Electronics in the BINDER endurance test

Testing of PCBs and assemblies in a BINDER MK environmental simulation chamber

Tuttlingen, (PresseBox) - The employees of Kraus Hardware GmbH in Großostheim near Frankfurt / Main develop and build individual measuring and control systems for the automobile industry and for their suppliers for research and development institutes and for aviation. Commissioned by their customers, they repair defective assemblies and put new developments as well as the revised assemblies through their paces before they are delivered to the customer. For temperature testing and traditional drying of components and circuit boards, the company relies on cold and heat test chambers from BINDER.

Highly complex and very specialized are the assemblies manufactured at Kraus Hardware in micro and small series. No challenge is avoided. With the help of state-of-the-art development tools from the requirement specification to the circuit diagram, circuit board layout and VHDL design to mechanics, four employees alone in Development implement on the computer the customer's requirements in a design for the assembly or for a complete measurement and control system. That can take a few weeks to several months depending on how big the challenges to be met are. The manufacturing documents then go to Production. The SMD pick-and-place machine then assembles the circuit board. Two assembly heads with up to four pipettes place 6,500 components at the designated place on the circuit board per hour. Assembly has to be very precise because microcomponents such as 0201 and flip chips with a pitch of 0.2 mm are processed. As a soldering method, Kraus has chosen condensation soldering with the vapor phase because it has turned out to be a good, flexible and reliable soldering method for micro and small scale production.

What was precisely assembled to within fractions of a millimeter in very short period of time now has to be subjected to a test. Can the circuit board do what is expected of it? After assembly, a Flying Probe ICT (in-circuit test) with integrated AOI (Automated Optical Inspection) tests all assemblies. The inspection is the basis of a target/actual comparison. The ICT works the node impedance analysis according to Lissajou. The camera looks for deviations in the stored image, e.g. if a polarized capacitor is applied twisted or a component is missing.

In the subsequent performance test, the temperature fluctuations as they occur in common use may not affect the functionality of the assembly. Like the newly developed assemblies, newly produced assemblies are also tested before use. To determine this, the circuit boards are tested in a BINDER MK 720 cold and heat test chamber. The temperature range of the test chamber ranges from -40 °C to +180 °C. The electronically controlled preheating chamber technology assures temperature accuracy and reproducible results. The chamber is controlled according to preset temperature profiles from the Kraus Hardware test programs directly and if necessary, any errors that occur on the assemblies are logged in terms of the environmental conditions.

Kraus Hardware also tests assemblies provided by the customer in the cold and heat test chamber. The dimensional control determines at which temperature what errors occur. This provides insight into possible causes. The company carries out several hundreds of tests of this type per year as commissioned by the customer.

Two BINDER FED 115 chambers are used for traditional drying of moisture-sensitive components, raw circuit boards and complete assemblies. At delivery, moisture-sensitive components are protected from moisture, vacuumed packed or packed in nitrogen. If they are exposed to the normal surrounding atmosphere for too long, they have to be dried before further processing. To prevent delamination (popcorning) of components, they are annealed for several hours to remove the residual moisture, which is particularly recommended for Flex and Starr-Flex circuit boards from several circuit board manufacturers before processing. An important pillar at Kraus is assembly repair, called reworking. Individual, faulty, twisted or missing components are removed from existing complex assemblies and replaced or re-assembled with new ones. That saves costs, is fast and protects the environment. These assemblies are annealed before processing to prevent induced damage during the rework process on the assembly due to residual moisture.

Like the BINDER climate chambers, the drying ovens are equipped with APT.line(TM) technology for even air circulation even when fully loaded and homogeneous temperature conditions on all test specimens. They were assembled with the maximum number of grids, so that in each pass, the maximum number of microcomponents can be annealed. Until processing, the components, circuit boards and assemblies are then stored at a relative humidity of 3% in the dry storage chamber. Above all, Kraus Hardware praises the good price/performance ratio of BINDER products that include many standard features which are otherwise only available at an additional cost. Even the open-access interface to integrating the chambers in the company's own measurement and testing programs is seen as a major advantage.

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