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Ideas & Solutions

- Printed Heat– Sink
- Impedance and Multilayer
- More Then "Just Copper-Foil"
- SMD Assembley Equipment
- Multilayer PCBs with special dielectric constant

 Printed Heat– Sink

As density of electrical components at PCBs is increasing, the problem of conduction off the heat produced by that parts gets more and more essential. The usual solutions are so called
“ Heat sinks” which are cooling elements made of metal (aluminium or copper) which are to be mounted at spots on the PCB from which the heat need to be leaded away. The disadvantages of these Heat Sinks are obvious :
- additional mounting work;
- precious space at PCB is kept away by Heat Sinks;
- as these are electricity conduction metals, a proper insulation from PCB layers is necessary to avoid shorts;
- Heat sinks causing additional weight and increasing the volume of the PCB assembly.

What are the technical alternatives to Heat Sinks ?

a) metal core PCBs (basic material is an aluminium or copper alloy itself – these metals have the higher specific heat conductivity (HC): copper – 400 W / mK, aluminium – 200 W / mK
compared to epoxy glass fibre, the PCB basic material which has only about 0.4 W/mK HC.
Disadvantages : expensive in material and workmanship, only 1and max. 2 Layer PCB possible.

b) thick copper foils as “Thermo – Layers” … these are available at thickness up to 400 micron. They can be used in Multilayer PCB constructions as inner layers or even outer
layers (with inner signal layers and isolated vias through the Thermo – Layer. Disadvantage : complicate construction and higher costs.

c) a new elegant solution is the “Heat Sink Paste” (also called“ Printed Heat Sink”) which is offer by a German producer of PCB– chemicals Lackwerke Peters GmbH + Co KG, Germany. The processing of that Heat Sink Paste is by screen printing directly to PCB through a screen like a solder paste stencil and curing afterwards. The HC of the paste – it consists of
solid particles based in an epoxy resin - is by 2 W/mK – as via hole of the PCB are partly filled, additionally head dissipation is achieved.

The advantages of such Heat Sink Paste are as follows :

- easy application by screen printing and usual drying methods;
- high definition for design of variable structures and layer thickness;
- heat is dissipated from source of its generation, possibility to fill heat vias with the paste;
- economical process compared with alternatives;
- continuous heat resistant to 155° C;
- electrical isolator itself (no insulation necessary);
- no volume shrinking, good mechanical, chemical and solder bath resistance;
- flame class V0 as per UL .


 Impedance and Multilayer

Developers and designers of high-frequency circuitry know that they must calculate the impedance of printed conductors and allow for it in drafting CAD layouts. What is less well known is that in many standard digital circuits the impedance of printed signal conductors and the power supply increasingly play a role that is functionally decisive. The reason for this lies in the shorter switching times (signal rising edge) of modern modules. Although not always essential to practical use, the clock-pulse rates of signal circuits now approach the 100 MHz range and that of chips the GHz range. The switching times of associated chips have fallen to 1 or 2 nanoseconds or even less. The end result is high-speed circuitry requiring allowance to be made for physical conditions that could previously be disregarded. Elementary design rules must be observed to ensure reliable future module function. This includes overall power planes offering wideband decoupling via capacitive properties. Strict routing strategies avoiding slot antennae (which can cause high-frequency noise interference emission from the planes) and ensuring optimal signal feedback must also be applied. The circuitry design and choice of components must guarantee signal transmission in an homogenous electrical field using impedance-controlled circuitry. A pre-condition in fulfilling this requirement is the application of these technical specifications to the PCB, which hence has a functionally decisive role as carrier of the module. There is no reason to believe the PCB might be unable to meet the specifications set.

If you have interest to find out more about this topic, we suggest you to read the Workshop Lecture "Impedance and Multilayer"  of a leading specialist in this field ? Mr. Arnold Wiemers, company ILFA Feinstleitertechnik GmbH.


 More Then "Just Copper-Foil"

We want to draw attention of our customers at the possibility of using different copper foil modifications, manufactured by the company GOULD ELECTRONICS INC., which are: ultra thin copper foil TCU (3-9 mkm), laser drillable foil (LD foil), as well as thin film resistor foil (TCR) and planar capacitor foil (TCC). Short description of the above listed copper foils you can find here. For more information, please download in PDF files from here. In case you are interested to purchase this products, you can inquire directly by manufacturer (http://www.gould.com) or (in case of ordering of printed circuit boards) at our company.


 SMD Assembley Equipment

                                       Product pallet of Co. ELLWEST KG include different kind of PCBs (single & double sided, multilayer, flexible, impedance controlled, metal core) also assembling of boards and shipment as per requirement of customer.    Product pallet of Co. ELLWEST KG include different kind of PCBs (single & double sided, multilayer, flexible, impedance controlled, metal core) also assembling of boards and shipment as per requirement of customer.    Product pallet of Co. ELLWEST KG include different kind of PCBs

Have you consided to establish your own through-hole assembly or (and) SMD assembly at your own production ?

We can offer you top level through-hole assembly equipment (e.g. for 25.000 - 30.000 typical (250 x 110 mm) units / month) and SMD assembly equipment (for 8.000 - 9.000 typical (235 x 110 mm) units / month).

Please find the details on our PCB Assembly Equipment list and send us your inquiry.


 Multilayer PCBs with special dielectric constant

Sometimes you need to have a special dielectric constant of PCB material, but it should be not expensive. For multilayer PCB’s we can offer you in this case following solution :

Click to enlarge

A schematic picture of Teflon and FR4 combination
DK of FR-4 is 4.1-4.8, DK of Teflon –2.1 – 3.0.

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