Feature: Interconnections
and precision require specialist manufacturing processes. We at the Micrometal Group
have developed a next-generation photochemical etching (PCE) process that is ideally suited to lead frame production and gives customers the opportunity to make innovatively- designed lead frames with tight tolerances repeatably and accurately whilst meeting the requirement for miniaturisation and weight saving. Micrometal has a long experience of
lead frame manufacture using PCE for an array of customers and applications. We etch simple or sometimes more complex lead frames from metal and alloys with very low expansion rate at room temperature. These low thermal expansion alloys are now widely used in modern applications, which may require joining of a metal to glass or ceramics and in areas where thermal expansion rates should be matched between materials to prevent any unwanted problems in the joints.
Tools and process complexity When stamping lead frames, complexity adds cost, whether in low-, medium- or high-volume applications. This complexity requires a complex moulding tool, which adds to costs and lead times, but also increases the potential of tool failure.
PCE is agnostic when it comes to tool
complexity, and it makes no difference in terms of costs or lead times how complex the geometry of the part is. PCE can produce lead frames with tighter tolerances and finer detail than is possible with stamping – all with minimal degradation and deformation of the metal being processed, and little to no likelihood of burrs or defects. Failure rates are minimal and, unlike in the stamping process, every lead frame produced is totally flat, a vital prerequisite. Using PCE is even more compelling
when the process refinements introduced by Micrometal are considered. Many an engineer will tell you that not all PCE providers are the same when it comes to meeting the key requirements of a project. Micrometal’s unique PCE process achieves dimensional tolerances as low as ±0.005mm, feature sizes of 25 microns, minimum hole diameter 80% of the material thickness, and single- digit-micron tolerances, repeatably. By comparison, traditional chemical etching only achieves a smallest feature size of 100 microns, and the smallest hole diameter only one or two times the material thickness.
Recognised advantages When considering PCE for lead frame manufacture, it is important to
recognise the process advantages that PCE brings, but supplier selection is also important, the focus being on the expertise and experience of your chosen manufacturing partner. There are many variables in the
PCE process that can lead to error and increased margins. Providing a robust, repeatable method of lead frame manufacturing is crucial for any OEM. The lead frame maker’s experience and knowledge also help when it comes to problems that may arise later with the metal lead frame – they must be able to mitigate any problems where PCE has shown a weakness. German company Micrometal has
invested heavily in process control to reduce variation in metal lead making, as well as optical inspection to achieve zero parts-per-million failure rates. We place enormous emphasis on quality control, operating under a 100% inspection process, with no failure allowed. This is why we are proud to produce bespoke lead frames for some of the world’s leading semiconductor packaging companies. Micrometal’s tight tolerance
manufacturing processes are appropriate for many lead frame applications, but are ideally suited to the high volume manufacture of high lead/pin-count, ultra-fine-pitch lead frames.
www.electronicsworld.co.uk May 2023 33
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