1. Laminated structure
2. Production process
Cutting → inner layer → inner layer etching → inner layer AOI → brown oxidation → pressing → browning → laser drilling → primary drilling → copper immersion → panel plating → outer layer→ pattern plating → secondary drilling Hole → half hole routing → outer layer etching → outer layer AOI → impedance test 1 → solder mask pretreatment → solder mask → impedance test 2 → immersion gold → sild screen → board routing → electrical test → FQC → packaging
3. Manufacturing difficulties
This circuit board is a half hole PCB with an HDI structure. So the manufacturing difficulty comes from two aspects:
3.1 Difficulties in manufacturing half holes
1) The definition of a half-hole PCB: once the hole is drilled and then drilled again, the shaping process will eventually retain half of the metalized hole (groove), in short, the metalized hole on the edge of the PCB is cut in half.
2) How to control the product quality after forming the semi-metalized hole on the edge of the board. If the copper thorns on the hole wall are raised and left, it has always been a problem in the processing process.
This type of PCB with a whole row of semi-metalized holes on the side of the board is characterized by a relatively small aperture and is mostly used on a carrier board, as a daughter board of a mother board, through these semi-metalized holes and the mother board and components lead The feet are soldered together.
Therefore, if there are copper thorns remaining in these semi-metalized holes when the plug-in manufacturer performs soldering, it will cause weak solder feet and false soldering, which will seriously cause a bridge short circuit between the two pins.
Aimed at the problem of oxidation, copper peeling, or burrs on the half-hole PCB. Our control measures are as follows: control the time (within 24H) from the pattern plating to the half hole of the routing, which effectively avoids the problem of the effective half hole.
Aiming at the problem of half hole board, copper peeling and burrs, we will reduce the speed of the board routing shaft and shorten the routing path, which can effectively reduce the defective rate of the routing half-hole.
3) Another relatively big problem of the half-hole board is that during the SMT process, the half-hole area is likely to be tinned with the vias, resulting in a short circuit. In response to this problem, we stipulate that all half-hole boards must use aluminum plug hole technology. To put it simply, fill the vias with ink to prevent tin from flowing into the vias during the SMT process.
3.2 Manufacturing difficulties in HDi
HDI is the abbreviation of High Density Interconnector. It is a (technology) for the production of printed circuit boards. It uses micro-blind and buried via technology for a circuit board with a relatively high line distribution density. HDI is a compact product designed for small-capacity users.
HDI board production mainly has the following two difficulties:
1) Blind buried hole drilling:
Blind and buried hole drilling has always been a core issue in HDI PCB manufacturing. There are two main drilling methods:
a. Mechanical drilling blind buried holes: For ordinary through-hole drilling, mechanical drilling is always the best choice for its high efficiency and low cost. However, for HDI boards, there is indeed a problem of poor reliability of machinery, so mechanical drilling of buried blind holes is not the mainstream production solution for HDI boards (unless it is HDI boards with relatively large apertures and relatively low difficulty).
b. Laser drilling of blind and buried holes: There are three types of laser systems used in the production of flexible and rigid boards, namely excimer laser, ultraviolet laser, and CO 2 laser. Although laser drilling equipment is costly, they have higher accuracy and more stable quality. Laser drilling is currently the most mainstream HDI board production method.
2) Blind buried hole filling problem:
Because the blind buried via is close to the pad, it is easy to occur during the SMT process: tin flows into the hole to cause a short circuit. Therefore, we must plug blind buried holes by plugging. There are two common plug hole methods: one is resin plug hole, the other is VCP electroplating hole filling. These two plug hole methods are relatively difficult to process. The space is limited and I will not introduce too much. To put it simply: resin plug holes are suitable for plugging larger holes or through holes. After plugging holes, a second copper sinking is generally required. , The area of the plug hole is also attached with copper; VCP electroplating hole filling is generally suitable for blind holes, while only suitable for plugging small holes. If the hole diameter is large, it will cause voids.
Therefore, the appropriate plugging method will be selected according to the characteristics of HDI PCB.
4. Application areas:
This half hole PCB is used in the field of consumer electronics. It is used as a Bluetooth module to be welded to various devices, such as Bluetooth audio, Bluetooth air conditioner, Bluetooth monitor, etc., to achieve Bluetooth connection.
As a circuit board manufacturer, we can clearly feel that the functions of the product are becoming more and more integrated in recent years. This is fed back to the circuit board. In many cases, it can be found that there are: HDI, fine circuit, and metal on a daughter board. Processes such as semi-hole, selective and chemical, undoubtedly greatly increase the difficulty and cost of PCB production. But this process will be irreversible because people prefer powerful electronic devices.
