In a society where we are always anxiously awaiting the next best thing to be released, we never think much about the design and production that goes into creating these items. As technology improves and devices get smaller, the components that make up these devices must get smaller as well. The machines used to develop the ever-evolving technology around us must be constantly evolving, too.
Take the average smartphone, for example. There was a time when cell phones were so large that there was no way you could carry one in your pocket. When LCD screens made their appearance on cell phones, they were not capable of displaying hundreds or thousands of colors. They only displayed the numbers being dialed and looked more like the display on a digital alarm clock.
We notice the obvious improvements to our devices, but we don’t think about all the advancements that have taken place to bring us to where we are. In the past three decades, we’ve gone from a phone that barely fits in a briefcase and which only handled calls to a compact computer that fits in our pocket and completely encompasses our lives. Our phones have replaced the need for carrying a multitude of separate devices. This one handheld device contains all our personal collections of music, pictures, and videos. It is our calendar, clock, and weatherman.
The Role of Adhesives
In the world of smartphones, the current goal seems to be providing the thinnest, lightest product possible. The problem is that the confined spaces inside our devices don’t leave much room for traditional fasteners. The solution to this problem is using adhesives.
Adhesives are a major player in the assembly of today’s portable electronics. Adhesives are used in nearly every aspect of the assembly process. They are more than just a means to put the case together. Adhesives are used to hold batteries in place and secure wires. These are just a few of the many roles adhesives play in the assembly of modern devices.
Challenges of Using Adhesives in Mobile Devices
However, the use of adhesives comes with its own set of challenges. Our modern phones are made of multiple materials, each of them having their own unique physical properties. Not all materials bond together in the same manner.
Also, as the components get smaller, the adhesives being used must get stronger. The smaller components lack adequate surface area for proper bonding. The adhesives used must also be capable of securing components in place without interfering with the use of the device.
For attaching glass to an LCD, an optically clear adhesive is needed. Common adhesives are a double-sided tape or UV cure resin. The resin has the benefit that it doesn’t dry until exposed to UV light, so repositioning of the components is still possible until the resin is cured.
Tape needs to be precise and die cut, and, with many newer phones having curved screens, a tape is difficult to apply. An alternative to double-sided tape is 3M’s innovative Plastic Bonding Adhesive 2665. This adhesive has the ability to grab and hold components, much like a double-sided tape, until it fully cures. The benefit to a liquid adhesive is that it forms to curved surfaces much more efficiently than tape. However, a tape has the benefit of being made to a certain thickness, which means the electronics manufacturer doesn’t need to worry about dispensing precise amounts of adhesive.
Many components are placed onto a drop of adhesive to hold them in place until they can be soldered permanently. After soldering, the adhesive acts as a strain relief for the solder joints.
Another problem with the ever-decreasing size of components is the increased build-up of heat. These smaller parts don’t have the surface area to properly dissipate heat. Heat is the number-one cause of premature failure.
Thermally conductive adhesives are commonly used to create a “pathway” for the excess heat to travel and move it away from the component. These types of adhesives are also used for attaching heatsinks for the same reason.
Thermo-bonding films are thin thermoplastic adhesive sheets. Like tape, these films need to be die cut in the shape of the part. The thermobonding film is a cross between the double-sided tape and hot melt adhesive. The film is put in place, and the component is attached to it. Heat is then applied until the film melts. Like a hot melt, the adhesive cools to secure the part in place.
Adhesives and Smartphone Production
We generally don’t look at an item and put much thought into the processes it has been through to make it what it is. We all walk around clinging to our devices like they are the very things keeping us alive, but we actually know very little about their inner workings.
Every time a new wave of must-have cutting-edge devices emerges claiming the latest and greatest technological advances, take the time to stop and think about all the innovations that must have been made to make it possible. That new smartphone would be nothing but a pile of components without the literal glue that holds it all together.
