What do you mean by opening the cover? Summary of common problems in cover opening test

Date：2021-11-08 18:25:01 Views：2932

CPU is the product crystal with the highest scientific and technological content, the most complex process and the most fine structure. It is mainly composed of a lot of arithmetic units, controllers and registers. What does CPU cover opening mean? CPU cover opening is nothing more than opening the metal cover on the top of the CPU through the CPU cover opener, mainly to replace the silicone grease on the wafer with liquid gold and further improve the heat dissipation performance of the CPU.

The necessity of chip opening?

The purpose of sample unsealing is to expose the internal device chip of the package for further electrical detection and morphology observation of the chip surface. Nondestructive failure analysis technologies such as X-ray fluoroscopy and scanning acoustic microscopy can only solve limited failure analysis problems (such as inner lead fracture, chip bonding failure, etc.) Due to the opacity of packaging materials such as single component and multilayer wiring structure, anatomical sample preparation technology must be used to realize the visibility and detectability of chip surface and interior.

Types and methods of chip unsealing?

According to the packaging materials and forms, the packaging types of electronic components include glass packaging (diode), metal shell packaging, ceramic packaging, plastic packaging, flip chip packaging, 3D laminated packaging, etc. the lead bonding wires include aluminum wire, gold wire and copper wire. The methods of unsealing include mechanical unsealing, chemical corrosion unsealing and laser unsealing.

The main steps of sample preparation technology for failure analysis include opening the package and removing the passivation layer. For multilayer chips, it is necessary to remove the interlayer medium. However, the metallization layer and the medium directly below the metallization layer must be retained, as well as the silicon material. In order to observe the internal defects of the chip, section plane technology and dyeing technology are often used.

What is chemical Kaifeng?

The packaging material of plastic encapsulated devices is mainly epoxy molding compound. With epoxy resin as the matrix resin, phenolic resin as the curing agent, plus some fillers (such as fillers, flame retardants, colorants, coupling agents and other trace components), under the action of heat and curing agent, the epoxy ring opening of epoxy resin reacts with phenolic resin to produce cross-linking and curing, making it a thermosetting plastic, which is epoxy molding compound. The type and proportion of epoxy resin directly affect the flow characteristics, thermal properties and electrical properties of epoxy plastics.

Plastic packaging devices need to be opened by chemical corrosion method, which can be divided into chemical dry corrosion and chemical wet corrosion.

What is laser unsealing?

Copper bonding wire has the advantages of cost advantage, high conductivity and thermal conductivity, low generation rate of intermetallic compounds and better reliability at high temperature. It has gradually become a good substitute for gold aluminum bonding wire and is used in the packaging of dense wire bonding. Generally, the copper bonding wire is used for plastic packaging, and the chemical unsealing method is used for unsealing. Due to the chemical action between acid and copper lead, the copper bonding wire will be corroded while removing the plastic packaging material, losing the significance of unsealing. Therefore, for copper wire bonded devices, laser unsealing method can be used. The laser unsealing machine removes the molding compound on the packaging machine by laser to avoid the corrosion damage to the copper lead caused by the direct unsealing method.

The laser unsealing machine sets the unsealing area and size by the computer, controls the laser energy and scanning times, and completes the sealing of copper wire bonded packaging devices. The laser wavelength is usually 1064nm, the power is 4.5w, and the laser level is class-4.

The laser unsealing method is mainly used in the following occasions

(1) Failure analysis of semiconductor devices. The high efficiency and removal of plastic packaging materials can replace the traditional low efficiency chemical unsealing and solve the damage of chemical unsealing to copper wires and internal devices.

(2) Validation of plastic packaging process design and process parameters. It solves the problem that X-ray fluoroscopy cannot detect the punching collapse of aluminum wire after plastic packaging, and makes it possible to carefully observe the wiring points of copper wire and gold wire after complete unpacking.

(3) It is applied to the module manufacturer. During the incoming inspection, the device is fully opened to observe whether there are design or production defects inside.

Can the CPU still be used when the cover is opened?

Whether the CPU can be used after the cover is opened can be divided into two cases:

1. Generally, the CPU is filled with silicone grease with low thermal conductivity, which makes overclocking difficult. Therefore, some people with high technical level open the cover and fill it with liquid metal to improve the heat dissipation performance. After the CPU cover is opened, the CPU is damaged internally and cannot continue to be used.

2. After the CPU is opened, it can be used if it is not damaged.

How to identify whether the CPU has opened the cover?

1. See if there are indentations on the two ears of the CPU. As long as it is used, it will be irreversible.

2. The glue between the watch cover and the bottom plate also needs attention. Some CPUs have a longer life than people. The three-year warranty is just comfort. There is no problem on the first day. Basically, there will be no CPU problem when replacing the computer.