Design sharing and discussion on acoustic Box waterproofing scheme

In this era of smart phones, smart phones have become an essential tool for everyone's life. They not only serve as communication tools, but also serve as digital cameras, game consoles, e-mails, and even wallets. It can bring us convenience, joy, and emotion. But there is one thing that makes us sad is that "mobile phone water, so mobile phone waterproof in many brands of mobile phones follow the industry trend to put waterproof as one of the selling points to join the new mobile phone, waterproof technology is expected to replicate the popularization of fingerprint identification technology, from Apple's Samsung, etc. The giant flagship mobile phones are popularized to other mid-to-high end users. Waterproofing of mobile phones is expected to be popularized to increase penetration rate rapidly. As an acoustic supplier, the demand for waterproof functions of acoustic products is greatly increased. This article is to share and discuss the design of acoustic box waterproof solutions.

Waterproof structure and related process requirements

Waterproof SPK structure - before and after the cavity isolation - design four sides of the stairs

Waterproof BOX needs to design four side steps as shown in Figure 3, ordinary box design three side steps as shown in Figure 1, the air pressure will separate the sound film and basin frame of the monomer, resulting in collusion of the back and front cavity leading to waterproof failure; cross-sectional differences shown in Figure 2 and Figure 4 Yellow area.

Waterproof SPK structure - the front cavity is isolated from the outside - design four side steps

1. The fourth side step will occupy the sound channel space. To ensure the acoustic energy, the boss needs to be designed below the fourth side, such as a yellow transparent area.

2. Step width needs 0.55mm.

Waterproof SPK structure - before and after the cavity isolation - double-sided adhesive steel sheet

Waterproof SPK structure - before and after the cavity isolation - double-sided adhesive steel sheet

Steel sheets have higher requirements for height space, and at the same time affect the minimum sound channel;

Take 0916 as an example, the distance from the top of the non-waterproof ball to the box surface needs 0.65 vibration space + 0.2 steel sheet = 0.85mm; the waterproof project needs 0.65 vibration space + 0.5 plastic + 0.2 double-sided tape + 0.2 steel sheet = 1.55mm .

Waterproof SPK structure - before and after the cavity isolation - steel injection + glue

The injection-molded steel sheet is designed to store glue, and the edge and storage tank form an uninterrupted glue to ensure its waterproof performance. The edge area needs to be glued to prevent collusion between the front and rear chambers. It is not recommended to use this scheme. There are many areas where the glue is used, the process is cumbersome, and the risk of air tightness is slightly higher.

The steel sheet design convex bulge applies glue to the sink tank area;

Space requirements: drop 0.2mm convex; glue width 0.6mm;

Waterproof SPK structure - sound hole and machine seal - two-color injection molding

Two shots of soft plastic injection, through the slope with the whole extrusion soft rubber to achieve waterproof requirements;

Two-color injection molding is easy to produce soft rubber flash, flash, weld lines, trapped air, and shrinkage. The height of soft rubber is more sensitive to the injection molding process. Above all, it is recommended to use this program with caution.

Waterproof SPK structure - sound hole and machine seal - sound hole polished

The red surface is polished, and the silicone pad and other parts are attached to the entire machine, and the box is formed to be extruded for waterproofing.