DE3311977A1 - Arrangement for the electrical scanning of an assembly - Google Patents

Abstract

In scanning devices for testing electrical assemblies (5), flux residues between the points of the assembly (5) to be scanned and the applied scanning heads (4) of scanning pins (3, 4) of the scanning device prevent reliable contact being made. By supplying heat energy, the scanning heads (4) and/or the contact point of the assembly (5) are heated to a temperature which exceeds the softening temperature of the flux. The flux residues are in consequence displaced by the spring force of the scanning pins (3, 4), which increases the contact reliability. <IMAGE>

Description

Arrangement for electrical scanning of an assembly

The invention relates to an arrangement for making electrical contact a contact point of an electrical assembly with an attachable probe head a stylus.

Such an arrangement is known from DE-OS 29 12 007, for example become. After that, an assembled or unassembled printed circuit board to be tested becomes a Assembly with its contact points by negative pressure against probe heads of probe pins drawn, which are fixed in a perforated plate. At the points to be scanned Printed circuit boards often adhere to flux residues, which ensure reliable contact to question. The flux residues also settle over time on the probes, which further reduces the contact reliability.

From US-PS 34 53 545 it is known to test the specimen in test adapters vibrate by using an electromagnetically actuated firing pin hits against the holder for the test item. This leads to a short-term Increase in the contact force, which helps to improve contact. But even here it is not prevented that the heads after a certain number contaminate from contacting processes.

The situation is similar with a test device according to DE-AS 23 44 239. Here, too, a pressure plate is placed on the circuit board against which a plunger of an ultrasonic transducer is pressed. The high frequency vibrations the circuit board increase the contact security.

According to DE-OS 29 18 948, the styli are instead of the circuit board the device is set in ultrasonic vibrations. This makes it possible to use stocked To test printed circuit boards without the components being affected by the vibrations to be pulled.

The invention is based on the object with little outlay on equipment to achieve a high level of contact security without handling the device to affect.

This object is achieved by the invention according to claim 1. That Colophony commonly used as a flux softens at just one temperature from 520 C.

By heating the probe head and / or the contact point E.g. 600 C is reached that existing rosin residues under the effect of the Contact force are displaced and that thus a safe direct contact between the probe and the contact point is established. The shape of the contact heads can be different depending on the type of contact point of the assembly.

A multi-tip contact head with the middle tip higher than the rest, is suitable for different types of contact points. Such probes naturally become very clogged with rosin residues. By heating the probe head, secure contact with the Contact point enables.

Advantageous developments of the invention are in the claims 2 to 16 characterized: Through the development according to claim 2, the thermal energy be introduced very specifically to the stylus. The entire heating power remains relatively limited, which facilitates the supply of electrical energy.

The probe head heats up due to thermal conduction. It will only be the Probe tip warmed up immediately adjacent rosin residues.

The development according to claim 3 ensures that the Heating current does not influence the test sequence. Need the preheated probes after placing it on the contact points for a short time to remove the rosin layers to penetrate. After that, the heater is no longer required and the test sequence can start undisturbed.

The development according to claim 4 allows with limited overall performance a short-term high heating output on the individual styli. The heating wire can in a strength that is advantageous for the manufacture and connection of the winding be used.

The developments according to claims 5, 6 and 7 require one less circuit effort. By connecting several heating coils in series can be worked with a relatively high voltage.

Through the development according to claim 8, the heating energy is immediate transferred to the stylus. The heating wire winding can in a simple manner e.g. attached to the sleeve by gluing. The probe head is due to the arrangement the heating wire winding is effectively heated.

By embedding the heating wire winding in the perforated plate Claim 9, the heat losses of the winding are reduced. The location of the pins does not need to be changed compared to a device without heating wire windings will.

The development according to claim 10 enables the supply of the electrical Energy in a simple way. the Use a conductor foil after Claim 11 helps to further reduce wiring costs with little space required. Due to the double-sided lamination of the conductor foil according to claim 12, it is possible the operating potential on one side and the ground potential on the other side of the Lead conductor foil. The ground lines can be meshed so tightly that results in a shield level that improves the electrical conditions during testing. The ground potential can be point-wise at suitable points via plated-through openings to the other side of the conductor foil. This makes it possible to use the Winding wire ends on the same side of the conductor foil to connect what the Assembly much easier.

For the connection of the winding wire to the operating potential you can also through-plated openings can be provided. Are several heating wire windings connected in series, two heating wire ends can be connected in through-plated Openings are connected to each other by soldering.

Through the development according to claim 13, the contact points or heat probes effectively in a simple manner. The advanced training according to claim 14 can easily be used in a scanning device that controls the pressing forces not created by vacuum. But the probes can also use a vacuum adapter be preheated by warm air so far that after switching off the warm air and switching on the flux parts are safely heated after the suction.

The development according to claim 15 enables a continuous Supply of warm air even during testing with the exhaust system switched on. at Sealing of the cavity between the two perforated plates, it is possible to use a to create a closed cycle with little energy consumption. A heat nuisance the operators will thus largely avoided.

The heating plate according to claim 16 can for example consist of ceramic material and heated by heating wires laid between the stylus. The hot plate heats the stationary sleeves of the contact pins and thus their probes. Even such an arrangement can be implemented with relatively little additional effort.

In the following the invention is illustrated in the drawing with reference to FIG Embodiments explained in more detail.

The figures show: FIG. 1, in cross section, part of an electrically tested device Assembly and a device for contacting the assembly with a not shown electrical test device, FIG. 2 shows an enlarged section of the device According to Fig. 1, Fig. 3, in cross section, the assembly according to Fig. 1 and another Kontaktiervörriohtung.

According to Fig. 1, the device consists of a perforated plate 1 with receiving bores 2 for styli 3, 4 their fixed sleeves 3 in a part of the mounting holes 2 are used. The probe heads 4, which are resiliently mounted in the sleeves 3, press each other to different contact points of an electrical assembly 5, which consists of a Printed circuit board and electrical components. The contacting device is also provided with a circumferential support web 6 on the outer edge of the perforated plate 1 is attached to the assembly 5 facing side. Furthermore is on the same On the side of the perforated plate 1, a frame 7 overlapping the receiving web 6 is releasably attached. A circumferential rubber strip 8 is airtight between the frame 7 and the web 6 trapped. Within the web 6 is a Pressure plate 9 arranged, which is provided with free bores 10 for the protruding probe heads # 4. the Pressure plate 9 is supported on the perforated plate 1 compression spring 11 in the direction of the frame 7 inwardly overlapping rubber strip 8 pressed. The assembly 5 is te with its circuit board on the perforated plate 1 facing away from the Inner edge of the rubber strip 8 is placed. On the side facing away from assembly 5 A film 12 in the form of a photographic negative is glued to the perforated plate 1 This negative is only provided with holes 13 at the points which the sleeves 3 are inserted into the perforated plate 1. The film 12 thus seals the perforated plate 1 against air penetration.

The one between the perforated plate 1 and the circuit board of the assembly 5 The space formed is largely sealed by the ring-like circumferential rubber strip 8. A vacuum is created in this room by sucking in the air. This will the printed circuit board is pulled in the direction of the perforated plate 1.

The contact points of the assembly 5 to be scanned are thus counteracted the spring-loaded ends of the probes 4 pressed.

These sleeves 3 are at their end facing away from the probe heads 4 provided with connecting pins for jumper wires 14, which are connected to the electrical part of the Test device are connected.

On the inside of the perforated plate is a double-laminated one Conductor foil 15 placed, the dimensions and through-penetration openings for the sleeves 3 of the film 12 is enough. The conductor foil 15 has conductor tracks on both sides provided, the ground potential being arranged on the side facing the perforated plate 1 is.

According to FIG. 2, around the end of the sleeve 3 facing the probe head 4 a heating wire 16 is wound and its ends are connected to the two electrical potentials the conductor foil 15 connected. The conductor foil 15 and the perforated plate 12 have a recess 17v # rs # ehen into which the heating wire winding is inserted is. The two ends of the heating wire 16 are led out of the recess 17 and connected to the conductor tracks of the conductor foil 15.

The scanning device according to FIG. 2 differs from that in FIG. 1 and 2 represented by the elimination of the depressions, heating wires and conductor foil. The perforated plate 1 is offset towards the ends of the sleeves 3 facing away from the assembly 5. Another perforated plate 18 is arranged parallel to the perforated plate 1 at a distance. The sleeves 3 are pushed through both perforated plates. Through an entrance opening 19 in the perforated plate 1 can be in the space between the two perforated plates Warm air can be blown in. As a result, the styli 3, 4 heat up in the desired manner Way.

16 claims 3 figures

Claims (16)

Claims fm f X arrangement for electrically contacting a Contact point of an electrical assembly with an attachable probe head Stylus of a scanning device, with between the probe head and the contact point Flux residues may be present, which are not indicated that the probe (4) and / or the contact point to a softening temperature the temperature exceeding the flux can be heated. 2. Arrangement according to claim 1, d a d u r c h g e k e n n -z e i c h n e t, that the stylus (3, 4) by means of an electrical heating wire winding (16) is heatable. 3. Arrangement according to claim 2, d a d u r c h g e k e n n -z e i c h n e t that the heater for the duration of the electrical testing of the assembly (5) can be switched off. 4. Arrangement according to claim 2 or 3, d a d u r c h g e -k e n n z E i c h n e t that with a scanning device with a plurality of stylus pens (3, 4) the heating wire windings (16) can be wired sequentially. 5. Arrangement according to claim 3 or 4, d a d u r c h g e -k e n n z e i c h n e t that the heating wire windings (16) are permanent between the test cycles are switched on. 6. Arrangement according to claim 5, d a d u r c h g e k e n n -z e i c h n e t that the heating wire windings (16) are connected to an alternating current source are. 7. Arrangement according to claim 5 or 6, d a d u r c h g e -k e n n z e i c h n e t that several heating wire windings (16) are connected in series. 8. Arrangement according to one of the preceding claims, d a -d u r c h g e k e n n n z e i c h n # t that the probe head (4) is in a fixed sleeve (3) of the Stylus (3, 4) resiliently mounted Ust that the sleeve (3) in a perforated plate (1) the scanning device is used and that the insulated heating wire (16) around the Sleeve (3) is wound at the end facing the probe (4). 9. Arrangement according to claim 8, d a d u r c h g e k e n n -z e i c h n e t that the perforated plate (1) on the probe head side with recesses for the Heating wire windings (16) is provided. 10. The arrangement according to claim 8 or 9, d a d u r c h g e -k e n n z e i c h n e t that the perforated plate is provided with conductor tracks to which the ends the heating wires are soldered on. 11. The arrangement according to claim 8 or 9, d a d-u r c h g e -k e n n z e i c'h n e t that a conductor foil (15) is placed over the perforated plate (1) whose conductor tracks are soldered to the heating wire ends. 12. The arrangement according to claim 11, d a d u r c h g e k e n n -z e i c h n e t that the conductor foil (15) laminated on both sides and with through-contacts Holes is provided. 13. The arrangement according to claim 1, d a d u r c h g e k e n n -z e i c h n e t that the contact points and / or probes (4) heat energy through a fluid medium can be supplied. 14. The arrangement according to claim 13, d a d u r c h g e k e n n -z e i c h n e t that warm air in the space between a circuit board and the perforated plate is inflatable. 15. The arrangement according to claim 13, d a d u r c h g e k e n n -z e i c h n e t that with a scanning device designed as a vacuum adapter the Stylus pins (3, 4) in two perforated plates arranged parallel to one another at a distance from one another (1, 18) are used and that the fluid medium through the space between the two perforated plates (1, 18) can be passed through. 16. The arrangement according to claim 1, d a d u r c h g e k e n n drawn that the stylus pins (3, 4) inserted into an electrically insulating heating plate are.