# RAM "Bus" IC chips



## kurtak (Dec 17, 2018)

Just wondering if anyone has processed the IC chips from RAM Bus --- RAM Bus is the RAM with the aluminum shield/heat sink riveted over the IC chips

Here is a pic with the aluminum shield removed

I don't remember them ever being discussed for processing for gold bond wires

They are BGA type ICs

But unlike regular RAM BGAs they don't have the epoxy on top of the silicon chip

However - they still have gold bond wires

The bond wires are in the little epoxy ribbon in the center of the chip on the ball grid side of the chip --- just like where the bond wires are in regular epoxy coated RAM BGAs

Might be a good one for Alex (Troax) to try in his thread about data of "particular" types of chips 8) :mrgreen: 

Kurt


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## silversaddle1 (Dec 17, 2018)

I have a couple hundred pounds of Rambus. I wonder how much it would take to get a sood sample.


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## Smack (Dec 18, 2018)

I thought these had the highest yield by weight of all the chips. I've processed them mixed with others, not by themselves.


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## g_axelsson (Dec 18, 2018)

Smack said:


> I thought these had the highest yield by weight of all the chips. I've processed them mixed with others, not by themselves.


Why would you think that?

I've never processed a rambus chip but I have a couple of kilos of rambus modules. Based on the pictures above I wouldn't expect too much in gold, there are few solder balls on these chips and you only need one bond wire per connection. Rambus used a serial data connection instead of the traditional parallel connection. So my expectation would be less gold than normal parallel ram chips with more data connections.

The fact that the chip in it self doesn't have a lot of extra metal as a lead frame and plastics to cover it makes it lighter so that might increase yield based on weight of the chip, at least compared with the contemporary SOIC plastic chips used in SDRAM and early DDR.

Some clues to the gold content can be found at the boardsort website, they pay 40% of the price of ordinary gold finger ram, but then there is the metal casing that makes a normal DIMM lighter than a RDRAM module.
I grabbed five RAMBUS modules and five DDR3 DIMM and put them on my scale, rambus was on average 28g/module and DDR3 16g/module, so the rambus module is 75% heavier than a DDR3. In the end a rambus module is paid 70% of a DIMM so I would expect a lower yield based on that number.

Göran


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## Smack (Dec 19, 2018)

I thought I read it here on the forum somewhere. That's why, I may be wrong, hence the lack of conviction in my comment.


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## kurtak (Dec 19, 2018)

g_axelsson said:


> Based on the pictures above I wouldn't expect too much in gold, there are few solder balls on these chips and you only need one bond wire per connection.
> Göran



Goran

I just counted the solder balls on the two chips in my pic 

The RAM Bus chip (on the right) has 68 next to the center epoxy ribbon & another 20 at the outside edge of the chip (I believe the 20 on the edge make the connection from the board to the the lead frame of the chip - so no bond wire on the edge) (so total of 88)

The regular RAM chip (on the left) has a TOTAL 60

So the RAM bus actually has more

Also - when I looked at the ash (from each chip) with my 15X loop - the RAM Bus bond wires "appeared" to be heavier/thicker 

Hence my question - I have always processed them together with other chips

Edited; - for ball count

Kurt


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## g_axelsson (Dec 19, 2018)

My bad, I thought it was two different models of rambus chips. Then the penalty of the price could be to pay for the extra work handling the metal shield.
But the thickness of the bond wires must be very specific for a certain model / era / manufacturer... but it's an older technology than the comparable DDR DIMM so maybe the thickness of the bond wires might have decreased over the years.

There isn't a lead frame on BGA chips that I'm aware of. It is only found in chips with legs.

Göran


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## kurtak (Dec 20, 2018)

g_axelsson said:


> There isn't a lead frame on BGA chips that I'm aware of.
> 
> Göran



"lead frame" my not be the thecnical term (I don't know) however there is a frame work of (copper) traces - the solder balls connect from the circuit board (RAM board) to the chip - the traces then lead to edge nearest the epoxy ribbon at the center of the chip - then the gold bond wires make the connection from that edge to the chip --- when looking at that edge with my 15X loop its gold plated & it looks just like the "fingers" on the RAM board (but VERY "small") each of those "fingers" has a bond wire connected to the copper leads (traces) which then connects to the chip (in that center epoxy ribbon)

so maybe its called a trace frame instead of a lead frame

you can see the leads/traces with 15x loop & it looks just like a VERY small circuit board - sorry but this is the best pic I could do

Kurt


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## Tzoax (Dec 20, 2018)

kurtak said:


> g_axelsson said:
> 
> 
> > There isn't a lead frame on BGA chips that I'm aware of.
> ...



Kurt, i think you are talking about this:




They are very interesting for testing, i will start to collect them - but i rarely see them around.

Here is what i found based on model of chip from your picture (K4R571669A)...

In a package footprint picture - the outer solder balls connections are not included - i wonder why.


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## g_axelsson (Dec 20, 2018)

Kurt, I would call that a substrate or carrier but I can be wrong there. Lead frame on the other hand is a well defined concept in chip packaging that applies on the metal conductors used in plastic chip, providing mechanical strength, electrical pathways and thermal paths. Observe that heat spreaders in form of a copper sheet are not part of the lead frame. For the small circuit board inside a BGA I haven't heard any specific term.

The term lead frame makes a lot mote sense if you see one before the plastic is molded and the outer part (the frame) is trimmed off.
https://en.wikipedia.org/wiki/Lead_frame

The reason for the unconnected solder balls along the outer edges on a rambus chip is purely for mechanical strength. Without them the chip could easily tip in one direction or another and create a failed product.

Göran


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