Definition
Reflowing is the controlled re-heating of a solder joint until the solder melts and re-forms, restoring an electrical and mechanical connection that has cracked, oxidized, or never bonded correctly. In ASIC repair it is the lightest-touch way to revive a board before resorting to removing and re-soldering components outright.
Also known as: reflow soldering, solder reflow, hot-air reflow.
Why reflowing matters in ASIC mining
A Bitcoin miner runs for years under constant heat and current. Every power cycle, every fan ramp, and every change in ambient temperature makes the board and its components expand and contract at slightly different rates. Over thousands of cycles this thermal stress can fatigue a solder joint until it develops a hairline crack — an intermittent or open connection that no amount of firmware tuning will fix. Reflowing aims to melt that joint just enough to let the solder re-wet and close the gap.
The most failure-prone joints sit along the signal chain that ties an entire hashboard together. Every Antminer hashboard daisy-chains its ASICs with a shared 5-signal scheme — CLK (clock) and TX/CI (command input) running forward through the chain, RX/RO (response output) running back, plus BO (busy) and RST (reset) — all of it reaching the control board through an 18-pin ribbon cable. A single cold or cracked joint anywhere on that chain can break enumeration, so a board that reports a missing chip count, zero chips detected, or a stubborn signal fault is a classic candidate for inspection and reflow before parts are replaced.
How a reflow repair actually works
The board is brought up to the solder’s melting point with a hot-air rework station or an infrared heater, ideally over a preheater or hot plate so the whole area rises together and the board is not thermally shocked. The technician applies flux to help the solder flow and watches for the joints to re-wet. Because the heat is broad rather than surgical, reflowing is well suited to re-seating connections under a chip or connector without lifting every neighbouring part.
An important distinction for Bitmain hardware: the mining ASICs themselves — BM1387 (S9), BM1397 (S17 family), BM1398 (S19/S19 Pro), BM1368 (S21), and so on — are QFN-style packages with leads or pads around the perimeter, not large ball-grid arrays. That means many ASIC-side faults are accessible to careful hand-rework and reflow rather than full BGA reballing. Reballing — completely removing a chip, cleaning off the old solder, and forming fresh solder balls before re-attaching — is generally reserved for the few true BGA components on a board, and is far more invasive than a localized reflow.
Where reflowing fits in the repair workflow
Reflowing is one tool inside a structured diagnosis, not a cure-all. The standard approach to a low or partial hashboard is to localize the fault first — for low-hashrate boards by identifying and replacing the lowest-performing chip iteratively, and for broken chains by the dichotomy (binary-search) method: isolate the chain at its midpoint to see which half recovers, then repeat until a single faulty chip or domain is found. Only once the bad joint or component is pinpointed does reflow, replacement, or domain bypass come into play.
It pays to be honest about its limits. A reflow can revive an intermittent joint, but if the underlying cause — chronic thermal stress, poor airflow, dried-out thermal interface material, or a genuinely dead chip — is still present, the same joint will likely fail again. Good preventative practice does more for board longevity than repeated reflows: proper thermal paste application, clean heatsink contact, and steady cooling keep joint temperatures stable and slow the thermal-cycling fatigue that cracks solder in the first place.
One safety note specific to mining hardware: on S19-class boards the power-on and disconnect order matters, and an out-of-sequence connection or a power interruption during sensitive operations can damage the control board. Bench work on hashboards should follow the documented connect/disconnect sequence and be done with the miner fully powered down.
Reflowing therefore lives in the same toolbox as chip-level work and broader board service — see hashboard repair, the role of each individual ASIC chip in the chain, and the daisy-chained hashboard it all sits on.
If a board is throwing chip-count or hashrate errors and you would rather not heat it yourself, our team performs structured diagnostics and board-level rework as part of ASIC troubleshooting — bring us the symptom and we will trace it to the joint, chip, or domain before any iron touches the board.
In Simple Terms
Reheating solder joints to fix broken connections. A common repair for intermittent chip failures.
Reflowing is the controlled re-heating of a solder joint until the solder melts and re-forms, restoring an electrical and mechanical connection that has cracked, oxidized, or never bonded correctly. In ASIC repair it is the lightest-touch way to revive a board before resorting to removing and re-soldering components outright.
Also known as: reflow soldering, solder reflow, hot-air reflow.
Why reflowing matters in ASIC mining
A Bitcoin miner runs for years under constant heat and current. Every power cycle, every fan ramp, and every change in ambient temperature makes the board and its components expand and contract at slightly different rates. Over thousands of cycles this thermal stress can fatigue a solder joint until it develops a hairline crack — an intermittent or open connection that no amount of firmware tuning will fix. Reflowing aims to melt that joint just enough to let the solder re-wet and close the gap.
The most failure-prone joints sit along the signal chain that ties an entire hashboard together. Every Antminer hashboard daisy-chains its ASICs with a shared 5-signal scheme — CLK (clock) and TX/CI (command input) running forward through the chain, RX/RO (response output) running back, plus BO (busy) and RST (reset) — all of it reaching the control board through an 18-pin ribbon cable. A single cold or cracked joint anywhere on that chain can break enumeration, so a board that reports a missing chip count, zero chips detected, or a stubborn signal fault is a classic candidate for inspection and reflow before parts are replaced.
How a reflow repair actually works
The board is brought up to the solder's melting point with a hot-air rework station or an infrared heater, ideally over a preheater or hot plate so the whole area rises together and the board is not thermally shocked. The technician applies flux to help the solder flow and watches for the joints to re-wet. Because the heat is broad rather than surgical, reflowing is well suited to re-seating connections under a chip or connector without lifting every neighbouring part.
An important distinction for Bitmain hardware: the mining ASICs themselves — BM1387 (S9), BM1397 (S17 family), BM1398 (S19/S19 Pro), BM1368 (S21), and so on — are QFN-style packages with leads or pads around the perimeter, not large ball-grid arrays. That means many ASIC-side faults are accessible to careful hand-rework and reflow rather than full BGA reballing. Reballing — completely removing a chip, cleaning off the old solder, and forming fresh solder balls before re-attaching — is generally reserved for the few true BGA components on a board, and is far more invasive than a localized reflow.
Where reflowing fits in the repair workflow
Reflowing is one tool inside a structured diagnosis, not a cure-all. The standard approach to a low or partial hashboard is to localize the fault first — for low-hashrate boards by identifying and replacing the lowest-performing chip iteratively, and for broken chains by the dichotomy (binary-search) method: isolate the chain at its midpoint to see which half recovers, then repeat until a single faulty chip or domain is found. Only once the bad joint or component is pinpointed does reflow, replacement, or domain bypass come into play.
It pays to be honest about its limits. A reflow can revive an intermittent joint, but if the underlying cause — chronic thermal stress, poor airflow, dried-out thermal interface material, or a genuinely dead chip — is still present, the same joint will likely fail again. Good preventative practice does more for board longevity than repeated reflows: proper thermal paste application, clean heatsink contact, and steady cooling keep joint temperatures stable and slow the thermal-cycling fatigue that cracks solder in the first place.
One safety note specific to mining hardware: on S19-class boards the power-on and disconnect order matters, and an out-of-sequence connection or a power interruption during sensitive operations can damage the control board. Bench work on hashboards should follow the documented connect/disconnect sequence and be done with the miner fully powered down.
Reflowing therefore lives in the same toolbox as chip-level work and broader board service — see hashboard repair, the role of each individual ASIC chip in the chain, and the daisy-chained hashboard it all sits on.
If a board is throwing chip-count or hashrate errors and you would rather not heat it yourself, our team performs structured diagnostics and board-level rework as part of ASIC troubleshooting — bring us the symptom and we will trace it to the joint, chip, or domain before any iron touches the board.