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SENSORS & DATA CONVERSION Fig. 3: Traditional test board profiling. Fig. 5: APS - speed sensor up close. an individual’s expertise to attach the thermocouple sensors correctly and in the right place. Capturing the true profile, then the ‘golden standard’, which is imperative to the product working correctly, is not easily achieved. Oven verification devices Because of these drawbacks to using traditional thermal profiling devices, combined with test cards, companies like SolderStar, worked on devising technologies that would give ease the process of capturing oven verification profiles. There was a need for a device that monitored oven temperatures effectively, without putting constraints on the machine, and the technicians working them. There was also the need for software that documented the profile accurately and could be easily traceable. This is especially important today with government regulations and original equipment manufacturers imposing higher standards. The medical and automotive industries are just two industries that have pushed demand for more critical control and traceability, therefore oven verification devices were born. One example of this technology is SolderStar’s DeltaProbe. This product was designed and developed to combat the problems of traditional manual profiling and gives manufacturers a more streamlined method for periodic profile. The DeltaProbe offers a process control and intelligence that matches manufacturers more intricate and detailed production requirements, without the need to use fragile test boards for daily oven checks. The DeltaProbe was designed to use the unique SolderStar ‘Smart link interface’, this makes for an intelligent fixture which can hold product and process recipe information to allow efficient profile capture, download and organisation. Smart link provides the secondary function of a quick connection system eliminating the possibility of channel mix-up error. Oven verification devices like the DeltaProbe include specially designed measurement sensors where all process records are captured without a test card or wires getting in the way of the procedure. This makes it not only robust, but the appropriate tool to generate highly repeatable results, an important requirement today, which stands up to regulatory requirements. By using an oven verification tool, a ‘golden’ process profile can be measured easily and tolerance limits can be set around the temperature traces and process parameters. This ensures measurements are precise and any oven performance changes or problems are quickly flagged and remedial action can be taken. This makes periodic testing of the oven more repeatable, convenient and user-friendly, resulting in better process documentation at a lower cost to the manufacturer. Platforms like DeltaProbe far outweigh test card methods for a number of reasons; • The usual use of test cards need constant maintenance and it is not easily repeatable. This results in false errors due to measurement platform problems. • Statistical Process Control (SPC) gathering is easy and offers a more accurate measurement. • Matched sensors show any performance problems across the width of the oven heater. • There are independent limit settings per oven zone which gives more control in critical zones. • A number of errors can be detected easily including speed, conveyor and recipe loading and editing errors. • It can be used to capture a benchmark for multiple of lines – a must for high production volumes All these benefits help to give a true picture of the process capability and result in higher quality soldering within the end product. Platforms like this can be used once a temperature profile is captured from a real test PCB. The ongoing process monitoring will then be achieved by measuring the difference from an established process baseline. The software used with such products also includes advanced SPC tools which create charts for ongoing process control measurement, trend evaluation and corrective action. This process, as you can see, far outshines traditional profiling methods. Continuous oven monitoring Safety critical or high value assemblies, combined with tighter processing constraints, and the need for complete process documentation has driven the development of profiling systems that can monitor every electronic assembly produced on the manufacturing line. The pinnacle of profiling systems today Fig. 4: Oven verification – Tolerance-band-error screen details. 44 Electronic Engineering Times Europe June 2015 www.electronics-eetimes.com


EETE JUN 2015
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