Timeline for TQFP and VQFN on same footprint: good idea or bad?
Current License: CC BY-SA 4.0
21 events
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| Nov 24, 2022 at 9:07 | vote | accept | jonathanjo | ||
| Nov 24, 2022 at 6:38 | history | edited | Voltage Spike♦ |
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| Nov 23, 2022 at 21:31 | history | became hot network question | |||
| Nov 23, 2022 at 15:54 | history | edited | jonathanjo | CC BY-SA 4.0 |
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| Nov 23, 2022 at 15:42 | comment | added | bobflux | @Lundin I meant stencils too, I wrote some Frenglish by mistake | |
| Nov 23, 2022 at 15:28 | comment | added | jonathanjo | @RussellH thank you: edited to clarify that the centres is grounded. | |
| Nov 23, 2022 at 15:23 | history | edited | jonathanjo | CC BY-SA 4.0 |
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| Nov 23, 2022 at 15:16 | comment | added | Lundin | @jonathanjo Some contractors might have selective paste dispenser machines that can be used instead of stencils. Goes slower to apply that way, so it is ideal for smaller series. A few thousand units may or may not be considered a small series depending on the contractor. | |
| Nov 23, 2022 at 15:12 | history | edited | jonathanjo | CC BY-SA 4.0 |
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| Nov 23, 2022 at 15:10 | comment | added | jonathanjo | @Lundin, thank you, very helpful. I did mean two solder paste stencils, yes. Not two different solder masks on the PCBs: I agree, that's two different PCB designs. | |
| Nov 23, 2022 at 15:07 | history | edited | jonathanjo | CC BY-SA 4.0 |
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| Nov 23, 2022 at 15:00 | history | tweeted | twitter.com/StackElectronix/status/1595431987749199872 | ||
| Nov 23, 2022 at 14:55 | answer | added | Voltage Spike♦ | timeline score: 14 | |
| Nov 23, 2022 at 14:53 | comment | added | Lundin | @jonathanjo Why would it be less difficult maintaining two different solder masks than two different PCB layouts? Do you mean two different paste stencils? Either way I'd ask your assembly contractor about their preference. My experience is that selective assembly/multiple BoM for one single PCB is almost always more trouble than it is worth. | |
| Nov 23, 2022 at 14:51 | comment | added | user319836 | If the thermal pad is not connected to any PCB net, then it will float when the TQFP is installed. | |
| Nov 23, 2022 at 14:26 | comment | added | jonathanjo | @bobflux that's a very good point, makes me think two masks is a very good idea, most especially when larger package being installed. | |
| Nov 23, 2022 at 14:07 | comment | added | bobflux | Will you be using two paste masks? I'd be worried about the larger chip sitting on the solder paste deposited on the large QFN center pad and floating up when soldered. But I've never done this, so just hand waving here. | |
| Nov 23, 2022 at 13:44 | comment | added | jonathanjo | @glen_geek thank you for your comment, edited question (internal osc, no analogue). | |
| Nov 23, 2022 at 13:43 | history | edited | jonathanjo | CC BY-SA 4.0 |
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| Nov 23, 2022 at 13:39 | comment | added | glen_geek | Analog input? Crystal oscillator? These might be adversely affected. Do be careful to terminate un-used pins. | |
| Nov 23, 2022 at 13:29 | history | asked | jonathanjo | CC BY-SA 4.0 |