This thread seems to cover your situation.
https://ubuntuforums.org/showthread.php?t=2255644

On Thu, Jan 10, 2019 at 9:32 AM Joe Lowder <joe@actionline.com> wrote:

> I finally got Linux Mint 18.1 installed on a
> Thinkpad T430u (it should not be this hard)
> but now I cannot get wifi connected.
>
> Todd gave me some good tips, and I've searched
> the 'net and found more tips, but still stuck.
>
> From https://community.linuxmint.com/tutorial/view/796
> I got this much:
>
> command: lspci -vnn | grep 1434
>
> result:
> 03:00.0 Network controller [0280]: Broadcom Corporation BCM43228
> 802.11a/b/g/n [14e4:4359]
> Subsystem: Broadcom Corporation BCM43228 802.11a/b/g/n [14e4:0607]
>
> I was then advised to check the driver support table at
> linuxwireless.org (which is a non-existent website.
>
> The "tip" said: "Once you confirm that your WLAN device is
> supported, install the driver by running this command":
>
> sudo apt-get install firmware-b43installer
>
> Tried that and the result indicated that the driver was
> installed ....... but now what?
>
> How can I get this wifi connection to work?
>
>
>
>
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-- 
A mouse trap, placed on top of your alarm clock, will prevent you from
rolling over and going back to sleep after you hit the snooze button.

Stephen