tm4c123gh6pmi populating or soldering in custom board

Feel your pain - what you're attempting is not easy (usually) for those w/out great experience & equipment.

Should your school project be, "Held hostage" to your creation of a difficult, custom pcb?   Really?

May I suggest that you confine your "custom board creation" to the added accessory chips & components (not present on the LPad) - which justify your efforts toward a custom board?    And then use the low cost Launch Pad to "plug-in" to the custom, "Alex board."   In this manner you've eliminated the difficulty of successfully soldering the fine pitch MCU - yet you retain those extra features/capabilities - which you (appear) to need.

Many have gone this route. (to include my firm - and we're blessed to have "pick-n-place" (automated placement of smt devices) and 20' long, multi-stage, reflow oven.)

It's hoped that your ability to "problem solve" w/the MCU - not (solder) the MCU - should be central to your school project!   

alex ruiz1 said:

Any idea?

Yes - but not sure (you) or vendor here will like them.

First - as ALL students operate under such requirement (not too bright - IMO) cannot you have one of those students who produced a "working MCU" assist you?

In the past - when the LM3S (earlier family of MCUs) walked here - 48 pin devices were available.   And these were easier to hand-solder than the far larger devices - now the only ones supplied.   Of note - other MCU vendors produce 48, 32, even fewer pin count ARM MCUs - which prove far easier to hand solder.  (the 32 pin QFP enjoys 0.65mm pitch - far easier to solder than 0.50mm!   Smaller ARM MCUs may have even wider pin pitch!)

When hand soldering - liquid FLUX - and more liquid FLUX - prove immensely helpful.

I've co-founded - taken past tech firm public.   I believe your instructors are (hugely) misguided to force pcb solder of fine-chip MCU upon you.   My firm hires many recent grads - and never/ever would we ask them to do such - NEVER!   As I stated earlier - IMCO (considered) those instructors are "HOLDING YOUR LEARNING HOSTAGE" due to an unjustifiable demand (fine pitch MCU soldering) which has NO place in a competitive, modern tech world!

You are your project's boss - and I wish you well.

Realize though - the time/effort/anguish spent "mastering fine pitch, MCU soldering" necessarily detracts/subtracts from the time/effort you'll have to do the real design & application solving - w/in your project. That "design & application" proves most important - does it not?

I would bet you - that your presentation of your (failed) MCU board (to prove that you've tried) ALONG WITH your working LPad which plugs-in to your "Alex board" would prove acceptable - under the conditions I've noted.   (at least ask the instructor - blame me - try to win his/her support!)

My fear - developed over many years of work in this field - is that your MCU may prove "intermittent" due to your lack of experience in board layout & fine-pitch assembly!     And that is "head of the class" Krazy Making!    And almost guaranteed for those in your position - and under deadline.

Use of the LPad - plugging into your pcb - (after approval by the instructor) is SURE to produce a better, faster and SAFER result.

Friend Robert's excellent post & pointers triggers (another) tip. His mention of the HASL finish reminds me of the great advantage provided by your soldering two - opposite corner MCU pins - first!   Insure that the MCU is exactly aligned (you may have to tape it down - or have an assistant hold it down in an "ESD approved" manner) and only solder one corner pin.  If successful - repeat that soldering procedure upon the MCU pin diagonally opposite the first pin (just) soldered.

With that done - and provided you do not disturb either of those two precious (MCU aligning) joints - soldering the remaining pins has far higher chance of success. Liberal use of flux - and perhaps "dragging" your iron across multiple pins (often pin to pin shorts result) will enable many acceptable joints.  When shorts evidence - most always use of "solder wick" can remove the short - yet enable the MCU pin to still be connected to the pcb. (most always)

Still the strong suggestion is NOT to attempt this. It will be challenging enough to fully/properly develop, debug & program your application.  Few firms are interested in employing new grads to, "Solder fine pitch devices - by hand."   They are interested in your ability to task the (properly) soldered MCU to solve problems - realize functions - and meet program objectives.   (hand soldering is "in the noise" - it is simply, "retarded!")

Horse & buggy - along w/"hand soldering" of fine pitch parts - (should) have, "Left the building."

Oh well Robert - at least two out of three here have argued against the attempt to, "Reinvent a perfectly sound wheel!"   (i.e. the LPad)

Days have already been lost in this (misguided) effort AND intermittent solder joints or cracked/fractured solder traces will wreak havoc.   Why risk that?

Trying to do that for which you're: unprepared - little skilled - and have failed at repeatedly makes NO sense.   Pity to see that encouraged - at least you/I have highlighted the misplacement of time/effort/and funds...

Silent in all of this is the (very) likely MISS of the excellent write-up by this vendor - outlining, "How to build an MCU pcb correctly."   For a first-timer - under deadline - to get all of this correct/proper is (extremely) wishful thinking.    Seat on the top deck of the Titanic, anyone?

Hi Amit,

I'm using a very fine tip at 200°c for solder wire (hard to get it melted), but I think is too hot, so I tried to do it with hot air at 145°c, with solder paste, but the solder paste is not for low temp, so I already ordered a low temp solder paste that melts at 138°c.

The PCB is made by OSHPARK, so it's kind of fine finished

While we (hope) that your problems are solved - it is unlikely that a full & proper test of all MCU signals was completed. In addition - as a "first ever" board creation - hairline fractures & intermittent solder joints are NOT uncommon!

As small biz operator - holding your ongoing project work "Hostage" to the creation of an "iffy" board - is not a path we'd (ever) take!

Should your board (appear) to work today - but fail or prove unreliable downstream - how will you (quickly & efficiently) differentiate between code error and hardware issues? (I don't believe that you can - thus you've created a condition of "maximum randomness" which stands in High Violation of KISS!)

Such prototype boards - and their projects - often receive extreme handling.   (everything is new)  Is this not likely to "stress" marginal joints - or introduce ESD - or suffer during (multiple) component changes/additions?

KISS argues for, "One battle at a time" (minimize unknowns)  - never/ever admit/invite too many "unknowns" - all thrown together - w/hope as your guide...  We note that a robust, tried/true LPad has been bypassed in favor of a "first creation!"   If that's "best practice" my firm's manuals require serious revision...

Hi Amit,

Yes - such specialized tools may help - yet there is a clear (& I believe even clever) analogy which best frames this thread.

DRM is one means to code your MCU. However - it is little "tried/true/tested" and the complexity demands great investment of time & energy - and (still) the end result may prove unacceptable.

Thus - DRM is to the API as "Poster's hand assembled pcb" is to a pro-designed/built LaunchPad.   One method is "sure/confirmed" - the other, "Headache in the making!"

And that's (exactly) the road this poster has taken - producing a board which is "uncertain at best" - and "who knows what" - if he's unlucky.   Earlier I proposed that the poster - if he must - produce a simpler accessory board - which accepts the LPad as a, "Plug-In."   Fine pitch MCU soldering often weakens board traces & proves injurious (often) to some MCU pins.   And the degree of failure may be expected to grow - adding more pain/suffering...

Recall this is a prototype - will be repeatedly flexed/handled - (perhaps even dropped) by several. That adds an unacceptable element of risk - and as poster is new at programming it will prove SO hard to recognize his (coming) difficulties & issues as software or his (essentially untired/tested) hardware creation.

Instructors who forced this "gimmick" would be unwelcome in my shop - & that of most all small tech biz owners I know.   Pity!
Violating KISS so strongly is like looking down the barrel of a misfiring cannon - the "Risk" clearly overwhelms (any) "Reward."

Never/ever would my firm allow (worse encourage) a "rookie" - w/out adequate tools & training - to produce a pcb where the success of the project is tied (really it's "Held HOSTAGE") to the correctness & robustness of such a board!   That's just ASKING for trouble and "retards" - rather than "boosts" - important, focused MCU learning...