Wave soldering


Avoidance of assembly errors through visual inspection

Preh updates Ersa Wave Soldering System with VERSAGUIDE system

Whether for climate control, seat adjustment or operating the touchscreen – nearly every car driver has come into contact with the innovative developments of Preh. The automotive supplier from Bad Neustadt an der Saale/Germany develops and manufactures in particular human machine interfaces (HMI) for passenger cars and commercial vehicles as well as e-mobility control units. To guarantee zero defects and avoid any rework, Preh GmbH retrofitted its Ersa POWERFLOW wave soldering system installed in 2019 with the VERSAGUIDE assistance system.

In 1919, when the great age of radio began, Jakob Preh, who gave the company its name, founded his company in Bad Neustadt a. d. Saale in Lower Franconia. As an expert in radio and later also television electronics, Preh initially manufactured electrical installation parts in a former tavern and was one of the first German manufacturers to develop the Preh Funk radio receiver. In the late eighties, the company entered the automotive industry with the production of electronic heating and air conditioning control systems. In its hundred-year history, Preh GmbH has grown into a globally active automotive supplier and today employs around 7,000 people at ten locations. In its anniversary year 2019, the Preh Group achieved record sales of over 1.5 billion Euros.

The company slogan is “Passion for Excellence”. This striving for excellence requires, among other things, continuous optimization of all process steps. Consequently, the Ersa POWERFLOW wave soldering system, which has been in operation at Preh since January 2019, was retrofitted with a complete control system.

The extension contains four placement workstations incl. VERSAGUIDE assistance system, a PCB buffer to realize machine-compatible cycle times, as well as a lifting and lowering station, so that the entire process can be carried out in a round trip and each carrier is returned to its workstation. Following the soldering process, a VERSAEYE automatic optical inspection (AOI) module was integrated to check for the presence of solder and the formation of a meniscus.

Prevention of assembly errors by image recognition

In the course of a targeted zero-defect strategy, the automotive supplier Preh decided to use VERSAGUIDE as part of its process to avoid rework as early as the first process step, i.e. assembly. Due to constantly repeated work steps during assembly, it cannot be prevented that mistakes are made or components are completely omitted.
Particularly in the automotive sector, the elimination of assembly errors has high priority because of the stringent requirements that have to be met. To ensure the functional reliability of the components that will be later in use, any reworking of a faulty assembly is ruled out from the outset. For this reason, only 100% fully intact components may be used right from the start.

Apart from these requirements, it is also a major challenge from a purely technical point of view to correct such errors in the downstream process. In the case of high-mass components, which are frequently used by Preh, rework is usually ruled out, since not enough thermal energy can be transferred into the PCB. Full wetting of the missing solder joint cannot be guaranteed, and cold solder joints may subsequently occur.

With the Ersa VERSAGUIDE for support and control during manual PCB assembly, mounting errors and costs for extensive rework can be avoided. The system is mounted above the assembly workstation. Retrofitting is therefore possible without any problems, as in the case of Preh GmbH. As standard, the camera is located directly above the PCB to be assembled and has thus the best view of the work steps.

Preh GmbH at a glance

  • Founded in 1919 by Jakob Preh
  • 7,000 employees worldwide, 2,000 of them at the headquarters in Neustadt a. d. Saale, Germany
  • Innovation leader in the fields of Human Machine Interfaces (HMI) for passenger cars and commercial vehicles as well as components for e-mobility applications
  • Annual sales in 2019: €1.5 billion
  • Locations in Germany, USA, Mexico, Sweden, Portugal, Romania, China

Simple operation as an all-in-one system

The inspection criteria can be easily set and monitored using image recognition software. Features such as character strings, patterns, colors and textures are reliably recognized, and even single components can be imported into the software as an image. It is important that the camera captures all assembled components and the complete PCB so that the inspection can be carried out without errors. The VERSAGUIDE then leads the user through the individual process steps whereas the main screen can be divided into three individual sections.

The so-called process instruction shows the correctly assembled printed circuit board – the goal of this process step. Depending on how complex this process step is, it is also possible to add explanations or intermediate steps. The live image of the camera shows the initially empty circuit board. The anchor point is used to fix the PCB from the beginning via the software. Thus, an x/y offset or a rotation can be corrected. Red frames are used to inform the operator at which position the next action is required. If a component is placed incorrectly, VERSAGUIDE detects this.

Which components are needed and in which order they have too be placed can be seen in the third section, directly below the Live View. There, single checkpoints are listed, which lead step by step to the finished PCB.

The included IO cable allows the camera to communicate with outside systems. This allows a reliable process control to be designed.

Within the assembly line installed at Preh, the following happens: The PCB is booked into the system at the placement workstation. VERSAGUIDE indicates the start of the placement process and provides step-by-step support during placement and control. Once this process is completed and the board is ready for soldering, VERSAGUIDE sends a signal to the outside via the IOs. A release button is then activated. After pressing the button, the PCB is transported towards the POWERFLOW and soldered there.

Traceability in Every Step

At Preh, the circuit boards finally pass the VERSAEYE module. This allows the soldering quality to be reliably inspected and documented. If the solder joints meet the defined criteria, the software reports this back. But is this good solder joint on the top of the PCB also accompanied by the correct component? The AOI cannot provide feedback on the basis of the solder joint alone. In this line, however, only a correctly assembled PCB can enter the AOI and so this question does not even have to be asked.
With the products previously checked on the VERSAGUIDE and the recorded DMC (Data Matrix Code), the result of the AOI is now transferred to the Host computer. Each individual step is traceable and can be verified at a later point in time.

Short distance, great business relationship

There are just 120 km between the Preh headquarters in Bad Neustadt a. d. Saale and those of Ersa GmbH in Wertheim. However, this geographic proximity is not the only reason for the good relationship of the two companies. The automotive supplier has been relying on Ersa soldering equipment since 2005. In addition to the now extended wave soldering system, the Bad Neustadt production site operates several HOTFLOW reflow ovens and VERSAFLOW selective soldering systems as well as i-CON soldering stations. “Whether PCB layout, traceability or PCB transport. Ersa is our number one contact for the entire soldering process”, says Justin Oppelt, Head of Electronics Manufacturing at Preh, and adds: “The technology seminars at Ersa in particular helped us to understand the individual process steps even better.”

Ersa VERSAGUIDE features

  • Check for correct components
  •  Color inspection
  • Assembly process
  • Structure inspection
  • Check of character strings for barcodes
  • Recording of the finished work

Article Author

Marcel Buck Application and process engineer, Ersa GmbH

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