2017年9月25日星期一

Thermally Conductive PCB

Hemeixinpcb, a thermal management technology company, announced its new MCPCB product, Copper Via embedded Aluminum Core PCB. This highly thermal conductive MCPCB is comprised of a regular aluminum core PCB and a specially embedded Copper Via that effectively draws the heat from the elements bonded on the top surface and distributes it to the aluminum core of the MCPCB. This innovation enables circuit engineers to have much less thermal restriction in circuit design and it offers more flexibility in components selection This unique and cost effective process developed by Cofan USA to embed Copper Via onto the Aluminum Core is completely contamination-free, and it makes it possible to integrate into conventional Aluminum Core PCB manufacturing processes. As a result, the MCPCB’s thermal conductivity is further enhanced through the Copper Vias, with no increase in cost. The cost is the same as an Aluminum Core PCBs which is relatively much lower than that of Copper Vias on Copper Core PCB. This Copper Via embedded Aluminum Core PCB is currently available for order, and ready for market consumption as with the conventional MCPCB with Copper Vias on Copper Core.
Metal Core PCB
    When the copper metal pricing went higher and higher, use small pieces of metal to solve the thermal dissipation problem become important. Locally bond the metal coin by bonding film or sweat bonding is one solution. Plug the metal inside the PCB is another. One advantage for this process is the metal can be fit into the multiplayer construction during lamination process. The coin grounding can be done by drill through hole or use sweat bonding.
Metal Core PCB
Metal Core PCB
      For the double side PCB, plug the metal in PCB is also possible. It can be done by a process similar to hole plugging which we fill the epoxy resin in the slit between PCB and metal coin. However, the metal thickness need to by the closeto the PCB. Usually designer will ask the metal coin should be very flat at least on one side. The quality control need to be careful.
Metal Core PCB
    Similar insertion design can be done by sweat bonding process. It is still in concept stage. But I think it can be done, too. It's a post bond process. One advantage is that only PCB pass the QA process will go to bonding procedure. Please see my article "Sweat solder bonding technology for metal PCB".
If the PCB is mutilayer,  and it needs to ground one of the layer to the metal coin, use electrically conductive paste is one solution. The slot needs to be edge plated first. The the conductive paste fill in before outter layer processing.  The conductive paste area on top layer can covered with solder mask to avoid any kind of circuit short.
    One advantage of coin insertion PCB is the light weight and easier assemble. For a metal bonded PCB, before the PCB assembly, a long time preheat is necessary. Cooling time is also longer for its high thermal capacity. For copper insertion PCB, if the coin size is small compare to whole PCB, the PCB assembly is almost not be affected. Compare to locally bonded coin, the flat structure can eliminate the using of special fixture.
8. High power LED substrate
    For a packed LED component, aluminum based IMS design is widely used in the industry (see Fig 5). The heat transfer from component go through a high thermal conductivity (no less than 1 W/m-k) material to aluminum plate. The thickness of the dilectric material needs to be select carefully. The thiner dielectric which have lower thermal resistance may cause dielectric breakdown problem.
Metal Core PCB
    The LED chip can put directly on a LED substrate with cup design and copper backing to reduce cost and resolve heat problem. The quality of LED chip maybe a problem needs to be concerned. The cup usually designed with an optimum angle and plated with silver to get better reflectivity. The bonindg pad need to be plated with bondable metal like thick gold, silver or Ni/Pd/Au.
Metal Core PCB
Boardtek also owned a patent which use a plastc or metal pre-formed cup to replace the cup that need to be machined in PCB. It can save a lot of cost and have better light performance.

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