IQD用石英基產(chǎn)品超聲波清洗印刷電路板

The use of an ultrasonic-bath is a common method of cleaning electronic components and printed circuit boards (PCBs).

This method uses ultrasound and a solvent to clean items by creating cavitation bubbles which are produced by high frequency pressure (sound) waves to agitate the cleaning liquid, forcing contamination to be removed.

Ultrasound is sound beyond the normal hearing range of humans with a typical bath operating around 40kHz although other frequency equipment is available.

Modern ultrasonic cleaning baths may have the facility to alter the bath frequency and this is useful as it may help to reduce self-resonance by sweeping the frequency up and down thus helping to alleviate damage that may be created at one specific frequency.

To date, little research on the use of ultrasonic cleaning of quartz components has been done. The only generally available background information was published by GEC-Marconi, Hirst Research Centre in England in 1992 and titled The Effects of Ultrasonic Cleaning on Device Degradation — Quartz Crystal Devices. The authors of the report are surprisingly optimistic in the tone of their conclusions, despite finding many failures even in their small sample size. Failures were found to be significantly higher in low cost high volume quartz devices. However if considering this report, it is important to recognise that quartz crystal manufacturing has changed very dramatically in the intervening years. The size, packaging and mounting structure of modern ceramic packages are not comparable to the metal can packages analysed in this report, additionally the general quality control of low cost high volume manufacturing is very different today than in 1992.

As a general comment, crystals in the MHz range (which use AT cut quartz blanks), should survive an ultrasonic cleaned process unharmed. Although the overall frequency and specification must be taken into account because higher frequencies use thinner quartz blanks which are more susceptible to breakage than thicker lower frequency devices.

However, crystals that use ‘tuning-fork’ technology to produce low frequencies such as the common 32.768kHz watch crystals are significantly higher risk. In their application these crystals are designed to work at very low drive levels, the internal architecture of these crystals is designed to excite resonance with very low input power levels, meaning higher power levels can cause physical damage more easily than other products. The frequencies used in ultrasonic are also much closer to the resonant frequency of the quartz, further increasing the likelihood of self-resonance.

With the above points it can be seen that the use of ultrasonic cleaning on PCB’s containing quartz products is not without risks. For low frequency crystals, in the kHz range, IQD Crystay do not recommend the use of ultrasonic cleaning. For other crystal types we recommend that experimentation is undertaken to assess the risk before use in production.

If you are considering using ultrasonic cleaning in your production process then we would recommend that some experimentation is undertaken working with the specific vibration frequencies and energy levels that the components will see in your cleaning equipment to prove suitability. We also recommend that the specific crystal to be used on the PCB is used in the assessment experimentation.

The Institute for Interconnecting and Packaging Electronic Circuits (IPC) paper IPC-TM-650, titled Test to Determine Sensitivity of Electronic Components to Ultrasonic Energy, this provides a good starting point for any experimentation.

IQD用石英基產(chǎn)品超聲波清洗印刷電路板

使用超聲波浴池是清洗電子元器件和印刷電路板（pcb）的一種常用方法。

這種方法使用超聲波和溶劑來清洗物品，產(chǎn)生空化氣泡是由高頻高壓（聲）波產(chǎn)生的氣泡來攪拌清洗液，迫使污染被清除。

超聲波的聲音超出了人類的正常聽力范圍，一個(gè)典型的浴缸運(yùn)行約40kHz，盡管有其他頻率設(shè)備。

現(xiàn)代超聲波清洗浴可能有改變?cè)☆l率的設(shè)備，這是有用的，因?yàn)樗赡苡兄跍p少自共振掃描頻率，從而幫助減輕可能在一個(gè)特定頻率造成的損害。

到目前為止，關(guān)于使用超聲波清洗石英組分的研究還很少。唯一普遍可用的背景信息是由英國(guó)赫斯特研究中心gec-馬可尼于1992年發(fā)表的，題為《超聲波清洗對(duì)器件降解的影響——石英晶體器件》。該報(bào)告的作者對(duì)他們的結(jié)論的基調(diào)令人驚訝地樂觀，盡管他們?cè)谛颖玖恐邪l(fā)現(xiàn)了許多失敗。在低成本的高容量石英器件中，故障明顯更高。然而，如果考慮到這個(gè)報(bào)告，重要的是要認(rèn)識(shí)到石英晶振的制造在這幾年里發(fā)生了非常巨大的變化?，F(xiàn)代陶瓷包裝的尺寸、包裝和安裝結(jié)構(gòu)無法與本報(bào)告中分析的金屬罐包裝相媲美，此外，目前低成本大批量制造的一般質(zhì)量控制與1992年非常不同。

一般來說，在MHz范圍內(nèi)的晶體（使用AT切割石英空白），應(yīng)該在超聲波清洗過程中安然存活下來。雖然必須考慮整體頻率和規(guī)格，因?yàn)楦叩念l率使用更薄的石英坯料，比更厚的低頻率設(shè)備更容易斷裂。

然而，使用“音叉”技術(shù)產(chǎn)生低頻率的晶體，如常見的32.768kHz手表時(shí)鐘晶振，其風(fēng)險(xiǎn)明顯更高。在它們的應(yīng)用中，這些晶體被設(shè)計(jì)為在非常低的驅(qū)動(dòng)水平下工作，這些晶體的內(nèi)部結(jié)構(gòu)被設(shè)計(jì)為在非常低的輸入功率水平下激發(fā)共振，這意味著更高的功率水平比其他產(chǎn)品更容易造成物理?yè)p傷。在超聲波中使用的頻率也更接近石英的共振頻率，進(jìn)一步增加了自共振的可能性。

從以上幾點(diǎn)可以看出，對(duì)含石英PCB的產(chǎn)品使用超聲波清洗并非沒有風(fēng)險(xiǎn)。對(duì)于低頻晶體，在千赫茲范圍內(nèi)，IQD不建議使用超聲波清洗。對(duì)于其他類型的晶體，我們建議在生產(chǎn)中使用前進(jìn)行實(shí)驗(yàn)以評(píng)估風(fēng)險(xiǎn)。

如果您正在考慮在生產(chǎn)過程中使用超聲波清洗，那么我們建議進(jìn)行一些實(shí)驗(yàn)，使用組件將在您的清洗設(shè)備中看到的特定振動(dòng)頻率和能級(jí)，以證明其適用性。我們還建議在評(píng)估實(shí)驗(yàn)中使用將在PCB上使用的特定晶體。

互聯(lián)和包裝電子電路研究所（IPC）論文IPC-TM-650，題為確定電子元件對(duì)超聲波能量靈敏度的測(cè)試，這為任何實(shí)驗(yàn)提供了一個(gè)很好的起點(diǎn)。

1/5