RU2552866C2 - Device for electronic printed circuit boards mechanical testing - Google Patents

Abstract

FIELD: testing equipment.

SUBSTANCE: invention relates to the testing equipment used during strength testing (in particular strength testing of electronic PCBs during manufacturing). Device contains power framework including fasteners for electronic PCB installation and support poles on which the pressing mechanism, metering probe and indicator are secured. The power frameworks is made out of four support poles connected by rods along the perimeter, at that to two opposite rods cross-bars are secured with installed fasteners for electronic PCBs with possibility of PCBs movement along the parallel rods and cross-bars. Above PCB of the support poles a conductor is installed made out of the ring with top and bottom meshes, in mesh cells indentors are installed till rest against PCB surface. Above the conductor in the support poles the press mechanism is installed, it contains crosspiece with plate, and metering probe and indicator are secured in the suspended assembly on the cross-bars under PCB. Number of points for the indentors installation is determined as per equations.

EFFECT: designing of simple loading device for mechanical testing of the electronic PCBs.

2 cl, 7 dwg

Description

The invention relates to a testing technique used in strength testing (in particular, to testing the strength of electronic circuit boards (EM) in the manufacture).

During the operation of instruments as part of various machines and equipment (for example, spacecraft), ES with electro-radio elements are exposed to various types of external influencing factors: mechanical, climatic, ionizing radiation, etc. The mechanical effects include: static, vibrational, linear, shock loads and acoustic noise. Products designed to function under mechanical stress must be strong and stable when exposed to these factors. This ability is tested in the process of conducting tests for mechanical stresses both at the stage of testing the devices and at the stage of manufacturing the EP included in the devices.

One of the recommended test methods for EM is the monotonic bending test method (IEC-PAS 62137-3 standard. Electronic wiring technology. Methods for testing the reliability of soldered joints. Appendix D). For testing the electric field, it is mounted on two supports with the surface mounted downward and, using an indenter (tip), pressure is applied to it from above to create the required level of electric field loading. There are various modifications to this test method. To implement this technology, a load device is required. Currently, there are various loading devices for testing: RF patent No. 1582063 [1], RF patent No. 1663497 [2], RF patent No. 1748007 [3], RF patent No. 2416084 [4], RF patent No. 2453823 [5] . The proposed solutions contain a power frame with a device placed on it for loading the test object, supporting elements for placing the test object on them, means of monitoring the movements of the test object.

Closest to the claimed solution is the device presented in the patent of the Russian Federation No. 2453823 (prototype). The disadvantage of the proposed devices is their bulkiness, the inability to accurately position the indenter necessary for loading small electromagnets taking into account the high density of electronic components on the boards, and, as a result, use such devices for testing.

The task to be solved by the claimed invention is directed is the elimination of these drawbacks, which will allow higher quality testing of ES for various equipment.

The technical result of the claimed invention is the development of a simple load device for testing the mechanical effects of EP.

The technical result is achieved by the fact that a device has been developed for testing EMs for mechanical stresses, which contains a power frame, including fasteners for installing EMs and support racks on which the pressure mechanism, measuring probe and indicator are fixed. The power frame is made of four support posts connected by rods around the perimeter, with cross members attached to two opposite rods with brackets for electric drives mounted on them, with the possibility of moving the electric drive along parallel rods and across. A conductor made of a ring with upper and lower grids is placed above the conductor on the support racks; the indenters are installed in the cells of them in the circuit board, and above the conductor, the support mechanism consisting of a cross with a plate is fixed to the support racks, and the measuring probe and indicator are fixed in the suspension unit on the crossbars under the EA, while the number of installation points of the indenters is determined by the formulas:

where δ _j (x _i , y _i ) is the displacement at the j point under the influence of the load applied at the i point; P _i (x _i , y _j ) is the load applied at point i;

G is the coefficient of proportionality connecting the displacement with the load and the cylindrical rigidity of the electric field;

- цилиндрическая жесткость ЭП, (Е - модуль упругости материала ЭП,

- the cylindrical stiffness of the EP, (E is the elastic modulus of the EP material,

h is the thickness of the electron beam, ν is the Poisson's ratio of the material of the electron beam), δ _max (x _j , y _j ) is the maximum displacement at point j;

- суммарное перемещение в j точке;

- total displacement at j point;

N is the number of points of application of the load (N≥1);

j is the number of the point with maximum displacement;

i is the number of the current point with movement;

Δ is the error of the job assignment.

The conductor and pressure mechanism are attached to the support posts using nuts.

The invention is illustrated by figures.

FIG. 1-3 - design of the test device.

In FIG. 1, a load device is shown, consisting of four posts 1 connected by rods 2 and screws 3, the crossbars 5 are attached to the rods 2 by the supports 4 and screws 3, the supports 4 are freely movable along the rods 2 and fixed by screws 6, the supports 7 and suspensions 8 are mounted on the crossbars , they freely move along the cross-beam 5 and are fixed with screws 6. Pendants 8, the crossbar 9, the clamp 10 and the screw 11 form a mount for the probe 36 and indicator 12.

A conductor 14 with grids 15 attached to it is installed above the EA 13 using rings 16 and bolts 17 and is fixed with nuts 18 on the racks.

Above, a push mechanism is installed (Fig. 2), consisting of a cross 19 with guide sleeves 20, which is fastened to the stands of the bench by nuts 21. A glass 22 is attached to the cross with four screws 23, a guide column 24 is attached to the plate 26 with screws 25, the disk 27 screws 28 - to the glass 22. A nut 29 with four handles 30 and a plate 26 combine the components of the mechanism into a single whole. In the conductor, we set the indenters 31 all the way to the surface of the board, due to them the deflection of the electromagnet is carried out (there can be one or more of them, depending on which one you want to recreate the deflection of the surface of the electromotive)

A device with a measuring probe 36 and an indicator 12 with an arm 32 (Fig. 3) is fixed under the EF on the mounting mechanism, which is bolted 33 to the plate 35 and the bolt 34 to the instrument housing 12. The probe 36 is brought to the surface of the EF 13 at the point of maximum deflection . The indicator scale 12 is zeroed. Under load, the EA will bend, and indicator 12 will display the amount of bend.

The figures demonstrate a method of installing a power supply on the supports of the device, explaining the possibility of connecting specialized equipment to check the operation of the power supply under load on four sides of the connecting cables (analog or digital signals).

FIG. 4a - finite element model of the control unit of one of the spacecraft (the ES in the unit is shown by an arrow); b) - finite element model of the electric field from this control unit;

Figure 5 - displacement fields obtained when calculating the block from the EF to quasistatic (a), vibration (b) and shock loads (c) [as an example, the displacements in the center of the EF are shown: the Y axis is the length of the board in width, the X axis is the magnitude of the deflection of the surface of the EA under load];

FIG. 6 is a graphical representation of the envelope of the maximum displacements of the surface of the electromagnet under shock load (a - without load, 6 - under load);

FIG. 7 is a calculation scheme of the proposed method: points 1,2,3,4 with coordinates (x _i , y _i ) are local loading points, point 5 with coordinates (x _j , y _j ) is the point of maximum displacements (maximum deflection).

Practical example

The application of the technology discussed above is demonstrated as follows. A finite element model of the control unit of one of the spacecraft is being developed; an example of the control unit is shown in FIG. 4 a. The block includes several electronic components. The dimensions of the considered EP are 292 × 150 × 30 mm (Fig. 4, b). ES is designed for quasistatic, vibrational and shock loads. The calculation results are the field of displacements of the surface of the electric field under load (Fig. 5). The maximum displacements throughout the EP became displacements under impact and amount to 2.36 mm. The maximum deflection point has the following coordinates (0.135,0.146). Using formula (1), the necessary load is determined for the deflection of a given value (that is, points i and j coincide) P _i = 221.2 N, while the stresses arising at the point of application of the load are σ = P / S = 70, 45 MPa, where S is the cross-sectional area of the indenter used to carry the load. The ultimate stresses for the material of the protective layer of EP σ _pr = 20 MPa. Thus, if one indenter acts on the surface of the electromagnet at the point of maximum displacements to create the desired deflection, the protective layer is damaged, because σ> σ, _etc. Therefore, in order not to damage the protective layer, the load is distributed on n points, the number of which is regulated by the value of the load and places on the board that are free from installation.

To obtain the fields of displacements during EC tests, the load is carried out at n = 4 points with the coordinates: 1 (0.125,0.136), 2 (0.125,0.146), 3 (0.130,0.156), 4 (0.132,0.130) (Fig. 7). Using formulas (1) and (2), the values of the loads necessary for the deflection of the surface of the EP, as in shock loads, are calculated. The magnitude of the deflection under the applied loads was δ _total (x _i , y _i ) = Σδ _j (x _i , y _i ) = 2.358 mm.

The coordinates of the application points and the load value are determined. The EF is fixed on the supports of the developed device so that the central axis of symmetry of the device passes through the point of maximum deflection of the EF. Indenters are installed in the conductor at the calculated points. The push mechanism is fixed. A probe and indicator are installed under the EA. The measuring probe is brought to the lower side of the EA, the indicator is zeroed. Rotating the handle, the plate presses on the indenters, the EA bends and the indicator displays the amount of deflection. At the same time, a testing device for electrical and logical circuits is connected to the electronic circuit. The testing device simulates the actual operation of the electronic drive as part of the equipment. A power supply is applied to the EA connected to the testing device and the corresponding electrical indicators are taken. In the process of loading (deflection), the registration of electrical indicators confirming the performance of the electric drive at a given load does not stop.

Of the sources of information and patent materials known to the authors, the totality of features similar to the totality of features of the claimed subject matter is not known.

Claims (2)

1. A device for testing electronic circuit boards (EM) for mechanical stresses, containing a power frame, including mounting brackets for installing the electronic components and support racks, on which the pressure mechanism, measuring probe and indicator are fixed, characterized in that the power frame is made of four support racks, connected by rods around the perimeter, with cross members attached to two opposite rods with mounts for EP installed on them, with the possibility of moving the EP along parallel rods and along the cross, with over A conductor made of a ring with upper and lower grids is placed on the racks; the indenters are installed in the cells of the plate against the surface of the board; moreover, a push mechanism consisting of a cross with a plate is fixed to the support racks above the conductor, and the measuring probe and indicator are fixed in the hanging unit on the crossbars under the EA, while the number of installation points of the indenters is determined by the formulas:

where δ _j (x _i , y _i ) is the displacement at the j point under the influence of the load applied at the i point;
P _i (x _i y _j ) is the load applied at point i;
G is the coefficient of proportionality connecting the displacement with the load and the cylindrical rigidity of the electric field

is the cylindrical rigidity of the EP (E is the elastic modulus of the EP material, h is the thickness of the EP, ν is the Poisson's ratio of the EP material), δ _max (x _j , y _j ) is the maximum displacement at point j;

- total displacement at j point;
N is the number of points of application of the load (N≥1);
j is the number of the point with maximum displacement;
i is the number of the current point with movement;
Δ is the error of the job definition. 2. The device according to p. 1, characterized in that the conductor and the pressure mechanism are attached to the support posts using nuts.

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