Polyimide (PI) is a thermosetting resin belonging to the category of super engineering plastics and is a typical representative of polymers. Its core characteristics include: long-term use temperature up to 200-300 ℃ excellent high temperature resistance, excellent mechanical stability, electrical insulation, chemical inertness and biocompatibility, so its processing technology in the field of high-end manufacturing applications.
In the semiconductor industry, polyimide is widely used as an insulating material for semiconductor-related components, and also has important applications in the fields of protective materials, high-performance adhesives, and heat-resistant coatings. In the field of microelectronic components, polyimide is used in wafer carriers, test fixtures, hard disc drive assemblies, electrical connectors, wire insulation, flexible printed circuit boards, and core components of digital copiers and inkjet printers.
With excellent chemical inertness and biocompatibility, polyimide is increasingly being used in a wide range of applications in the medical field, such as cardiovascular catheters, recycling devices, push rings, marking bands, angioplasty devices, stent delivery systems, neuro-interventional devices and drug delivery devices.
Processing Difficulties:
1, When handling medical grade polyimide hoses (e.g. drilling and cutting), the core standard is to ensure that no harmful substances are introduced during the manufacturing process, so the cleanliness of the material body and the surrounding environment must be maintained throughout.
2, Polyimide "high temperature" refers to the long-term use of thermal stability, but the processing of low thermal conductivity, very sensitive to heat, local instantaneous high temperature will lead to molecular chain fracture, carbonisation, resulting in significant heat-affected zone, the material warping, especially for thin-walled products, the edge of the laser cutting edge of the thermal damage is often more obvious. Therefore, the need for "cold processing".
3, Picosecond laser can be processed in the polyimide film on the precise micron-level features, but there are obvious limitations: First, after processing, the features around the easy generation of molten debris, the need for sample post-processing to remove surface residues, increasing the overall cost; Second, the processing of the features of the spacing is limited, restricting the feature density enhancement and product miniaturisation development.
Figure: Comparison of picosecond processing and femtosecond laser processing effects
Advantages of Femtosecond Laser Processing:
As a non-contact processing tool, femtosecond laser technology focuses the beam down to the micron level and is "cold", making it ideally suited for precision processing of polyimide materials.
- Extremely low thermal impact: the high peak power of the femtosecond laser pulse instantly vaporises the polyimide film, ensuring that no debris remains on the surface, avoiding significant thermal effects and allowing the processedicrovias to be aligned more closely together without interacting with each other, which facilitates the enhancement of the feature density;
- No post-processing required: the processed aperture has smooth sidewalls and edges, eliminating the need to additionally grind or polish the edges to remove the raised edges, thus streamlining the process
- Wide range of materials: almost any material can be processed. Polymers such as polyimide have a weak infrared absorption, so for most transparent PI materials, a UV ultrafast laser is required to ensure processing efficiency.
-Processable deep holes: deep hole structures with aspect ratios greater than 10:1 can be realised.
-Flexibility: Integrated cutting and drilling can improve productivity, processing speed and process flexibility. The shape and size can be adjusted by real-time monitoring through the software system.
Femtosecond laser processing applications:
1. Polyimide micro-hole array processing
On the polyimide sheet, it realises the stable processing of micro-hole with aperture Φ3μm, and the precision is controlled in the range of ±1μm.
2. Polyimide tube through-hole processing
can be processed without damage to the other side of the tube, high cleanliness, excellent accuracy of the hole, and does not require post-processing.
3. Polyimide Film Cutting
High repetition rate femtosecond laser cutting equipment allows high throughput processing of polymers at cutting speeds of nearly 300 mm/sec. It should be noted that the use of shorter wavelengths improves the quality of the process, but may come at the cost of reduced speed due to the lower average power at shorter wavelengths.
4. Polyimide mould etching
PI film surface bump microstructure etching, bump depth 0.026mm, surface roughness Ra ≤ 0.4μm, no burr, no deformation.
5.Polyimide wire stripping femtosecond laser precision stripping of medical wires on the polyimide coating, to avoid damage to the wire substrate, to ensure that the stripping edge is smooth, to meet the requirements of medical grade cleanliness.
Typical applications of femtosecond lasers in polymer and polyimide microstructuring also include:
- Flexible, ultra-thin printed circuit boards (PCBs) for small mobile devices;
- Flexible solar cells; - Miniature hearing aid components;
- Flexible organic light-emitting diode (OLED) display panels; and - Perforated filters for the food and medical sectors.
