump (RP) as an evacuation means for evacuating oil
3 and a turbo molecular pump (TMP) 4, an atmosphere opening section 5 for venting the inside of the chamber 2, and a switching circuit for interconnecting the mass spectrometry section 1, the chamber 2, the RP 3, the TMP 4 and the atmosphere opening section 5. And a microcomputer unit 7 serving as control means for controlling the switching circuit 6.
And The switching circuit 6 is mainly composed of a roughing line 61 for directly communicating between the chamber 2 and the RP 3, and the work W can be attached to and detached from a starting end 61 a of the roughing line 61, and the connection portion is in an airtight state. It is attached to become. In the course of the roughing line 61, the first exhaust valve B
V, an intake port 3a of RP3 is provided at an end 61b of the roughing line 61 downstream of the first exhaust valve BV.
And a test valve TV connected to a line 62 branched from a roughing line 61 upstream of the first exhaust valve BV.
and a are connected in parallel. Also, the exhaust port 4 of TMP4
b is connected to the intake port 3a of the RP3 through a line 63 provided with a second exhaust valve FV. Further, the atmosphere opening portion 5 is connected to the vicinity of the starting end 61a of the roughing line 61 through a leak line 64 provided with a leak valve LV, and a Pirani vacuum gauge (PM) 8 is provided in the roughing line 61 immediately downstream thereof. I have. The microcomputer unit 7 has a CP
It is a general one comprising a U71, a memory 72 and an interface 73, in which a predetermined program is stored. The CPU 71 sends the roughing line 6 from the Pirani vacuum gauge 8 according to the program.
1 is inputted, and based on the detected pressure P, predetermined control signals a, b, c, d are output to the valves BV, FV, TV, LV of the switching circuit 6. FIG. 4 is a flowchart showing the outline of the control, and FIGS. 5 to 8 are schematic circuit diagrams showing the exhaust state. Hereinafter, the outline of the control will be described with reference to these flowcharts and circuit diagrams. First, in FIG. 4, it is assumed that the power of the RP3 and the TMP4 is turned on at the start time. From this start point, in step 11, the first exhaust valve BV, the leak valve LV, and the test valve TV are closed, and the second exhaust valve FV is opened. As a result, an exhaust line shown by a thick line in FIG. 5 is formed, and the mass spectrometer 1 is evacuated by the TMP4,
At this time, RP3 functions as a back pump of TMP4. During this time, the CPU 71 determines in step 12 whether or not the startup of the leak test apparatus has been completed, that is, whether or not the mass spectrometer 1 has been evacuated to a predetermined degree of vacuum and the indicated value has dropped below a certain background value. , YES
When it is determined, the operator is asked in step 13 to indicate whether or not to perform a leak test. This apparatus is configured so that an operator can make an input through an appropriate input means. When the operator indicates this intention of YES, the work W in which helium is sealed in the chamber 2 by that time is displayed. Is inserted. Then, if there is a YES intention display, the CPU 71 proceeds to step 14 and proceeds to the second step.
Is closed, and the first exhaust valve BV is opened. Thereby, an exhaust line shown by a thick line in FIG. 6 is formed, and the chamber 2 is
Start the exhaust inside. Thereafter, the CPU 71 proceeds to step 1
5 the detected pressure P of the vacuum gauge 8 monitors whether falls below the set pressure P ₂ which defines in advance. The set pressure P ₂ is a threshold value for determining whether or not the inside of the chamber 2 has reached a reduced pressure suitable for starting a leak test.
It is set to about Pa. Then, when this condition is satisfied, the routine proceeds to step 16, where the first exhaust valve BV is closed, the second exhaust valve FV is opened, and the test valve TV is opened. As a result, as shown by the thick line in FIG.
The vacuum is drawn by P3. At this time, if there is a leak of helium from the measured object W, the mass spectrometric unit 1 detects the helium and indicates the leak amount. At this time, the CPU 71 determines in parallel whether or not the determination is completed in step 17 based on the stability of the measured value or the like. If it is determined that the determination is completed, the process proceeds to step 18 to close the test valve TV. , Open the leak valve LV. Thus, while maintaining the exhaust line shown by the thick line in FIG. 8, a leak line shown by the shaded thick line in the figure is formed, and the inside of the chamber 2 is vented. During this time, the CPU 71 monitors in step 19 whether the pressure of the vacuum gauge 8 has exceeded a predetermined set value P ₀ ,
If it is determined that the value exceeds the threshold value, the leak valve LV is closed in step 20 to return to the state shown in FIG. 5, and then the operator is asked in step 21 whether to perform a retest. The set value P ₀ is set to a pressure at which the inside of the chamber 2 can be opened to take out the work W, for example, about 1 × 10 ⁵ Pa. If the worker answers YES in step 21, the CPU 71 returns to the trouble of step 14, and again executes the leak test according to the same procedure. When performing the retest, the operator replaces the work W in the chamber 2 before answering. If the answer is NO, the second exhaust valve FV is closed at step 22 to end the leak test. If the leak test is not performed in step 13, the user can jump to the position before step 22 by answering NO. [0006] However, the conventional leak test apparatus described above has a problem that the detection in the mass spectrometric unit 1 is likely to be erroneously determined. That is,
In general, when the work W is accommodated in the chamber 2, helium from the helium enclosing operation may be adsorbed on the surface of the work W, and the helium released during the previous leak test may also be in the chamber 2. May adhere and remain. In particular, when the work W is relatively large or when a gross leak has occurred during the previous measurement, such a state is remarkable. When the leak test is started in this state, step 16
At the stage where the exhaust line shown in FIG. 7 is configured, the helium flows into the mass spectrometer 1 and the work W
Even when there is no leak in itself, the mass spectrometric unit 1 may detect an excess leak and determine that the leak is present. Under such circumstances, it is difficult for the conventional helium leak test apparatus to improve the measurement accuracy. Further, the presence of such helium prolongs the evacuation time in FIG. 6 in step S14, and causes a significant decrease in the efficiency of the leak test. SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method in which the roughing is temporarily interrupted during roughing in the chamber to release the atmosphere into the chamber. After that, roughing will be started again. For this reason,
Helium remaining in the chamber due to causes other than leakage can be flushed by the introduction of air at this time and discharged out of the chamber. [0008] The present invention provides a mass spectrometer for detecting only helium, a chamber for accommodating an object to be measured, exhaust means for evacuating the mass spectrometer and the chamber, and a chamber. An atmosphere opening section for venting the inside, a switching circuit for associating the mass analysis section, the chamber, the exhaust means and the atmosphere opening section with each other, and control means for controlling the switching circuit. From the state in which the control means shuts off the air release part to the chamber and connects the exhaust means to perform roughing, temporarily shuts off the exhaust means and connects the air release part, and then reopens the air release part. It is characterized in that it is configured to perform control for shutting off and connecting the exhaust means. With such a structure, the inside of the chamber is once released to the atmosphere after a certain roughing step, and at that time the atmosphere is vigorously introduced into the chamber. The surface of the object is effectively flushed, and the helium adhering to those parts is blown off and diffuses into the chamber. Then, when the roughing is started again thereafter, the helium is effectively discharged out of the chamber through the exhaust means. An embodiment of the present invention will be described below with reference to FIGS. 3 to 8 are denoted by the same reference numerals, and description thereof will be omitted. The helium leak test apparatus shown in FIG. 2 has an apparently similar configuration to the conventional one shown in FIG. 3, but as apparent from comparison with the flowcharts in FIGS. The CPU 71 of the computer system 7 executes step 1
4 and 15 is that the new steps D to G are configured to be executed. [0011] That is, after the roughing line indicated by a thick line in FIG. 6 is configured in step 14, is not directly detected pressure P at the step 15 to wait to below P _2, lower setting of slightly vacuum than It is determined in step D whether or not the pressure is lower than the pressure P ₁ (for example, about 1 × 10 ⁴ Pa), and in the case of YES, the process proceeds to step E to close the first exhaust valve BV, to temporarily stop roughing, and Control to open the leak valve LV. As a result, while maintaining the exhaust air to the mass spectrometry unit 1 as shown in FIG. 2, a leak line as shown by a shaded thick line in FIG. 2 is formed, and the chamber 2 is vented through the atmosphere opening unit 5. Then, the CPU 71 sets the pressure P ₀ (for example, 1 × 10 ⁵ Pa) set slightly lower than the atmosphere in step F.
It is determined whether or not the exhaust gas amount has exceeded the above-described value. If YES, the process proceeds to step G to close the leak valve LV, open the first exhaust valve BV, return to the exhaust state shown in FIG. To resume. Therefore, during this period, the residual helium in the chamber 2 is effectively released. That is, by performing steps D to G during the roughing, the inside of the chamber 2 is once opened to the atmosphere after a certain roughing process, and at that time, the atmosphere is vigorously introduced into the chamber 2, The flushing action is performed on the inner wall and the surface of the work W. And
The helium adhering to the inner wall of the chamber 2 and the surface of the work W is blown off and diffused into the chamber 2 by the flushing action. Therefore, when the roughing is started again thereafter, the helium can be effectively discharged out of the chamber 2 through the RP3. In such a process, it seems that the processing time is prolonged by the extra steps D to G as compared with the conventional process. However, actually, the removal of the residual helium is performed only by roughing. Progresses more effectively than
Since the evacuation of the roughing line 61 up to step 15 is completed in a shorter time, the processing time is rather shortened. The effect varies depending on the application target, but the present inventor has confirmed that there is an effect that the roughing time can be reduced to about half of the conventional value as an average value. As described above, in the helium leak test apparatus of the present embodiment, helium adhering to the surface of helium when the helium is sealed in the work W and helium remaining in the chamber 2 during the previous leak test are removed. However, since they can be efficiently discharged out of the chamber 2 within a short time and the state can be quickly shifted to a state where a leak test can be performed, not only the time required for the roughing process is shortened as compared with the conventional one, but also In addition, the mass spectrometry unit 1 does not detect residual helium, and an excellent effect that the efficiency of the leak test can be drastically improved as compared with the conventional one without lowering the accuracy of the leak test. The specific configuration of each section is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, a normal leak line is used to vent the inside of the chamber during rough evacuation, but a separate leak line may be configured. In this case, the direction of the connection portion may be appropriately set so that the introduced atmosphere is directly blown onto the workpiece, or a nozzle may be provided in the chamber to eject the air. It is also effective to introduce air into the atmosphere by intermittent pulses. Further, in the above-described embodiment, the present invention is applied to detect the degree of sealing of the work. However, the present invention is also useful when applied to a method of detecting the presence or absence of cracks in an IC (helium bombing). The present invention is embodied in the form described above, and has the following effects. That is,
In the helium leak test apparatus of the present invention, during roughing of the chamber, the roughing is temporarily interrupted and the atmosphere is introduced into the chamber. The helium remaining in the chamber can be discharged in a shorter time than in the case of. For this reason, it is possible to prevent a problem that helium adhering to a work surface or the like is detected as a leak in the mass spectrometry unit, and it is possible to effectively improve the efficiency of the leak test without lowering the accuracy thereof. It will be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart showing an outline of control according to an embodiment of the present invention. FIG. 2 is a schematic circuit diagram showing a state in which air introduction is performed in the embodiment. FIG. 3 is a schematic circuit diagram showing a conventional device configuration. FIG. 4 is a flowchart showing an outline of conventional control and corresponding to FIG. FIG. 5 is a schematic circuit diagram showing one process of control in the conventional example. FIG. 6 is a schematic circuit diagram showing one process of control in the conventional example. FIG. 7 is a schematic circuit diagram showing one process of control in the conventional example. FIG. 8 is a schematic circuit diagram showing one process of control in the conventional example. [Description of Signs] 1 Mass analysis unit (ANAL) 2 Chamber 3 Exhaust unit (oil rotary vacuum pump; RP) 4 Exhaust unit (turbo molecular pump; TMP) 5 Air release unit 6 Switching circuit 7 Control means (microcomputer unit) W: Workpiece (workpiece)

Claims (1)

(57) Claims 1. A mass spectrometer for detecting only helium, a chamber for accommodating an object to be measured, exhaust means for evacuating the mass spectrometer and the chamber, and a chamber. An atmosphere opening section for venting the inside, a switching circuit for associating the mass analysis section, the chamber, the exhaust means and the atmosphere opening section with each other, and control means for controlling the switching circuit. From the state in which the control means shuts off the air release part to the chamber and connects the exhaust means to perform roughing, temporarily shuts off the exhaust means and connects the air release part, and then reopens the air release part. A helium leak test device configured to perform control for shutting off and connecting an exhaust means.