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Does anyone have 15C LE dissection pics?
Message #1 Posted by Hugh Evans on 20 Sept 2011, 9:26 p.m.

I'm curious if anyone has done this yet. HP seems to have taken a liking to screws over heat stakes in recent years. If that is indeed the case with the 15C LE, I will take a stab at improving a couple of minor issues involving the keys. The first step will be that of taking the wiggle out of f and g. Then I will move on to filling them, probably with some polyurethane reactive hot melt to minimize downtime.

      
Re: Does anyone have 15C LE dissection pics?
Message #2 Posted by Lincoln R. on 20 Sept 2011, 10:05 p.m.,
in response to message #1 by Hugh Evans

I've opened the back of one. It's heat-staked, there's foam tape behind the LCD to keep it from bouncing around in the case, and the Atmel CPU is in an LQFP package instead of being a raw die underneath epoxy like my 12C+ is. I have a picture but the quality's not that great, I'll see if I can clean it up a bit.

            
Re: Does anyone have 15C LE dissection pics?
Message #3 Posted by Katie Wasserman on 20 Sept 2011, 10:49 p.m.,
in response to message #2 by Lincoln R.

It's the same as the 12C+. I've posted these pictures before:

                  
Re: Does anyone have 15C LE dissection pics?
Message #4 Posted by Eric Smith on 21 Sept 2011, 1:14 a.m.,
in response to message #3 by Katie Wasserman

Nice pictures of the 12C, but if Lincoln R. is correct, the 15C LE does NOT look the same. That seems rather surprising since there isn't any need for the hardware to differ.. I haven't opened mine, though, so I can't confirm.

                        
Re: Does anyone have 15C LE dissection pics?
Message #5 Posted by Tim Wessman on 21 Sept 2011, 1:28 a.m.,
in response to message #4 by Eric Smith

I believe the 15c uses a packaged IC. That is the only difference IIRC.

TW

Edited: 21 Sept 2011, 1:28 a.m.

                              
Re: Does anyone have 15C LE dissection pics?
Message #6 Posted by Thomas Radtke on 21 Sept 2011, 1:35 a.m.,
in response to message #5 by Tim Wessman

Does the AE 12C have bad keys, too?

                              
Re: Does anyone have 15C LE dissection pics?
Message #7 Posted by Katie Wasserman on 21 Sept 2011, 3:32 a.m.,
in response to message #5 by Tim Wessman

Indeed, the PCB on the 15C LE doesn't have the potted chip on board, it's got the real packaged Atmel chip in all it's glory showing.

15C PCB

and the back of the case

If I'm reading this correctly the date code on this chip is from September 2009, ancient!

Why the switch away from the potted chip on board? Is this the same in the 12C 30th AE and newer 12C+ calculators too?

Edited: 21 Sept 2011, 3:34 a.m.

                                    
Re: Does anyone have 15C LE dissection pics?
Message #8 Posted by Thomas Chrapkiewicz on 21 Sept 2011, 8:56 a.m.,
in response to message #7 by Katie Wasserman

Katie:

Nice work!

This is indeed good news in enabling any potential hardware modifications or studies.

TomC

                                    
Re: Does anyone have 15C LE dissection pics?
Message #9 Posted by Masaki Adachi on 21 Sept 2011, 12:01 p.m.,
in response to message #7 by Katie Wasserman

Are there instructions to open up the 12C+/15C LE posted somewhere?

Edited: 21 Sept 2011, 12:02 p.m.

                                          
Re: Does anyone have 15C LE dissection pics?
Message #10 Posted by Katie Wasserman on 21 Sept 2011, 12:08 p.m.,
in response to message #9 by Masaki Adachi

There are 6 screws to remove, one under each foot and two inside the battery compartment (one of these is smaller than the other 5). Once you do this it prys apart quite easily.

                                                
Re: Does anyone have 15C LE dissection pics?
Message #11 Posted by Thomas Chrapkiewicz on 21 Sept 2011, 12:41 p.m.,
in response to message #10 by Katie Wasserman

The only mechanical constraints appear to be along the top and bottom edges of the case.

ALSO BE CAREFUL: Try to have the calc face down as you pry it apart as there are three springs in plastic collars in the keyboard half of the calc which can fall out. (These are used to electrically connect the keyboard to the metal plate on the battery compartment half of the calc - for ESD protection.)

TomC

                                    
Re: Does anyone have 15C LE dissection pics?
Message #12 Posted by Kerem Kapkin (Silicon Valley, CA) on 21 Sept 2011, 12:49 p.m.,
in response to message #7 by Katie Wasserman

Spec details on Atmel AT91SAM7L128

A member of the Atmel SAM7L series of microcontrollers based on the 32-bit ARM7TDMI processor. It operates at a maximum speed of 36MHz and features 128KB of flash and 6KB of SRAM. The peripheral set includes a 40-segment LCD controller, two USARTs, UART, SPI, TWI (I2C), three 16-bit timers, RTC and four 10-bit ADC. The SAM7L128 operates in single-supply mode down to 1.8V and consumes 0.5mA/MHz typical in active mode when executing code out of its flash memory, and a mere 100nA in power-down mode. The SAM7L128 is supplied in a 128-pin LQFP and 144-pin LFBGA packages.

It is the SAME Chip on HP20b Calculator: HP20b Calculator using ATMEL 91SAM7L128 Chip

Another good article about the 15c and ATMEL Processor EDA360 15C and ATMEL AT91SAM7L128 (BTW, I think that's where the "inmate" discussion started in the forums.)

Edited: 21 Sept 2011, 1:26 p.m.

                                    
Re: Does anyone have 15C LE dissection pics?
Message #13 Posted by hpnut on 21 Sept 2011, 12:52 p.m.,
in response to message #7 by Katie Wasserman

Katie,

is that lipstick on the Atmel chip? LOL!

                                          
Re: Does anyone have 15C LE dissection pics?
Message #14 Posted by Katie Wasserman on 21 Sept 2011, 3:59 p.m.,
in response to message #13 by hpnut

Yes, but not mine. Probably whoever did the assembly in China was kissing it goodbye.

If it were an HP-16C+, that might be another story.

                                    
Re: Does anyone have 15C LE dissection pics?
Message #15 Posted by DaveJ on 21 Sept 2011, 9:46 p.m.,
in response to message #7 by Katie Wasserman

I haven't checked, but if there is a bigger memory chip in the same package, it could be replaced fairly easily.

Dave.

                                          
Re: Does anyone have 15C LE dissection pics?
Message #16 Posted by Katie Wasserman on 22 Sept 2011, 12:52 a.m.,
in response to message #15 by DaveJ

Quote:
if there is a bigger memory chip in the same package

There isn't one with a larger non-volatile RAM at least last time I checked.

                                          
Re: Does anyone have 15C LE dissection pics?
Message #17 Posted by Kerem Kapkin (Silicon Valley, CA) on 22 Sept 2011, 2:19 a.m.,
in response to message #15 by DaveJ

I remember seeing an AT91SAM7L256, I think that is double the memory. I will confirm and check on the packaging.

                                                
Re: Does anyone have 15C LE dissection pics?
Message #18 Posted by Katie Wasserman on 22 Sept 2011, 3:48 a.m.,
in response to message #17 by Kerem Kapkin (Silicon Valley, CA)

There's a AT91SAM7S256 with lots of RAM, but without the LCD driver and requires higher voltage and more power.

                                                      
Re: Does anyone have 15C LE dissection pics?
Message #19 Posted by Paul Dale on 22 Sept 2011, 3:57 a.m.,
in response to message #18 by Katie Wasserman

Flash isn't the big problem. RAM is.

The 34S could use more RAM. Lots more.

I know how to squeeze more into flash. It will require recoding many of the mathematics routines but it is possible.

Oh and the display needs to be a lot better. 400 segments isn't enough to do the hardware justice.

- Pauli

                                                            
Re: Does anyone have 15C LE dissection pics?
Message #20 Posted by Katie Wasserman on 22 Sept 2011, 11:02 a.m.,
in response to message #19 by Paul Dale

There are a few spare i/o pins that are made available on the 20b and 30b PCBs. Have you experimented with adding a small serial non-volatile RAM chip? Such RAM wouldn't be in the calculator's memory space but you could write routines to page it in as needed or it might be fast enough to use for all memory access.

                                                                  
Re: Does anyone have 15C LE dissection pics?
Message #21 Posted by Paul Dale on 23 Sept 2011, 5:00 a.m.,
in response to message #20 by Katie Wasserman

We've not experimented but this possibility has been mentioned :-)

- Pauli

                                    
Re: Does anyone have 15C LE dissection pics?
Message #22 Posted by uhmgawa on 22 Sept 2011, 11:37 a.m.,
in response to message #7 by Katie Wasserman

Quote:
Indeed, the PCB on the 15C LE doesn't have the potted chip on board, it's got the real packaged Atmel chip in all it's glory showing.

15C PCB


Very nice indeed.

Quote:
Why the switch away from the potted chip on board? Is this the same in the 12C 30th AE and newer 12C+ calculators too?

The change to (and developemnt cost of) a new board layout with an lqfp package is puzzling. Maybe a design/layout modification was pending for whatever reason and the projected volumes didn't justify the setup cost for COB a this stage.

Frankly I'm still not sure how a bare sam7l die ended up in the 12c+ version. There isn't a motivation due to high die pin count. Perhaps it was an early attempt to discourage reverse engineering over a concern of using an off the shelf commercial SoC. Hard to see an economic motivation but Atmel doesn't appear to openly sell the part in bare die form so that's inconclusive.

                                          
Re: Does anyone have 15C LE dissection pics?
Message #23 Posted by Eric Smith on 22 Sept 2011, 11:52 a.m.,
in response to message #22 by uhmgawa

Cost. In the quantities that HP makes the 12C, they are able to buy the bare die, attach and bond it, and encapsulate it, for less than what it costs to buy the packaged part.

The reason Atmel doesn't "openly sell" the part in bare die form is that they don't want to sell it that way to anyone that isn't buying a large volume and prepared to deal with the complexity of chip-on-board assembly. If you design a high-volume product, you can negotiate a bare die contract with Atmel too.

                                                
Re: Does anyone have 15C LE dissection pics?
Message #24 Posted by Kerem Kapkin (Silicon Valley, CA) on 22 Sept 2011, 12:13 p.m.,
in response to message #23 by Eric Smith

Packaged chips go through extensive relaibility and retention tests including at high temperatures. Sometime the defects are not detectible until a high temperature test is performed. However bare die only goes through a simple probbing test. Testing becomes much more complex and difficult once the bare SoC chip is sureface mounted on a board, and some tests such as high temperature testing are not possible.

Therefore I would argue that 15C could be more reliable than 12C at least as far as the reliability of the SoC is concerned.

                                                
Re: Does anyone have 15C LE dissection pics?
Message #25 Posted by uhmgawa on 22 Sept 2011, 4:44 p.m.,
in response to message #23 by Eric Smith

Quote:
Cost. In the quantities that HP makes the 12C, they are able to buy the bare die, attach and bond it, and encapsulate it, for less than what it costs to buy the packaged part.

Possibly, but I believe the answer is only known to HP. There is also the need for precision die handling, die adhesion to pcb, wire welding, and encapsulation which add to the manufacturing process cost traded off against the uneventful alternative of reflowing a 128 pin lqfp on a board to be printed and reflow processed anyway.

Quote:
The reason Atmel doesn't "openly sell" the part in bare die form..

Apparently they do but through specialized die distributors and wafer processing third parties rather than directly.

                                                      
Re: Does anyone have 15C LE dissection pics?
Message #26 Posted by Eric Smith on 22 Sept 2011, 5:45 p.m.,
in response to message #25 by uhmgawa

Quote:
There is also the need for precision die handling, die adhesion to pcb, wire welding, and encapsulation which add to the manufacturing process cost

I stated that, less precisely. However, they don't add very much to the manufacturing cost, because the ODM in China is already equipped to do all of that, and does it routinely for many products.

This is why if you open up just almost any sub-$50 electronic item, you'll find that it uses CoB assembly. SMT assembly in low-cost items is the exception.

This is what makes it particularly bizarre that the 15C LE has moved to SMT assembly.

                                                            
Re: Does anyone have 15C LE dissection pics?
Message #27 Posted by Mike Morrow on 22 Sept 2011, 6:33 p.m.,
in response to message #26 by Eric Smith

Quote:
This is why if you open up just almost any sub-$50 electronic item, you'll find that it uses CoB assembly.

An interesting (to me) example of that is the Casio fx-115/991ES. It has a 204-connection chip die under the black epoxy blob, most of which go to the 31x96 dot-matrix LCD with 18 annunciators (2994 elements). It sells for less than $13 at some US major retailers.

                                                                  
Re: Does anyone have 15C LE dissection pics?
Message #28 Posted by uhmgawa on 22 Sept 2011, 8:45 p.m.,
in response to message #27 by Mike Morrow

Quote:
An interesting (to me) example of that is the Casio fx-115/991ES. It has a 204-connection chip die under the black epoxy blob, most of which go to the 31x96 dot-matrix LCD with 18 annunciators (2994 elements). It sells for less than $13 at some US major retailers.

Most contemporary graphic lcd controllers of such density are as well only available in die form due to the sheer number of pins present on the device. But obviously a valid argument as the process must be economical at that price point.

                                                            
Re: Does anyone have 15C LE dissection pics?
Message #29 Posted by uhmgawa on 24 Sept 2011, 9:17 a.m.,
in response to message #26 by Eric Smith

Quote:
This is what makes it particularly bizarre that the 15C LE has moved to SMT assembly.

After a chat with an Atmel die reseller today it isn't quite as intuitive as I'd expected. The pricing is all over the map and in some cases singulated die will have an OEM cost greater than its packaged counterpart due to "market forces". Even if you're interested in buying full wafers from a semi vendor you may be stuck going through a reseller due to a vendor's traceability and liability concerns of the die ending up in unapproved hands, or being packaged for resale via unapproved parties. Other lesser logistical issues exist such as vendors only shipping full wafers so if your production pipe isn't continuous you may need to warehouse unbonded die in a nitrogen bath to avoid atmospheric contamination of the die's metalization.

No idea if any of the above applies to the 15c le's manufacturing disposition. However this tends to confirm the suspicion a few other variables exist in the equation concerning the economics of bare vs. package die use.

                                          
Re: Does anyone have 15C LE dissection pics?
Message #30 Posted by sylvandb on 22 Sept 2011, 5:03 p.m.,
in response to message #22 by uhmgawa

Quote:

The change to (and developemnt cost of) a new board layout with an lqfp package is puzzling. Maybe a design/layout modification was pending for whatever reason and the projected volumes didn't justify the setup cost for COB a this stage.


speculation follows...

The lqfp might be the new design/layout.

Has anyone opened a recent 12c (30th AE or similar vintage) to see if it is still using the COB?

Perhaps the bare chip contract ended, and rather than extend it the board was redesigned for the lqfp.

Maybe the lqfp price was near enough the COB not to matter?

Maybe the 12c volume has declined so that the COB was no longer justified/cost-effective?

                                    
Re: Does anyone have 15C LE dissection pics?
Message #31 Posted by Marcus von Cube, Germany on 23 Sept 2011, 12:45 p.m.,
in response to message #7 by Katie Wasserman

This opens up opportunities to connect the missing JTAG connector and crystal for repurposing.

                                          
Re: Does anyone have 15C LE dissection pics?
Message #32 Posted by Katie Wasserman on 23 Sept 2011, 3:30 p.m.,
in response to message #31 by Marcus von Cube, Germany

Yes it does if you're good at doing some very precise soldering, it's a 0.5mm lead pitch.

                                                
Re: Does anyone have 15C LE dissection pics?
Message #33 Posted by uhmgawa on 24 Sept 2011, 9:05 a.m.,
in response to message #32 by Katie Wasserman

Quote:
Yes it does if you're good at doing some very precise soldering, it's a 0.5mm lead pitch.

0.5mm pitch gull wing packages aren't too formidable. You can have at it relatively comfortably using a 5x jeweler's loupe and fine point soldering tip. Assuming the rework will be done in place with the pcb mounted, one caution would be to keep the typical flux drenching in check to avoid contamination via creepage through vias into the key matrix. Then again IIRC the vias may be small enough to have been closed by the solder mask. If so this may prevent the flux from migrating.

Alternatively (judging from the autopsy above) the 15c le as well uses hollow studs securing the pcb to the frame. I'd assume as for the 12c+ the ID of the stud bore is just under 1.2mm. So after cutting the heat staked heads the pcb could be reattached with 1.2~1.4mm self threading, flange head screws -- a major simplification relative to the trauma of pcb replacement for legacy voyagers.


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