Has this actually been addressed in the source files? The latest development build (3.38) still doesn’t support these. Also missing are:

• U+02D2 through U+02D7, the standalone forms of the relative articulation diacritics,
• U+02E5 through U+02E9, the official tone letters which require OpenType substitutions to render properly,
• U+025D, the conventional transcription of the vowel in American English nurse or term,
• U+0296 and U+0297, obsolete symbols for clicks which can still be found in the literature,
• and a lot of superscript modifier letters, which can indicate either secondary articulation or optional sounds; U+1D51, U+1D5D, U+1DAE and U+02B4 are some of the most common. (The full list can be found on Wikipedia, though not all of them are commonly used in practice. Note that superscript ç doesn’t exist in Unicode as a unitary codepoint; it has to be encoded as a sequence U+1D9C U+0327.)

I noticed that when typing affricates with a tie bar ([t͡s t͡ʃ] etc.), they convert to ligatures ([ʦ ʧ] etc.). It’s true that digraphs with a tie bar and ligatures are functionally identical within IPA, but they’re still different glyph sequences and should render differently.

@projectshifter The source files are on my end, when something is marked as addressed in source files it means in my own private branch of this project. The four characters requested (plus a handful more including U+025D) are in the pipeline to be released in the next update to Source Sans.
Regarding ligatures, if you prefer not to have them, turn off the ligatures (liga) feature. I haven’t gone through your first comment on this thread, but if you are requesting additional characters to be added to the fonts, please open a separate issue, thanks.

Will do. Thanks for the information though.

Any feature that replaces the ligature tie sequences with the ligature symbols is wrong.

The IPA deprecated the ligature symbols ʣ ʥ ʤ ʨ ʦ ʧ in 1989 and recommended the use of ligature ties, because many more sounds can be represented with ties rather than having to create new ligature symbols. These ligature symbols should not be used anymore but are still very common in documents.
The official IPA way to represent those affricate consonants or doubly articulated segments is with the top or bottom ligature ties when there's ambiguity with a sequence of consonant or no ties at all when there is no ambiguity:

• d͡z d͡ʑ d͡ʒ t͡ɕ t͡s t͡ʃ k͡x k͡p ...
• d͜z d͜ʑ d͜ʒ t͜ɕ t͜s t͜ʃ k͜x k͜p ...
• dz dʑ dʒ tɕ ts tʃ kx kp ...

See International Phonetic Association, ”Report on the 1989 Kiel Convention“, Journal of the International Phonetic Association, 19 (2),‎ 1989

See also International Phonetic Association, Handbook of the International Phonetic Association : a guide to the use of the International Phonetic Alphabet, Cambridge University Press, 1999

It makes no sense to have any ligature feature substitute the official symbols with the obsolete forms.
If someone wants to use the obsolete symbols, they can and should use their characters.