CN101261302B - open circuit detection system and method thereof - Google Patents

Abstract

The invention discloses a detection system and a method for judging whether a pin of an electronic element is properly coupled to a circuit device. The detection system comprises a test signal source, a signal sensing unit, a signal processor and an analysis unit. The signal processor is configured to filter and oversample the detected sensing signal corresponding to the test signal input through the electronic component. In addition, the analysis unit controls the change of the frequency and the amplitude of the test signal according to whether the sensing signal is an error signal or not.

Description

Circuit open detection system and method thereof

field of invention

The invention relates to a detection system and a method thereof, and in particular to a detection system and a method thereof for detecting whether there is empty welding between pins of an electronic component and a circuit assembly.

technical background

In the test of the assembled circuit board (Print Circuit Board Assembly, PCBA), when testing at the front end of the production line, a very important step is to check each integrated circuit (Integrated Circuits, ICs) on the printed circuit board (Print Circuit Boards) Whether electronic components such as connectors or connectors are firmly and correctly connected to the printed circuit board, such a test can reduce defects that occur during the back-end functional test (Functional Test), and effectively detect front-end process defects ( Manufacturing Defects). Generally, In-Circuit Tester (ICT) uses the so-called Manufacture Defect Analyzer (MDA) to automatically and quickly find out the electronic components distributed on the printed circuit board caused by the front-end process. , component short circuit, component empty soldering, component error and other process errors, but this process defect analyzer only has an advantage in testing analog components. For digital circuit testing, such as client-customized ASICs, etc., complex testing is required. The test file can achieve a more complete test.

For the test of the connection between the integrated circuit or the connector and the printed circuit board, the capacitive coupling test (Capacitive Coupling Test) is a very convenient, reliable, non-vector-less (Vector-less) mode and non-destructive contact test method. This detection method utilizes the equivalent inductive capacitance formed between the lead frame of the integrated circuit and the external sensor plate (Sensor Plate), so that there is a weak connection relationship between the connecting wire of the integrated circuit and the external sensor plate, and the coupling The size of the final signal is for us to judge the connection status of the electronic component. Apply a small AC signal to the test pin of the integrated circuit. If the connection between the integrated circuit or the connector and the printed circuit board is normal, the small AC signal will be coupled to the sensing electrode sheet through the inductive capacitance generated by this interface to obtain a reference potential A. Conversely, if the connection between the integrated circuit and the printed circuit board is abnormal, the sensing capacitance value of this interface will decrease, and the signal will not be easily coupled to the sensing electrode sheet. At this time, the reference potential B can also be obtained. Whether the integrated circuit is normally connected to the printed circuit board can be judged by the change in the magnitude of the small AC signal. This technology was patented by Agilent Technologies in 1993 (patent number US5254953), and is widely used in foundries in the production line. However, with the advancement of semiconductor and integrated circuit manufacturing processes, the packaging of integrated circuits has evolved towards high density and small volume. This result has caused the connecting wires of integrated circuits to be greatly reduced. , BGA) or some advanced process packages are particularly evident. In terms of connectors, the wires of new connectors such as PCI-E, DDR2/3, CPU Socket and other connectors are shrunk a lot, and the change or shrinkage of the wire geometry will cause the induction capacitance between the sensing electrode sheet and the connecting wire to be greatly reduced , the signal is not easy to be coupled to the sensing electrode, so that the rear signal processing is not easy, which will cause the signal to noise ratio (Signal to Noise Ratio, S/NRatio) of the detection signal to drop sharply, increase the misjudgment rate and reduce the integrated circuit or connector and printed circuit Scalability of board connections.

The capacitive coupling detection patent proposed by the known technology has a test critical value of about 20fF (1fF=10 ^-15 Farad), and the sensing capacitance value lower than this value cannot be detected and judged. Usually, a standard solder ball gate array package is about 30-40% of the pins are lower than this test value. Therefore, it is known that the signal processing method proposed by this known technology is not enough to cover the situation where a large number of tin ball gate array packages are used in the production line, especially in the integrated circuit with high-density pins, the situation that the value of the inductive capacitance drops is more obvious, so there is It is necessary to propose a new signal processing method to solve the problem of low test coverage during detection.

Another example is the simultaneous and multi-channel detection method proposed by US Patent Nos. US5486753 and US539199, which also uses capacitive coupling, but the structure is complex and difficult to implement in an online tester with low-cost requirements. In addition, in the electric field detection device proposed in Taiwan Patent No. TW540709, its structure is complicated, and the probes and jigs used for detection are not in line with the mainstream market, and the cost is relatively high.

Therefore, there is a need to improve the disadvantages of the above-mentioned known technologies in order to increase the detection rate and reduce the cost.

Contents of the invention

The invention provides a detection system and detection method thereof to effectively detect whether the pins of electronic components are correctly connected to the circuit assembly.

The detection system of the present invention includes a signal source, a signal sensing unit, a signal processing unit, and an analysis unit. Wherein the signal source outputs a test signal to the point to be tested of the electronic component, and the signal sensing unit detects an induction signal corresponding to the test signal. The signal processing unit is provided with an analog signal amplifier and a filter to process the induction signal and filter the noise therein. The signal processing unit is also provided with an over-sampling device for over-sampling and digitizing the induction signal for subsequent analysis and processing by the analysis unit. In order to ensure that the sensing signal is not an error signal, the analysis unit will analyze the digitized sensing signal to determine whether it conforms to the reference value or the range of the reference value. If the sensing signal causes an error signal due to low signal-to-noise ratio and/or insufficient signal coupling, the analysis unit will increase the frequency and amplitude of the test signal through the controller to adjust the sensing signal to a correct signal. After the correct induction signal is digitized, it is converted into spectrum data, so that the analysis unit can analyze and process it, and then judge whether the electrical connection of the pin is correct.

The detection device and detection method of the present invention can increase the signal-to-noise ratio by increasing the frequency or amplitude of the test, and then cooperate with the specific filtering process and over-sampling rate of the induction signal, so that the electrical connection of the electronic components can be judged more correctly and the misjudgment situation can be reduced. occur.

Description of drawings

Fig. 1 shows a schematic diagram of a detection system according to an embodiment of the present invention.

Fig. 2 shows a flowchart of a detection method according to an embodiment of the present invention.

Fig. 3a and Fig. 3b show schematic diagrams of frequency spectrum analysis and comparison according to an embodiment of the present invention.

Detailed ways

Embodiments of the detection system and method of the present invention will be described below. It should be understood that the embodiments described in this application are not intended to limit the scope of the present invention, that is, the present invention can be implemented using other features, elements, methods, and embodiments. The detection system and detection method of the present invention can use but not limited to capacitive coupling to detect whether there is an open circuit in the electronic device, so as to determine whether the electrical connection is correct.

Fig. 1 shows a schematic diagram of a detection system according to an embodiment of the present invention. Component number 100 refers to a test system, which is suitable for testing an electronic device composed of a printed circuit board 126 and an integrated circuit 129 . The detection system 100 includes a test signal source 110 , a channel selection device 120 , a signal sensing unit 130 , a signal processing unit 140 , a computer 160 , and a controller 170 .

The test signal source 110 includes a signal source controller 112 , a programmable frequency regulator 114 , a programmable amplitude regulator 116 and a lumper 118 . The signal source controller 112 controls the frequency adjuster 114 and the amplitude adjuster 116 , and then uses the concentrator 118 to make the test signal Si output by the test signal source 110 have adjustable frequency and amplitude. The channel selection device 120 is, for example, a drivable matrix switch for receiving the test signal Si, and its output terminal 124 is connected to a test point on the printed circuit board 126 , which corresponds to the pin 128 of the integrated circuit 129 . The channel selection device 120 is used for selecting the pin 128 to be tested, and connecting the other pins of the integrated circuit 129 to the system ground 122 except the pin to be tested.

The signal sensing unit 130 includes a sensing chip 134 and a multi-function card 132 . The sensing chip 134 is assembled on each corresponding integrated circuit 129 and connected to the input of the multiplexing card 132 . When the test signal Si is input to the test point through the channel selection device 120, the test pin 128 of the integrated circuit 129 will generate an analog AC induction signal (St1, St1') coupled with a small capacitance with the induction chip 134, which is multiplexed The card 132 is input to the signal processing unit 140 . The pin to be tested of the integrated circuit 129 is selected by the selection signal Sc2 sent by the controller 170 to the channel selection device 120, and the enable signal Se corresponding to the control signal Sc2 is output by the controller 170 to the multiplexer card 132, and The sensing signal ( St1 , St1 ′) corresponding to the test pin is selected to be sent to the signal processing unit 140 .

The signal processing unit 140 is used to process the sensing signals (St1, St1') to obtain the frequency spectrum St7 to be measured and remove noise outside the frequency to be measured. In the embodiment shown in FIG. 1 , the signal processing unit 140 includes a high-frequency signal amplifier 142a/low-frequency signal amplifier 142b, a high-frequency signal filter 144a/low-frequency signal filter 144b, an oversampling device 146, and a spectrum analyzer 149. The induction signal output by the multiplexing card 132 determines the switching state of the switches SW1 and SW2 according to its frequency, so that the induction signal passes through the high-frequency signal amplifier 142a and the high-frequency signal filter 144a or the low-frequency signal amplifier 142b and the low-frequency signal filter 144b Choose one of the two processing paths. For example, if the induction signal frequency is higher than about 100 kHz and is a high-frequency signal St1, it is transformed into an amplified signal St2 through the high-frequency signal amplifier 142a, and then the noise existing in the signal St2 is filtered out by the high-frequency signal filter 144a. When the induction signal frequency is less than about 100 kHz and is a low-frequency signal St1', it is converted into an amplified signal St2' through the low-frequency signal amplifier 142b, and then the noise existing in the signal St2' is filtered out by the low-frequency signal filter 144b.

The signal St3 provided by the high-frequency signal filter 144a/low-frequency signal filter 144b will be input to the over-sampling device 146, which may include an anti-alias filter 146a, an over-sampler 146b and an adjustable digital filter 146c . Wherein, the anti-aliasing filter 146a filters the signal St3 to generate the signal St4, and the over-sampler 146b performs over-sampling on the signal St4 to generate the digitized signal St5, and the adjustable digital filter 146c will digitally filter the signal St5 to reduce the noise Filter out to generate a digital signal St6. In an exemplary embodiment of the present invention, the adjustable digital filter 146c may be a 256-order finite impulse response filter (finite impulse response filter), and when the test signal is, for example, 100 kHz, the over-sampling ratio (over-sampling ratio) can reach 25 times.

The spectrum analyzer 149 and the computer 160 form an analysis unit, which first analyzes the signal St6 to determine whether it is a correct induction signal, and is suitable for determining whether the pin to be tested of the integrated circuit 129 is exactly coupled to the printed circuit board. As far as the analysis of the signal St6 is concerned, the computer 160 stores the corresponding reference value or reference value range of the test feature, which is, for example, the standard coupling capacitance that the integrated circuit should detect under different conditions. Based on the reference data pre-stored in the computer, the system will use the signal St6 to calculate whether it meets the corresponding reference value or reference value range. If the signal St6 conforms to its corresponding reference value, the spectrum analyzer 149 will perform a spectrum analysis such as Fast Fourier Transform (FFT) on the signal St6, so that the signal St6 is converted from a time-domain function into a spectrum St7 composed of complex transformation values, Then, the conversion value is analyzed and compared to determine whether the pin to be tested of the integrated circuit 129 is correctly coupled to the printed circuit board. Although this embodiment uses Fourier transform to obtain the frequency spectrum, other algorithms or processing methods are also applicable.

If the signal St6 does not meet its corresponding reference value, it means that the signal coupling is improper, resulting in the obtained sensing signal being an incorrect signal. Due to the influence of miniaturization of the integrated circuit 129 , the signal is less likely to be coupled and the signal-to-noise ratio is lowered. Therefore, the sensing signal may be incorrect and cannot be used as a basis for judging the electrical connection of the pins. In order to solve the problem of false signals such as signal coupling and signal-to-noise ratio reduction, the capacitive reactance of the sensing capacitor can be expressed as:

X _c =1/jωC, where ω=2πf is the angular frequency, and C is the capacitance value.

Therefore, when the frequency f of the test signal Si passing through the sensing capacitor increases, the capacitive reactance of the sensing capacitor will decrease, making signal coupling easier. Therefore, according to one embodiment, the frequency of the test signal Si can preferably be increased to above 100 kHz, such as 100 kHz to 500 kHz, through the programmable frequency adjustment signal source 114, so as to greatly increase the amount of the test signal Si coupled to the sensing chip 134, thus effectively Increase the signal-to-noise ratio. In addition, the combined use of the programmable amplitude adjustment signal source 116 to adjust the magnitude of the amplitude can also increase the amount of the coupled signal. Therefore, the computer 160 sends the control signal Sc1 to the signal source 110 through the controller 170 to increase the frequency and amplitude of the test signal Si, and switches the switches SW1 and SW2 so that the induction signal is converted into a high-frequency induction signal St1 and Appropriate subsequent signal processing is then performed.

Because the system uses feedback control to adjust the frequency and amplitude of the test signal Si, the test threshold of the signal sensing unit 130 can be significantly lower than the known capacitive coupling detection of about 20fF (1fF= ^10-15 Farad) The test threshold, so the energy can measure the smaller inductive capacitance, thus improving the test coverage.

Please refer to FIG. 3 a and FIG. 3 b , which are graphs illustrating that the computer 160 analyzes and compares the conversion values to determine whether the pins to be tested of the integrated circuit 129 are correctly coupled to the printed circuit board. The computer 160 analyzes the spectrum to separate the target data and normalizes it, and then judges whether the converted value is within the preset standard range [v1, v2]. If the target data is within the range [v1, v2], it can be inferred that the pins to be tested of the integrated circuit 129 are definitely coupled to the printed circuit board, as shown in FIG. 3a. If the target data is less than the range [v1, v2], it means that the connection between the pin to be tested and the printed circuit board is abnormal, as shown in FIG. 3b.

Fig. 2 shows a flowchart of a detection method according to an embodiment of the present invention. Please refer to FIG. 2 and FIG. 1 to further illustrate the detection method of the embodiment of the present invention. In step 202 , a test signal Si is output through the test signal source 110 to test whether the pin 128 of the integrated circuit 129 is electrically connected correctly.

In step 204, the analog sensing signal is detected by the signal sensing unit 130, such as the low frequency sensing signal St1' corresponding to the lower frequency test signal Si. Subsequently, the detected sensing signal St1' is processed to an analog signal, and after the sensing signal St1' is amplified by the amplifier 142b (step 206), the noise is filtered out by the filter 144b (step 208). Then, the noise-filtered signal is over-sampled and converted into a digital signal (step 210), and then the digital signal is filtered out by the digital filter 146c (step 212). Next, it is judged whether the sensing signal is an error signal by comparing the digital signal with the corresponding reference value (step 213 ). If the sensing signal is an error sensing signal, the controller 170 controls the test signal source 110 to increase the frequency and amplitude of the test signal Si (step 218 ), and then performs signal testing and processing through steps 202 - 212 .

If the sensing signal is a correct sensing signal, the digital signal is converted into a spectrum composed of converted values through the spectrum analyzer 149 by step 214 . Subsequently, the computer 160 will proceed to step 220 , extracting the conversion value of the target data corresponding to the test signal Si from the frequency spectrum and judging whether the electrical connection of the pins is correct or not according to its magnitude. As shown in FIG. 3 a , when the conversion value is greater than the minimum value of the preset standard range, it indicates that the electrical connection of the pin is correct; otherwise, the electrical connection of the pin is abnormal, as shown in FIG. 3 b .

As can be seen from the above description, the present invention can automatically adjust the frequency and amplitude of the signal source according to different sensing capacitance values through feedback control, so as to increase the test coverage, thereby improving the testability of electronic components, and at the same time pulling High signal-to-noise ratio.

Compared with the known detection method, the present invention can increase the frequency or amplitude of the test by means of feedback control, and cooperate with the specific filtering process and over-sampling rate of the induction signal, thereby increasing the signal-to-noise ratio by more than 20 times of the known technology The signal-to-noise ratio makes the judgment of the electrical connection of electronic components more correct and effectively reduces the rate of misjudgment. The detection system of the present invention completely adopts the existing jigs and probes, and does not need to increase the cost of jigs, so the cost is greatly saved.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, this The scope of protection of the invention shall prevail as defined by the appended claims.

Claims (13)

1. whether detection method between the contact in order to the pin of judging electronic component and circuit assembling empty weldering takes place, and it is characterized in that comprising:

The output test signal also makes its pin through electronic component;

The induced signal that detection produces with capacitive coupling, the parameter that it is electrically connected for this pin of reflection;

Make this induced signal carry out the program of a signal Processing, it comprises:

Excessive this induced signal of sampling is to obtain the digitizing induced signal; And

Extrapolate this digitizing induced signal and whether meet a preset reference value, use and judge whether this induced signal is correct induced signal;

When this digitizing induced signal does not meet this preset reference value, heighten the frequency and/or the amplitude of this test signal;

When this digitizing induced signal meets this preset reference value, this digitizing induced signal is handled, make this digitizing induced signal be converted to frequency spectrum data; And

Based on this frequency spectrum data, judge whether the electrical connection of this pin is correct.

2. detection method as claimed in claim 1 is characterized in that: the program that makes this induced signal carry out signal Processing comprises makes this induced signal through signal amplifier and wave filter.

3. detection method as claimed in claim 1 is characterized in that: the program that makes this induced signal carry out signal Processing comprises makes this induced signal behind antialiasing filter, excessively takes a sample again.

4. detection method as claimed in claim 1 is characterized in that: the program that makes this induced signal carry out signal Processing comprise this induced signal excessively taken a sample after, handled through digital filter in addition.

5. detection method as claimed in claim 1 is characterized in that: the step that makes this digitizing induced signal be converted to frequency spectrum data comprises carries out fast fourier transform.

6. detection method as claimed in claim 1 is characterized in that: this preset reference value is the capacity coupled reference value of expression.

7. detection method as claimed in claim 1 is characterized in that also comprising:

Test signal based on this tool frequency and/or amplitude are heightened detects another induced signal; And

Make this another induced signal carry out the program of this signal Processing.

8. whether detection system between the contact in order to the pin of judging electronic component and circuit assembling empty weldering takes place, and it is characterized in that comprising:

One signal source is suitable for exporting test signal and makes it through this pin;

One induction of signal unit is suitable for detecting the induced signal that produces with capacitive coupling, the parameter that it is electrically connected for this pin of reflection;

One signal processing unit is suitable for this induced signal of excessively taking a sample, to obtain the digitizing induced signal; And

One analytic unit is implemented a signal handler to this digitizing induced signal, and wherein this signal handler comprises:

Extrapolate this digitizing induced signal and whether meet a preset reference value, use and judge whether this induced signal is correct induced signal; And

When this digitizing induced signal meets this preset reference value, this digitizing induced signal is handled, make this digitizing induced signal be converted to frequency spectrum data, whether correct with the electrical connection of judging this pin based on this frequency spectrum data; And

One controller, when this digitizing induced signal did not meet this preset reference value, this controller can be heightened the frequency and/or the amplitude of this test signal.

9. detection system as claimed in claim 8 is characterized in that: this signal processing unit is with this induced signal process signal amplifier and wave filter.

10. detection system as claimed in claim 9 is characterized in that: this signal processing unit makes this induced signal through this signal amplifier and wave filter after going out the frequency height of this induced signal respectively again.

11. detection system as claimed in claim 8 is characterized in that: this signal processing unit is excessively taken a sample for making this induced signal behind antialiasing filter again.

12. detection system as claimed in claim 8 is characterized in that: this signal processing unit is handled through digital filter after this induced signal is excessively taken a sample again.

13. detection system as claimed in claim 8 is characterized in that: this preset reference value is the capacity coupled reference value of expression.

Images