Is a Custom LCD Display a Good Fit For My Product?

Custom LCD displays are becoming more common with manufactures in the United States and Canada.

The Custom LCD display requires time and effort to design, although not as long as most engineers think.

In the not too distant past it was uncommon for an OEM, or manufacture to design and purchase a customized LCD display. The main reason was that the MOQs (Minimum Order Quantities) were very high, the tooling (NRE or Non-Recurring Engineering) was prohibitive and the lead times would stretch out for several weeks. This has changed drastically in the last four to five years. Many of these barriers and restrictions have been reduced.

Recent Changes In Custom LCD Displays:

In the last few years there have been many changes in custom LCD display technology. Many of these changes include new types of display technologies, new manufacturing process and increased efficiency in the display industry.

These changes include:

• Faster proto-typing of samples
• Lower MOQ
• Lower tooling cost for custom color displays

Types of Custom LCD Displays

The scope of this article covers five custom LCD Display technologies.

1. STATIC / SEGMENT CUSTOM LCD DISPLAY OVERVIEW:

Static LCD Displays also referenced as static, direct-drive or segmented displays are the oldest of the five display technologies. These types of displays are very common in such applications as gas pumps, clocks, and thermometers. They are monochrome, meaning that they have one common color such as gray or yellow/green. The popularity of these displays has not decreased, but actually increased with the reduction in cost of customized modules.

Earlier versions of these displays were only available in TN (twisted nematic), options now include STN (super-twisted nematic) and FSTN (Film compensated STN). FSTN offers a sharper contrast than STN, STN offers a sharper contrast than TN. The cost difference between FSTN, STN and TN is roughly 5% to 8%.

Seven segment, fourteen segment and sixteen segment displays are excellent for applications that require both low cost and low power. In fact, static displays with no backlight and operating at 25C can operate in the range of 2uA per CM^2.

MOQ’s (Minimum order quantities) range from 1,000 to 2,500 displays. If your goal is to display data such as basic letters and numbers, without needing flashy color, this is your best bet.

Static / Segment Custom LCD Display Options:

Static / Segmented Custom LCD Displays offer the following customization.

Size of glass: The display can be built as large as 10 inches (250mm) in the diagonal. The advantage of custom sized glass is that the display is built around your product and not the other way around.

Segment size: Segmented displays contain either seven segments or some number of segments to displays numbers and a few letters. The engineer or designer can choose how many segments and the size of each segment. It is possible to have different segment sizes on the same display. The variance in segment sizes does not affect the cost of the tooling (NRE).

Custom Icons: There are many standard icons such as battery indicator, AM/PM and F/C. A customized Static display allows the customer to incorporate unique icons. We have supplied custom LCD displays that included icons of the company name or logo. Products that will be used outside of the United States offer icons specific to metric values such as mm, kg, celsius, as with other options on a custom segmented display. The number of icons does not affect the tooling cost. Each additional segment or icon has a very small increase on the total cost of the display.

Backlight Options: Standard and custom static displays do not contain a backlight. The backlight needs to be designed around such factors as the size of the glass and the type of polarizer. The tooling cost of the backlight tends to be greater than the cost of the LCD. This leads many companies not to incorporate a backlight or switch over to a monochrome graphics LCD module with a built in backlight.

2. CHARACTER OR ALPHANUMERIC CUSTOM LCD DISPLAY OVERVIEW:

Character LCD Displays, also referred to as alphanumeric modules, have been in the main stream for several years. Common applications of characters include credit card readers, test and measurement equipment, pool filters, and scales. This display does not offer a variety of colors or the ability to display graphics. They are able to display all the numbers, letters and punctuation marks in the English language. With a change in the controller driver chip other languages can be displayed.

These displays are available in standardized configurations such as 16×2. The first number, 16, is the number of characters, letter/numbers/ punctuation marks. The second number, 2, is the number of rows. In short a 16×2 is two rows with each row holding 16 characters, for a total of 32 characters. The most common configurations are 8×1, 8×2, 16×1, 16×2, 20×1, 20×2, (20×4, 40×1, 40×2, 40×4 and 16×4 decreasing in popularity)

One key advantage of the standardized configurations is that the display you purchase from LCD supplier “A” will also be available from LCD supplier “B”. This reduces the probability of a single source LCD module.

Character Custom LCD Display Options:

Character Custom LCD Displays offer the following customization.

Backlight Options: The majority of character LCD’s have the option of a backlight with no tooling cost. Backlights are available in 3V, 3.3v and 5V; although 3V and 3.3V backlights may have a slightly higher cost and MOQ at this time. Look for this price difference to go away in the near future.

The most popular backlight type at this time is LED (light-emitting diode). LED’s are available in many colors including yellow-green (the most common), Blue (the next most common) followed by white. Other colors include pure green, red, amber, pure yellow. It should be noted that white and blue backlights cost slightly more than other colors. White LED’s also emits more heat than the other colors.

LED’s are either mounted behind the LCD (aka backlit) or they are attached on the side of the display (aka side lit). Backlit displays tend to be 3mm to 7mm thicker than side lit LED’s.

At this time we recommend that white LED’s be side lit only. Backlit white LED’s will produce hot spots, areas of brightness and areas of darkness; this will give the display a polka dot pattern.

The second backlight type for a character display is EL. EL (Electro-luminescent) is being phased out. Although it will not be a legacy product for some time, the MOQ of these backlights is 500. The advantage of EL is that it has a more even light and allows the display to be thinner. The down-side to EL is that it requires an inverter, a device to convert DC to AC, and emits noise that can interfere with neighboring circuits.

Bezel height: The bezel is the metal frame that holds the glass to the PCB. Bezels are generally 10mm to 15mm thick for a LED backlight and 8mm to 10mm thick for either no backlight, EL backlight or side lit LED backlight. The bezel can be modified as the customer requires. There is a one-time tooling cost to design and build the unique sized bezel.

PCB/Pin out: Character LCD modules that are mounted on a PCB (printed circuit board) are called COB, Chip on board. This is the most common type of character display. COB module sizes are standardized, but the size of the PCB can be modified to meet the customer’s needs. There are times when the customer’s product lacks enough room for the PCB and sections of the board need to be removed. Some applications require the location of the connecting cable to be moved. The pin out on the PCB can easily be modified to meet the designers need. Modified PCB’s require a one-time tooling fee.

Note: Never, never, never drill out the mounting holes or cut away sections of the PCB. This will damage the display. Even if the display works after you make the cuts, it is prone to failure after it has been out in the field for some time. If you need parts of the PCB changed, have the board redesigned.

3. MONOCHROME GRAPHIC CUSTOM LCD DISPLAY OVERVIEW:

Monochrome Graphic LCD Displays, also referred to as dot matrix modules, has been around almost as long as character displays. Common applications of Graphic display modules include older cell phones, ATM’s, credit card readers, and diagnostics equipment. This display, like the monochrome character display, does not offer a variety of colors or the ability to change colors. The main advantage of a graphic display over a character or static display is the ability to generate and change graphics through the use of software.

Some Graphics provide a fast enough frame rate to display videos. These displays are available in standardized configurations such as 128×64. The first number, 128, is the quantity of dots along the Horizontal, or X direction. The second number, 64, is the quantity of dots along the vertical, or Y direction. There are a total number of 128×64 = 8,192 dots that can be turned ON and OFF independently of each other. The most popular versions of a graphics display is the 128×64 (most common), 122×32, 240×120, 320×240, and 128 x 128.

Dot matrix displays have the option of a backlight without the need to pay tooling. The most common type of backlight is the LED. EL backlights are not as common but do offer a more even flow of light. CCFL (Cold Cathode Fluorescent Lamps) backlights were very popular with larger graphics display. Unfortunately this type of backlight has been discontinued by most suppliers. A large number of older products still make use of CCFL. The bad news is that there is no drop-in equivalent for this display. The best option is to design in a new display with a LED backlight.

Graphic Custom LCD Display Options:

Monochrome Graphic custom LCD displays offer the following customization.

Graphic LCD Displays can be customized in the same way as a character display. The tooling cost and MOQ is much higher. Your best option is to locate a standard off-the-shelf display that will work. Then, before you begin your design, locate a second source for the exact module. It is not wise to be locked into a single source.

4. COLOR SEGMENT CUSTOM LCD DISPLAY OVERVIEW:

Color Segment Custom LCD Displays are more commonly called FSC, Field sequential Color LCDs. This is a newer technology that has been on the market for about two years. Common applications of FSC include automotive, marine, aviation, and equipment that needs a display that is visible at a distance.

This display allows the designer to upgrade the custom static/segment display from monochrome (one color) to eight colors. The colors Red, Green, Blue, Yellow, Cyan, Purple, Black and White can be changed via software. The display offers a controller/driver interface that is both parallel and serial. Although this cannot display video, it does offer the following advantages over other color technology.

Contrast Ratios of FSC vs. CSTN and STN

• FSC LCD = 100:1
• CSTN = 55:1
• STN = 5:1

Response Time of FSC vs. TFT and STN

• FSC LCD = 4ms
• TFT = 40ms
• STN = 150ms

Color Segment Custom LCD Display Options:

FSC Displays, unlike character and graphics LCD’s, are not an off-the-shelf standardized item. Each display is customized to meet the needs of each customer. MOQ’s for this technology are around 500 to 1K displays. There is a one-time NRE fee to build to match your specs.

The main option of this module is the ability to choose the size of glass. At this time the largest size FSC is a 7-inch diagonal. This is expected to increase as the technology matures.

5. ULTRA-HIGH CONTRAST EBT CUSTOM LCD DISPLAY OVERVIEW:

EBT stands for Excellent Black Technology. The name comes from the sharpness of the black background vs. the color of the characters and segments. This is also known as VA for vertical alignment. EBT/VA is similar to FSC in that it is a newer technology. There are no standard off-the-shelf configurations. You order it the way you need it.

Two advantages include a contrast ratio of >300:1 and an operating temperature range of -30C to +90C. This makes it excellent for outdoor and harsh environments.

OLED’s are able to operate at -40C, but the half-life of the EBT is much longer.

Ultra-high Contrast EBT Custom LCD Display Options:

The options for the EBT are the same as for the FSC. You choose the size of the glass and the icons/segments you need. MOQ’s can be as low as 500 displays.

Design summary:

In designing your custom LCD display, keep in mind the following details:

1. Avoid the use of an EL backlight unless the volume is high enough.
2. White LED backlights, not side lit, are not the best option at this time due to hot spots.
3. CCFL is no longer available for monochrome displays. Work with LED. This will also save you having to make use of an inverter.