Composite Plastic Smartphone Back Cover Production Process

Overview

With the adoption of 5G and wireless charging technologies, and to meet the trend toward thinner, more personalized smartphones and the higher signal transmission requirements of 5G communications, composite materials (PC/PMMA), glass, and ceramics have become mainstream alternatives to traditional metal back covers.

A PC/PMMA composite sheet by Dafu New Materials, produced by co-extrusion, combines PC's impact resistance with PMMA's scratch resistance; flexural performance is significantly improved and the material offers strong printability.

Plastic materials are commonly used in lower-end 5G phone back covers to meet functional demands. The main surface treatments for PC/PMMA composite sheets include screen printing, UV transfer printing, electroplating, and decorative printing.

Compared with glass, the process for composite sheets is similar, but composite back covers have lower cost, can achieve various textures and color effects, and their thinness meets the trend for slimmer smartphones.

Production Process

The production process for composite sheet back covers is as follows:

1. Initial cleaning: Use a flat-panel cleaning machine to clean purchased PMMA and PC sheets for subsequent UV transfer processing. No chemicals are added during this cleaning.
2. UV transfer printing: Apply a layer of UV transfer adhesive to the PMMA or PC sheet, print the required pattern on the adhesive surface using a UV transfer machine, then cure the adhesive in a UV oven.
3. Vacuum coating: Place the UV-transferred semi-finished parts into a vacuum coating machine to deposit an alloy film. Vacuum coating here refers to sputtering in a vacuum chamber: a magnetic target is used to control secondary electrons, and ion bombardment of the target ejects particles that accumulate on the workpiece.
4. Screen printing and drying: Use a semi-automatic screen printing machine or roll-to-roll screen printer to apply the required patterns on the semi-finished surface, then dry and cure in an IR oven or conventional oven.
5. High-pressure forming: Use a Xintaiming high-pressure forming machine to heat and soften the dried semi-finished parts (approximately 180°C), then press them into the required shape.
6. Laser processing: Use a laser to engrave textures or perform cutting as required by the process.
7. CNC machining: Use CNC machines to drill holes, trim edges, and perform other finishing operations on the laser-processed semi-finished parts.
8. Secondary cleaning: Use an ultrasonic cleaner to clean the semi-finished parts.
9. UV lamination (partial): For some products, apply a UV bonding adhesive by a UV laminating machine and bond the part to a purchased PET sheet.
10. Inspection: Inspect products manually or with 2D optical inspection equipment.
11. Packaging: Manually package the products as finished goods.

Key Technical Features

1. Nano processing produces a very smooth surface. An electroplated AF coating reduces fingerprint and oil adhesion and allows easy cleaning.
2. Wear and scratch resistance: 9H hardness resists scratches from sharp objects and helps maintain surface clarity.
3. After electroplated oil- and water-repellent treatment, the water contact angle exceeds 105°, allowing water droplets to roll off on an inclined panel.
4. Available in various colors. Colors can be customized according to customer requirements.