Detailed explanation of LDS process

1. Selection of raw materials
PA6/6T (semi aromatic polyamide)
·Strong stability of thermal deformation, suitable for reflow soldering (also suitable for lead-free soldering)
·Good mechanical properties
Thermoplastic polyester (PBT, PET and their mixtures)
·Good mechanical and electrical performance
·Their mixtures have good thermal deformation stability
Crosslinked PBT
·Free fire resistance
·Irradiation crosslinking makes it have high temperature resistance (suitable for all welding processes)
LCP (liquid crystal polymer)
·Good liquidity
·Good dimensional stability under hot pressing
PC/ABS (polycarbonate/acrylonitrile/butadiene/styrene)
·Good surface characteristics
·Good mechanical properties
2. Injection molding
The visible part to be processed by laser circuit forming is manufactured by one-component injection molding method. The dried and preheated plastic particles are injected into the mold under high pressure. After cooling, this hard part becomes a replica of the mold. The next step of this injection molding MID component is to use the LPKF MicroLine3D laser machine for circuit processing.
3. Laser activation
Thermoplastics that can be activated by laser contain a special organometallic complex form additive, which can be activated by physical and chemical reaction under the irradiation of focused laser beam. In the crack processed in the plastic mixed with impurities, the complex is opened and metal atoms are released from the organic ligand. These metal particles act as nucleons for reducing copper.
In addition to activation, the laser also coarsens the surface. The laser only melts the polymer matrix, not the filler. In this way, tiny pits and notches are formed to make copper firmly adhere to it during metallization. (See figure)
4. Metallization
The first step of the metallization part of LPKF-LDS process is to clean to remove the debris of laser processing, and then to soak in organic copper plating to form a conductive circuit.
One advantage of this process is that it does not need the initial activation process in the common copper plating process. Its sedimentation rate is 3 - 5 microns/hour. If thicker copper layer is required, common electroplating copper plating can be followed. Nickel, gold, tin, tin/lead, silver, silver/palladium, etc. can also be plated to meet special application requirements.
5. Assembly
Many plastics that can be activated by laser have high thermal deformation stability, such as PA6/6T, LCP and cross-linked PBT, which can be reflow welded, thus completely matching with the standard SMT process.
You can use stencil printing for solder coating. However, this is only feasible if the surface is on the same plane. If the coating needs to be carried out at different heights or in the cavity, the step-by-step tin injection method is ideal.
The same is true for SMD components. If all components are on the same plane, the standard automatic placement equipment can be used to complete automatic placement. If the element pickup has the Z-axis adjustment function, the raised surface can also be automatically mounted. Automatic mounting on inclined surfaces and irregular surfaces is very complex and often requires manual mounting.
In addition, SMD components of MID components produced by LPKF-LDS method can also be assembled by chip contact method such as Bonding. Generally, thick aluminum wire or thick/thin gold wire (such as diameter 25um) is used for bonding connection.