Aluminia Thin Film Circuit Boards 2

[Carlsberg73]

Hi mates

just want to ask if anyone has ever worked with alumina thin film circuit boards. How would you rate them in terms of cost and use. Am planning to use it for a high speed circuit. would it work and what is the cost like.

Jeffrey

 

[IRstuff]

Why would you want to?

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[MacGyverS2000]

Same ? as IR... what advantages are you trying to gain by using it compared to standard practice?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[Carlsberg73]

for one my device is very sensitive to levelness and i have carried out surface levelness of PCB and it ain't that good.

 

[ScottyUK]

Alumina is usually a thick film substrate. Thin film is on a special glass. I used to work for a facility manufacturing both types of hybrids, but the thin film line was virtually idle.

Assuming you're thinking about thick film, for small quantities they have a high per-unit cost. For larger volumes the costs can drop quite dramatically to the extent where they are used in commodity markets such as automotive, but you need the volume throughput to get this economy of scale. Alumina can handle fairly high power applications, and on beryllia can handle very high power densities. Frequency limits tend to be due to the dielectric properties of the substrate, which are generally better and considerably more stable than for FR4.

Thin film - where it's used at all these days - is the preserve of high-end military and telecoms. Expensive, and for low power applications. I'm not even sure my old place - TT Welwyn - still has a thin film capability.


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If we learn from our mistakes I'm getting a great education!

 

[IRstuff]

Please elucidate: for one my device is very sensitive to levelness; datasheet??

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[pstuckey]

Before you go to alumina, you should look at high performance "FR4-like" materials. The attachment has a good summary of materials in table 1 and table 2. Rogers (and others) make laminates with much tighter tolerances than FR4, but they can still be fabricated with standard FR4 processes.

Peter

 

[biff44]

Alumina thin film circuits are primarily used for very high frequency circuits, in the 2 to 30 GHz region. They used to be very popular, because you can directly attach unpackaged semiconductor die to them, and if plated with gold traces, you can directly wirebond to them. They are expensive because to make a via hole you have to drill thru the ceramic and plate them...an expensive process. Also, these substrates do not attach easily to metal surfaces--they can pop off under thermal cycling.

They are expensive, though, and you typically have to place them inside of another housing (often one that is hermetically sealed) to protect the semiconductor chips from humidity and abuse.

Nowadays, even very high frequency circuits are available in leadless chip carrier plastic packages, and direct wirebonding to the chips is much rarer. Today, you are much more likely to see a flexible substrate with such packaged chips soldered on. Those substrates are available from Arlon, Taconic, Rogers, etc.

http://www.MaguffinMicrowave.com

Maguffin Microwave wireless design consulting

 

[zappedagain]

'levelness'? Have you checked out an ENIG finish instead of a HASL finish on FR-4?

We use Alumina all the time around here and I agree with the above responses; it is much more expensive. We only use it when we are attaching ICs in die form, and want to go below the 0.004" trace width that FR-4 can handle (typically).

Z