How to distinguish the quality of LCD screen flexible cable

     Customers often ask how to distinguish the quality of LCD screen flexible cables. First of all, we must know what flexible cables are. Flexible cables are also called flexible flat cables (FFC). They are mainly used to connect LCD screens and other circuit boards to transmit signals or power. The quality directly affects the display effect and stability.

      If customers encounter screen display problems and want to check whether they are caused by flexible cables, they can check from the following aspects, including appearance, material, process, and functional testing to distinguish:

It should be noted that the display screen may not display normally sometimes not because of the flexible cable itself, but because of interface oxidation or motherboard problems, but the flexible cable is the easiest to check as a connecting component. Therefore, when distinguishing problems, multiple factors should be considered comprehensively, and you cannot just look at one point.

A. Appearance inspection: preliminary judgment of FPC quality

1. Surface integrity

· High-quality flexible cable: smooth and flat surface, without scratches, cracks, indentations or creases (especially at the edges and folds).

· Poor quality flexible cable: There may be obvious scratches, peeling of the surface, or local protrusions/depressions due to poor production process (easy to hide dirt or break).

2. Gold finger (contact end) status

The gold finger is the key part of the connection between the flexible cable and the interface, which directly affects the contact performance:

· High quality: The gold finger has uniform color (bright gold), no oxide layer on the surface (no black or white), no scratches or deformation, and neat edges.

· Poor quality: The gold finger may be dark, oxidized (black/white), scratched, or the edge may be rough due to poor mold precision (easy to get stuck or poor contact when inserted into the interface).

3. Flexibility and strength of the cable body

The flexible cable needs to take into account both "softness" and "toughness", and it is not easy to break after repeated bending:

· High quality: The cable body can be naturally rebounded when gently folded by hand (non-violent bending), without obvious creases; the conductor (internal copper wire) has no breaking sound when stretched.

· Poor quality: may be too rigid (insulation layer is too thick) or too soft (conductor is too thin), and may break or delaminate after bending several times (insulation layer and conductor are separated).

B. Material and process: determines durability and signal transmission

1. Insulation layer and covering layer material

The material of the insulation layer (outer layer wrapping the conductor) and covering layer (coating to protect the gold finger) of the flexible cable directly affects the temperature resistance and corrosion resistance:

· High quality: usually PET (polyester) or high temperature resistant PVC is used, with strong temperature resistance (-40℃~125℃) and chemical corrosion resistance;

· Poor quality: may use recycled plastic or low-cost PVC, with poor temperature resistance (softening and deformation at high temperature).

2. Conductor material and structure

Conductors are mostly copper foil or tinned copper wire, which directly affects conductivity and oxidation resistance:

· High quality: The conductor is high-purity electrolytic copper (≥99.9%), tinned evenly (moderate thickness), and has no oxidation spots; the cross-sectional area meets the standard (such as 0.1mm², 0.15mm², etc.), and the resistance value is low (can be verified by measuring the on-resistance with a multimeter).

· Poor quality: Recycled copper or impure copper may be used, the tinning layer is thin and uneven (local copper exposure is easy to oxidize), the conductor is too thin (insufficient cross-sectional area), and the resistance value is high (causing signal attenuation or insufficient power supply).

3. Crimping process (assembly with connector)

If the flexible cable has been crimped with the connector (such as FPC connector), the crimping quality needs to be checked:

· High quality: The crimping is tight, the conductor is in full contact with the connector pins (no dislocation or looseness), the insulation layer is accurately cut off (no residual adhesion), and the overall firmness.

· Poor quality: loose crimping (insufficient contact between conductor and pin), residual insulation layer (possible short circuit), or offset crimping position (causing some pins to fail to conduct).

C. Functional test: verify actual performance

Judging by appearance and material alone may not be enough, and actual test confirmation is required:

1. Continuity test (multimeter)

Use the resistance range (beep range) of the multimeter to measure the continuity of the pins corresponding to the gold fingers at both ends of the flexible cable:

· Good quality: All pins that need to be conducted should beep (resistance ≤ a few ohms); pins without connection requirements should not be conducted (infinite).

· Poor quality: There may be a circuit break (no beep on a certain pin), a short circuit (conduction of irrelevant pins), or abnormal resistance value (such as >10Ω, resulting in signal attenuation).

2. Signal transmission test (replacement method)

If the LCD screen has problems such as screen noise, flickering, black screen, etc., it can be replaced with a known high-quality soft cable:

· Normal display after replacement → The original soft cable may be damaged or of poor quality;

· Still abnormal after replacement → The problem may be in the screen, motherboard or interface.

3. Durability test (long-term use observation)

For high-frequency use scenarios (such as mobile phones, monitors), the performance of the soft cable after repeated plugging and unplugging and bending can be observed:

· High quality: No poor contact or breakage after several months of use;

· Low quality: Gold finger oxidation, cable body breakage or signal instability in a short period of time (such as 1~2 weeks).

      Based on the above judgments, high-quality soft cables must meet the following requirements: no damage to the appearance, bright gold fingers without oxidation, heat-resistant and corrosion-resistant materials, good conductor conduction, and precise crimping process. If the display is abnormal, give priority to checking the soft cable (especially the gold fingers and bends), which can be quickly verified by replacement method and multimeter test. Shenzhen Hongjia Technology focuses on the research and development, production and sales of 1.14-inch-12.1-inch LCD screens and supporting touch screens, with 12 years of industry experience. The FPCs we use are highly reliable, resistant to oxidation, and have good flexibility. The gold content of the plug-in gold fingers is 1.5-2.0μ, which is suitable for military industry, instruments and equipment, consumer electronics and other products. We have served many Fortune 500 companies and have received praise from customers. Our products must go through 12 inspection processes from incoming materials to shipment, so that customers have no worries.