SU1486914A1 - Method for evaluation of quality of microcircuit lead junction with contact pad of printed circuit board - Google Patents

Description

The invention relates to non-destructive testing and can be used in the electronic industry to assess the quality of the soldered joints of the outputs of the microcircuits with the contact pads of printed circuit boards. When AC power is applied

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current on the electromagnetic transducer 10, its movable part - coil 9 inductance - transmits the force to the grip 3. This creates an alternating load on the edge of the connection 2 of the output of the microcircuit with the printed circuit board. If the connection quality is unsatisfactory, microcracks are formed in it. The process of the formation of microcracks is accompanied by an acoustic signal, which is perceived by the piezoelectric transducer 5, amplified by the preamplifier! 1, by the amplifier 12 and converted into rectangular pulses at the output of the former 13.

The total number of pulses at the output of the counter 14 is judged on the quality of the connection. Mechanical stresses are determined only by the Attached

load when current is applied to an inductance coil of an electromagnetic converter and is caused not by dynamic overloads, but by static stretching and compression, since the vibration frequency is incommensurably less than the natural frequency of the monitored products. And the change of the sign of mechanical loading is necessary to create conditions for moving the output within 0.1- 0.2 mm and the formation of new adhesive bonds and their subsequent rupture, while maintaining the conditions for the restoration of the connection after the discovery of the defect. It is significant that only the weakest part of the products with regard to mechanical strength - the edge of the solder joint - is subjected to alternating loading. 1 il.

The invention relates to non-destructive testing and can be used in the electronic industry to assess the quality of the soldered joints of the outputs of the microcircuits.

The purpose of the invention is to increase the reliability of the evaluation of the compound.

The drawing shows a diagram of the device for assessing the quality of the connection output of the chip with the contact pad of the printed circuit board, the vertical section 35 of the output of the chip is compressed by the grip when the electromagnet is turned on.

Plot 1 chip output, immediately adjacent to the controlled connection 2, the capture 3 40

connected to an electromagnet 4, the casing of which is fixedly connected to the piezoelectric transducer 3 enclosed in the casing 6. The latter is suspended from the fixed bed 7 on the membranes 8. On the casing 6 the inductance coil 9 of the electromagnetic transducer 10 is fixedly mounted. The piezoelectric transducer 5 is electrically connected to the pre-amplifier 11, the amplifier 12, the shaper of 13 rectangular pulses and a summing counter 14 "

The method is as follows. 55

AC voltage is supplied to the electromagnetic transducer 10, its movable part - inductor 9, connected to housing 6 mounted on the membranes 8, in which piezotransducer 5 is located and preamplifier 11, transmits the force to the clamp 3. Thus, the force is transmitted to the vertical part of the output of the chip, and therefore on the edge of the connection. The amplitude of oscillation is 0.1-0.2 mm. The lower limit corresponds to the experimentally established limit for the detection of the “Nespay” type defect. The upper limit corresponds to the permissible limit angular displacement of the horizontal output area of the product. Normal voltage ό, I / mm ^, occurs in a small area of the connection. With efforts, when this stress exceeds the allowable, the formation of a crack at the junction begins, which is accompanied by an acoustic signal. This signal is perceived by the piezoelectric transducer 5 (£ r _es = 300 kHz) is supplied to the preamplifier 11 (bandwidth 46 MHz = 0.1-1.2, _yc = 100 K), the amplifier 12 - (SK4-58) shaper 13 rectangular pulses and a summing counter 14. The presence of an acoustic emission signal of the threshold level indicates a poor-quality connection.

Claims (1)

Claim The method of assessing the quality of the connection of the output circuit with the contact PCB pad,. turn on5 6 the mechanical loading of the joint and the recording of acoustic emission signals, distinguished by the fact that, in order to increase the reliability of the evaluation of the quality of the joint, the mechanical loading 1486914 the connections are made with an alternating load directed along the output section of the microcircuit adjacent to the connection under control, with the amplitude of the output O, ΙΟ, 2 mm.