General Usage Considerations

[As of April, 2011]

Mounting

There are two types of device packages: lead insertion and surface mount. The items that affect reliability during circuit board mounting include contamination by flux and thermal stress during the soldering process. With surface-mount devices in particular, the most significant problem is thermal stress from solder reflow, when the entire package is subjected to heat. In addition, the mounting method differs according to factors such as chip size and frame design, even for the same package type. For details, refer to the respective technical datasheets and databooks for each device.
When a location such as a soldered area, connecting area or top surface of a device is subjected to vibration, impact or in actual equipment, bonding fault or device destruction may result. Therefore, be sure to keep this in mind at the time of mounting. If a device is subject to especially strong vibration, impact or stress, the package or chip may crack. Thus, at the time of mounting, carefully consider vibration, impact and stress.

Lead Forming

	Do not touch the lead tips of a device. Some devices have leads with sharp tips. Contact to sharp tips may result in a puncture wound.
	Always wear safety glasses when cutting the leads of a device with clippers or a similar tool. Failure to do so may result in eye damage from the small shavings that fly off the cut ends.

Semiconductor devices sometimes undergo a process in which the leads are cut and formed before the devices are installed on a printed circuit board. If abnormal stress is applied to the interior of a device during this process, mechanical breakdown or reliability deterioration may result. This is attributable mainly to the relative stress applied between the device itself and the lead, and can result in internal lead damage, adhesive property deterioration and sealant breakdown. Observe the following precautions during the lead-forming process.
(This does not apply to surface-mount devices.)

Socket Mounting

1. When socket-mounting devices on a printed circuit board, use sockets that match the package.
2. Use sockets with contacts that have the appropriate contact pressure. If the contact pressure is insufficient, the contact may become poor when the device is repeatedly inserted and removed. If the contact pressure is too high, the device leads may bend or become damaged when they are inserted into or removed from the socket.
3. When soldering sockets to the printed circuit board, use sockets designed to prevent flux from penetrating the contacts and to allow flux to be completely cleaned off.
4. Ensure that the coating agent applied to the printed circuit board for moisture-proofing does not adhere to the socket contacts.
5. If the leads are severely bent when inserted into or removed from a socket and you want to repair the leads and continue using the device, repair the leads once only. Do not use devices whose leads have been corrected multiple times.
6. If external vibration will be applied to a printed circuit board with devices mounted on it, use sockets with strong contact pressure so as to prevent vibration between the devices and sockets.

Soldering Temperature Profile

Perform soldering following the methods and conditions described in the respective technical datasheets and databooks for the device used. The soldering method, temperature and time may be restricted, depending on the device. All soldering temperature profiles and conditions described in the mounting methods below are representative. The profiles and conditions vary from product to product. Therefore, mount the product after first confirming the information described in the respective technical datasheets and databooks with the customer.
Reflow soldering and flow soldering must not be combined when performed. For details regarding special soldering including lead(Pb) soldering, please contact your nearest Toshiba office or distributor.

Using a Soldering Iron

Complete soldering within 10 seconds for soldering iron temperatures of up to 260°C, or within 3 seconds for soldering iron temperatures of up to 350°C.

Using Infrared Reflow

1. It is recommended the top and bottom heating method with long or medium infrared rays.
2. Complete the infrared ray reflow process with a maximum package surface temperature of 260°C, within 30 to 50 seconds when a package surface temperature is 230°C or higher.
3. Refer to Figure 1 for an example of a temperature profile.
   

   Figure 1 Example of Temperature Profile

   This profile is based on the device’s maximum heat resistance guaranteed value.
   Set the preheat temperature/heating temperature to the optimum temperature corresponding to the solder paste type used by the customer within the above-described profile.

Using Hot Air Reflow

1. Complete hot air reflow with a maximum package surface temperature of 260°C, within 30 to 50 seconds when a package surface temperature is 230°C or higher.
2. For an example of a temperature profile, refer to Figure 1 above.

Using Solder Flow/Dip

1. Apply preheating for 60 to 120 seconds at a temperature of 150°C.
2. Mount the device within 10 seconds of solder flow with a maximum temperature of 260°C.
3. For insertion-type packages, mount the device at the stopper or at a location more than 1.5mm from the body.
4. Surface-mount packages are greatly affected by thermal stress compared with the insertion-type packages; therefore, mount the device lower temperature and shorter mounting time than the condition listed in the above 2. to avoid thermal stress.

Flux Cleaning

1. When cleaning circuit boards to remove flux, make sure that no reactive ions such as sodium or chlorine remain. Some organic solvents react with water to generate hydrogen chloride and other corrosive gases which can result in device deterioration.
2. When washing devices with water, make sure that no reactive ions such as sodium or chlorine remain particularly.
3. When washing devices, do not rub markings with a brush or with your hand while the cleansing liquid is still on the device. Doing so can rub off the markings.
4. Dip cleaning, shower cleaning and steam cleaning processes are performed based on the chemical action of a solvent. When immersing devices in a solvent or steam bath, complete the cleaning for a period of one minute or less at a liquid temperature of 50°C or less, taking into consideration the effects on the devices.
5. Avoid use of ultrasonic cleaning with hermetically sealed ceramic packages such as a leadless chip carrier (LCC), pin grid array (PGA) or charge-coupled device (CCD). Using the ultrasonic cleaning may cause the internal wires to become disconnected due to resonance. Even if a device package allows ultrasonic cleaning, keep the duration of ultrasonic cleaning in a brief time. Long hours of ultrasonic cleaning may deteriorate the adhesion between the mold resin and frame material.

   The basic recommended conditions are as follows:

   • Recommended Ultrasonic Cleaning Conditions
   • Frequency: 27 to 29kHz
   • Ultrasonic output: 15W/L or less
   • Cleaning time: 30 seconds or less

   Suspend the printed circuit board in the solvent bath to ensure that the circuit board and device do not come in direct contact with the ultrasonic vibrator.

No Cleaning

It is recommended that you clean analog devices and high-speed devices. If such devices are not cleaned, flux may cause minute leakage between leads or migration, depending on the flux grade. Be sure therefore to check cleanliness at the time of use. If you are considering no cleaning, be sure to use a flux that does not require cleaning.

Tape Carrier Packages (TCPs) Mounting

1. When tape carrier packages are mounted, measures must be taken to prevent electrostatic breakdown of the devices.
2. When separating devices from tape, or carrying out outer lead bonding (OLB) mounting, be sure to take work safety into consideration.
3. The base film, which is made of polyimide, is hard and thin. Be careful not to injury yourself or damage any objects during handling.
4. When punching tape, take countermeasures to prevent minute broken pieces from scattering. Scattered pieces may cause injury.
5. Appropriately treat the tape, reels and spacers left after separating the device as industrial waste.
6. With tape carrier package (TCPs) devices, the backside of the LSI chips is exposed. To ensure that the chip will not crack, mount the device so that mechanical shock is not applied to the LSI backside. In addition, electrical contact may also cause LSI failure. Mount the device so that there is no electrical contact with the backside of the LSI chip.
   If you are mounting the backside of the LSI chip to improve device characteristics, please contact your nearest Toshiba office or distributor in advance.

Chips Mounting

Devices delivered in chip form readily deteriorate or become damaged due to external factors in comparison with plastic-packaged products. Attention is therefore required during handling.

1. Mount devices in a properly maintained environment so that the chip will not be exposed to contaminated ambient air or other substances.
2. When handling chips, be careful not to expose the chips to static electricity. In particular, measures must be taken to prevent electrostatic breakdown during chip mounting. For this purpose, it is recommended that you mount all peripheral devices before you mount the chips.
3. Use chip mounting circuit boards (such as PCBs) that do not have any chemical residue on them (such as the chemicals used during PCB etching).
4. When mounting chips, use the method of assembly that is most suitable for achieving the appropriate electrical, thermal and mechanical characteristics of the semiconductor product used.
   • * For chip details, refer to the relevant specification sheet.

Circuit Board Coating

When using devices that require high reliability or devices used under extreme environments (where moisture, corrosive gas or dust is present), circuit boards are sometimes coated with a moisture-proof coating. When using a coating resin, choose the coating resin which results in minimal stress to the device.

Heat Sinks

	Do not touch the device and its heat sink while the device is on or immediately after the device has been turned off. Devices and Heat sinks become hot. Contact to the heat sink may result in a burn.

Tightening Torque

1. Tighten screws to a tightening torque that is within the specified values described in the respective technical datasheets and databooks for the device used.
2. Be careful not to allow a pneumatic screwdriver to come in contact with devices. Device damage may result.

Repeated Device Mounting and Usage

Do not remount or reuse devices that have histories such as that described below. These devices may cause significant problems with regard to device characteristics and reliability.

1. Devices that have been removed from the board after soldering.
2. Devices that have been inserted in the wrong orientation or with reverse polarity and charged.
3. Devices that have undergone lead forming more than once.

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