Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Terry Keen

#14715

Printing and Reflow with Ceramics | 12 August, 1998

We are taking enquiries for sub-contract work that we hope to be doing by Christmas. One of the enquiries is to assemble chip capacitors and an SO14 onto ceramic. Does the printing process, paste used and reflow process remain the same, or are there major differences when using ceramic board.

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Earl Moon

#14716

Re: Printing and Reflow with Ceramics | 12 August, 1998

| We are taking enquiries for sub-contract work that we hope to be doing by Christmas. One of the enquiries is to assemble chip capacitors and an SO14 onto ceramic. Does the printing process, paste used and reflow process remain the same, or are there major differences when using ceramic board. Terry, Good to see from you again. Got your email. Couple of questions. 1) Are we talking alumina substrates as the ceramic material? 2) Are we co-firing gold as the conductors on the substrate surface? 3) In other words, is this a hybrid thick film circuit? 4) If so, how large or small? Earl Moon

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Terry Keen

#14717

Re: Printing and Reflow with Ceramics | 13 August, 1998

| Couple of questions. | 1) Are we talking alumina substrates as the ceramic material? | 2) Are we co-firing gold as the conductors on the substrate surface? | 3) In other words, is this a hybrid thick film circuit? | 4) If so, how large or small?

Sorry Earl, I havent a clue what you are talking about.

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Earl Moon

#14718

Re: Printing and Reflow with Ceramics | 13 August, 1998

| | Couple of questions. | | 1) Are we talking alumina substrates as the ceramic material? | | 2) Are we co-firing gold as the conductors on the substrate surface? | | 3) In other words, is this a hybrid thick film circuit? | | 4) If so, how large or small? | | Sorry Earl, I havent a clue what you are talking about.

Terry, I too am sorry. It's just that I could provide some help if these circuits you will be assembling were of the hybrid thick film variety. That is, hybrids are circuit boards usually made of aluminum oxide (alumina)often having as their circuit pattern gold (as a paste) that has been screen printed then "fired" in an infrared reflow oven. Circuit traces are in the one mil range and often have a glass layer, or more than one, fired on top of them allowing multiple layers of circuit patterns to be added as required. Often too, resistor paste is screened and cured where needed as are capacitors. On larger ceramic circuits, approaching normal PCB sizes (say 4 x 6 inches), surface mount devices may be placed and soldered. The problems encountered with this type attachment primarily are related to thermal profiles and possible gold contaminated solder joints (only when gold thickness is excessive on solder termination areas). As ceramic is a very effective insulating material (space shuttle re-entry tiles, etc), it can present a barrier to reflow soldering. What all this comes down too is a better understanding of what these circuits are that you will be building. If they are as described, the circuitry can be produced with relatively conventional processes (stencil printing paste, placement, and reflowing). You will have to run the experiment to determine what works and you will have to be very carful handling these circuits as alumina is very brittle and breaks easily. Earl Moon

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