Bonding PCB

What is Bonding PCB?

Bonding circuit board is a kind of wiring method in chip production technology. It is generally used to connect the internal circuit of the chip with gold or aluminum wire before encapsulation to the encapsulated pin or circuit board with gold-plated copper foil. Ultrasound from 40-140kHz ultrasonic generator generates high-frequency vibration through the transducer and transmits it to splitter by amplitude changer. When the splitter touches the lead and soldered parts, Under the action of pressure and vibration, the metal surface to be welded rubs against each other, the oxide film is destroyed, and plastic deformation occurs. As a result, two pure metal surfaces are closely contacted, reaching a combination of atomic distances, resulting in a strong mechanical connection. Usually, the printed circuit board is encapsulated with black glue after bonding.

How to identify Bonding PCB?

Bangding printed circuit board is a regular rectangular array, mostly square and circular bonding pads are thin and dense, the spacing between PAD and PAD is small, resistance bonding open window is open window, there is a regular square or circular open window PAD in the middle of Bangding IC, most of the bonding feet have lines leading out. The PCB state positioning acceptance standard is (+) 10% bonding foot width tolerance, spacing requirement is more than 3mil, the bonding foot is not allowed to be disabled, and etching edges are not allowed to reduce spacing.

The advantage of the bonding circuit board packaging method is that the PCB prepared is much higher in anti-corrosion, anti-shock, and stability than the traditional SMT patch method. The bonding chip of the printed circuit board connects the internal circuit of the chip with the package pin of the printed circuit board through golden wires, and then precisely covers it with organic materials with special protection functions to complete the later packaging. The chip is completely protected by organic materials, isolated from the outside world, and there is no occurrence of humidity, static electricity, and corrosion. At the same time, organic materials are melted at high temperature, covered on the chip, dried by the instrument, and seamlessly connected with the chip, which completely eliminates the physical wear and tear of the chip, and has higher stability.

PCB Bonding Process Requirements

Process flow: Clean PCB-Drop Adhesive-Chip Paste-Bond-Seal-Test

1. Clean PCB circuit board

Scrub the oil, dust, and oxide layers on the State Position with skin, then brush the test position with a brush or blow it with an air gun.

2. Drop adhesive

Medium droplets, 4 rubber points, even distribution in four corners; Pollution of the bonding pads is strictly prohibited.

3. chip pasting (crystallization)

With a vacuum suction pen, the nozzle must be flat to avoid scratching the wafer surface. Check the wafer orientation and stick to the PCB "smoothly": flat, the wafer is parallel to the PCB and there is no vacancy; Stable, wafer, and PCB are not easy to fall off during the whole process. Positive, the reserved bits of the wafer and the PCB are positively pasted and cannot be deflected. Note that the wafer direction must not be reversed.

4. State Lines

Bonding PCB passed the Bonding pull test: 1.0 lines greater than or equal to 3.5G, 1.25 lines greater than or equal to 4.5G.

Standard Aluminum Line at Bonding Melting Point: Line tail greater than or equal to 0.3 times line diameter, less than or equal to 1.5 times line diameter.

The shape of the aluminum wire solder joint is an ellipse.

Solder joint length: greater than or equal to 1.5 times line diameter, less than or equal to 5.0 times line diameter.

Width of solder joints: greater than or equal to 1.2 times line diameter, less than or equal to 3.0 times line diameter.

The state line process should be handled lightly and handled accurately. Operators should observe the state line process with a microscope to see if there are any bad phenomena such as breaking state, winding line, offset, hot and cold welding, starting aluminum, etc. If there is any, relevant technical personnel must be notified to solve them in time.

Before formal production, there must be a first inspection by a special person to check whether there are any state errors, such as Shaobang, Leaky State, and so on. During the production process, there must be a special person to check its correctness regularly (up to 2 hours interval).

5. Sealing

Before sealing, check the regularity of the plastic ring before placing it on the wafer to ensure that its center is square and there is no visible distortion. During installation, make sure that the bottom of the plastic ring fits closely with the surface of the wafer and that the light-sensitive area in the center of the wafer is not blocked.

When dispensing, the black glue should completely cover the aluminum wire of the PCB solar circle and the bonding wafer, no rubbing, the black glue cannot seal out the PCB solar circle, the glue leakage should be erased in time, and the black glue cannot penetrate the wafer through the plastic ring.

During the gel dripping process, the pin or the hair pick, etc. cannot touch the wafer surface and the bonded wires inside the plastic ring.

The drying temperature is strictly controlled: the preheating temperature is 120 +5 degrees Celsius and the time is 1.5-3.0 minutes. The drying temperature is 140 +5 degrees Celsius and the drying time is 40-60 minutes.

The dry black rubber surface must not have air holes, and no cured appearance and the black rubber height must not be higher than the plastic ring.

6. Bonding PCB Testing

Combining multiple testing methods:

A. Artificial Visual Detection

B. Automatic wire quality detection for bonding machine

C. Automatic Optical Image Analysis (AOI) X-ray analysis to check the quality of inner solder joints