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Principles of PCBA ICT Testing

Principles of PCBA ICT Testing
I. Introduction:

The IN CIRCUIT TESTER is designed to detect all parts of the circuit board product by measuring all parts of the circuit board, including resistors, capacitors, inductors, diodes, transistors, FETs, SCRs, LEDs, and ICs. Disadvantages such as: short circuit, circuit break, missing parts, bad parts, poor parts or poor assembly, etc., and clearly pointed out the location of the shortcomings to help users ensure product quality and improve the efficiency of defective maintenance. The REED RELAY, which is the highest test coverage today, is the most reliable and easy to use, providing the most complete online testing machine.


Second, isolation (GUARDING) test principle:

The biggest feature of the test ACT test is the use of GUARDING's technique, which isolates the component under test and is not affected by its line (as shown below). The computer program automatically selects the appropriate isolation point to select multiple


3. Measurement of resistance:

(1) constant current measurement method:

Using the constant current measurement method, the computer program will automatically set the current source size according to the resistance of the resistance to be measured.


(2) constant voltage measurement method:

When the measured resistance parallel to the large capacitor, if the use of constant current measurement method, large capacitor charging time is too long, but the use of constant voltage measurement method can shorten the test time.


(3) phase measurement method:

When the resistance and capacitance in parallel, if the current measurement method can not be properly measured, you need to use the phase measurement method to measure the test.This method uses the AC voltage as the signal source, measuring the voltage and current across the part Of the phase difference, in order to calculate the individual electrical impedance, capacitance or resistance.


(4) small resistance measurement:

General small resistance measurement (0.1Ω ~ 2Ω), it can be measured as JUMPER way but only to measure whether there is no missing parts. For more accurate measurement, we must use four-terminal measurement. Principle is as follows:


The signal source and the measurement have their own circuits, so the voltage drop on RX can be accurately measured.


Applications: Small resistors such as 0.1Ω ~ 10Ω, small inductors, small capacitance measurement will be affected by cable and probe contact bad, resulting in test instability, and four-line measurement can solve these problems.

From the two-wire type to four-line measurement method is modified as follows:

A. Relay board need to make the following changes, JA, JB, JC jumper removed, so open OPEN.

B. JA0, JA1, JA2, JA3, JB0, JB1, JB2, JB3, JG0, JG1, JG2, JG3


C. At this time Relay board only 32 points, because the second connector has been used as sense.

D. The program must be set as follows:


E. In this setting, the resistance value can be measured to a minimum of 0.01Ω.

4. Capacitance measurement:

(1) AC constant voltage source measurement: slightly (this test method and the above resistance test method similar)

(2) DC constant current source: slightly (this test method and the above resistance test method similar)

(3) phase measurement method: slightly (this test method and the above resistance test method similar)

(4) Leakage current measurement: Suppose C1 is 100uF25V, change the program to STEP 2, press F9 test to measure the normal leakage current of the capacitor, and fill it into STDVAL, if C1 reverse the leakage current will increase.


Note: Each capacitor voltage is different, so the voltage in ACTVAL is not necessarily.

(5) three end point measurement:

This method is used to measure the electrolytic capacitor, this measurement method must be in the top of the capacitor pin (Figure), the program is amended as follows:



V. Bipolar measurement method:

(1) .DIODE general measurement:


(2). Two parallel DIODE measurement method:


The diode should be measured in parallel using CM mode. The program should be set as follows:


STEP2 to be added voltage (ACTVAL) 0.6V or so, adjust the ACTVAL voltage to the current to about 40mA.

6. Triode (FEA) measurement method:

FETs can be divided into two types: a. JFET, b. MOSFET vacant and enhanced.

(1) MOSFET enhanced as shown


The program is set as follows:


Control the gate (gate) voltage from 2V ~ 3V until the conduction so far, you can test out.



The program is set as follows:


Control the gate voltage until it is clipped.

(3) Three-terminal measurement method to test the transistor

Daily regulation of the transistor measurement only need to BC, BE both ends of the diode, can be measured to whether the empty welding reverse (such as the program 1,2), but the US regulatory transistor due to Base in the middle, so The use of three endpoints to measure (program 3), in order to detect the reverse of the problem.


The program is set as follows


Control the base (B) voltage, so that the transistor is saturated.


7. Voltage measurement method: (for example)

First need to add power, the machine modification method as shown

A. A rule with a Molex 7 pin female base.

B. Pin 1 (output is 5V) Connect to NET NAME as VCC probe (default is probe # 2).

C. Pin 2 (GND for power supply output) Connect the probe with NET NAME as GND (default is probe number 5).

D.Pin 7 (output is 3.3V) Connect to NET NAME as VCC3 probe (default is probe 10).

E. Refer to Figure B and the following procedure to test the output voltage VCC2, VTT of the power regulator IC.


Assuming STEP 8, 10 and 12 are not placed below 0.1V, increase the TM values of STEP 7, 9 and 11 and continue to measure until STD values of STEP 8, 10 and 12 are below 0.1V




<< Annex 1 >>

Agilent TestJet Technology

Agilent Agilent has developed a technology for the Agilent TestJet Technology to address the problem of seamless detection of SMD ICs. The JET-300 ICT system is equipped with this technology, greatly improving the detection rate of digital circuit boards. Computer motherboards, adapter cards or fax machines, the modem board can be a satisfactory test results. The advantages of its application are as follows:


1. The Agilent TestJet Technology is used to measure the capacitance between a copper foil board and an IC frame to detect pin breakage. This technique does not need to write any program, you can do the right and rapid testing.

2. Agilent TestJet Technology can test a variety of different packaging IC, such as Insertion type, PLCC type, QFP type, TAB type, PGA type (no grounding), BGA type (OMPAC) and so can be tested.

3. Agilent TestJet Technology can also be used to detect a variety of socket pin break, whether it is Insertion type or SMD type can be detected.

Broadband and accurate phase separation measurement

For RLC in RC or RL parallel circuits, the phase value can be measured by the phase measurement method. Since the signal source is wide (100Hz to 1MHz), it can be detected in a range that is superior to the general ICT, Of the parts can be accurately measured.

Three end point, four end point measurement

Can be three terminal parts such as TRANSISTOR, DIGITAL TRANSISTOR, FET, SCR and so on. Or four terminal parts such as PHOTO COUPLER, do the right test, if the anti-plug or parts damage, will be measured. The value of TRANSISTOR can also be measured.

The same time as the above-

Electrolytic capacitor polarity test

Three-terminal method to detect the polarity of aluminum electrolytic capacitor anti-plug, the measured rate of 100%; to detect leakage current detection electrolytic capacitor polarity anti-plug, high rate of measurable.

Software system

The JET-300 has a high level of performance beyond the general ICT capabilities, whether it is pre-test programming support software, or post-test bad information and data analysis. In the Microsoft Chinese window environment to implement the system program, easy to operate, powerful.

Worst case (solder) list

The system can print out the most bad parts (the top ten) and the most bad number of solder joints (the top ten) for manufacturers to do quality control or process improvement reference.

Test daily reports and monthly reports for data statistics

The top bar graph of the chart shows the cumulative daily OPEN / SHORT, the defect rate of the parts and the acceptable rate for the entire test. The second half of the chart is used to clearly show the percentage of the bad causes of the day.

Network real - time monitoring system

If multiple ICTs are connected to an internal network system, the test statistics for each ICT can be displayed on any computer on the network, and managers can easily view the status of the production line at any time.

Network error message query system

As long as the ICT and the depot are connected to the internal network system, you can view all the bad messages of the defective board at the depot, including the printer's printed message and the error graphic display.

Graphical display function to be measured board

The position of the defective part or the solder joint can be displayed when the defect of the board to be measured, and the position of the part can be displayed when the part position is inquired. This function can greatly shorten the time and program adjustment time of the defective product maintenance. If there is a network connection system in the factory, this graphic can also be displayed on the screen of the service station.

Key advantages

· Test speed is fast

· Good test stability

· Low false alarm rate

Easy to operate and easy to maintain.

<< Annex II >>

Production of needle bed customers need to provide the following information:

* Solid plate 1 block

* Material Table 1 copies

* Line diagram 1 copies

* Empty board 1 block

* CAD data format for computer automatic selection system

(1) files generated by Cadence, Allegro, Valid. (Eg: *. Fab, *. Val, etc.)

(2) files generated by Mentor. (Such as: neutral.vss, pf.vss, route.vss, etc.)

(3) files generated by Pads. (Eg: *. Asc, etc.)

(4) files generated by Pcad. (Eg, *. Pdf, etc.)

(5) files generated by Protel. (Eg: *. Pcb, * .pro, etc.)

(6) files generated by Zuken. (Eg: *. Udf, * .mdf, * .ccf, etc.)

* GERBER data required for computer automatic selection system

The same time as the above-

(1) Aperture file (D-Code)

(2) Component side layer (Top layer)

(3) Solder side layer (Bottom layer)

(4) Silk screen component layer

(5) Silk screen solder layer

(6) Solder mask component layer

(7) Solder mask solder layer

(8) VCC plane layer

(9) GND plane layer

(10) Drill map layer

(11) Inner layer1-10

<< Annex III >>


1. When R1> 10R2, R1 can not be measured

2. When XL> 10R2, L can not be measured; XL = 2πfL.

When R2> 10XL, R2 can not be measured.

3. When the capacitance value is large, the amount of R need to increase Delay or CV MODE, when 10R2 <Xc, C can not be measured.

4. When R2> 10, D can be detected when the reverse, or can not be measured.

5. When L2> 10L1, L2 can not be measured.

6. When 10XL <Xc, C can not be measured, when 10Xc <XL, L can not be measured.

7. When RL (ie, inductor DC resistance) <10, D can not be measured.

8. When C2> 10C1, C1 is not measurable, note that this characteristic is opposite to R, L.

9. When the capacitance value is large, the amount of D need to increase Delay, the amount of C should pay attention to the direction of.

10. When D1, D2 in parallel with the parallel, you must use CM MODE, or can not be measured.

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