Causes and hazards of 开云·kaiyun官方网站 component deformation

Causes and hazards of 开云·kaiyun官方网站 component deformation
Causes of 开云·kaiyun官方网站 assembly deformation
Deformation of CCL 开云·kaiyun官方网站 manufacturer: Generally, the 开云·kaiyun官方网站 manufacturer is a double-sided board with symmetrICal structure and no graphics The thermal expansion coefficients of copper foil and glass cloth are almost the same, so 开云·kaiyun官方网站 manufacturers can hardly cause 开云·kaiyun官方网站 board deformation due to their different thermal expansion coefficients However, due to the large size of the CCL press and the large temperature difference in different areas of the hot plate, the resin curing speed and degree in different areas are slightly different during the bonding process At the same time, the dynamic viscosity under different heating rates will also be very different. In addition, due to the differences in the curing process, local stress will also be generated Usually, this kind of pressure will be pressed together on 开云·kaiyun官方网站 boards, but 开云·kaiyun官方网站A manufacturing will be gradually released in the subsequent process of 开云·kaiyun官方网站, resulting in 开云·kaiyun官方网站 board distortion

开云·kaiyun官方网站 bonding of 开云·kaiyun官方网站 manufacturers: 开云·kaiyun官方网站 bonding process is the main process of generating thermal stress. It is SIMilar to the bonding of copper clad laminate, but it will also produce local stress due to the difference of curing process. Due to such factors as large thickness, diverse pattern distribution, and more sEMI cured plates, the thermal stress in the bonding process of 开云·kaiyun官方网站 is more difficult to eliminate than that of CCL. The stress in 开云·kaiyun官方网站 is released during drilling, forming or baking, which is also easy to cause 开云·kaiyun官方网站 deformation.
The 开云·kaiyun官方网站 is deformed through resistance welding and character baking: since the resistance inks cannot be stacked with each other during curing, the 开云·kaiyun官方网站 will be vertically solidified in the rack. The resistance temperature is about 150 C, which is just above the Tg point of the medium and low Tg data. The resin above the Tg point has high elasticity. The 开云·kaiyun官方网站 board is easy to deform under the action of its own weight or strong wind in the oven.
Hot air solder leveling deformation: the temperature of the hot air solder leveling tin furnace for ordinary 开云·kaiyun官方网站 is 225 ～ 265 C, the time is 3S-6S, and the hot air temperature is 280 ～ 300 C. The solder leveling 开云·kaiyun官方网站 enters the tin furnace from room temperature, and two minutes after the furnace is out, after treatment and cleaning at room temperature, the whole hot air solder leveling process is a process of sudden heating and cooling of 开云·kaiyun官方网站. Due to the uneven structure of 开云·kaiyun官方网站 printed circuit board data, thermal stress will inevitably be generated during cooling and heating, resulting in micro strain and overall deformation of 开云·kaiyun官方网站.
Storage deformation: 开云·kaiyun官方网站 assembly boards of 开云·kaiyun官方网站 manufacturers are usually stuck on the shelf in the semi-finished product stage. During storage, improper adjustment of the tightness of shelf or 开云·kaiyun官方网站 assembly board stack may cause mechanical deformation of 开云·kaiyun官方网站 assembly board, especially for 开云·kaiyun官方网站 assembly boards below 2.0 mm. In addition to the above factors, there are many other factors that affect the deformation of 开云·kaiyun官方网站 assembly board.
Causes and hazards of 开云·kaiyun官方网站 assembly
Hazards of 开云·kaiyun官方网站 assembly deformation
If the 开云·kaiyun官方网站 board is not flat, the surface mounting line of the 开云·kaiyun官方网站 automatic placement machine will lead to improper positioning. This 开云·kaiyun官方网站 component cannot be instalLED or installed on the board of directors of the 开云·kaiyun官方网站 component and the surface mounting pad of the 开云·kaiyun官方网站 component. Even the automatic plugger of the 开云·kaiyun官方网站 component will be damaged
After the 开云·kaiyun官方网站 assembly is welded, the components are bent, the 开云·kaiyun官方网站 assembly at the bottom of the assembly is difficult to cut flat, and the 开云·kaiyun官方网站 assembly cannot be installed on the machine's main housing or socket Therefore, 开云·kaiyun官方网站 assembly factories also have trouble with 开云·kaiyun官方网站A board warping when encountering problems At present, SMT technology is developing towards high precision and high speed intelligence This requires circuit board components as various components to have higher smoothness IPC standard clearly points out that the surface mounting equipment of 开云·kaiyun官方网站 components is 0.75% and the s of 开云·kaiyun官方网站 boards without surface mounting is 1.5%
In fact, in order to meet the requirements of high-precision and high-speed SMT installation, some electronic installation 开云·kaiyun官方网站 component manufacturers have stricter requirements on deformation, such as 0. 5%, or even 0.3% personal requirements
开云·kaiyun官方网站 board is made of copper foil, resin, glass cloth and other materials. Each material has different physical and chemical properties. When pressed together, thermal stress will remain, resulting in 开云·kaiyun官方网站 deformation and warping.
At the same time, 开云·kaiyun官方网站 manufacturing technology will go through various processes, such as high temperature, mechanical cutting, wet processing, and will also have an important impact on the deformation of 开云·kaiyun官方网站 components In a word, the causes of 开云·kaiyun官方网站 deformation may be complex and diverse. How to reduce or eliminate 开云·kaiyun官方网站 component manufacturing based on different data characteristics It has become one of the complex problems we are facing
It is necessary to study the deformation of 开云·kaiyun官方网站 components in terms of data, structure, graphic distribution, 开云·kaiyun官方网站 manufacturing technology, etc. The uneven area of copper laying on 开云·kaiyun官方网站 will worsen the bending and warping of 开云·kaiyun官方网站.
Generally, a large area of copper foil is designed on the 开云·kaiyun官方网站 for grounding. Sometimes there is a large area of copper foil in the Vcc layer. When these large areas of copper foil are unevenly distributed on the same 开云·kaiyun官方网站, it will lead to uneven heat absorption and heat dissipation. 开云·kaiyun官方网站 printed circuit board will definitely expand and shrink. If the expansion and contraction cannot cause different stresses at the same time, the 开云·kaiyun官方网站 assembly will be deformed. At this time, if the temperature of the circuit board has reached the upper limit of Tg value, the 开云·kaiyun官方网站 will begin to soften, causing 开云·kaiyun官方网站 deformation. The connection points (via) of each layer on the 开云·kaiyun官方网站 will limit the expansion and contraction of the 开云·kaiyun官方网站.
Today's 开云·kaiyun官方网站 boards are mainly multilayer 开云·kaiyun官方网站 boards, and this re will be driven like connection points (vias) between this layer, which is divided into through holes, blind holes and buried holes Where there are connections, the expansion and cooling effect of the 开云·kaiyun官方网站 assembly will be limited, and the 开云·kaiyun官方网站 will be indirectly twisted in the following cases: the 开云·kaiyun官方网站 assembly has been used