DE8621171U1 - Test device for double-sided contacting of assembled circuit boards - Google Patents

Description

Siemens Aktiengesellschaft Our symbol

Berlin and Munich VPA

86 P 14 8 9 EN

Test device for side-contacting of assembled printed circuit boards

The invention relates to a testing device for assembled printed circuit boards, with a lower needle adapter ^which carries test needles for contacting the underside of the printed circuit board, and with several upper pressure tappets arranged specifically for ^the test item.

For the electrical testing of assembled circuit boards, which can also be referred to as flat modules, needle adapters with contact pins arranged specifically for the test item are used. A distinction is made between circuit tests or function or partial function tests. In the case of on

For testing, the assembled circuit board is pressed with the solder side against spring-loaded contact needles arranged in the needle adapter. If both a circuit test and a function or partial function test are to be carried out in the same test device, a two-stage contact with contact needles of different lengths is required.

In the first stage of contacting, only the long contact needles are used during the function or partial function test, while in the second stage of contacting, the short contact needles are used during the circuit test.

Simultaneous contacting on the component side of the circuit board is not provided for in the known needle adapters. However, as SMD technology becomes more and more widespread, this requirement for a two-

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step-by-step contacting is becoming increasingly common. In addition, plug connections can often only be contacted from above} if the complex

side contacts of the plugs. 5

The pressing of the assembled circuit boards required for contact can be carried out mechanically using appropriately distributed pressure tappets. However, so-called vacuum adapters are more frequently used, in which the assembled circuit board is manually placed on a rubber seal and pressed down by creating a vacuum. With such vacuum adapters, the advantage of better accessibility on the component side is offset by several disadvantages. Since optimal dosing of the vacuum is not possible, excessive deflection of the circuit boards caused by the high surface pressure cannot be reliably avoided. In addition, sealing represents a significant problem, so that reliable contact can often only be achieved by pressing on certain points or using other methods.

additional manual intervention can be ensured.

Furthermore, the range of circuit boards suitable for testing in vacuum adapters is limited, since, for example, there should be no open vias or breakthroughs. With regard to automating the final testing of assembled circuit boards, the problems mentioned above become even more apparent. In particular, the contact reliability would be further reduced by additional sealing problems when the circuit boards are automatically changed.

The invention is based on the object of creating a test device for the double-sided contacting of assembled circuit boards in which a clearly defined and reliable fixation of the

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Circuit board and a high level of contact reliability is guaranteed.

This object is achieved according to the invention in a test device of the type mentioned at the beginning in that an upper needle adapter is additionally provided, which carries spring-loaded upper contact needles arranged specifically for the test item, and that several lower pressure plungers arranged specifically for the test item are additionally provided, whereby the circuit boards can be pressed against opposite, rigidly arranged pressure plungers using spring-loaded pressure plungers.

The test device according to the invention thus enables contacting of populated circuit boards on both sides, which is made possible by the mechanical clamping of the circuit boards between upper and lower pressure tappets.

An essential prerequisite for a high level of contact reliability is the combination of fixed and spring-loaded pressure plungers. When contacting a first side of the board, the circuit board is pressed by the spring-loaded pressure plungers against the opposite contact needles and against the opposite fixed pressure plungers, with the latter acting as a kind of stop and ensuring a clearly defined contact state. The spring-loaded pressure plungers then give way further until contact with a clearly defined contact state is also achieved on the opposite side of the board.

In practice, it has proven particularly advantageous for carrying out the test if the upper pressure tappets are designed to be spring-loaded and the lower pressure tappets are designed to be spring-loaded.

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pressure rods are arranged in a rigid manner.

Furthermore, in order to make the test device as simple as possible, it is advisable if the lower needle adapter is fixed in place and the upper needle adapter is adjustable in the vertical direction. In this case, the spring-loaded upper pressure plungers can be fixed in the upper needle adapter. The upper needle adapter and the upper pressure plungers can thus be moved via a common drive.

According to a particularly preferred embodiment of the invention, it is provided that the lower needle adapter carries first and second spring-loaded lower contact needles of different lengths, arranged for the specific test, for two-stage contacting of the undersides of the circuit boards, and that the lower pressure plungers are adjustable in two stages in the vertical direction. This two-stage adjustability enables two-stage contacting of the

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Bottom side with clearly defined contact states.

The lower pressure tappets are preferably guided in the lower needle adapter and can be actuated via a lower common pressure plate. In the case of a test item-specific exchange 25

of the lower needle adapter with the lower pressure tappets, the pressure plate and its drive can always remain in the test device.

In order to be able to achieve a two-stage contacting of assembled circuit boards on both sides, it is also possible for the upper needle adapter to have third and fourth spring-loaded pins arranged specifically for the test item and of different lengths for two-stage contacting of the top sides of the circuit boards.

upper contact needles.
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Finally, precise and particularly simple positioning of the circuit boards is achieved by arranging at least two centering pins in the upper needle adapter that precede the upper pressure tappets.

Embodiments of the invention are illustrated in the drawing and are described in more detail below.

Shown are: Figure 1 the contacting principle of a two-sided single-stage contacting of assembled circuit boards,

Figure 2 shows the contacting principle of a two-stage contacting of assembled circuit boards on both sides and

Figure 3 shows a test device suitable for implementing the contacting principle shown in Figure 2 in a highly simplified schematic representation.

Corresponding parts are identified by the same reference numerals in Figures 1 to 3.

Figure 1 shows the sequence of a two-sided, single-stage contacting of a circuit board Lp. On the left-hand side of Figure 1, a lower, stationary pressure plunger Asu, a lower contact needle KnI, a centering pin Zs, an upper, spring-loaded pressure plunger Aso and an upper contact needle Kn3 are shown in a highly simplified schematic representation. A position is shown in the initial stage of the contacting stroke, in which the centering pin Zs has penetrated the associated centering hole in the circuit board Lp and the spring-loaded upper pressure plunger ^üu is already resting on the circuit board Lp. To the right of this representation, the contact needles, which are only indicated here by arrows, are

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the two consecutive contact stages StI and St2 are shown.

In the first contacting stage StI, the contact is made with the underside of the circuit board Lp by the lower contact needle KnI. The lower pressure plunger Asu acts here practically as a stop that limits the downward stroke of the circuit board Lp. The circuit board Lp is firmly clamped between the lower pressure plunger Asu and the upper pressure plunger Aso, i.e. the contacting state of the contacting stage StI is clearly defined.

In the second contact stage St2, the upper pressure plungers Aso have given way to such an extent that the upper side of the circuit board Lp is now securely contacted by the upper contact needles Kn3.

Figure 2 shows the sequence of a two-stage contacting of a printed circuit board Lp on both sides. On the left side

Figure 2 shows the parts already shown in Figure 1 and a shorter second lower contact needle Kn2 arranged next to the first lower contact needle Kn1 as well as a shorter upper fourth contact needle Kn3 arranged next to the upper third contact needle Kn3.

needle KnA is shown. To the right of this illustration, the four consecutive contact stages StI, StI, St3 and St4 are shown with the contact needles, which are only indicated by arrows.

The first two contact stages StI and St2 do not need to be discussed in more detail, since they correspond to the contact stages StI and St2 already explained in connection with Figure 1.

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In the third contact stage St3, the lower pressure plunger Asu is in a lower position than in the contact stages StI and St2. This lower position of the lower pressure plunger Asu now ensures secure contact with the underside of the plate by the second contact needles Kn2.

In the fourth contacting stage St4, the upper pressure plunger Aso finally gives way to further elasticity, and the fourth contact needles Kn4 make contact with the upper side of the plate.

It can be seen that in all contact stages StI to StA, clearly defined contact states are ensured by fine, firm clamping of the circuit board Lp between the lower pressure tappets Asu and the upper pressure tappets Aso. It can also be seen that there are a number of variations in the order of the contacts.

possible are.
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Figure 3 shows a test device for two-sided two-stage contacting of assembled circuit boards in a highly simplified schematic representation. The test device shown in Figure 3 can thus be used to test the

shown contacting principle can be realized;

According to Figure 3, the circuit board Lp to be tested is equipped with components Bt and placed in an outer frame marked Ra. Arrows PfI and Pf2 indicate that the frame Ra can move vertically upwards and downwards, whereby this mobility of the frame Ra and the circuit board Lp arranged therein can be achieved, for example, by a spring-loaded suspension of the frame Ra.

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Below the circuit board Lp there is a stationary lower needle adapter Nau, which carries the first spring-loaded contact needles KnI and the slightly shorter second spring-loaded contact needles Kn2. At one point it is indicated that the contact needles KnI and Kn2 are connected to the associated wrap spikes WS via lines L. The wrap spikes WS arranged outside the contact area in the lower needle adapter Nau are in turn connected to the needles of a connecting element Ag, which are also not specified, via an intermediate element Zg with spring-loaded needles (not specified in more detail). This connecting element Ag is part of the actual test machine, which is, for example, the "Series 700" from Factron-Schlumberger, Albert Schweitzer Str. 66,

D- 8000 Munich 83, can act.

In the lower needle adapter Nau, lower pressure tappets, designated Asu, are also guided, which are held in the needle adapter Nau by springs Fl so that they can move in the vertical direction.

The lower pressure tappets Asu are therefore not spring-loaded, but are adjustable in two stages in the vertical direction via a common lower pressure plate Dp. This two-stage adjustability, indicated by double arrows Pf3, can be achieved, for example, by

arranged pneumatically or hydraulically actuated adjustment cylinders can be implemented.

Above the circuit board Lp there is an upper needle adapter Nao which is vertically adjustable and which carries third spring-loaded contact needles Kn3 and a slightly shorter fourth spring-loaded contact needle Kn4. The further wiring of the contact needles Kn3 and Kn4 (not shown in detail) includes transfer contacts to the lower needle adapter Nau, so that the upper test contacts, which are usually only a few in number, are also

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if connected to the test machine via the interface of the intermediate link Zg.

In the upper needle adapter Nao, upper pressure plungers marked Aso are fixedly arranged. These upper pressure plungers Asu are designed to be telescopically springy, whereby this springy design is indicated at one point by a corresponding spring F3. Two centering pins Zs also arranged in the upper needle adapter Nao have the task of penetrating into assigned centering holes in the circuit board Lp and thus precisely positioning the circuit board Lp.

The vertical adjustability of the upper needle adapter Nao is shown by arrows Pf4, Pf5 and Pf6, whereby the two downward-pointing arrows Pf5 and Pf6 symbolize the two-stage contacting. The vertical adjustment can be achieved, for example, by mounting the upper needle adapter Nao in a solid

Four-column frame and depending on the adapter size by

One to four spindles synchronized by toothed belts are driven by a DC motor. The described drive of the pressure mechanism is designed as a programmable positioning axis.
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3 figures

Claims (8)

IB > I * a * * _10_ 88 P H 8 9 DE isprüche 1. Test device for assembled printed circuit boards (Lp), with ^J a lower needle adapter (Nau) which carries spring-loaded lower contact needles (KnI, Kn2) arranged specifically for the test item for contacting the underside of the printed circuit board (Lp), and with several upper pressure plungers (Aso) arranged specifically for the test item, characterized in that an upper needle adapter (Nao) is additionally provided, which carries spring-loaded upper contact needles (Kn3, Kn4) arranged specifically for the test item, and that a plurality of lower Asr pressure plungers (Asu) arranged specifically for the test item are additionally provided, whereby the circuit boards (Lp) can be pressed with spring-loaded pressure plungers (Aso or Asu) against opposite, unyieldingly arranged pressure plungers (Asu or Aso). 2. Testing device according to claim 1, characterized in that the upper pressure tappets (Aso) are designed to be resilient and that the lower pressure tappets (Asu) are arranged to be rigid. 3. Testing device according to claim 1 or 2, characterized in that the lower needle adapter (Nau) is arranged in a fixed position and that the upper needle adapter (Nao) is arranged so as to be adjustable in the vertical direction. 4. Test device according to claims 2 and 3, characterized by that the upper spring pressure tappets (Aso) are firmly in the 35 Il t * * · · .11. 86 P H 8 9 EN upper needle adapter (Nao). 5. Test device according to one of the preceding claims, characterized in that the lower needle adapter (Nau) carries first and second spring-loaded lower contact needles (KnI, Kn2) which are arranged specifically for the test item and have different lengths for two-stage contacting of the undersides of the circuit boards (Lp) and that the lower pressure plungers (Asu) are adjustable in two stages in the vertical direction. 6. Test device according to claim 5,
characterized in that the lower pressure tappets (Asu) are guided in the lower needle adapter (Nau) and can be actuated via a lower common pressure plate (Dp). 7. Test device according to one of the preceding claims, characterized , that the upper needle adapter (Nao) carries third and fourth spring-loaded upper contact needles (Kn3, Kn4) which are arranged specifically for the test item and have different lengths for two-stage contacting of the upper sides of the printed circuit boards (Lp). 8. Test device according to one of the preceding claims, characterized in that at least two centering pins (Zs) are arranged in advance of the upper pressure tappets (Aso) in order to position the circuit boards (Lp) in the upper needle adapter (Nao). * * lift