Packaging Base Material #4

yunusdawji · 2021-01-11T22:21:05Z

Hi,

I am looking for cheaper alternatives for the packaging substrate. I see that N5000 and FR370HR have been used. I was wondering if there are cheaper more commonly used alternative? Also I see the chip need 30uin gold on top layer. I have in past used 2uin immersion gold (by mistake) and they bonded quite nicely. Do you think I could use 2uin or 3uin gold on top layer

Yunus

taylor-bsg · 2021-01-12T01:04:42Z

How many substrates are you trying to make? most of the cost is in the NRE anyway, but if you are planning to make 1000's, maybe it would make a difference. The gold used on the top is based on what the assembly house is okay with -- usually there are a few emails between you, the assembly house and package fab to resolve this. If you are the assembly house, then you can do whatever you and the substrate fab agree to. =) M

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On Mon, Jan 11, 2021 at 2:21 PM Yunus Dawji ***@***.***> wrote: Hi, I am looking for cheaper alternatives for the packaging substrate. I see that N5000 and FR370HR have been used. I was wondering if there are cheaper more commonly used alternative? Also I see the chip need 30uin gold on top layer. I have in past used 2uin immersion gold (by mistake) and they bonded quite nicely. Do you think I could use 2uin or 3uin gold on top layer Yunus — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#4>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEFG5AGIXBM6U3TQAVI53K3SZN2WDANCNFSM4V6ITWXA> .

yunusdawji · 2021-01-12T01:17:16Z

Thanks for the reply. I am looking to save whatever I can. If I do with pcbway.com, they are charging 1k for 100 boards but they don't any BT-epoxy based base material. We don't have big fundings right now, so whatever we can save is good.

We will most like use quickpak for wirebonding, so I will ask them.

taylor-bsg · 2021-01-12T01:46:09Z

Well that would be cool if you can pull it off! Most packaging is optimized for 10 year kinds of reliability and potential life or death consequences of failure, and probably you need much less. In that case,... I would ask the assembly house about whether there would be any issues in attaching solder balls and bond wires to FR4 (or high temp FR4 if it is better for them.) The other issues are lower performance and less reliability due to thermal expansion, but presumably those bond wires have a little bit of flex in them.

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On Mon, Jan 11, 2021 at 5:17 PM Yunus Dawji ***@***.***> wrote: Thanks for the reply. I am looking to save whatever I can. If I do with pcbway.com, they are charging 1k for 100 boards but they don't any BT-epoxy based base material. We don't have big fundings right now, so whatever we can save is good. We will most like use quickpak for wirebonding, so I will ask them. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEFG5AGZDORTED6YK7PM7MTSZOPKTANCNFSM4V6ITWXA> .

yunusdawji · 2021-01-12T02:22:17Z

Thanks for the ideas. Guys at PCB way suggested TU-862 HF. This material has similar Tg as N5000, same permitivity and CTE. I will ask the ppl at quickpak if they can work with substrate. I will let you know how it goes.

yunusdawji · 2021-01-19T17:56:13Z

Hi Prof.,

One more question. I see in an image that on BSG Motherboard has an ironwood reusable socket. How does that interface with chip packaging substrate and where can I buy this socket?

Yunus

taylor-bsg · 2021-01-20T00:01:32Z

New material: cool! Ironwood socket is custom, we can give you the part number. Tell your assembly house what the dimensions are when they do encapsulation. Socket has some PCB decal pattern as direct attach, but you need a little more space around it, and some holes for the retention clips. M

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On Tue, Jan 19, 2021 at 9:56 AM Yunus Dawji ***@***.***> wrote: Hi Prof., One more question. I see in an image that on BSG Motherboard has an ironwood reusable socket. How does that interface with chip packaging substrate and where can I buy this socket? Yunus — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEFG5AFYP7EK7LI3RQ7YR43S2XBU7ANCNFSM4V6ITWXA> .

yunusdawji · 2021-01-20T00:12:36Z

Thanks for the reply. Yeah it would be great if you can give us the part number/datasheet for socket. We are using quickpak for assembly, so I think they will be familiar. But if you have dimensions for encapsulation, then that should be good aswell.

taylor-bsg · 2021-01-20T00:15:02Z

If you are doing Quickpak then you are fine and can just wait until you are packaging your die and we’ll give you all the info

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On Tue, Jan 19, 2021 at 4:12 PM Yunus Dawji ***@***.***> wrote: Thanks for the reply. Yeah it would be great if you can give us the part number/datasheet for socket. We are using quickpak for assembly, so I think they will be familiar. But if you have dimensions for encapsulation, then that should be good aswell. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEFG5ABLHGSQKIPI4CUTK5DS2YNYJANCNFSM4V6ITWXA> .

yunusdawji · 2021-01-20T00:19:49Z

Ok thanks! Our tapeout is in couple of days, so we should be there in soon.

taylor-bsg · 2021-01-20T00:20:50Z

Good luck!

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On Tue, Jan 19, 2021 at 4:20 PM Yunus Dawji ***@***.***> wrote: Ok thanks! Our tapeout is in couple of days, so we should be there in soon. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEFG5AAQIEV42WMLNP42TVTS2YOTLANCNFSM4V6ITWXA> .

yunusdawji · 2021-02-26T04:52:35Z

Hi,

I was wondering I could get access to this wiki. https://bitbucket.org/taylor-bsg/bsg_fpga/wiki/Home

We want to test our loopback board.

Thanks

Yunus

taylor-bsg · 2021-02-26T18:30:33Z

Just to refresh my memory, what components are you using in the system?

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On Thu, Feb 25, 2021 at 8:52 PM Yunus Dawji ***@***.***> wrote: Hi, I was wondering I could get access to this wiki. https://bitbucket.org/taylor-bsg/bsg_fpga/wiki/Home We want to test our loopback board. Thanks Yunus — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEFG5AG5SOTA6AAFPK3H7GDTA4SJ7ANCNFSM4V6ITWXA> .

yunusdawji · 2021-10-21T17:40:38Z

We are about to fabricate the substrate for wire bonding and I have couple of questions.

Does the thickness of pcb package matters for the iron wood socket? Or that can be adjusted using the screw.
Do the pcb package needs gold bumps on underside or just a gold finish is good enough?
Is this the correct package files for the ironwood socket?
https://github.com/bespoke-silicon-group/bsg_packaging/blob/master/ucsd_bga_332/pcb/for_fab_sierra_proto_express/UCSD001_Gerber_2014-05-21.zip
https://github.com/bespoke-silicon-group/bsg_packaging/blob/master/ucsd_bga_332/pcb/for_socket_maker_ironwood/SO47885.pdf

Thanks

Yunus

taylor-bsg · 2021-10-21T18:19:35Z

@gaozihou can also fill in some of these questions; my guesses:

I assume when you say pcb package, you mean the substrate itself.

not especially (could be wrong on this)
I believe the bumps on the bottom of the substrate are just standard solderballs, there is no gold. the bumps are placed on there by the assembly house.
LGTM; paul can confirm

gaozihou · 2021-10-21T19:23:53Z

Hi @yunusdawji, here is the link to detailed information of the Ironwood socket: https://github.com/bespoke-silicon-group/bsg_motherboards/blob/master/bsg_trouble/real_trouble/misc_docs/C16459%20Dwg.PDF

It is not recommended to be too much thicker than the original design (31mil, 0.7mm). Although the compression screw is adjustable, the shoulder screws and socket lid are fixed. If the assembled chip is too thick then it will be hard to install the lid. As shown in the PDF, the recommended total assembled thickness (substrate + encapsulation) is 0.7mm + 1mm = 1.7mm. We also tried 2mm before, which worked but it was tricky to close the lid...
The BGA substrate must have soft bondable gold for all "bumps" (I guess you meant bond pads right). Gold finish (like ENIG) is not ideal for wire bond design. Please refer to this doc for fabrication guidelines: https://github.com/bespoke-silicon-group/bsg_packaging/blob/master/ucsd_bga_332/pcb/for_fab_sierra_proto_express/Q219234-5.docx
Yes, this is the correct Gerber.
When assembling (packaging) the BGA, the solder ball must be 0.6mm in diameter to be compatible with the Ironwood socket. Please refer to this doc for detailed specs: https://github.com/bespoke-silicon-group/bsg_packaging/blob/master/ucsd_bga_332/pinouts/bsg_two/common/to_assembly_house/example_files_for_assembly_house/assembly_build_sheet_bsg_ten.pdf

taylor-bsg · 2021-10-21T21:01:27Z

Definitely soft gold for the bondpads. For the bottom of the substrate where the solder balls go, I am not sure whether they ever asked us. To be clear though, these are questions that you typically ask your assembly house, and they will tell you what they want and then you relay back that to the substrate fab people.

yunusdawji · 2021-10-21T23:45:02Z

Thanks for the reply! I see in one of the document there are bumps on underside but maybe its just illustration.

Also I see for uw bga you have ENIPIG finish in the stack up document. Can ENIPIG work?

https://github.com/bespoke-silicon-group/bsg_packaging/blob/master/uw_bga/pcb/UWCS001_BGA_A03_PAUL_MODIFIED_2_fab.pdf

gaozihou · 2021-10-22T00:11:13Z

Hi @yunusdawji,
I would suggest asking the assembly house about ENEPIG finish for gold wire bond, different assembly house may have different requirements.

taylor-bsg · 2021-10-22T01:35:56Z

To be clear “assembly is king” — you ask the assembly house what they require and then talk to the substrate fabrication house. Fabrication house will tell what is convenient for them versus what assembly will want.

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On Thu, Oct 21, 2021 at 5:11 PM Paul Gao ***@***.***> wrote: Hi @yunusdawji <https://github.com/yunusdawji>, I would suggest asking the fabrication house about ENEPIG finish for gold wire bond, different fab house may have different requirements. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEFG5ACLWCTP34KKGYVMFDDUICT2ZANCNFSM4V6ITWXA> .

yunusdawji · 2021-10-22T01:58:50Z

Ok. I will tell them to do electrolytic gold. QP needs 8-15 uin of gold in ENEPIG but I have never seen this with any PCB manufacturer. The most I have seen is 4uin.

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On Thu, Oct 21, 2021 at 9:36 PM taylor-bsg ***@***.***> wrote: To be clear “assembly is king” — you ask the assembly house what they require and then talk to the substrate fabrication house. Fabrication house will tell what is convenient for them versus what assembly will want. On Thu, Oct 21, 2021 at 5:11 PM Paul Gao ***@***.***> wrote: > Hi @yunusdawji <https://github.com/yunusdawji>, > I would suggest asking the fabrication house about ENEPIG finish for gold > wire bond, different fab house may have different requirements. > > — > You are receiving this because you commented. > > > Reply to this email directly, view it on GitHub > < #4 (comment) >, > or unsubscribe > < https://github.com/notifications/unsubscribe-auth/AEFG5ACLWCTP34KKGYVMFDDUICT2ZANCNFSM4V6ITWXA > > . > — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABA7VRDXGC74TDWX6DF4AWDUIC5YPANCNFSM4V6ITWXA> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

yunusdawji · 2021-10-22T02:10:55Z

Sorry one more thing for the package substrate, are there solder balls on the underside of your chip? I dont see anything in this chip in youtube video.
https://www.youtube.com/watch?v=pumrNqkXjfI&list=PLD1QnhK1caR3IrAtVAd1-leMkus7dVy6a&index=18

gaozihou · 2021-10-22T02:17:18Z

Hi @yunusdawji,
Yes, it needs 0.6mm solder balls on the underside of the BGA substrate to be compatible with the Ironwood socket.

yunusdawji · 2021-10-22T02:24:23Z

Ok thanks.

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On Thu, Oct 21, 2021 at 10:17 PM Paul Gao ***@***.***> wrote: Hi @yunusdawji <https://github.com/yunusdawji>, Yes, it needs 0.6mm solder balls on the underside of the BGA substrate to use the Ironwood socket. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABA7VRGZ6OSW3VE24DBHS33UIDCTRANCNFSM4V6ITWXA> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

taylor-bsg · 2021-10-22T17:54:25Z

Haha no solder balls on the bottom of the substrate, even though the die has been mounted and wirebonded -- good catch. Yeah, that is a little weird. M

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On Thu, Oct 21, 2021 at 7:11 PM Yunus Dawji ***@***.***> wrote: Sorry one more thing for the package substrate, are there solder balls on the underside of your chip? I dont see anything in this chip in youtube video. https://www.youtube.com/watch?v=pumrNqkXjfI&list=PLD1QnhK1caR3IrAtVAd1-leMkus7dVy6a&index=18 — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEFG5AGTQAQDUWAVKQQWHLLUIDB3VANCNFSM4V6ITWXA> .

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Packaging Base Material #4

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Packaging Base Material #4

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