There seems to be some confusion about cell phone and tablet screen replacement and the repair in general; the terminology, the components involved and what exactly can and should be replaced when the inevitable happens; your screen breaks. So I wrote this informational to help everyone understand what exactly makes up the "screen", what each component does and some details about my most requested repair, the glass only repair.
Frame: The supporting core structure of your device to which the screen, logic board and other internal components attach.LCD: Liquid Crystal Display; the component that displays the images and information you see on your device.Backlight: Used behind an LCD to illuminate the images and information displayed by the LCD.
AMOLED: Active Matrix Organic Light Emitting Diode; this component also displays the images and information you see on your device, but differs from an LCD as it uses LED's to render the images and does not require a backlight. Mainly used on Samsung phones but may be found in other high end phones as well.
Super AMOLED: Same as above but also has a digitizer integrated into the display.
Digitizer: A very thin transparent film component located between the display and outer glass that is responsible for sensing your finger touch and movements; i.e. the touch functions.
Outer Glass: A tempered or toughened glass that protects the internal components of your phone from the elements and from your finger constantly poking at it.
Outer Gasket: This is a special adhesive tape precision cut to match the outline of the frame's surface area and of a proper thickness, used to attach the outside edge of the outer glass to the frame. On many devices this is the only means of keeping the screen assembly attached to the frame.
Screen (assembly): By definition; "A flat panel or area on an electronic device on which images and data are displayed." In the cell phone repair industry this is considered to be the LCD or AMOLED display, digitizer and outer glass already bonded together as a complete assembly.
Bond: By definition; "Join or be joined securely to something else typically by means of an adhesive substance, heat, or pressure." Bond is generally used to describe the attachment of the display and/or digitizer to the outer glass by the means of an optically clear adhesive.
OCA: Optically Clear Adhesive; screen manufacturers use an OCA tape which is in a semi solid form, pre-cut to the dimensions of the display and of a specific thickness. Specialized equipment is required to apply, assemble and cure a screen assembly using OCA tape. A laminator is required to accurately place the tape and once the separate components have been assembled, the screen assembly must be placed into a high pressure high temperature autoclave to remove any air bubbles and cure the optically clear adhesive.
LOCA: Liquid Optically Clear Adhesive; used by most repair shops when replacing the original OCA tape during a "glass only" repair. LOCA does not require the specialized equipment that OCA tape does, and is cured by subjecting it to ultra violet light. Most LOCA is silicone based, and if not used properly it can damage your phone either immediately or over time. Silicone based adhesives will also prevent the other adhesive tapes used to attach the screen assembly to the frame from properly adhering and can deteriorate the bond of existing adhesive tapes over time.
OEM: Original Equipment Manufacturer; can be either the primary manufacturer, i.e. Samsung, Apple, LG, etc or a secondary manufacturer who supplies components to the primary manufacturer. While you may see many screens and other components sold online as OEM, few if any actually are. The primary manufacturers or the secondaries that supply them generally do not sell replacement components to the public, repair facilities or resellers. Many of the screens listed as OEM are actually refurbished, where the LCD is a used original but the glass and possibly digitizer will be aftermarket.
In the early days of the smart phone, few manufacturers used a bonded screen assembly. This allowed for the easy replacement of either the LCD display or outer glass/digitizer assembly, which ever had failed or broken. But today, almost all phones now use a bonded screen assembly and this is even becoming the norm with tablets. A bonded screen assembly produces a much better image quality as well as adding structural strength to the now very thin and fragile LCD and AMOLED displays.
So, even if the outer glass is the only thing broken on your screen, with the display and touch functions still working correctly, the proper way to repair your phone is by replacing the screen assembly. While more expensive, this will guarantee that that your screen fits and performs just as it did from the factory. This is also the quickest repair if time without your phone is going to be a factor, as performing a proper glass only repair is very time consuming. The tolerances of the screen assembly and the frame that it fits into are very precise, and without using OCA tape and the equipment required it is impossible to assure that these tolerances are met.
However it is possible to replace just the outer glass on many phones by melting the OCA bonding the display to the outer glass, allowing for the removal of the glass for replacement. There are a few different variants of this repair, but common to all is the risk of damaging the LCD or AMOLED display. The heat required to melt the OCA must be precise; too hot and you will end up with a discolored display, too cold and the display will break while removing the glass. Either failure will require the replacement of the complete screen assembly to bring your phone back to working order.
The glass only repair variants below are for most phones except for the iPhone and a few others where the screen assembly is mechanically held into, and is designed to be removed from the frame. The iPhone repair will be described later below.
Glass Only Without LOCA: Many will perform this repair to avoid the problems associated with using LOCA, but bonding of the display to the outer glass with an optically clear adhesive is mandatory for a couple reasons. First; without the OCA your display quality will diminish, especially in the sunlight where screen glare will be significant. Also, if you press too hard on the newly replaced outer glass it will make contact with and can stick to the display below causing a "wet spot" in the center of your display. Usually this contact will eventually release, but it is annoying. This is most common when an inferior outer glass or outer plastic is used because of their ability to flex. But the main problem with not using an OCA is when working with a Super AMOLED display or when the digitizer is bonded to the LCD. Without the OCA in place you now have an air gap between the outer glass and the digitizer, which reduces the digitizer's touch sensitively greatly causing loss of touch functions, inaccuracy and even freezing.
Glass Only With LOCA in Frame: This is the most common glass only repair as it eliminates a second possibility of breaking the display and assures that the new outer glass and display align correctly in the phone's frame, but it does come with its own set of problems; some just annoying but others fatal to the internal components of your phone. Because LOCA is cured (hardened) by being subjected to ultraviolet light, which will only be the LOCA directly underneath the clear portion of the outer glass, any uncured excess LOCA will seep into other areas of your phone causing LOCA contamination. On phones that use an LCD and backlight, the LOCA will eventually migrate into the backlight causing dark areas in the display. It can also easily end up in the home button, front facing camera and proximity sensor and eventually cause problems with functionality or failure to all. Over time it will also deteriorate the bond of the adhesive tapes and outer gasket used to keep your screen assembly in the frame resulting in the screen detaching from the frame later on.
Glass Only With LOCA in Alignment Mould: This is by far the most professional way to perform a glass only repair and it is the procedure that I use, but it is also the most difficult. Instead of using the phone's frame to assemble and align the new outer glass, the display is also removed from the frame and then the display and outer glass are bonded in a special alignment mould. On phones that have an AMOLED display this can be especially difficult as the display is also attached to the frame with a strong adhesive tape, so not only is there a risk of damaging the display while removing the outer glass but also while removing the display from the frame. But the benefit of this procedure is that all uncured excess LOCA can be removed, preventing any LOCA contamination to your phone and its internal components, leaving a completely clean attachment surface for the outer gasket and display adhesives to securely attach to the frame.
The iPhone Glass Only Repair: The iPhone screen assembly is not attached to the phone's frame by adhesive but rather mechanically, by a sub-frame bezel that is glued to the outer glass. For this reason LOCA and an alignment mould must be used to perform a glass only repair on the iPhone. Since the iPhone uses an LCD with backlight, special care must be taken to protect the backlight from LOCA contamination. As well as the outer glass, a new frame bezel must be attached to the glass with a special adhesive. Many will attempt to re-use the original bezel and re-attach it with double sided tape, but both will always cause failure, resulting in the screen assembly eventually falling out of the phone. Because of the generally low cost of iPhone screen assemblies vs. the labor and components required for a proper glass only repair, this repair is not recommended on the iPhone.